- Qt 6.9
- Qt Core
- C++ Classes
- QByteArray
- Qt 6.9.3 Reference Documentation

# QByteArray Class

The QByteArray class provides an array of bytes. More...

Header: | `#include <QByteArray>`
CMake: | `find_package(Qt6 REQUIRED COMPONENTS Core)` `target_link_libraries(mytarget PRIVATE Qt6::Core)`
qmake: | `QT += core`

- List of all members, including inherited members
- Deprecated members
- QByteArray is part of Implicitly Shared Classes and Classes for string data.

This class is strongly comparable.

This class is strongly comparable with const char * and QByteArrayView.

This class is strongly comparable with QChar, char16_t, QString, QStringView, QLatin1StringView, and QUtf8StringView.

When comparing with string types, the content is interpreted as UTF-8.

Note: All functions in this class are reentrant.

## Public Types

class | FromBase64Result
enum | Base64Option { Base64Encoding, Base64UrlEncoding, KeepTrailingEquals, OmitTrailingEquals, IgnoreBase64DecodingErrors, AbortOnBase64DecodingErrors }
flags | Base64Options
| const_iterator
| const_reverse_iterator
| iterator
| reverse_iterator

## Public Functions

| QByteArray()
`(since 6.8)` | QByteArray(QByteArrayView v)
| QByteArray(const char *data, qsizetype size = -1)
| QByteArray(qsizetype size, Qt::Initialization)
| QByteArray(qsizetype size, char ch)
| QByteArray(const QByteArray &other)
| QByteArray(QByteArray &&other)
| ~QByteArray()
QByteArray & | append(const QByteArray &ba)
QByteArray & | append(QByteArrayView data)
QByteArray & | append(char ch)
QByteArray & | append(const char *str)
QByteArray & | append(const char *str, qsizetype len)
QByteArray & | append(qsizetype count, char ch)
`(since 6.6)` QByteArray & | assign(QByteArrayView v)
`(since 6.6)` QByteArray & | assign(InputIterator first, InputIterator last)
`(since 6.6)` QByteArray & | assign(qsizetype n, char c)
char | at(qsizetype i) const
char & | back()
char | back() const
QByteArray::iterator | begin()
QByteArray::const_iterator | begin() const
qsizetype | capacity() const
QByteArray::const_iterator | cbegin() const
QByteArray::const_iterator | cend() const
void | chop(qsizetype n)
QByteArray | chopped(qsizetype len) &&
QByteArray | chopped(qsizetype len) const &
void | clear()
`(since 6.0)` int | compare(QByteArrayView bv, Qt::CaseSensitivity cs = Qt::CaseSensitive) const
QByteArray::const_iterator | constBegin() const
const char * | constData() const
QByteArray::const_iterator | constEnd() const
`(since 6.0)` bool | contains(QByteArrayView bv) const
bool | contains(char ch) const
`(since 6.0)` qsizetype | count(QByteArrayView bv) const
qsizetype | count(char ch) const
QByteArray::const_reverse_iterator | crbegin() const
QByteArray::const_reverse_iterator | crend() const
char * | data()
const char * | data() const
QByteArray::iterator | end()
QByteArray::const_iterator | end() const
`(since 6.0)` bool | endsWith(QByteArrayView bv) const
bool | endsWith(char ch) const
`(since 6.1)` QByteArray::iterator | erase(QByteArray::const_iterator first, QByteArray::const_iterator last)
`(since 6.5)` QByteArray::iterator | erase(QByteArray::const_iterator it)
QByteArray & | fill(char ch, qsizetype size = -1)
`(since 6.0)` QByteArray | first(qsizetype n) &&
`(since 6.0)` QByteArray | first(qsizetype n) const &
char & | front()
char | front() const
`(since 6.0)` qsizetype | indexOf(QByteArrayView bv, qsizetype from = 0) const
qsizetype | indexOf(char ch, qsizetype from = 0) const
`(since 6.0)` QByteArray & | insert(qsizetype i, QByteArrayView data)
QByteArray & | insert(qsizetype i, const QByteArray &data)
QByteArray & | insert(qsizetype i, const char *s)
QByteArray & | insert(qsizetype i, char ch)
QByteArray & | insert(qsizetype i, const char *data, qsizetype len)
QByteArray & | insert(qsizetype i, qsizetype count, char ch)
bool | isEmpty() const
bool | isLower() const
bool | isNull() const
bool | isUpper() const
`(since 6.3)` bool | isValidUtf8() const
`(since 6.0)` QByteArray | last(qsizetype n) &&
`(since 6.0)` QByteArray | last(qsizetype n) const &
`(since 6.0)` qsizetype | lastIndexOf(QByteArrayView bv, qsizetype from) const
`(since 6.2)` qsizetype | lastIndexOf(QByteArrayView bv) const
qsizetype | lastIndexOf(char ch, qsizetype from = -1) const
QByteArray | left(qsizetype len) &&
QByteArray | left(qsizetype len) const &
QByteArray | leftJustified(qsizetype width, char fill = ' ', bool truncate = false) const
qsizetype | length() const
`(since 6.8)` qsizetype | max_size() const
QByteArray | mid(qsizetype pos, qsizetype len = -1) &&
QByteArray | mid(qsizetype pos, qsizetype len = -1) const &
`(since 6.4)` QByteArray | percentDecoded(char percent = '%') const
QByteArray & | prepend(QByteArrayView ba)
QByteArray & | prepend(char ch)
QByteArray & | prepend(const QByteArray &ba)
QByteArray & | prepend(const char *str)
QByteArray & | prepend(const char *str, qsizetype len)
QByteArray & | prepend(qsizetype count, char ch)
void | push_back(const QByteArray &other)
`(since 6.0)` void | push_back(QByteArrayView str)
void | push_back(char ch)
void | push_back(const char *str)
void | push_front(const QByteArray &other)
`(since 6.0)` void | push_front(QByteArrayView str)
void | push_front(char ch)
void | push_front(const char *str)
QByteArray::reverse_iterator | rbegin()
QByteArray::const_reverse_iterator | rbegin() const
QByteArray & | remove(qsizetype pos, qsizetype len)
`(since 6.5)` QByteArray & | removeAt(qsizetype pos)
`(since 6.5)` QByteArray & | removeFirst()
`(since 6.1)` QByteArray & | removeIf(Predicate pred)
`(since 6.5)` QByteArray & | removeLast()
QByteArray::reverse_iterator | rend()
QByteArray::const_reverse_iterator | rend() const
QByteArray | repeated(qsizetype times) const
QByteArray & | replace(qsizetype pos, qsizetype len, QByteArrayView after)
`(since 6.0)` QByteArray & | replace(QByteArrayView before, QByteArrayView after)
QByteArray & | replace(char before, QByteArrayView after)
QByteArray & | replace(char before, char after)
QByteArray & | replace(const char *before, qsizetype bsize, const char *after, qsizetype asize)
QByteArray & | replace(qsizetype pos, qsizetype len, const char *after, qsizetype alen)
void | reserve(qsizetype size)
void | resize(qsizetype size)
`(since 6.4)` void | resize(qsizetype newSize, char c)
`(since 6.8)` void | resizeForOverwrite(qsizetype size)
QByteArray | right(qsizetype len) &&
QByteArray | right(qsizetype len) const &
QByteArray | rightJustified(qsizetype width, char fill = ' ', bool truncate = false) const
QByteArray & | setNum(int n, int base = 10)
QByteArray & | setNum(long n, int base = 10)
QByteArray & | setNum(qlonglong n, int base = 10)
QByteArray & | setNum(qulonglong n, int base = 10)
QByteArray & | setNum(short n, int base = 10)
QByteArray & | setNum(uint n, int base = 10)
QByteArray & | setNum(ulong n, int base = 10)
QByteArray & | setNum(ushort n, int base = 10)
QByteArray & | setNum(double n, char format = 'g', int precision = 6)
QByteArray & | setNum(float n, char format = 'g', int precision = 6)
QByteArray & | setRawData(const char *data, qsizetype size)
void | shrink_to_fit()
QByteArray | simplified() const
qsizetype | size() const
`(since 6.8)` QByteArray & | slice(qsizetype pos, qsizetype n)
`(since 6.8)` QByteArray & | slice(qsizetype pos)
`(since 6.0)` QByteArray | sliced(qsizetype pos, qsizetype n) &&
`(since 6.0)` QByteArray | sliced(qsizetype pos, qsizetype n) const &
`(since 6.0)` QByteArray | sliced(qsizetype pos) &&
`(since 6.0)` QByteArray | sliced(qsizetype pos) const &
QList<QByteArray> | split(char sep) const
void | squeeze()
`(since 6.0)` bool | startsWith(QByteArrayView bv) const
bool | startsWith(char ch) const
void | swap(QByteArray &other)
QByteArray | toBase64(QByteArray::Base64Options options = Base64Encoding) const
CFDataRef | toCFData() const
double | toDouble(bool *ok = nullptr) const
`(since 6.5)` emscripten::val | toEcmaUint8Array()
float | toFloat(bool *ok = nullptr) const
QByteArray | toHex(char separator = '\0') const
int | toInt(bool *ok = nullptr, int base = 10) const
long | toLong(bool *ok = nullptr, int base = 10) const
qlonglong | toLongLong(bool *ok = nullptr, int base = 10) const
QByteArray | toLower() const
NSData * | toNSData() const
QByteArray | toPercentEncoding(const QByteArray &exclude = QByteArray(), const QByteArray &include = QByteArray(), char percent = '%') const
CFDataRef | toRawCFData() const
NSData * | toRawNSData() const
short | toShort(bool *ok = nullptr, int base = 10) const
std::string | toStdString() const
uint | toUInt(bool *ok = nullptr, int base = 10) const
ulong | toULong(bool *ok = nullptr, int base = 10) const
qulonglong | toULongLong(bool *ok = nullptr, int base = 10) const
ushort | toUShort(bool *ok = nullptr, int base = 10) const
QByteArray | toUpper() const
QByteArray | trimmed() const
void | truncate(qsizetype pos)
const char * | operator const char *() const
const void * | operator const void *() const
QByteArray & | operator+=(const QByteArray &ba)
QByteArray & | operator+=(char ch)
QByteArray & | operator+=(const char *str)
QByteArray & | operator=(QByteArray &&other)
QByteArray & | operator=(const QByteArray &other)
QByteArray & | operator=(const char *str)
char & | operator[](qsizetype i)
char | operator[](qsizetype i) const

## Static Public Members

QByteArray | fromBase64(const QByteArray &base64, QByteArray::Base64Options options = Base64Encoding)
QByteArray::FromBase64Result | fromBase64Encoding(QByteArray &&base64, QByteArray::Base64Options options = Base64Encoding)
QByteArray::FromBase64Result | fromBase64Encoding(const QByteArray &base64, QByteArray::Base64Options options = Base64Encoding)
QByteArray | fromCFData(CFDataRef data)
`(since 6.5)` QByteArray | fromEcmaUint8Array(emscripten::val uint8array)
QByteArray | fromHex(const QByteArray &hexEncoded)
QByteArray | fromNSData(const NSData *data)
QByteArray | fromPercentEncoding(const QByteArray &input, char percent = '%')
QByteArray | fromRawCFData(CFDataRef data)
QByteArray | fromRawData(const char *data, qsizetype size)
QByteArray | fromRawNSData(const NSData *data)
QByteArray | fromStdString(const std::string &str)
`(since 6.8)` qsizetype | maxSize()
QByteArray | number(int n, int base = 10)
QByteArray | number(long n, int base = 10)
QByteArray | number(qlonglong n, int base = 10)
QByteArray | number(qulonglong n, int base = 10)
QByteArray | number(uint n, int base = 10)
QByteArray | number(ulong n, int base = 10)
QByteArray | number(double n, char format = 'g', int precision = 6)

