QByteArray Class

The QByteArray class provides an array of bytes.

All functions in this class are reentrant.

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Publié le 26 janvier 2024 - Mis à jour le 26 janvier 2024

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QByteArray Class▲

Header: QByteArray
CMake:

find_package(Qt6 REQUIRED COMPONENTS Core)

target_link_libraries(mytarget PRIVATE Qt6::Core)
qmake: QT += core
Group: QByteArray is part of tools, Implicitly Shared Classes, string-processing

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":

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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:

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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():

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for (qsizetype i = 0; i &lt; ba.size(); ++i) {
    if (ba.at(i) &gt;= 'a' &amp;&amp; ba.at(i) &lt;= 'f')
        cout &lt;&lt; "Found character in range [a-f]" &lt;&lt; Qt::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:

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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:

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

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.

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:

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QByteArray ba("We must be &lt;b&gt;bold&lt;/b&gt;, very &lt;b&gt;bold&lt;/b&gt;");
qsizetype j = 0;
while ((j = ba.indexOf("&lt;b&gt;", j)) != -1) {
    cout &lt;&lt; "Found &lt;b&gt; tag at index position " &lt;&lt; j &lt;&lt; Qt::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:

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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.

Member Type Documentation▲

[since 5.2] 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.

This enum was introduced or modified in Qt 5.2.

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.

[since 5.6] QByteArray::const_reverse_iterator▲

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

This typedef was introduced in Qt 5.6.

QByteArray::iterator▲

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

[since 5.6] QByteArray::reverse_iterator▲

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

This typedef was introduced in Qt 5.6.

Member Function Documentation▲

const char QByteArray::operator const char () const▲

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

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.

[static, since 5.15] QByteArray::FromBase64Result QByteArray::fromBase64Encoding(QByteArray &&base64, QByteArray::Base64Options options = Base64Encoding)▲

[static, since 5.15] QByteArray::FromBase64Result QByteArray::fromBase64Encoding(const QByteArray &base64, QByteArray::Base64Options options = Base64Encoding)

This is an overloaded function.

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:

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void process(const QByteArray &amp;);

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.

This function was introduced in Qt 5.15.

[constexpr] QByteArray::QByteArray()▲

Constructs an empty byte array.

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.

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

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

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.

[since 5.2] QByteArray::QByteArray(QByteArray &&other)▲

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

This function was introduced in Qt 5.2.

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:

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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.

QByteArray &QByteArray::append(char ch)▲

This is an overloaded function.

Appends the byte ch to this byte array.

[since 5.7] QByteArray &QByteArray::append(qsizetype count, char ch)▲

This is an overloaded function.

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 function was introduced in Qt 5.7.

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

This is an overloaded function.

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

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

This is an overloaded function.

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.

QByteArray &QByteArray::append(QByteArrayView data)▲

This is an overloaded function.

Appends data to this byte array.

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()).

[since 5.10] char QByteArray::back() const▲

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

This function is provided for STL compatibility.

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

This function was introduced in Qt 5.10.

[since 5.10] 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.

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

This function was introduced in Qt 5.10.

QByteArray::iterator QByteArray::begin()▲

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

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

QByteArray::const_iterator QByteArray::begin() const▲

This function overloads 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().

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

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.

[since 5.0] QByteArray::const_iterator QByteArray::cbegin() const▲

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

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

This function was introduced in Qt 5.0.

[since 5.0] QByteArray::const_iterator QByteArray::cend() const▲

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

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

This function was introduced in Qt 5.0.

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:

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

[since 5.10] QByteArray QByteArray::chopped(qsizetype len) const▲

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

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

This function was introduced in Qt 5.10.

void QByteArray::clear()▲

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

[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.

QByteArray::const_iterator QByteArray::constBegin() const▲

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

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

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.

QByteArray::const_iterator QByteArray::constEnd() const▲

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

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

[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.

bool QByteArray::contains(char ch) const▲

This is an overloaded function.

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

[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.

qsizetype QByteArray::count(char ch) const▲

This is an overloaded function.

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

[since 5.6] 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.

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

This function was introduced in Qt 5.6.

[since 5.6] 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.

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

This function was introduced in Qt 5.6.

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:

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QByteArray ba("Hello world");
char *data = ba.data();
while (*data) {
    cout &lt;&lt; "[" &lt;&lt; *data &lt;&lt; "]" &lt;&lt; Qt::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:

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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:

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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.