## Related Non-Members

`(since 6.1)` qsizetype | erase(QByteArray &ba, const T &t)
`(since 6.1)` qsizetype | erase_if(QByteArray &ba, Predicate pred)
quint16 | qChecksum(QByteArrayView data, Qt::ChecksumType standard = Qt::ChecksumIso3309)
QByteArray | qCompress(const QByteArray &data, int compressionLevel = -1)
QByteArray | qCompress(const uchar *data, qsizetype nbytes, int compressionLevel = -1)
QByteArray | qUncompress(const QByteArray &data)
QByteArray | qUncompress(const uchar *data, qsizetype nbytes)
int | qstrcmp(const char *str1, const char *str2)
char * | qstrcpy(char *dst, const char *src)
char * | qstrdup(const char *src)
int | qstricmp(const char *str1, const char *str2)
size_t | qstrlen(const char *str)
int | qstrncmp(const char *str1, const char *str2, size_t len)
char * | qstrncpy(char *dst, const char *src, size_t len)
int | qstrnicmp(const char *str1, const char *str2, size_t len)
size_t | qstrnlen(const char *str, size_t maxlen)
bool | operator!=(const QByteArray &lhs, const QByteArray &rhs)
bool | operator!=(const QByteArray &lhs, const char *const &rhs)
bool | operator!=(const char *const &lhs, const QByteArray &rhs)
`(since 6.4)` QByteArray | operator""_ba(const char *str, size_t size)
`(since 6.9)` QByteArray | operator+(QByteArrayView lhs, const QByteArray &rhs)
QByteArray | operator+(char a1, const QByteArray &a2)
`(since 6.9)` QByteArray | operator+(const QByteArray &lhs, QByteArrayView rhs)
QByteArray | operator+(const QByteArray &a1, char a2)
QByteArray | operator+(const QByteArray &a1, const QByteArray &a2)
QByteArray | operator+(const QByteArray &a1, const char *a2)
QByteArray | operator+(const char *a1, const QByteArray &a2)
bool | operator<(const QByteArray &lhs, const QByteArray &rhs)
bool | operator<(const QByteArray &lhs, const char *const &rhs)
bool | operator<(const char *const &lhs, const QByteArray &rhs)
QDataStream & | operator<<(QDataStream &out, const QByteArray &ba)
bool | operator<=(const QByteArray &lhs, const QByteArray &rhs)
bool | operator<=(const QByteArray &lhs, const char *const &rhs)
bool | operator<=(const char *const &lhs, const QByteArray &rhs)
bool | operator==(const QByteArray &lhs, const QByteArray &rhs)
bool | operator==(const QByteArray &lhs, const char *const &rhs)
bool | operator==(const char *const &lhs, const QByteArray &rhs)
bool | operator>(const QByteArray &lhs, const QByteArray &rhs)
bool | operator>(const QByteArray &lhs, const char *const &rhs)
bool | operator>(const char *const &lhs, const QByteArray &rhs)
bool | operator>=(const QByteArray &lhs, const QByteArray &rhs)
bool | operator>=(const QByteArray &lhs, const char *const &rhs)
bool | operator>=(const char *const &lhs, const QByteArray &rhs)
QDataStream & | operator>>(QDataStream &in, QByteArray &ba)

## Macros

| QByteArrayLiteral(ba)
| QT_NO_CAST_FROM_BYTEARRAY
`(since 6.8)` | QT_NO_QSNPRINTF

## Detailed Description

QByteArray can be used to store both raw bytes (including '\0's) and traditional 8-bit '\0'-terminated strings. Using QByteArray is much more convenient than using `const char *`. Behind the scenes, it always ensures that the data is followed by a '\0' terminator, and uses implicit sharing (copy-on-write) to reduce memory usage and avoid needless copying of data.

In addition to QByteArray, Qt also provides the QString class to store string data. For most purposes, QString is the class you want to use. It understands its content as Unicode text (encoded using UTF-16) where QByteArray aims to avoid assumptions about the encoding or semantics of the bytes it stores (aside from a few legacy cases where it uses ASCII). Furthermore, QString is used throughout in the Qt API. The two main cases where QByteArray is appropriate are when you need to store raw binary data, and when memory conservation is critical (e.g., with Qt for Embedded Linux).

One way to initialize a QByteArray is simply to pass a `const char *` to its constructor. For example, the following code creates a byte array of size 5 containing the data "Hello":

     QByteArray ba("Hello");

Although the size() is 5, the byte array also maintains an extra '\0' byte at the end so that if a function is used that asks for a pointer to the underlying data (e.g. a call to data()), the data pointed to is guaranteed to be '\0'-terminated.

QByteArray makes a deep copy of the `const char *` data, so you can modify it later without experiencing side effects. (If, for example for performance reasons, you don't want to take a deep copy of the data, use QByteArray::fromRawData() instead.)

Another approach is to set the size of the array using resize() and to initialize the data byte by byte. QByteArray uses 0-based indexes, just like C++ arrays. To access the byte at a particular index position, you can use operator[](). On non-const byte arrays, operator[]() returns a reference to a byte that can be used on the left side of an assignment. For example:

     QByteArray ba;
     ba.resize(5);
     ba[0] = 0x3c;
     ba[1] = 0xb8;
     ba[2] = 0x64;
     ba[3] = 0x18;
     ba[4] = 0xca;

For read-only access, an alternative syntax is to use at():

     for (qsizetype i = 0; i < ba.size(); ++i) {
         if (ba.at(i) >= 'a' && ba.at(i) <= 'f')
             cout << "Found character in range [a-f]" << endl;
     }

at() can be faster than operator[](), because it never causes a deep copy to occur.

To extract many bytes at a time, use first(), last(), or sliced().

A QByteArray can embed '\0' bytes. The size() function always returns the size of the whole array, including embedded '\0' bytes, but excluding the terminating '\0' added by QByteArray. For example:

     QByteArray ba1("ca\0r\0t");
     ba1.size();                     // Returns 2.
     ba1.constData();                // Returns "ca" with terminating \0.

     QByteArray ba2("ca\0r\0t", 3);
     ba2.size();                     // Returns 3.
     ba2.constData();                // Returns "ca\0" with terminating \0.

     QByteArray ba3("ca\0r\0t", 4);
     ba3.size();                     // Returns 4.
     ba3.constData();                // Returns "ca\0r" with terminating \0.

     const char cart[] = {'c', 'a', '\0', 'r', '\0', 't'};
     QByteArray ba4(QByteArray::fromRawData(cart, 6));
     ba4.size();                     // Returns 6.
     ba4.constData();                // Returns "ca\0r\0t" without terminating \0.

If you want to obtain the length of the data up to and excluding the first '\0' byte, call qstrlen() on the byte array.

After a call to resize(), newly allocated bytes have undefined values. To set all the bytes to a particular value, call fill().

To obtain a pointer to the actual bytes, call data() or constData(). These functions return a pointer to the beginning of the data. The pointer is guaranteed to remain valid until a non-const function is called on the QByteArray. It is also guaranteed that the data ends with a '\0' byte unless the QByteArray was created from raw data. This '\0' byte is automatically provided by QByteArray and is not counted in size().

QByteArray provides the following basic functions for modifying the byte data: append(), prepend(), insert(), replace(), and remove(). For example:

     QByteArray x("and");
     x.prepend("rock ");         // x == "rock and"
     x.append(" roll");          // x == "rock and roll"
     x.replace(5, 3, "&");       // x == "rock & roll"

In the above example the replace() function's first two arguments are the position from which to start replacing and the number of bytes that should be replaced.

When data-modifying functions increase the size of the array, they may lead to reallocation of memory for the QByteArray object. When this happens, QByteArray expands by more than it immediately needs so as to have space for further expansion without reallocation until the size of the array has greatly increased.

The insert(), remove() and, when replacing a sub-array with one of different size, replace() functions can be slow (linear time) for large arrays, because they require moving many bytes in the array by at least one position in memory.

If you are building a QByteArray gradually and know in advance approximately how many bytes the QByteArray will contain, you can call reserve(), asking QByteArray to preallocate a certain amount of memory. You can also call capacity() to find out how much memory the QByteArray actually has allocated.

Note that using non-const operators and functions can cause QByteArray to do a deep copy of the data, due to implicit sharing.

QByteArray provides STL-style iterators (QByteArray::const_iterator and QByteArray::iterator). In practice, iterators are handy when working with generic algorithms provided by the C++ standard library.

Note: Iterators and references to individual QByteArray elements are subject to stability issues. They are often invalidated when a QByteArray-modifying operation (e.g. insert() or remove()) is called. When stability and iterator-like functionality is required, you should use indexes instead of iterators as they are not tied to QByteArray's internal state and thus do not get invalidated.

Note: Iterators over a QByteArray, and references to individual bytes within one, cannot be relied on to remain valid when any non-const method of the QByteArray is called. Accessing such an iterator or reference after the call to a non-const method leads to undefined behavior. When stability for iterator-like functionality is required, you should use indexes instead of iterators as they are not tied to QByteArray's internal state and thus do not get invalidated.

If you want to find all occurrences of a particular byte or sequence of bytes in a QByteArray, use indexOf() or lastIndexOf(). The former searches forward starting from a given index position, the latter searches backward. Both return the index position of the byte sequence if they find it; otherwise, they return -1. For example, here's a typical loop that finds all occurrences of a particular string:

     QByteArray ba("We must be <b>bold</b>, very <b>bold</b>");
     qsizetype j = 0;
     while ((j = ba.indexOf("<b>", j)) != -1) {
         cout << "Found <b> tag at index position " << j << endl;
         ++j;
     }

If you simply want to check whether a QByteArray contains a particular byte sequence, use contains(). If you want to find out how many times a particular byte sequence occurs in the byte array, use count(). If you want to replace all occurrences of a particular value with another, use one of the two-parameter replace() overloads.

QByteArrays can be compared using overloaded operators such as operator<(), operator<=(), operator==(), operator>=(), and so on. The comparison is based exclusively on the numeric values of the bytes and is very fast, but is not what a human would expect. QString::localeAwareCompare() is a better choice for sorting user-interface strings.

For historical reasons, QByteArray distinguishes between a null byte array and an empty byte array. A null byte array is a byte array that is initialized using QByteArray's default constructor or by passing (const char *)0 to the constructor. An empty byte array is any byte array with size 0. A null byte array is always empty, but an empty byte array isn't necessarily null:

     QByteArray().isNull();          // returns true
     QByteArray().isEmpty();         // returns true

     QByteArray("").isNull();        // returns false
     QByteArray("").isEmpty();       // returns true

     QByteArray("abc").isNull();     // returns false
     QByteArray("abc").isEmpty();    // returns false

All functions except isNull() treat null byte arrays the same as empty byte arrays. For example, data() returns a valid pointer (not nullptr) to a '\0' byte for a null byte array and QByteArray() compares equal to QByteArray(""). We recommend that you always use isEmpty() and avoid isNull().

### Maximum size and out-of-memory conditions

The maximum size of QByteArray depends on the architecture. Most 64-bit systems can allocate more than 2 GB of memory, with a typical limit of 2^63 bytes. The actual value also depends on the overhead required for managing the data block. As a result, you can expect the maximum size of 2 GB minus overhead on 32-bit platforms, and 2^63 bytes minus overhead on 64-bit platforms. The number of elements that can be stored in a QByteArray is this maximum size.

When memory allocation fails, QByteArray throws a `std::bad_alloc` exception if the application is being compiled with exception support. Out of memory conditions in Qt containers are the only case where Qt will throw exceptions. If exceptions are disabled, then running out of memory is undefined behavior.

Note that the operating system may impose further limits on applications holding a lot of allocated memory, especially large, contiguous blocks. Such considerations, the configuration of such behavior or any mitigation are outside the scope of the QByteArray API.

### C locale and ASCII functions

QByteArray generally handles data as bytes, without presuming any semantics; where it does presume semantics, it uses the C locale and ASCII encoding. Standard Unicode encodings are supported by QString, other encodings may be supported using QStringEncoder and QStringDecoder to convert to Unicode. For locale-specific interpretation of text, use QLocale or QString.

#### C Strings

Traditional C strings, also known as '\0'-terminated strings, are sequences of bytes, specified by a start-point and implicitly including each byte up to, but not including, the first '\0' byte thereafter. Methods that accept such a pointer, without a length, will interpret it as this sequence of bytes. Such a sequence, by construction, cannot contain a '\0' byte.

Other overloads accept a start-pointer and a byte-count; these use the given number of bytes, following the start address, regardless of whether any of them happen to be '\0' bytes. In some cases, where there is no overload taking only a pointer, passing a length of -1 will cause the method to use the offset of the first '\0' byte after the pointer as the length; a length of -1 should only be passed if the method explicitly says it does this (in which case it is typically a default argument).

#### Spacing Characters

A frequent requirement is to remove spacing characters from a byte array (`'\n'`, `'\t'`, `' '`, etc.). If you want to remove spacing from both ends of a QByteArray, use trimmed(). If you want to also replace each run of spacing characters with a single space character within the byte array, use simplified(). Only ASCII spacing characters are recognized for these purposes.

#### Number-String Conversions

Functions that perform conversions between numeric data types and string representations are performed in the C locale, regardless of the user's locale settings. Use QLocale to perform locale-aware conversions between numbers and strings.

#### Character Case

In QByteArray, the notion of uppercase and lowercase and of case-independent comparison is limited to ASCII. Non-ASCII characters are treated as caseless, since their case depends on encoding. This affects functions that support a case insensitive option or that change the case of their arguments. Functions that this affects include compare(), isLower(), isUpper(), toLower() and toUpper().

This issue does not apply to QStrings since they represent characters using Unicode.

See also QByteArrayView, QString, and QBitArray.

## Member Type Documentation

### enum QByteArray::Base64Option
flags QByteArray::Base64Options

This enum contains the options available for encoding and decoding Base64. Base64 is defined by RFC 4648, with the following options:

Constant | Value | Description
--- | --- | ---
`QByteArray::Base64Encoding` | `0` | (default) The regular Base64 alphabet, called simply "base64"
`QByteArray::Base64UrlEncoding` | `1` | An alternate alphabet, called "base64url", which replaces two characters in the alphabet to be more friendly to URLs.
`QByteArray::KeepTrailingEquals` | `0` | (default) Keeps the trailing padding equal signs at the end of the encoded data, so the data is always a size multiple of four.
`QByteArray::OmitTrailingEquals` | `2` | Omits adding the padding equal signs at the end of the encoded data.
`QByteArray::IgnoreBase64DecodingErrors` | `0` | When decoding Base64-encoded data, ignores errors in the input; invalid characters are simply skipped. This enum value has been added in Qt 5.15.
`QByteArray::AbortOnBase64DecodingErrors` | `4` | When decoding Base64-encoded data, stops at the first decoding error. This enum value has been added in Qt 5.15.

QByteArray::fromBase64Encoding() and QByteArray::fromBase64() ignore the KeepTrailingEquals and OmitTrailingEquals options. If the IgnoreBase64DecodingErrors option is specified, they will not flag errors in case trailing equal signs are missing or if there are too many of them. If instead the AbortOnBase64DecodingErrors is specified, then the input must either have no padding or have the correct amount of equal signs.

The Base64Options type is a typedef for QFlags<Base64Option>. It stores an OR combination of Base64Option values.

### QByteArray::const_iterator

This typedef provides an STL-style const iterator for QByteArray.

See also QByteArray::const_reverse_iterator and QByteArray::iterator.

### QByteArray::const_reverse_iterator

This typedef provides an STL-style const reverse iterator for QByteArray.

See also QByteArray::reverse_iterator and QByteArray::const_iterator.

### QByteArray::iterator

This typedef provides an STL-style non-const iterator for QByteArray.

See also QByteArray::reverse_iterator and QByteArray::const_iterator.

### QByteArray::reverse_iterator

This typedef provides an STL-style non-const reverse iterator for QByteArray.

See also QByteArray::const_reverse_iterator and QByteArray::iterator.

## Member Function Documentation

### `[static constexpr noexcept, since 6.8]` qsizetype QByteArray::maxSize()

### `[constexpr noexcept, since 6.8]` qsizetype QByteArray::max_size() const

It returns the maximum number of elements that the byte array can theoretically hold. In practice, the number can be much smaller, limited by the amount of memory available to the system.

This function was introduced in Qt 6.8.

### const char *QByteArray::operator const char *() const

### const void *QByteArray::operator const void *() const

Note: Use constData() instead in new code.

Returns a pointer to the data stored in the byte array. The pointer can be used to access the bytes that compose the array. The data is '\0'-terminated.

The pointer remains valid as long as no detach happens and the QByteArray is not modified.

This operator is mostly useful to pass a byte array to a function that accepts a `const char *`.

You can disable this operator by defining `QT_NO_CAST_FROM_BYTEARRAY` when you compile your applications.

Note: A QByteArray can store any byte values including '\0's, but most functions that take `char *` arguments assume that the data ends at the first '\0' they encounter.

See also constData().

### QByteArray QByteArray::left(qsizetype len) &&

### QByteArray QByteArray::left(qsizetype len) const &

Returns a byte array that contains the first len bytes of this byte array.

If you know that len cannot be out of bounds, use first() instead in new code, because it is faster.

The entire byte array is returned if len is greater than size().

Returns an empty QByteArray if len is smaller than 0.

See also first(), last(), startsWith(), chopped(), chop(), and truncate().

### QByteArray QByteArray::right(qsizetype len) &&

### QByteArray QByteArray::right(qsizetype len) const &

Returns a byte array that contains the last len bytes of this byte array.

If you know that len cannot be out of bounds, use last() instead in new code, because it is faster.

The entire byte array is returned if len is greater than size().

Returns an empty QByteArray if len is smaller than 0.

See also endsWith(), last(), first(), sliced(), chopped(), chop(), truncate(), and slice().

### QByteArray QByteArray::mid(qsizetype pos, qsizetype len = -1) &&

### QByteArray QByteArray::mid(qsizetype pos, qsizetype len = -1) const &

Returns a byte array containing len bytes from this byte array, starting at position pos.

If you know that pos and len cannot be out of bounds, use sliced() instead in new code, because it is faster.

If len is -1 (the default), or pos + len >= size(), returns a byte array containing all bytes starting at position pos until the end of the byte array.

See also first(), last(), sliced(), chopped(), chop(), truncate(), and slice().

### `[since 6.0]` QByteArray QByteArray::first(qsizetype n) &&

### `[since 6.0]` QByteArray QByteArray::first(qsizetype n) const &

Returns the first n bytes of the byte array.

Note: The behavior is undefined when n < 0 or n > size().

Example:

     QByteArray x("Pineapple");
     QByteArray y = x.first(4);
     // y == "Pine"

This function was introduced in Qt 6.0.

See also last(), sliced(), startsWith(), chopped(), chop(), truncate(), and slice().

### `[since 6.0]` QByteArray QByteArray::last(qsizetype n) &&

### `[since 6.0]` QByteArray QByteArray::last(qsizetype n) const &

Returns the last n bytes of the byte array.

Note: The behavior is undefined when n < 0 or n > size().

Example:

     QByteArray x("Pineapple");
     QByteArray y = x.last(5);
     // y == "apple"

This function was introduced in Qt 6.0.

See also first(), sliced(), endsWith(), chopped(), chop(), truncate(), and slice().

### `[since 6.0]` QByteArray QByteArray::sliced(qsizetype pos, qsizetype n) &&

### `[since 6.0]` QByteArray QByteArray::sliced(qsizetype pos, qsizetype n) const &

Returns a byte array containing the n bytes of this object starting at position pos.

Note: The behavior is undefined when pos < 0, n < 0, or pos + n > size().

Example:

     QByteArray x("Five pineapples");
     QByteArray y = x.sliced(5, 4);     // y == "pine"
     QByteArray z = x.sliced(5);        // z == "pineapples"

This function was introduced in Qt 6.0.

See also first(), last(), chopped(), chop(), truncate(), and slice().

### `[since 6.0]` QByteArray QByteArray::sliced(qsizetype pos) &&

### `[since 6.0]` QByteArray QByteArray::sliced(qsizetype pos) const &

Returns a byte array containing the bytes starting at position pos in this object, and extending to the end of this object.

Note: The behavior is undefined when pos < 0 or pos > size().

This function was introduced in Qt 6.0.

See also first(), last(), chopped(), chop(), truncate(), and slice().

### QByteArray QByteArray::chopped(qsizetype len) &&

### QByteArray QByteArray::chopped(qsizetype len) const &

Returns a byte array that contains the leftmost size() - len bytes of this byte array.

Note: The behavior is undefined if len is negative or greater than size().

See also endsWith(), first(), last(), sliced(), chop(), truncate(), and slice().

### `[static]` QByteArray::FromBase64Result QByteArray::fromBase64Encoding(QByteArray &&base64, QByteArray::Base64Options options = Base64Encoding)

### `[static]` QByteArray::FromBase64Result QByteArray::fromBase64Encoding(const QByteArray &base64, QByteArray::Base64Options options = Base64Encoding)

Decodes the Base64 array base64, using the options defined by options. If options contains `IgnoreBase64DecodingErrors` (the default), the input is not checked for validity; invalid characters in the input are skipped, enabling the decoding process to continue with subsequent characters. If options contains `AbortOnBase64DecodingErrors`, then decoding will stop at the first invalid character.

For example:

     void process(const QByteArray &);

     if (auto result = QByteArray::fromBase64Encoding(encodedData))
         process(*result);

The algorithm used to decode Base64-encoded data is defined in RFC 4648.

Returns a QByteArrayFromBase64Result object, containing the decoded data and a flag telling whether decoding was successful. If the `AbortOnBase64DecodingErrors` option was passed and the input data was invalid, it is unspecified what the decoded data contains.

See also toBase64().

### `[constexpr noexcept]` QByteArray::QByteArray()

Constructs an empty byte array.

See also isEmpty().

### `[explicit, since 6.8]` QByteArray::QByteArray(QByteArrayView v)

Constructs a byte array initialized with the byte array view's data.

The QByteArray will be null if and only if v is null.

This function was introduced in Qt 6.8.

### QByteArray::QByteArray(const char *data, qsizetype size = -1)

Constructs a byte array containing the first size bytes of array data.

If data is 0, a null byte array is constructed.

If size is negative, data is assumed to point to a '\0'-terminated string and its length is determined dynamically.

QByteArray makes a deep copy of the string data.

See also fromRawData().

### QByteArray::QByteArray(qsizetype size, Qt::Initialization)

Constructs a byte array of size size with uninitialized contents.

### QByteArray::QByteArray(qsizetype size, char ch)

Constructs a byte array of size size with every byte set to ch.

See also fill().

### `[noexcept]` QByteArray::QByteArray(const QByteArray &other)

Constructs a copy of other.

This operation takes constant time, because QByteArray is implicitly shared. This makes returning a QByteArray from a function very fast. If a shared instance is modified, it will be copied (copy-on-write), taking linear time.

See also operator=().

### `[noexcept]` QByteArray::QByteArray(QByteArray &&other)

Move-constructs a QByteArray instance, making it point at the same object that other was pointing to.

### `[noexcept]` QByteArray::~QByteArray()

Destroys the byte array.

### QByteArray &QByteArray::append(const QByteArray &ba)

Appends the byte array ba onto the end of this byte array.

Example:

     QByteArray x("free");
     QByteArray y("dom");
     x.append(y);
     // x == "freedom"

This is the same as insert(size(), ba).

Note: QByteArray is an implicitly shared class. Consequently, if you append to an empty byte array, then the byte array will just share the data held in ba. In this case, no copying of data is done, taking constant time. If a shared instance is modified, it will be copied (copy-on-write), taking linear time.

If the byte array being appended to is not empty, a deep copy of the data is performed, taking linear time.

The append() function is typically very fast (constant time), because QByteArray preallocates extra space at the end of the data, so it can grow without reallocating the entire array each time.

See also operator+=(), prepend(), and insert().

### QByteArray &QByteArray::append(QByteArrayView data)

Appends data to this byte array.

This is an overloaded function.

### QByteArray &QByteArray::append(char ch)

Appends the byte ch to this byte array.

This is an overloaded function.

### QByteArray &QByteArray::append(const char *str)

Appends the '\0'-terminated string str to this byte array.

This is an overloaded function.

### QByteArray &QByteArray::append(const char *str, qsizetype len)

Appends the first len bytes starting at str to this byte array and returns a reference to this byte array. The bytes appended may include '\0' bytes.

If len is negative, str will be assumed to be a '\0'-terminated string and the length to be copied will be determined automatically using qstrlen().

If len is zero or str is null, nothing is appended to the byte array. Ensure that len is not longer than str.

This is an overloaded function.

### QByteArray &QByteArray::append(qsizetype count, char ch)

Appends count copies of byte ch to this byte array and returns a reference to this byte array.

If count is negative or zero nothing is appended to the byte array.

This is an overloaded function.

### `[since 6.6]` QByteArray &QByteArray::assign(QByteArrayView v)

Replaces the contents of this byte array with a copy of v and returns a reference to this byte array.

The size of this byte array will be equal to the size of v.

This function only allocates memory if the size of v exceeds the capacity of this byte array or this byte array is shared.

This function was introduced in Qt 6.6.

### `[since 6.6]` template <typename InputIterator, QByteArray::if_input_iterator<InputIterator> = true> QByteArray &QByteArray::assign(InputIterator first, InputIterator last)

Replaces the contents of this byte array with a copy of the elements in the iterator range [first, last) and returns a reference to this byte array.

The size of this byte array will be equal to the number of elements in the range [first, last).

This function will only allocate memory if the number of elements in the range exceeds the capacity of this byte array or this byte array is shared.

Note: The behavior is undefined if either argument is an iterator into *this or [first, last) is not a valid range.

#### Constraints

Participates in overload resolution only if `InputIterator` meets the requirements of a LegacyInputIterator.

This function was introduced in Qt 6.6.

### `[since 6.6]` QByteArray &QByteArray::assign(qsizetype n, char c)

Replaces the contents of this byte array with n copies of c and returns a reference to this byte array.

The size of this byte array will be equal to n, which has to be non-negative.