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.

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

QByteArray::const_iterator QByteArray::end() const▲

This function overloads 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:

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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.

bool QByteArray::endsWith(char ch) const▲

This is an overloaded function.

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

[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.

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:

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

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

[since 6.0] QByteArray QByteArray::first(qsizetype n) const▲

Returns the first n bytes of the byte array.

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

Example:

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

This function was introduced in Qt 6.0.

[static, since 5.2] 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:

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

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

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.

The fromBase64Encoding() function is recommended in new code.

This function was introduced in Qt 5.2.

[static, since 5.3] QByteArray QByteArray::fromCFData(CFDataRef data)▲

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

This function was introduced in Qt 5.3.

[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:

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

[static, since 5.3] QByteArray QByteArray::fromNSData(const NSData *data)▲

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

This function was introduced in Qt 5.3.

[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:

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

[static, since 5.3] 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.

This function was introduced in Qt 5.3.

[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:

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 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(&amp;data, QIODevice::ReadOnly);
...

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.

[static, since 5.3] 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.

This function was introduced in Qt 5.3.

[static, since 5.4] QByteArray QByteArray::fromStdString(const std::string &str)▲

Returns a copy of the str string as a QByteArray.

This function was introduced in Qt 5.4.

[since 5.10] char QByteArray::front() const▲

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

This function is provided for STL compatibility.

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

This function was introduced in Qt 5.10.

[since 5.10] 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.

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

This function was introduced in Qt 5.10.

[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:

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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.

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

This is an overloaded function.

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:

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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

[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:

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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.

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))

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.

[since 5.7] QByteArray &QByteArray::insert(qsizetype i, qsizetype count, char ch)▲

This is an overloaded function.

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 function was introduced in Qt 5.7.

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

This is an overloaded function.

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.

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

This is an overloaded function.

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.

bool QByteArray::isEmpty() const▲

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

Example:

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

[since 5.12] 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.

This function was introduced in Qt 5.12.

bool QByteArray::isNull() const▲

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

Example:

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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().

[since 5.12] 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.

This function was introduced in Qt 5.12.

[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] QByteArray QByteArray::last(qsizetype n) const▲

Returns the last n bytes of the byte array.

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

Example:

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

This function was introduced in Qt 6.0.

[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 from is -2, at the next to last character and so on. Returns -1 if no match is found.

Example:

Sélectionnez

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

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.

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

This is an overloaded function.

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:

Sélectionnez

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

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

This is an overloaded function.

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:

Sélectionnez

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 function was introduced in Qt 6.2.

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.

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:

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

qsizetype QByteArray::length() const▲

Same as size().

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.

[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:

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

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.

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

This is an overloaded function.

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

This is an overloaded function.

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

This is an overloaded function.

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

This is an overloaded function.

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

This is an overloaded function.

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

This is an overloaded function.

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:

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

[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:

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

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.

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:

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

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

QByteArray &QByteArray::prepend(char ch)▲

This is an overloaded function.

Prepends the byte ch to this byte array.

[since 5.7] QByteArray &QByteArray::prepend(qsizetype count, char ch)▲

This is an overloaded function.

Prepends count copies of byte ch to this byte array.

This function was introduced in Qt 5.7.

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

This is an overloaded function.

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

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

This is an overloaded function.

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

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

This is an overloaded function.

Prepends ba to this byte array.

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

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

void QByteArray::push_back(char ch)▲

This is an overloaded function.

Same as append(ch).

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

This is an overloaded function.

Same as append(str).

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

This is an overloaded function.

Same as append(str).

This function was introduced in Qt 6.0.

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

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

void QByteArray::push_front(char ch)▲

This is an overloaded function.

Same as prepend(ch).

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

This is an overloaded function.

Same as prepend(str).

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

This is an overloaded function.

Same as prepend(str).

This function was introduced in Qt 6.0.

[since 5.6] QByteArray::reverse_iterator QByteArray::rbegin()▲

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

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

This function was introduced in Qt 5.6.

[since 5.6] QByteArray::const_reverse_iterator QByteArray::rbegin() const▲

This is an overloaded function.

This function was introduced in Qt 5.6.

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:

Sélectionnez

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.

[since 6.1] 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.