This function will only allocate memory if n exceeds the capacity of this byte array or this byte array is shared.

This function was introduced in Qt 6.6.

See also fill().

### char QByteArray::at(qsizetype i) const

Returns the byte at index position i in the byte array.

i must be a valid index position in the byte array (i.e., 0 <= i < size()).

See also operator[]().

### char &QByteArray::back()

Returns a reference to the last byte in the byte array. Same as `operator[](size() - 1)`.

This function is provided for STL compatibility.

Warning: Calling this function on an empty byte array constitutes undefined behavior.

See also front(), at(), and operator[]().

### char QByteArray::back() const

Returns the last byte in the byte array. Same as `at(size() - 1)`.

This function is provided for STL compatibility.

Warning: Calling this function on an empty byte array constitutes undefined behavior.

See also front(), at(), and operator[]().

### QByteArray::iterator QByteArray::begin()

Returns an STL-style iterator pointing to the first byte in the byte-array.

Warning: The returned iterator is invalidated on detachment or when the QByteArray is modified.

See also constBegin() and end().

### `[noexcept]` QByteArray::const_iterator QByteArray::begin() const

This function overloads QByteArray::begin().

### qsizetype QByteArray::capacity() const

Returns the maximum number of bytes that can be stored in the byte array without forcing a reallocation.

The sole purpose of this function is to provide a means of fine tuning QByteArray's memory usage. In general, you will rarely ever need to call this function. If you want to know how many bytes are in the byte array, call size().

Note: a statically allocated byte array will report a capacity of 0, even if it's not empty.

Note: The free space position in the allocated memory block is undefined. In other words, one should not assume that the free memory is always located after the initialized elements.

See also reserve() and squeeze().

### `[noexcept]` QByteArray::const_iterator QByteArray::cbegin() const

Returns a const STL-style iterator pointing to the first byte in the byte-array.

Warning: The returned iterator is invalidated on detachment or when the QByteArray is modified.

See also begin() and cend().

### `[noexcept]` QByteArray::const_iterator QByteArray::cend() const

Returns a const STL-style iterator pointing just after the last byte in the byte-array.

Warning: The returned iterator is invalidated on detachment or when the QByteArray is modified.

See also cbegin() and end().

### void QByteArray::chop(qsizetype n)

Removes n bytes from the end of the byte array.

If n is greater than size(), the result is an empty byte array.

Example:

     QByteArray ba("STARTTLS\r\n");
     ba.chop(2);                 // ba == "STARTTLS"

See also truncate(), resize(), and first().

### void QByteArray::clear()

Clears the contents of the byte array and makes it null.

See also resize() and isNull().

### `[noexcept, since 6.0]` int QByteArray::compare(QByteArrayView bv, Qt::CaseSensitivity cs = Qt::CaseSensitive) const

Returns an integer less than, equal to, or greater than zero depending on whether this QByteArray sorts before, at the same position as, or after the QByteArrayView bv. The comparison is performed according to case sensitivity cs.

This function was introduced in Qt 6.0.

See also operator== and Character Case.

### `[noexcept]` QByteArray::const_iterator QByteArray::constBegin() const

Returns a const STL-style iterator pointing to the first byte in the byte-array.

Warning: The returned iterator is invalidated on detachment or when the QByteArray is modified.

See also begin() and constEnd().

### `[noexcept]` const char *QByteArray::constData() const

Returns a pointer to the const data stored in the byte array. The pointer can be used to access the bytes that compose the array. The data is '\0'-terminated unless the QByteArray object was created from raw data.

The pointer remains valid as long as no detach happens and the QByteArray is not modified.

This function is mostly useful to pass a byte array to a function that accepts a `const char *`.

Note: A QByteArray can store any byte values including '\0's, but most functions that take `char *` arguments assume that the data ends at the first '\0' they encounter.

See also data(), operator[](), and fromRawData().

### `[noexcept]` QByteArray::const_iterator QByteArray::constEnd() const

Returns a const STL-style iterator pointing just after the last byte in the byte-array.

Warning: The returned iterator is invalidated on detachment or when the QByteArray is modified.

See also constBegin() and end().

### `[since 6.0]` bool QByteArray::contains(QByteArrayView bv) const

Returns `true` if this byte array contains an occurrence of the sequence of bytes viewed by bv; otherwise returns `false`.

This function was introduced in Qt 6.0.

See also indexOf() and count().

### bool QByteArray::contains(char ch) const

Returns `true` if the byte array contains the byte ch; otherwise returns `false`.

This is an overloaded function.

### `[since 6.0]` qsizetype QByteArray::count(QByteArrayView bv) const

Returns the number of (potentially overlapping) occurrences of the sequence of bytes viewed by bv in this byte array.

This function was introduced in Qt 6.0.

See also contains() and indexOf().

### qsizetype QByteArray::count(char ch) const

Returns the number of occurrences of byte ch in the byte array.

This is an overloaded function.

See also contains() and indexOf().

### `[noexcept]` QByteArray::const_reverse_iterator QByteArray::crbegin() const

Returns a const STL-style reverse iterator pointing to the first byte in the byte-array, in reverse order.

Warning: The returned iterator is invalidated on detachment or when the QByteArray is modified.

See also begin(), rbegin(), and rend().

### `[noexcept]` QByteArray::const_reverse_iterator QByteArray::crend() const

Returns a const STL-style reverse iterator pointing just after the last byte in the byte-array, in reverse order.

Warning: The returned iterator is invalidated on detachment or when the QByteArray is modified.

See also end(), rend(), and rbegin().

### char *QByteArray::data()

Returns a pointer to the data stored in the byte array. The pointer can be used to access and modify the bytes that compose the array. The data is '\0'-terminated, i.e. the number of bytes you can access following the returned pointer is size() + 1, including the '\0' terminator.

Example:

     QByteArray ba("Hello world");
     char *data = ba.data();
     while (*data) {
         cout << "[" << *data << "]" << endl;
         ++data;
     }

The pointer remains valid as long as no detach happens and the QByteArray is not modified.

For read-only access, constData() is faster because it never causes a deep copy to occur.

This function is mostly useful to pass a byte array to a function that accepts a `const char *`.

The following example makes a copy of the char* returned by data(), but it will corrupt the heap and cause a crash because it does not allocate a byte for the '\0' at the end:

     QString tmp = "test";
     QByteArray text = tmp.toLocal8Bit();
     char *data = new char[text.size()];
     strcpy(data, text.data());
     delete [] data;

This one allocates the correct amount of space:

     QString tmp = "test";
     QByteArray text = tmp.toLocal8Bit();
     char *data = new char[text.size() + 1];
     strcpy(data, text.data());
     delete [] data;

Note: A QByteArray can store any byte values including '\0's, but most functions that take `char *` arguments assume that the data ends at the first '\0' they encounter.

See also constData() and operator[]().

### `[noexcept]` const char *QByteArray::data() const

This is an overloaded function.

### QByteArray::iterator QByteArray::end()

Returns an STL-style iterator pointing just after the last byte in the byte-array.

Warning: The returned iterator is invalidated on detachment or when the QByteArray is modified.

See also begin() and constEnd().

### `[noexcept]` QByteArray::const_iterator QByteArray::end() const

This function overloads QByteArray::end().

### `[since 6.0]` bool QByteArray::endsWith(QByteArrayView bv) const

Returns `true` if this byte array ends with the sequence of bytes viewed by bv; otherwise returns `false`.

Example:

     QByteArray url("http://qt-project.org/doc/qt-5.0/qtdoc/index.html");
     if (url.endsWith(".html"))
         ...

This function was introduced in Qt 6.0.

See also startsWith() and last().

### bool QByteArray::endsWith(char ch) const

Returns `true` if this byte array ends with byte ch; otherwise returns `false`.

This is an overloaded function.

### `[since 6.1]` QByteArray::iterator QByteArray::erase(QByteArray::const_iterator first, QByteArray::const_iterator last)

Removes from the byte array the characters in the half-open range [ first , last ). Returns an iterator to the character referred to by last before the erase.

This function was introduced in Qt 6.1.

### `[since 6.5]` QByteArray::iterator QByteArray::erase(QByteArray::const_iterator it)

Removes the character denoted by `it` from the byte array. Returns an iterator to the character immediately after the erased character.

     QByteArray ba = "abcdefg";
     auto it = ba.erase(ba.cbegin()); // ba is now "bcdefg" and it points to "b"

This is an overloaded function.

This function was introduced in Qt 6.5.

### QByteArray &QByteArray::fill(char ch, qsizetype size = -1)

Sets every byte in the byte array to ch. If size is different from -1 (the default), the byte array is resized to size size beforehand.

Example:

     QByteArray ba("Istambul");
     ba.fill('o');
     // ba == "oooooooo"

     ba.fill('X', 2);
     // ba == "XX"

See also resize().

### `[static]` QByteArray QByteArray::fromBase64(const QByteArray &base64, QByteArray::Base64Options options = Base64Encoding)

Returns a decoded copy of the Base64 array base64, using the options defined by options. If options contains `IgnoreBase64DecodingErrors` (the default), the input is not checked for validity; invalid characters in the input are skipped, enabling the decoding process to continue with subsequent characters. If options contains `AbortOnBase64DecodingErrors`, then decoding will stop at the first invalid character.

For example:

     QByteArray text = QByteArray::fromBase64("UXQgaXMgZ3JlYXQh");
     text.data();            // returns "Qt is great!"

     QByteArray::fromBase64("PHA+SGVsbG8/PC9wPg==", QByteArray::Base64Encoding); // returns "<p>Hello?</p>"
     QByteArray::fromBase64("PHA-SGVsbG8_PC9wPg==", QByteArray::Base64UrlEncoding); // returns "<p>Hello?</p>"

The algorithm used to decode Base64-encoded data is defined in RFC 4648.

Returns the decoded data, or, if the `AbortOnBase64DecodingErrors` option was passed and the input data was invalid, an empty byte array.

Note: The fromBase64Encoding() function is recommended in new code.

See also toBase64() and fromBase64Encoding().

### `[static]` QByteArray QByteArray::fromCFData(CFDataRef data)

Constructs a new QByteArray containing a copy of the CFData data.

See also fromRawCFData(), fromRawData(), toRawCFData(), and toCFData().

### `[static, since 6.5]` QByteArray QByteArray::fromEcmaUint8Array(emscripten::val uint8array)

Constructs a new QByteArray containing a copy of the Uint8Array uint8array.

This function transfers data from a JavaScript data buffer - which is not addressable from C++ code - to heap memory owned by a QByteArray. The Uint8Array can be released once this function returns and a copy has been made.

The uint8array argument must an emscripten::val referencing an Uint8Array object, e.g. obtained from a global JavaScript variable:

     emscripten::val uint8array = emscripten::val::global("g_uint8array");
     QByteArray byteArray = QByteArray::fromEcmaUint8Array(uint8array);

This function returns a null QByteArray if the size of the Uint8Array exceeds the maximum capacity of QByteArray, or if the uint8array argument is not of the Uint8Array type.

This function was introduced in Qt 6.5.

See also toEcmaUint8Array().

### `[static]` QByteArray QByteArray::fromHex(const QByteArray &hexEncoded)

Returns a decoded copy of the hex encoded array hexEncoded. Input is not checked for validity; invalid characters in the input are skipped, enabling the decoding process to continue with subsequent characters.

For example:

     QByteArray text = QByteArray::fromHex("517420697320677265617421");
     text.data();            // returns "Qt is great!"

See also toHex().

### `[static]` QByteArray QByteArray::fromNSData(const NSData *data)

Constructs a new QByteArray containing a copy of the NSData data.

See also fromRawNSData(), fromRawData(), toNSData(), and toRawNSData().

### `[static]` QByteArray QByteArray::fromPercentEncoding(const QByteArray &input, char percent = '%')

Decodes input from URI/URL-style percent-encoding.

Returns a byte array containing the decoded text. The percent parameter allows use of a different character than '%' (for instance, '_' or '=') as the escape character. Equivalent to input.percentDecoded(percent).

For example:

     QByteArray text = QByteArray::fromPercentEncoding("Qt%20is%20great%33");
     qDebug("%s", text.data());      // reports "Qt is great!"

See also percentDecoded().

### `[static]` QByteArray QByteArray::fromRawCFData(CFDataRef data)

Constructs a QByteArray that uses the bytes of the CFData data.

The data's bytes are not copied.

The caller guarantees that the CFData will not be deleted or modified as long as this QByteArray object exists.

See also fromCFData(), fromRawData(), toRawCFData(), and toCFData().

### `[static]` QByteArray QByteArray::fromRawData(const char *data, qsizetype size)

Constructs a QByteArray that uses the first size bytes of the data array. The bytes are not copied. The QByteArray will contain the data pointer. The caller guarantees that data will not be deleted or modified as long as this QByteArray and any copies of it exist that have not been modified. In other words, because QByteArray is an implicitly shared class and the instance returned by this function contains the data pointer, the caller must not delete data or modify it directly as long as the returned QByteArray and any copies exist. However, QByteArray does not take ownership of data, so the QByteArray destructor will never delete the raw data, even when the last QByteArray referring to data is destroyed.

A subsequent attempt to modify the contents of the returned QByteArray or any copy made from it will cause it to create a deep copy of the data array before doing the modification. This ensures that the raw data array itself will never be modified by QByteArray.

Here is an example of how to read data using a QDataStream on raw data in memory without copying the raw data into a QByteArray:

      static const char mydata[] = {
         '\x00', '\x00', '\x03', '\x84', '\x78', '\x9c', '\x3b', '\x76',
         '\xec', '\x18', '\xc3', '\x31', '\x0a', '\xf1', '\xcc', '\x99',
         ...
         '\x6d', '\x5b'
     };

     QByteArray data = QByteArray::fromRawData(mydata, sizeof(mydata));
     QDataStream in(&data, QIODevice::ReadOnly);
     ...

Warning: A byte array created with fromRawData() is not '\0'-terminated, unless the raw data contains a '\0' byte at position size. While that does not matter for QDataStream or functions like indexOf(), passing the byte array to a function accepting a `const char *` expected to be '\0'-terminated will fail.

See also setRawData(), data(), and constData().

### `[static]` QByteArray QByteArray::fromRawNSData(const NSData *data)

Constructs a QByteArray that uses the bytes of the NSData data.

The data's bytes are not copied.

The caller guarantees that the NSData will not be deleted or modified as long as this QByteArray object exists.

See also fromNSData(), fromRawData(), toRawNSData(), and toNSData().

### `[static]` QByteArray QByteArray::fromStdString(const std::string &str)

Returns a copy of the str string as a QByteArray.

See also toStdString() and QString::fromStdString().

### char &QByteArray::front()

Returns a reference to the first byte in the byte array. Same as `operator[](0)`.

This function is provided for STL compatibility.

Warning: Calling this function on an empty byte array constitutes undefined behavior.

See also back(), at(), and operator[]().

### char QByteArray::front() const

Returns the first byte in the byte array. Same as `at(0)`.

This function is provided for STL compatibility.

Warning: Calling this function on an empty byte array constitutes undefined behavior.

See also back(), at(), and operator[]().

### `[since 6.0]` qsizetype QByteArray::indexOf(QByteArrayView bv, qsizetype from = 0) const

Returns the index position of the start of the first occurrence of the sequence of bytes viewed by bv in this byte array, searching forward from index position from. Returns -1 if no match is found.

Example:

     QByteArray x("sticky question");
     QByteArrayView y("sti");
     x.indexOf(y);               // returns 0
     x.indexOf(y, 1);            // returns 10
     x.indexOf(y, 10);           // returns 10
     x.indexOf(y, 11);           // returns -1

This function was introduced in Qt 6.0.

See also lastIndexOf(), contains(), and count().

### qsizetype QByteArray::indexOf(char ch, qsizetype from = 0) const

Returns the index position of the start of the first occurrence of the byte ch in this byte array, searching forward from index position from. Returns -1 if no match is found.

Example:

     QByteArray ba("ABCBA");
     ba.indexOf("B");            // returns 1
     ba.indexOf("B", 1);         // returns 1
     ba.indexOf("B", 2);         // returns 3
     ba.indexOf("X");            // returns -1

This is an overloaded function.

See also lastIndexOf() and contains().

### `[since 6.0]` QByteArray &QByteArray::insert(qsizetype i, QByteArrayView data)

Inserts data at index position i and returns a reference to this byte array.

Example:

     QByteArray ba("Meal");
     ba.insert(1, QByteArrayView("ontr"));
     // ba == "Montreal"

For large byte arrays, this operation can be slow (linear time), because it requires moving all the bytes at indexes i and above by at least one position further in memory.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i.

This function was introduced in Qt 6.0.

See also append(), prepend(), replace(), and remove().

### QByteArray &QByteArray::insert(qsizetype i, const QByteArray &data)

Inserts data at index position i and returns a reference to this byte array.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i.

See also append(), prepend(), replace(), and remove().

### QByteArray &QByteArray::insert(qsizetype i, const char *s)

Inserts s at index position i and returns a reference to this byte array.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i.

The function is equivalent to `insert(i, QByteArrayView(s))`

See also append(), prepend(), replace(), and remove().

### QByteArray &QByteArray::insert(qsizetype i, char ch)

Inserts byte ch at index position i in the byte array.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i.

This is an overloaded function.

### QByteArray &QByteArray::insert(qsizetype i, const char *data, qsizetype len)

Inserts len bytes, starting at data, at position i in the byte array.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i.

This is an overloaded function.

### QByteArray &QByteArray::insert(qsizetype i, qsizetype count, char ch)

Inserts count copies of byte ch at index position i in the byte array.

This array grows to accommodate the insertion. If i is beyond the end of the array, the array is first extended with space characters to reach this i.

This is an overloaded function.

### `[noexcept]` bool QByteArray::isEmpty() const

Returns `true` if the byte array has size 0; otherwise returns `false`.

Example:

     QByteArray().isEmpty();         // returns true
     QByteArray("").isEmpty();       // returns true
     QByteArray("abc").isEmpty();    // returns false

See also size().

### bool QByteArray::isLower() const

Returns `true` if this byte array is lowercase, that is, if it's identical to its toLower() folding.

Note that this does not mean that the byte array only contains lowercase letters; only that it contains no ASCII uppercase letters.

See also isUpper() and toLower().

### `[noexcept]` bool QByteArray::isNull() const

Returns `true` if this byte array is null; otherwise returns `false`.

Example:

     QByteArray().isNull();          // returns true
     QByteArray("").isNull();        // returns false
     QByteArray("abc").isNull();     // returns false

Qt makes a distinction between null byte arrays and empty byte arrays for historical reasons. For most applications, what matters is whether or not a byte array contains any data, and this can be determined using isEmpty().

See also isEmpty().

### bool QByteArray::isUpper() const

Returns `true` if this byte array is uppercase, that is, if it's identical to its toUpper() folding.

Note that this does not mean that the byte array only contains uppercase letters; only that it contains no ASCII lowercase letters.

See also isLower() and toUpper().

### `[noexcept, since 6.3]` bool QByteArray::isValidUtf8() const

Returns `true` if this byte array contains valid UTF-8 encoded data, or `false` otherwise.

This function was introduced in Qt 6.3.

### `[since 6.0]` qsizetype QByteArray::lastIndexOf(QByteArrayView bv, qsizetype from) const

Returns the index position of the start of the last occurrence of the sequence of bytes viewed by bv in this byte array, searching backward from index position from.

If from is -1, the search starts at the last character; if it is -2, at the next to last character and so on.

Returns -1 if no match is found.

Example:

     QByteArray x("crazy azimuths");
     QByteArrayView y("az");
     x.lastIndexOf(y);           // returns 6
     x.lastIndexOf(y, 6);        // returns 6
     x.lastIndexOf(y, 5);        // returns 2
     x.lastIndexOf(y, 1);        // returns -1

Note: When searching for a 0-length bv, the match at the end of the data is excluded from the search by a negative from, even though `-1` is normally thought of as searching from the end of the byte array: the match at the end is after the last character, so it is excluded. To include such a final empty match, either give a positive value for from or omit the from parameter entirely.

This function was introduced in Qt 6.0.

See also indexOf(), contains(), and count().

### `[since 6.2]` qsizetype QByteArray::lastIndexOf(QByteArrayView bv) const

Returns the index position of the start of the last occurrence of the sequence of bytes viewed by bv in this byte array, searching backward from the end of the byte array. Returns -1 if no match is found.

Example:

     QByteArray x("crazy azimuths");
     QByteArrayView y("az");
     x.lastIndexOf(y);           // returns 6
     x.lastIndexOf(y, 6);        // returns 6
     x.lastIndexOf(y, 5);        // returns 2
     x.lastIndexOf(y, 1);        // returns -1

This is an overloaded function.

This function was introduced in Qt 6.2.

See also indexOf(), contains(), and count().

### qsizetype QByteArray::lastIndexOf(char ch, qsizetype from = -1) const

Returns the index position of the start of the last occurrence of byte ch in this byte array, searching backward from index position from. If from is -1 (the default), the search starts at the last byte (at index size() - 1). Returns -1 if no match is found.

Example:

     QByteArray ba("ABCBA");
     ba.lastIndexOf("B");        // returns 3
     ba.lastIndexOf("B", 3);     // returns 3
     ba.lastIndexOf("B", 2);     // returns 1
     ba.lastIndexOf("X");        // returns -1

This is an overloaded function.

See also indexOf() and contains().

### QByteArray QByteArray::leftJustified(qsizetype width, char fill = ' ', bool truncate = false) const

Returns a byte array of size width that contains this byte array padded with the fill byte.

If truncate is false and the size() of the byte array is more than width, then the returned byte array is a copy of this byte array.

If truncate is true and the size() of the byte array is more than width, then any bytes in a copy of the byte array after position width are removed, and the copy is returned.

Example:

     QByteArray x("apple");
     QByteArray y = x.leftJustified(8, '.');   // y == "apple..."

See also rightJustified().

### `[noexcept]` qsizetype QByteArray::length() const

Same as size().

### `[static]` QByteArray QByteArray::number(int n, int base = 10)

Returns a byte-array representing the whole number n as text.

Returns a byte array containing a string representing n, using the specified base (ten by default). Bases 2 through 36 are supported, using letters for digits beyond 9: A is ten, B is eleven and so on.

Example:

     int n = 63;
     QByteArray::number(n);              // returns "63"
     QByteArray::number(n, 16);          // returns "3f"
     QByteArray::number(n, 16).toUpper();  // returns "3F"

Note: The format of the number is not localized; the default C locale is used regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

See also setNum() and toInt().

### `[static]` QByteArray QByteArray::number(long n, int base = 10)

This is an overloaded function.

See also toLong().

### `[static]` QByteArray QByteArray::number(qlonglong n, int base = 10)

This is an overloaded function.

See also toLongLong().

### `[static]` QByteArray QByteArray::number(qulonglong n, int base = 10)

This is an overloaded function.

See also toULongLong().

### `[static]` QByteArray QByteArray::number(uint n, int base = 10)

This is an overloaded function.

See also toUInt().

### `[static]` QByteArray QByteArray::number(ulong n, int base = 10)

This is an overloaded function.

See also toULong().

### `[static]` QByteArray QByteArray::number(double n, char format = 'g', int precision = 6)

Returns a byte-array representing the floating-point number n as text.

Returns a byte array containing a string representing n, with a given format and precision, with the same meanings as for QString::number(double, char, int). For example:

     QByteArray ba = QByteArray::number(12.3456, 'E', 3);
     // ba == 1.235E+01

This is an overloaded function.

See also toDouble() and QLocale::FloatingPointPrecisionOption.

### `[since 6.4]` QByteArray QByteArray::percentDecoded(char percent = '%') const

Decodes URI/URL-style percent-encoding.

Returns a byte array containing the decoded text. The percent parameter allows use of a different character than '%' (for instance, '_' or '=') as the escape character.

For example:

     QByteArray encoded("Qt%20is%20great%33");
     QByteArray decoded = encoded.percentDecoded(); // Set to "Qt is great!"

Note: Given invalid input (such as a string containing the sequence "%G5", which is not a valid hexadecimal number) the output will be invalid as well. As an example: the sequence "%G5" could be decoded to 'W'.

This function was introduced in Qt 6.4.

See also toPercentEncoding() and QUrl::fromPercentEncoding().

### QByteArray &QByteArray::prepend(QByteArrayView ba)

Prepends the byte array view ba to this byte array and returns a reference to this byte array.

This operation is typically very fast (constant time), because QByteArray preallocates extra space at the beginning of the data, so it can grow without reallocating the entire array each time.

Example:

     QByteArray x("ship");
     QByteArray y("air");
     x.prepend(y);
     // x == "airship"

This is the same as insert(0, ba).

See also append() and insert().

### QByteArray &QByteArray::prepend(char ch)

Prepends the byte ch to this byte array.

This is an overloaded function.

### QByteArray &QByteArray::prepend(const QByteArray &ba)

Prepends ba to this byte array.

This is an overloaded function.

### QByteArray &QByteArray::prepend(const char *str)

Prepends the '\0'-terminated string str to this byte array.

This is an overloaded function.

### QByteArray &QByteArray::prepend(const char *str, qsizetype len)

Prepends len bytes starting at str to this byte array. The bytes prepended may include '\0' bytes.