[since 5.6] QByteArray::reverse_iterator QByteArray::rend()▲

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

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

This function was introduced in Qt 5.6.

[since 5.6] QByteArray::const_reverse_iterator QByteArray::rend() const▲

This is an overloaded function.

This function was introduced in Qt 5.6.

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:

Sélectionnez

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:

Sélectionnez

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

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

This is an overloaded function.

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

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

This is an overloaded function.

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

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

This is an overloaded function.

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.

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

This is an overloaded function.

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

Example:

Sélectionnez

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

This function was introduced in Qt 6.0.

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

This is an overloaded function.

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

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.

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.

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.

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

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.

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.

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:

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

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:

Sélectionnez

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

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.

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

This is an overloaded function.

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

This is an overloaded function.

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

This is an overloaded function.

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

This is an overloaded function.

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

This is an overloaded function.

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

This is an overloaded function.

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

This is an overloaded function.

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

This is an overloaded function.

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.

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

This is an overloaded function.

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.

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.

[since 5.10] void QByteArray::shrink_to_fit()▲

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

This function was introduced in Qt 5.10.

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:

Sélectionnez

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

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:

Sélectionnez

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

[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.

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

Example:

Sélectionnez

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.

[since 6.0] QByteArray QByteArray::sliced(qsizetype pos) const▲

This is an overloaded function.

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

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

This function was introduced in Qt 6.0.

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.

[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:

Sélectionnez

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

This function was introduced in Qt 6.0.

bool QByteArray::startsWith(char ch) const▲

This is an overloaded function.

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

void QByteArray::swap(QByteArray &other)▲

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

[since 5.2] QByteArray QByteArray::toBase64(QByteArray::Base64Options options = Base64Encoding) const▲

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

Sélectionnez

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

QByteArray text("&lt;p&gt;Hello?&lt;/p&gt;");
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.

This function was introduced in Qt 5.2.

[since 5.3] CFDataRef QByteArray::toCFData() const▲

Creates a CFData from a QByteArray.

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

This function was introduced in Qt 5.3.

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.

Sélectionnez

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

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

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.

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.

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.

Sélectionnez

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

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

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.

[since 5.9] 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:

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

This function was introduced in Qt 5.9.

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.

Sélectionnez

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

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.

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

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.

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.

Sélectionnez

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

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.

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

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.

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.

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.

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

QByteArray QByteArray::toLower() const▲

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

Example:

Sélectionnez

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

[since 5.3] NSData *QByteArray::toNSData() const▲

Creates a NSData from a QByteArray.

The NSData object is autoreleased.

This function was introduced in Qt 5.3.

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:

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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.

[since 5.3] 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.

This function was introduced in Qt 5.3.

[since 5.3] 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.

This function was introduced in Qt 5.3.

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.

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.

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.

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

[since 5.4] 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.

This function was introduced in Qt 5.4.

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.

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.

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.

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

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.

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.

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.

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

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.

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.

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.

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

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.

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.

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.

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

QByteArray QByteArray::toUpper() const▲

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

Example:

Sélectionnez

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

QByteArray QByteArray::trimmed() const▲

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

Example:

Sélectionnez

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

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

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:

Sélectionnez

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

bool QByteArray::operator!=(const QString &str) const▲

Returns true if this byte array is not equal to the UTF-8 encoding of str; otherwise returns false.

The comparison is case sensitive.

You can disable this operator by defining QT_NO_CAST_FROM_ASCII when you compile your applications. You then need to call QString::fromUtf8(), QString::fromLatin1(), or QString::fromLocal8Bit() explicitly if you want to convert the byte array to a QString before doing the comparison.

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:

Sélectionnez

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

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.

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

This is an overloaded function.

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

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

This is an overloaded function.

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

bool QByteArray::operator<(const QString &str) const▲

Returns true if this byte array is lexically less than the UTF-8 encoding of str; otherwise returns false.

The comparison is case sensitive.

bool QByteArray::operator<=(const QString &str) const▲

Returns true if this byte array is lexically less than or equal to the UTF-8 encoding of str; otherwise returns false.

The comparison is case sensitive.

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)▲

This is an overloaded function.

Assigns str to this byte array.

[since 5.2] QByteArray &QByteArray::operator=(QByteArray &&other)▲

Move-assigns other to this QByteArray instance.