This is an overloaded function.

### QByteArray &QByteArray::prepend(qsizetype count, char ch)

Prepends count copies of byte ch to this byte array.

This is an overloaded function.

### void QByteArray::push_back(const QByteArray &other)

This function is provided for STL compatibility. It is equivalent to append(other).

### `[since 6.0]` void QByteArray::push_back(QByteArrayView str)

Same as append(str).

This is an overloaded function.

This function was introduced in Qt 6.0.

### void QByteArray::push_back(char ch)

Same as append(ch).

This is an overloaded function.

### void QByteArray::push_back(const char *str)

Same as append(str).

This is an overloaded function.

### void QByteArray::push_front(const QByteArray &other)

This function is provided for STL compatibility. It is equivalent to prepend(other).

### `[since 6.0]` void QByteArray::push_front(QByteArrayView str)

Same as prepend(str).

This is an overloaded function.

This function was introduced in Qt 6.0.

### void QByteArray::push_front(char ch)

Same as prepend(ch).

This is an overloaded function.

### void QByteArray::push_front(const char *str)

Same as prepend(str).

This is an overloaded function.

### QByteArray::reverse_iterator QByteArray::rbegin()

Returns a STL-style reverse iterator pointing to the first byte in the byte-array, in reverse order.

Warning: The returned iterator is invalidated on detachment or when the QByteArray is modified.

See also begin(), crbegin(), and rend().

### `[noexcept]` QByteArray::const_reverse_iterator QByteArray::rbegin() const

This is an overloaded function.

### QByteArray &QByteArray::remove(qsizetype pos, qsizetype len)

Removes len bytes from the array, starting at index position pos, and returns a reference to the array.

If pos is out of range, nothing happens. If pos is valid, but pos + len is larger than the size of the array, the array is truncated at position pos.

Example:

     QByteArray ba("Montreal");
     ba.remove(1, 4);
     // ba == "Meal"

Element removal will preserve the array's capacity and not reduce the amount of allocated memory. To shed extra capacity and free as much memory as possible, call squeeze() after the last change to the array's size.

See also insert(), replace(), and squeeze().

### `[since 6.5]` QByteArray &QByteArray::removeAt(qsizetype pos)

Removes the character at index pos. If pos is out of bounds (i.e. pos >= size()) this function does nothing.

This function was introduced in Qt 6.5.

See also remove().

### `[since 6.5]` QByteArray &QByteArray::removeFirst()

Removes the first character in this byte array. If the byte array is empty, this function does nothing.

This function was introduced in Qt 6.5.

See also remove().

### `[since 6.1]` template <typename Predicate> QByteArray &QByteArray::removeIf(Predicate pred)

Removes all bytes for which the predicate pred returns true from the byte array. Returns a reference to the byte array.

This function was introduced in Qt 6.1.

See also remove().

### `[since 6.5]` QByteArray &QByteArray::removeLast()

Removes the last character in this byte array. If the byte array is empty, this function does nothing.

This function was introduced in Qt 6.5.

See also remove().

### QByteArray::reverse_iterator QByteArray::rend()

Returns a STL-style reverse iterator pointing just after the last byte in the byte-array, in reverse order.

Warning: The returned iterator is invalidated on detachment or when the QByteArray is modified.

See also end(), crend(), and rbegin().

### `[noexcept]` QByteArray::const_reverse_iterator QByteArray::rend() const

This is an overloaded function.

### QByteArray QByteArray::repeated(qsizetype times) const

Returns a copy of this byte array repeated the specified number of times.

If times is less than 1, an empty byte array is returned.

Example:

     QByteArray ba("ab");
     ba.repeated(4);             // returns "abababab"

### QByteArray &QByteArray::replace(qsizetype pos, qsizetype len, QByteArrayView after)

Replaces len bytes from index position pos with the byte array after, and returns a reference to this byte array.

Example:

     QByteArray x("Say yes!");
     QByteArray y("no");
     x.replace(4, 3, y);
     // x == "Say no!"

See also insert() and remove().

### `[since 6.0]` QByteArray &QByteArray::replace(QByteArrayView before, QByteArrayView after)

Replaces every occurrence of the byte array before with the byte array after.

Example:

     QByteArray ba("colour behaviour flavour neighbour");
     ba.replace(QByteArray("ou"), QByteArray("o"));
     // ba == "color behavior flavor neighbor"

This is an overloaded function.

This function was introduced in Qt 6.0.

### QByteArray &QByteArray::replace(char before, QByteArrayView after)

Replaces every occurrence of the byte before with the byte array after.

This is an overloaded function.

### QByteArray &QByteArray::replace(char before, char after)

Replaces every occurrence of the byte before with the byte after.

This is an overloaded function.

### QByteArray &QByteArray::replace(const char *before, qsizetype bsize, const char *after, qsizetype asize)

Replaces every occurrence of the bsize bytes starting at before with the asize bytes starting at after. Since the sizes of the strings are given by bsize and asize, they may contain '\0' bytes and do not need to be '\0'-terminated.

This is an overloaded function.

### QByteArray &QByteArray::replace(qsizetype pos, qsizetype len, const char *after, qsizetype alen)

Replaces len bytes from index position pos with alen bytes starting at position after. The bytes inserted may include '\0' bytes.

This is an overloaded function.

### void QByteArray::reserve(qsizetype size)

Attempts to allocate memory for at least size bytes.

If you know in advance how large the byte array will be, you can call this function, and if you call resize() often you are likely to get better performance.

If in doubt about how much space shall be needed, it is usually better to use an upper bound as size, or a high estimate of the most likely size, if a strict upper bound would be much bigger than this. If size is an underestimate, the array will grow as needed once the reserved size is exceeded, which may lead to a larger allocation than your best overestimate would have and will slow the operation that triggers it.

Warning: reserve() reserves memory but does not change the size of the byte array. Accessing data beyond the end of the byte array is undefined behavior. If you need to access memory beyond the current end of the array, use resize().

The sole purpose of this function is to provide a means of fine tuning QByteArray's memory usage. In general, you will rarely ever need to call this function.

See also squeeze() and capacity().

### void QByteArray::resize(qsizetype size)

Sets the size of the byte array to size bytes.

If size is greater than the current size, the byte array is extended to make it size bytes with the extra bytes added to the end. The new bytes are uninitialized.

If size is less than the current size, bytes beyond position size are excluded from the byte array.

Note: While resize() will grow the capacity if needed, it never shrinks capacity. To shed excess capacity, use squeeze().

See also size(), truncate(), and squeeze().

### `[since 6.4]` void QByteArray::resize(qsizetype newSize, char c)

Sets the size of the byte array to newSize bytes.

If newSize is greater than the current size, the byte array is extended to make it newSize bytes with the extra bytes added to the end. The new bytes are initialized to c.

If newSize is less than the current size, bytes beyond position newSize are excluded from the byte array.

Note: While resize() will grow the capacity if needed, it never shrinks capacity. To shed excess capacity, use squeeze().

This function was introduced in Qt 6.4.

See also size(), truncate(), and squeeze().

### `[since 6.8]` void QByteArray::resizeForOverwrite(qsizetype size)

Resizes the byte array to size bytes. If the size of the byte array grows, the new bytes are uninitialized.

The behavior is identical to `resize(size)`.

This function was introduced in Qt 6.8.

See also resize().

### QByteArray QByteArray::rightJustified(qsizetype width, char fill = ' ', bool truncate = false) const

Returns a byte array of size width that contains the fill byte followed by this byte array.

If truncate is false and the size of the byte array is more than width, then the returned byte array is a copy of this byte array.

If truncate is true and the size of the byte array is more than width, then the resulting byte array is truncated at position width.

Example:

     QByteArray x("apple");
     QByteArray y = x.rightJustified(8, '.');    // y == "...apple"

See also leftJustified().

### QByteArray &QByteArray::setNum(int n, int base = 10)

Represent the whole number n as text.

Sets this byte array to a string representing n in base base (ten by default) and returns a reference to this byte array. Bases 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

Example:

     QByteArray ba;
     int n = 63;
     ba.setNum(n);           // ba == "63"
     ba.setNum(n, 16);       // ba == "3f"

Note: The format of the number is not localized; the default C locale is used regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

See also number() and toInt().

### QByteArray &QByteArray::setNum(long n, int base = 10)

This is an overloaded function.

See also toLong().

### QByteArray &QByteArray::setNum(qlonglong n, int base = 10)

This is an overloaded function.

See also toLongLong().

### QByteArray &QByteArray::setNum(qulonglong n, int base = 10)

This is an overloaded function.

See also toULongLong().

### QByteArray &QByteArray::setNum(short n, int base = 10)

This is an overloaded function.

See also toShort().

### QByteArray &QByteArray::setNum(uint n, int base = 10)

This is an overloaded function.

See also toUInt().

### QByteArray &QByteArray::setNum(ulong n, int base = 10)

This is an overloaded function.

See also toULong().

### QByteArray &QByteArray::setNum(ushort n, int base = 10)

This is an overloaded function.

See also toUShort().

### QByteArray &QByteArray::setNum(double n, char format = 'g', int precision = 6)

Represent the floating-point number n as text.

Sets this byte array to a string representing n, with a given format and precision (with the same meanings as for QString::number(double, char, int)), and returns a reference to this byte array.

This is an overloaded function.

See also toDouble() and QLocale::FloatingPointPrecisionOption.

### QByteArray &QByteArray::setNum(float n, char format = 'g', int precision = 6)

Represent the floating-point number n as text.

Sets this byte array to a string representing n, with a given format and precision (with the same meanings as for QString::number(double, char, int)), and returns a reference to this byte array.

This is an overloaded function.

See also toFloat().

### QByteArray &QByteArray::setRawData(const char *data, qsizetype size)

Resets the QByteArray to use the first size bytes of the data array. The bytes are not copied. The QByteArray will contain the data pointer. The caller guarantees that data will not be deleted or modified as long as this QByteArray and any copies of it exist that have not been modified.

This function can be used instead of fromRawData() to re-use existing QByteArray objects to save memory re-allocations.

See also fromRawData(), data(), and constData().

### void QByteArray::shrink_to_fit()

This function is provided for STL compatibility. It is equivalent to squeeze().

### QByteArray QByteArray::simplified() const

Returns a copy of this byte array that has spacing characters removed from the start and end, and in which each sequence of internal spacing characters is replaced with a single space.

The spacing characters are those for which the standard C++ `isspace()` function returns `true` in the C locale; these are the ASCII characters tabulation '\t', line feed '\n', carriage return '\r', vertical tabulation '\v', form feed '\f', and space ' '.

Example:

     QByteArray ba("  lots\t of\nwhitespace\r\n ");
     ba = ba.simplified();
     // ba == "lots of whitespace";

See also trimmed(), QChar::SpecialCharacter, and Spacing Characters.

### `[noexcept]` qsizetype QByteArray::size() const

Returns the number of bytes in this byte array.

The last byte in the byte array is at position size() - 1. In addition, QByteArray ensures that the byte at position size() is always '\0', so that you can use the return value of data() and constData() as arguments to functions that expect '\0'-terminated strings. If the QByteArray object was created from a raw data that didn't include the trailing '\0'-termination byte, then QByteArray doesn't add it automatically unless a deep copy is created.

Example:

     QByteArray ba("Hello");
     qsizetype n = ba.size();    // n == 5
     ba.data()[0];               // returns 'H'
     ba.data()[4];               // returns 'o'
     ba.data()[5];               // returns '\0'

See also isEmpty() and resize().

### `[since 6.8]` QByteArray &QByteArray::slice(qsizetype pos, qsizetype n)

Modifies this byte array to start at position pos, extending for n bytes, and returns a reference to this byte array.

Note: The behavior is undefined if pos < 0, n < 0, or pos + n > size().

Example:

     QByteArray x = "Five pineapples"_ba;
     x.slice(5);     // x == "pineapples"
     x.slice(4, 3);  // x == "app"

This function was introduced in Qt 6.8.

See also sliced(), first(), last(), chopped(), chop(), and truncate().

### `[since 6.8]` QByteArray &QByteArray::slice(qsizetype pos)

Modifies this byte array to start at position pos, extending to its end, and returns a reference to this byte array.

Note: The behavior is undefined if pos < 0 or pos > size().

This is an overloaded function.

This function was introduced in Qt 6.8.

See also sliced(), first(), last(), chopped(), chop(), and truncate().

### QList<QByteArray> QByteArray::split(char sep) const

Splits the byte array into subarrays wherever sep occurs, and returns the list of those arrays. If sep does not match anywhere in the byte array, split() returns a single-element list containing this byte array.

### void QByteArray::squeeze()

Releases any memory not required to store the array's data.

The sole purpose of this function is to provide a means of fine tuning QByteArray's memory usage. In general, you will rarely ever need to call this function.

See also reserve() and capacity().

### `[since 6.0]` bool QByteArray::startsWith(QByteArrayView bv) const

Returns `true` if this byte array starts with the sequence of bytes viewed by bv; otherwise returns `false`.

Example:

     QByteArray url("ftp://ftp.qt-project.org/");
     if (url.startsWith("ftp:"))
         ...

This function was introduced in Qt 6.0.

See also endsWith() and first().

### bool QByteArray::startsWith(char ch) const

Returns `true` if this byte array starts with byte ch; otherwise returns `false`.

This is an overloaded function.

### `[noexcept]` void QByteArray::swap(QByteArray &other)

Swaps this byte array with other. This operation is very fast and never fails.

### QByteArray QByteArray::toBase64(QByteArray::Base64Options options = Base64Encoding) const

Returns a copy of the byte array, encoded using the options options.

     QByteArray text("Qt is great!");
     text.toBase64();        // returns "UXQgaXMgZ3JlYXQh"

     QByteArray text("<p>Hello?</p>");
     text.toBase64(QByteArray::Base64Encoding | QByteArray::OmitTrailingEquals);      // returns "PHA+SGVsbG8/PC9wPg"
     text.toBase64(QByteArray::Base64Encoding);                                       // returns "PHA+SGVsbG8/PC9wPg=="
     text.toBase64(QByteArray::Base64UrlEncoding);                                    // returns "PHA-SGVsbG8_PC9wPg=="
     text.toBase64(QByteArray::Base64UrlEncoding | QByteArray::OmitTrailingEquals);   // returns "PHA-SGVsbG8_PC9wPg"

The algorithm used to encode Base64-encoded data is defined in RFC 4648.

See also fromBase64().

### CFDataRef QByteArray::toCFData() const

Creates a CFData from a QByteArray.

The caller owns the CFData object and is responsible for releasing it.

See also toRawCFData(), fromCFData(), fromRawCFData(), and fromRawData().

### double QByteArray::toDouble(bool *ok = nullptr) const

Returns the byte array converted to a `double` value.

Returns an infinity if the conversion overflows or 0.0 if the conversion fails for other reasons (e.g. underflow).

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

     QByteArray string("1234.56");
     bool ok;
     double a = string.toDouble(&ok);   // a == 1234.56, ok == true

     string = "1234.56 Volt";
     a = str.toDouble(&ok);             // a == 0, ok == false

Warning: The QByteArray content may only contain valid numerical characters which includes the plus/minus sign, the character e used in scientific notation, and the decimal point. Including the unit or additional characters leads to a conversion error.

Note: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

This function ignores leading and trailing whitespace.

See also number().

### `[since 6.5]` emscripten::val QByteArray::toEcmaUint8Array()

Creates a Uint8Array from a QByteArray.

This function transfers data from heap memory owned by a QByteArray to a JavaScript data buffer. The function allocates and copies into an ArrayBuffer, and returns a Uint8Array view to that buffer.

The JavaScript objects own a copy of the data, and this QByteArray can be safely deleted after the copy has been made.

     QByteArray byteArray = "test";
     emscripten::val uint8array = byteArray.toEcmaUint8Array();

This function was introduced in Qt 6.5.

See also fromEcmaUint8Array().

### float QByteArray::toFloat(bool *ok = nullptr) const

Returns the byte array converted to a `float` value.

Returns an infinity if the conversion overflows or 0.0 if the conversion fails for other reasons (e.g. underflow).

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

     QByteArray string("1234.56");
     bool ok;
     float a = string.toFloat(&ok);    // a == 1234.56, ok == true

     string = "1234.56 Volt";
     a = str.toFloat(&ok);              // a == 0, ok == false

Warning: The QByteArray content may only contain valid numerical characters which includes the plus/minus sign, the character e used in scientific notation, and the decimal point. Including the unit or additional characters leads to a conversion error.

Note: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

This function ignores leading and trailing whitespace.

See also number().

### QByteArray QByteArray::toHex(char separator = '\0') const

Returns a hex encoded copy of the byte array.

The hex encoding uses the numbers 0-9 and the letters a-f.

If separator is not '\0', the separator character is inserted between the hex bytes.

Example:

     QByteArray macAddress = QByteArray::fromHex("123456abcdef");
     macAddress.toHex(':'); // returns "12:34:56:ab:cd:ef"
     macAddress.toHex(0);   // returns "123456abcdef"

See also fromHex().

### int QByteArray::toInt(bool *ok = nullptr, int base = 10) const

Returns the byte array converted to an `int` using base base, which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

If base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0b", it is assumed to be binary (base 2); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

     QByteArray str("FF");
     bool ok;
     int hex = str.toInt(&ok, 16);     // hex == 255, ok == true
     int dec = str.toInt(&ok, 10);     // dec == 0, ok == false

Note: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

Note: Support for the "0b" prefix was added in Qt 6.4.

See also number().

### long QByteArray::toLong(bool *ok = nullptr, int base = 10) const

Returns the byte array converted to a `long` int using base base, which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

If base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0b", it is assumed to be binary (base 2); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

     QByteArray str("FF");
     bool ok;
     long hex = str.toLong(&ok, 16);   // hex == 255, ok == true
     long dec = str.toLong(&ok, 10);   // dec == 0, ok == false

Note: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

Note: Support for the "0b" prefix was added in Qt 6.4.

See also number().

### qlonglong QByteArray::toLongLong(bool *ok = nullptr, int base = 10) const

Returns the byte array converted to a `long long` using base base, which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

If base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0b", it is assumed to be binary (base 2); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

Note: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

Note: Support for the "0b" prefix was added in Qt 6.4.

See also number().

### QByteArray QByteArray::toLower() const

Returns a copy of the byte array in which each ASCII uppercase letter converted to lowercase.

Example:

     QByteArray x("Qt by THE QT COMPANY");
     QByteArray y = x.toLower();
     // y == "qt by the qt company"

See also isLower(), toUpper(), and Character Case.

### NSData *QByteArray::toNSData() const

Creates a NSData from a QByteArray.

The NSData object is autoreleased.

See also fromNSData(), fromRawNSData(), fromRawData(), and toRawNSData().

### QByteArray QByteArray::toPercentEncoding(const QByteArray &exclude = QByteArray(), const QByteArray &include = QByteArray(), char percent = '%') const

Returns a URI/URL-style percent-encoded copy of this byte array. The percent parameter allows you to override the default '%' character for another.

By default, this function will encode all bytes that are not one of the following:

ALPHA ("a" to "z" and "A" to "Z") / DIGIT (0 to 9) / "-" / "." / "_" / "~"

To prevent bytes from being encoded pass them to exclude. To force bytes to be encoded pass them to include. The percent character is always encoded.

Example:

     QByteArray text = "{a fishy string?}";
     QByteArray ba = text.toPercentEncoding("{}", "s");
     qDebug("%s", ba.constData());
     // prints "{a fi%73hy %73tring%3F}"

The hex encoding uses the numbers 0-9 and the uppercase letters A-F.

See also fromPercentEncoding() and QUrl::toPercentEncoding().

### CFDataRef QByteArray::toRawCFData() const

Constructs a CFData that uses the bytes of the QByteArray.

The QByteArray's bytes are not copied.

The caller guarantees that the QByteArray will not be deleted or modified as long as this CFData object exists.

See also toCFData(), fromRawCFData(), fromCFData(), and fromRawData().

### NSData *QByteArray::toRawNSData() const

Constructs a NSData that uses the bytes of the QByteArray.

The QByteArray's bytes are not copied.

The caller guarantees that the QByteArray will not be deleted or modified as long as this NSData object exists.

See also fromRawNSData(), fromNSData(), fromRawData(), and toNSData().

### short QByteArray::toShort(bool *ok = nullptr, int base = 10) const

Returns the byte array converted to a `short` using base base, which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

If base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0b", it is assumed to be binary (base 2); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

Note: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

Note: Support for the "0b" prefix was added in Qt 6.4.

See also number().

### std::string QByteArray::toStdString() const

Returns a std::string object with the data contained in this QByteArray.

This operator is mostly useful to pass a QByteArray to a function that accepts a std::string object.

See also fromStdString() and QString::toStdString().

### uint QByteArray::toUInt(bool *ok = nullptr, int base = 10) const

Returns the byte array converted to an `unsigned int` using base base, which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

If base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0b", it is assumed to be binary (base 2); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

Note: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

Note: Support for the "0b" prefix was added in Qt 6.4.

See also number().

### ulong QByteArray::toULong(bool *ok = nullptr, int base = 10) const

Returns the byte array converted to an `unsigned long int` using base base, which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

If base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0b", it is assumed to be binary (base 2); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

Note: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

Note: Support for the "0b" prefix was added in Qt 6.4.

See also number().

### qulonglong QByteArray::toULongLong(bool *ok = nullptr, int base = 10) const

Returns the byte array converted to an `unsigned long long` using base base, which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

If base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0b", it is assumed to be binary (base 2); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

Note: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

Note: Support for the "0b" prefix was added in Qt 6.4.

See also number().

### ushort QByteArray::toUShort(bool *ok = nullptr, int base = 10) const

Returns the byte array converted to an `unsigned short` using base base, which is ten by default. Bases 0 and 2 through 36 are supported, using letters for digits beyond 9; A is ten, B is eleven and so on.

If base is 0, the base is determined automatically using the following rules: If the byte array begins with "0x", it is assumed to be hexadecimal (base 16); otherwise, if it begins with "0b", it is assumed to be binary (base 2); otherwise, if it begins with "0", it is assumed to be octal (base 8); otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

If ok is not `nullptr`, failure is reported by setting *ok to `false`, and success by setting *ok to `true`.

Note: The conversion of the number is performed in the default C locale, regardless of the user's locale. Use QLocale to perform locale-aware conversions between numbers and strings.

Note: Support for the "0b" prefix was added in Qt 6.4.

See also number().

### QByteArray QByteArray::toUpper() const

Returns a copy of the byte array in which each ASCII lowercase letter converted to uppercase.

Example:

     QByteArray x("Qt by THE QT COMPANY");
     QByteArray y = x.toUpper();
     // y == "QT BY THE QT COMPANY"

See also isUpper(), toLower(), and Character Case.

### QByteArray QByteArray::trimmed() const

Returns a copy of this byte array with spacing characters removed from the start and end.

The spacing characters are those for which the standard C++ `isspace()` function returns `true` in the C locale; these are the ASCII characters tabulation '\t', line feed '\n', carriage return '\r', vertical tabulation '\v', form feed '\f', and space ' '.

Example:

     QByteArray ba("  lots\t of\nwhitespace\r\n ");
     ba = ba.trimmed();
     // ba == "lots\t of\nwhitespace";

Unlike simplified(), trimmed() leaves internal spacing unchanged.

See also simplified(), QChar::SpecialCharacter, and Spacing Characters.

### void QByteArray::truncate(qsizetype pos)

Truncates the byte array at index position pos.

If pos is beyond the end of the array, nothing happens.

Example:

     QByteArray ba("Stockholm");
     ba.truncate(5);             // ba == "Stock"

See also chop(), resize(), and first().

### QByteArray &QByteArray::operator+=(const QByteArray &ba)

Appends the byte array ba onto the end of this byte array and returns a reference to this byte array.

Example:

     QByteArray x("free");
     QByteArray y("dom");
     x += y;
     // x == "freedom"

Note: QByteArray is an implicitly shared class. Consequently, if you append to an empty byte array, then the byte array will just share the data held in ba. In this case, no copying of data is done, taking constant time. If a shared instance is modified, it will be copied (copy-on-write), taking linear time.

If the byte array being appended to is not empty, a deep copy of the data is performed, taking linear time.

This operation typically does not suffer from allocation overhead, because QByteArray preallocates extra space at the end of the data so that it may grow without reallocating for each append operation.

See also append() and prepend().

### QByteArray &QByteArray::operator+=(char ch)

Appends the byte ch onto the end of this byte array and returns a reference to this byte array.

This is an overloaded function.

### QByteArray &QByteArray::operator+=(const char *str)

Appends the '\0'-terminated string str onto the end of this byte array and returns a reference to this byte array.

This is an overloaded function.

### `[noexcept]` QByteArray &QByteArray::operator=(QByteArray &&other)

Move-assigns other to this QByteArray instance.

### `[noexcept]` QByteArray &QByteArray::operator=(const QByteArray &other)

Assigns other to this byte array and returns a reference to this byte array.

### QByteArray &QByteArray::operator=(const char *str)

Assigns str to this byte array.

str is assumed to point to a null-terminated string, and its length is determined dynamically.

This is an overloaded function.