This function was introduced in Qt 5.2.

bool QByteArray::operator==(const QString &str) const▲

Returns true if this byte array is equal to the UTF-8 encoding of str; otherwise returns false.

The comparison is case sensitive.

bool QByteArray::operator>(const QString &str) const▲

Returns true if this byte array is lexically greater than the UTF-8 encoding of str; otherwise returns false.

The comparison is case sensitive.

bool QByteArray::operator>=(const QString &str) const▲

Returns true if this byte array is greater than or equal to the UTF-8 encoding of str; otherwise returns false.

The comparison is case sensitive.

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:

Sélectionnez

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

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

This is an overloaded function.

Same as at(i).

Related Non-Members▲

[since 6.1] 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.

[since 6.1] 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.

[since 5.9] 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.

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

This function was introduced in Qt 5.9.

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.

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

This is an overloaded function.

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

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.

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.

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

This is an overloaded function.

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

int qsnprintf(char str, size_t n, const char fmt, ...)▲

A portable snprintf() function, calls qvsnprintf.

fmt is the printf() format string. The result is put into str, which is a buffer of at least n bytes.

Call this function only when you know what you are doing since it shows different behavior on certain platforms. Use QString::asprintf() to format a string instead.

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).

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.

If dst and src overlap, the behavior is undefined.

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).

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.

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).

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 and returns a pointer to dst. Guarantees that dst is '\0'-terminated. If src or dst is nullptr, returns nullptr immediately.

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

If dst and src overlap, the behavior is undefined.

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).

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.

int qvsnprintf(char str, size_t n, const char fmt, va_list ap)▲

A portable vsnprintf() function. Will call ::vsnprintf(), ::_vsnprintf(), or ::vsnprintf_s depending on the system, or fall back to an internal version.

fmt is the printf() format string. The result is put into str, which is a buffer of at least n bytes.

The caller is responsible to call va_end() on ap.

Since vsnprintf() shows different behavior on certain platforms, you should not rely on the return value or on the fact that you will always get a 0 terminated string back.

Ideally, you should never call this function but use QString::asprintf() instead.

bool operator!=(const QByteArray &a1, const QByteArray &a2)▲

This is an overloaded function.

Returns true if byte array a1 is not equal to byte array a2; otherwise returns false.

bool operator!=(const QByteArray &a1, const char *a2)▲

This is an overloaded function.

Returns true if byte array a1 is not equal to the '\0'-terminated string a2; otherwise returns false.

bool operator!=(const char *a1, const QByteArray &a2)▲

This is an overloaded function.

Returns true if '\0'-terminated string a1 is not equal to byte array a2; otherwise returns false.

[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:

Sélectionnez

using namespace Qt::Literals::StringLiterals;

auto str = "hello"_ba;

This function was introduced in Qt 6.4.

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.

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

This is an overloaded function.

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

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

This is an overloaded function.

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

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

This is an overloaded function.

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

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

This is an overloaded function.

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

bool operator<(const QByteArray &a1, const QByteArray &a2)▲

This is an overloaded function.

Returns true if byte array a1 is lexically less than byte array a2; otherwise returns false.

bool operator<(const QByteArray &a1, const char *a2)▲

This is an overloaded function.

Returns true if byte array a1 is lexically less than the '\0'-terminated string a2; otherwise returns false.

bool operator<(const char *a1, const QByteArray &a2)▲

This is an overloaded function.

Returns true if '\0'-terminated string a1 is lexically less than byte array a2; otherwise returns false.

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

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

bool operator<=(const QByteArray &a1, const QByteArray &a2)▲

This is an overloaded function.

Returns true if byte array a1 is lexically less than or equal to byte array a2; otherwise returns false.

bool operator<=(const QByteArray &a1, const char *a2)▲

This is an overloaded function.

Returns true if byte array a1 is lexically less than or equal to the '\0'-terminated string a2; otherwise returns false.

bool operator<=(const char *a1, const QByteArray &a2)▲

This is an overloaded function.

Returns true if '\0'-terminated string a1 is lexically less than or equal to byte array a2; otherwise returns false.

bool operator==(const QByteArray &a1, const QByteArray &a2)▲

This is an overloaded function.

Returns true if byte array a1 is equal to byte array a2; otherwise returns false.

bool operator==(const QByteArray &a1, const char *a2)▲

This is an overloaded function.