### char &QByteArray::operator[](qsizetype i)

Returns the byte at index position i as a modifiable reference.

i must be a valid index position in the byte array (i.e., 0 <= i < size()).

Example:

     QByteArray ba("Hello, world");
     cout << ba[0]; // prints H
     ba[7] = 'W';
     // ba == "Hello, World"

See also at().

### char QByteArray::operator[](qsizetype i) const

Same as at(i).

This is an overloaded function.

## Related Non-Members

### `[since 6.9]` QByteArray operator+(QByteArrayView lhs, const QByteArray &rhs)

### `[since 6.9]` QByteArray operator+(const QByteArray &lhs, QByteArrayView rhs)

Returns a byte array that is the result of concatenating lhs and rhs.

This function was introduced in Qt 6.9.

See also QByteArray::operator+=().

### `[since 6.1]` template <typename T> qsizetype erase(QByteArray &ba, const T &t)

Removes all elements that compare equal to t from the byte array ba. Returns the number of elements removed, if any.

This function was introduced in Qt 6.1.

See also erase_if.

### `[since 6.1]` template <typename Predicate> qsizetype erase_if(QByteArray &ba, Predicate pred)

Removes all elements for which the predicate pred returns true from the byte array ba. Returns the number of elements removed, if any.

This function was introduced in Qt 6.1.

See also erase.

### quint16 qChecksum(QByteArrayView data, Qt::ChecksumType standard = Qt::ChecksumIso3309)

Returns the CRC-16 checksum of data.

The checksum is independent of the byte order (endianness) and will be calculated accorded to the algorithm published in standard. By default the algorithm published in ISO 3309 (Qt::ChecksumIso3309) is used.

Note: This function is a 16-bit cache conserving (16 entry table) implementation of the CRC-16-CCITT algorithm.

### QByteArray qCompress(const QByteArray &data, int compressionLevel = -1)

Compresses the data byte array and returns the compressed data in a new byte array.

The compressionLevel parameter specifies how much compression should be used. Valid values are between 0 and 9, with 9 corresponding to the greatest compression (i.e. smaller compressed data) at the cost of using a slower algorithm. Smaller values (8, 7, ..., 1) provide successively less compression at slightly faster speeds. The value 0 corresponds to no compression at all. The default value is -1, which specifies zlib's default compression.

See also qUncompress(const QByteArray &data).

### QByteArray qCompress(const uchar *data, qsizetype nbytes, int compressionLevel = -1)

Compresses the first nbytes of data at compression level compressionLevel and returns the compressed data in a new byte array.

This is an overloaded function.

### QByteArray qUncompress(const QByteArray &data)

Uncompresses the data byte array and returns a new byte array with the uncompressed data.

Returns an empty QByteArray if the input data was corrupt.

This function will uncompress data compressed with qCompress() from this and any earlier Qt version, back to Qt 3.1 when this feature was added.

Note: If you want to use this function to uncompress external data that was compressed using zlib, you first need to prepend a four byte header to the byte array containing the data. The header must contain the expected length (in bytes) of the uncompressed data, expressed as an unsigned, big-endian, 32-bit integer. This number is just a hint for the initial size of the output buffer size, though. If the indicated size is too small to hold the result, the output buffer size will still be increased until either the output fits or the system runs out of memory. So, despite the 32-bit header, this function, on 64-bit platforms, can produce more than 4GiB of output.

Note: In Qt versions prior to Qt 6.5, more than 2GiB of data worked unreliably; in Qt versions prior to Qt 6.0, not at all.

See also qCompress().

### QByteArray qUncompress(const uchar *data, qsizetype nbytes)

Uncompresses the first nbytes of data and returns a new byte array with the uncompressed data.

This is an overloaded function.

### int qstrcmp(const char *str1, const char *str2)

A safe `strcmp()` function.

Compares str1 and str2. Returns a negative value if str1 is less than str2, 0 if str1 is equal to str2 or a positive value if str1 is greater than str2.

If both strings are `nullptr`, they are deemed equal; otherwise, if either is `nullptr`, it is treated as less than the other (even if the other is an empty string).

See also qstrncmp(), qstricmp(), qstrnicmp(), Character Case, and QByteArray::compare().

### char *qstrcpy(char *dst, const char *src)

Copies all the characters up to and including the '\0' from src into dst and returns a pointer to dst. If src is `nullptr`, it immediately returns `nullptr`.

This function assumes that dst is large enough to hold the contents of src.

Note: If dst and src overlap, the behavior is undefined.

See also qstrncpy().

### char *qstrdup(const char *src)

Returns a duplicate string.

Allocates space for a copy of src, copies it, and returns a pointer to the copy. If src is `nullptr`, it immediately returns `nullptr`.

Ownership is passed to the caller, so the returned string must be deleted using `delete[]`.

### int qstricmp(const char *str1, const char *str2)

A safe `stricmp()` function.

Compares str1 and str2, ignoring differences in the case of any ASCII characters.

Returns a negative value if str1 is less than str2, 0 if str1 is equal to str2 or a positive value if str1 is greater than str2.

If both strings are `nullptr`, they are deemed equal; otherwise, if either is `nullptr`, it is treated as less than the other (even if the other is an empty string).

See also qstrcmp(), qstrncmp(), qstrnicmp(), Character Case, and QByteArray::compare().

### size_t qstrlen(const char *str)

A safe `strlen()` function.

Returns the number of characters that precede the terminating '\0', or 0 if str is `nullptr`.

See also qstrnlen().

### int qstrncmp(const char *str1, const char *str2, size_t len)

A safe `strncmp()` function.

Compares at most len bytes of str1 and str2.

Returns a negative value if str1 is less than str2, 0 if str1 is equal to str2 or a positive value if str1 is greater than str2.

If both strings are `nullptr`, they are deemed equal; otherwise, if either is `nullptr`, it is treated as less than the other (even if the other is an empty string or len is 0).

See also qstrcmp(), qstricmp(), qstrnicmp(), Character Case, and QByteArray::compare().

### char *qstrncpy(char *dst, const char *src, size_t len)

A safe `strncpy()` function.

Copies at most len bytes from src (stopping at len or the terminating '\0' whichever comes first) into dst. Guarantees that dst is '\0'-terminated, except when dst is `nullptr` or len is 0. If src is `nullptr`, returns `nullptr`, otherwise returns dst.

This function assumes that dst is at least len characters long.

Note: If dst and src overlap, the behavior is undefined.

Note: Unlike strncpy(), this function does not write '\0' to all len bytes of dst, but stops after the terminating '\0'. In this sense, it's similar to C11's strncpy_s().

See also qstrcpy().

### int qstrnicmp(const char *str1, const char *str2, size_t len)

A safe `strnicmp()` function.

Compares at most len bytes of str1 and str2, ignoring differences in the case of any ASCII characters.

Returns a negative value if str1 is less than str2, 0 if str1 is equal to str2 or a positive value if str1 is greater than str2.

If both strings are `nullptr`, they are deemed equal; otherwise, if either is `nullptr`, it is treated as less than the other (even if the other is an empty string or len is 0).

See also qstrcmp(), qstrncmp(), qstricmp(), Character Case, and QByteArray::compare().

### size_t qstrnlen(const char *str, size_t maxlen)

A safe `strnlen()` function.

Returns the number of characters that precede the terminating '\0', but at most maxlen. If str is `nullptr`, returns 0.

See also qstrlen().

### `[noexcept]` bool operator!=(const QByteArray &lhs, const QByteArray &rhs)

Returns `true` if byte array lhs is not equal to byte array rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator!=(const QByteArray &lhs, const char *const &rhs)

Returns `true` if byte array lhs is not equal to the '\0'-terminated string rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator!=(const char *const &lhs, const QByteArray &rhs)

Returns `true` if '\0'-terminated string lhs is not equal to byte array rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept, since 6.4]` QByteArray operator""_ba(const char *str, size_t size)

Literal operator that creates a QByteArray out of the first size characters in the char string literal str.

The QByteArray is created at compile time, and the generated string data is stored in the read-only segment of the compiled object file. Duplicate literals may share the same read-only memory. This functionality is interchangeable with QByteArrayLiteral, but saves typing when many string literals are present in the code.

The following code creates a QByteArray:

     using namespace Qt::Literals::StringLiterals;

     auto str = "hello"_ba;

This function was introduced in Qt 6.4.

See also Qt::Literals::StringLiterals.

### QByteArray operator+(char a1, const QByteArray &a2)

Returns a byte array that is the result of concatenating byte a1 and byte array a2.

This is an overloaded function.

### QByteArray operator+(const QByteArray &a1, char a2)

Returns a byte array that is the result of concatenating byte array a1 and byte a2.

This is an overloaded function.

### QByteArray operator+(const QByteArray &a1, const QByteArray &a2)

Returns a byte array that is the result of concatenating byte array a1 and byte array a2.

See also QByteArray::operator+=().

### QByteArray operator+(const QByteArray &a1, const char *a2)

Returns a byte array that is the result of concatenating byte array a1 and '\0'-terminated string a2.

This is an overloaded function.

### QByteArray operator+(const char *a1, const QByteArray &a2)

Returns a byte array that is the result of concatenating '\0'-terminated string a1 and byte array a2.

This is an overloaded function.

### `[noexcept]` bool operator<(const QByteArray &lhs, const QByteArray &rhs)

Returns `true` if byte array lhs is lexically less than byte array rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator<(const QByteArray &lhs, const char *const &rhs)

Returns `true` if byte array lhs is lexically less than the '\0'-terminated string rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator<(const char *const &lhs, const QByteArray &rhs)

Returns `true` if '\0'-terminated string lhs is lexically less than byte array rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### QDataStream &operator<<(QDataStream &out, const QByteArray &ba)

Writes byte array ba to the stream out and returns a reference to the stream.

See also Serializing Qt Data Types.

### `[noexcept]` bool operator<=(const QByteArray &lhs, const QByteArray &rhs)

Returns `true` if byte array lhs is lexically less than or equal to byte array rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator<=(const QByteArray &lhs, const char *const &rhs)

Returns `true` if byte array lhs is lexically less than or equal to the '\0'-terminated string rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator<=(const char *const &lhs, const QByteArray &rhs)

Returns `true` if '\0'-terminated string lhs is lexically less than or equal to byte array rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator==(const QByteArray &lhs, const QByteArray &rhs)

Returns `true` if byte array lhs is equal to byte array rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator==(const QByteArray &lhs, const char *const &rhs)

Returns `true` if byte array lhs is equal to the '\0'-terminated string rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator==(const char *const &lhs, const QByteArray &rhs)

Returns `true` if '\0'-terminated string lhs is equal to byte array rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator>(const QByteArray &lhs, const QByteArray &rhs)

Returns `true` if byte array lhs is lexically greater than byte array rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator>(const QByteArray &lhs, const char *const &rhs)

Returns `true` if byte array lhs is lexically greater than the '\0'-terminated string rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator>(const char *const &lhs, const QByteArray &rhs)

Returns `true` if '\0'-terminated string lhs is lexically greater than byte array rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator>=(const QByteArray &lhs, const QByteArray &rhs)

Returns `true` if byte array lhs is lexically greater than or equal to byte array rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator>=(const QByteArray &lhs, const char *const &rhs)

Returns `true` if byte array lhs is lexically greater than or equal to the '\0'-terminated string rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### `[noexcept]` bool operator>=(const char *const &lhs, const QByteArray &rhs)

Returns `true` if '\0'-terminated string lhs is lexically greater than or equal to byte array rhs; otherwise returns `false`.

This is an overloaded function.

See also QByteArray::compare().

### QDataStream &operator>>(QDataStream &in, QByteArray &ba)

Reads a byte array into ba from the stream in and returns a reference to the stream.

See also Serializing Qt Data Types.

## Macro Documentation

### QByteArrayLiteral(ba)

The macro generates the data for a QByteArray out of the string literal ba at compile time. Creating a QByteArray from it is free in this case, and the generated byte array data is stored in the read-only segment of the compiled object file.

For instance:

     QByteArray ba = QByteArrayLiteral("byte array contents");

Using QByteArrayLiteral instead of a double quoted plain C++ string literal can significantly speed up creation of QByteArray instances from data known at compile time.

See also QStringLiteral.

### QT_NO_CAST_FROM_BYTEARRAY

Disables automatic conversions from QByteArray to const char * or const void *.

See also QT_NO_CAST_TO_ASCII and QT_NO_CAST_FROM_ASCII.

### `[since 6.8]` QT_NO_QSNPRINTF

Defining this macro removes the availability of the qsnprintf() and qvsnprintf() functions. See the functions' documentation for why you may want to disable them.

This macro was introduced in Qt 6.8.

See also qsnprintf() and qvsnprintf().