Returns true if byte array a1 is equal to the '\0'-terminated string a2; otherwise returns false.

bool operator==(const char *a1, const QByteArray &a2)▲

This is an overloaded function.

Returns true if '\0'-terminated string a1 is equal to byte array a2; otherwise returns false.

bool operator>(const QByteArray &a1, const QByteArray &a2)▲

This is an overloaded function.

Returns true if byte array a1 is lexically greater than byte array a2; otherwise returns false.

bool operator>(const QByteArray &a1, const char *a2)▲

This is an overloaded function.

Returns true if byte array a1 is lexically greater than the '\0'-terminated string a2; otherwise returns false.

bool operator>(const char *a1, const QByteArray &a2)▲

This is an overloaded function.

Returns true if '\0'-terminated string a1 is lexically greater than byte array a2; otherwise returns false.

bool operator>=(const QByteArray &a1, const QByteArray &a2)▲

This is an overloaded function.

Returns true if byte array a1 is lexically greater than or equal to byte array a2; otherwise returns false.

bool operator>=(const QByteArray &a1, const char *a2)▲

This is an overloaded function.

Returns true if byte array a1 is lexically greater than or equal to the '\0'-terminated string a2; otherwise returns false.

bool operator>=(const char *a1, const QByteArray &a2)▲

This is an overloaded function.

Returns true if '\0'-terminated string a1 is lexically greater than or equal to byte array a2; otherwise returns false.

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

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

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:

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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.

QT_NO_CAST_FROM_BYTEARRAY▲

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

Obsolete Members for QByteArray▲

The following members of class QByteArray are deprecated. We strongly advise against using them in new code.

Obsolete Member Function Documentation▲

qsizetype QByteArray::count() const▲

This function is deprecated since 6.4. We strongly advise against using it in new code.

Use size() or length() instead.

This is an overloaded function.

Same as size().

Obsolete Related Non-Members▲

[since 6.2] QByteArray operator""_qba(const char *str, size_t size)▲

This function is deprecated since 6.8. We strongly advise against using it in new code.

Use _ba from Qt::StringLiterals namespace instead.

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

The following code creates a QByteArray:

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auto str = "hello"_qba;

This function was introduced in Qt 6.2.

QByteArray Class

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QByteArray Class▲

Detailed Description▲

Maximum size and out-of-memory conditions▲

C locale and ASCII functions▲

C Strings▲

Spacing Characters▲

Number-String Conversions▲

Character Case▲

See Also▲

Member Type Documentation▲

[since 5.2] enum QByteArray::Base64Option▲

QByteArray::const_iterator▲

See Also▲

[since 5.6] QByteArray::const_reverse_iterator▲

See Also▲

QByteArray::iterator▲

See Also▲

[since 5.6] QByteArray::reverse_iterator▲

See Also▲

Member Function Documentation▲

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

See Also▲

[static, since 5.15] QByteArray::FromBase64Result QByteArray::fromBase64Encoding(QByteArray &&base64, QByteArray::Base64Options options = Base64Encoding)▲

See Also▲

[constexpr] QByteArray::QByteArray()▲

See Also▲

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

See Also▲

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

See Also▲

QByteArray::QByteArray(const QByteArray &other)▲

See Also▲

[since 5.2] QByteArray::QByteArray(QByteArray &&other)▲

QByteArray::~QByteArray()▲

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

See Also▲

QByteArray &QByteArray::append(char ch)▲

[since 5.7] QByteArray &QByteArray::append(qsizetype count, char ch)▲

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

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

QByteArray &QByteArray::append(QByteArrayView data)▲

char QByteArray::at(qsizetype i) const▲

See Also▲

[since 5.10] char QByteArray::back() const▲

See Also▲

[since 5.10] char &QByteArray::back()▲

See Also▲

QByteArray::iterator QByteArray::begin()▲

See Also▲

QByteArray::const_iterator QByteArray::begin() const▲

qsizetype QByteArray::capacity() const▲

See Also▲

[since 5.0] QByteArray::const_iterator QByteArray::cbegin() const▲

See Also▲

[since 5.0] QByteArray::const_iterator QByteArray::cend() const▲

See Also▲

void QByteArray::chop(qsizetype n)▲

See Also▲

[since 5.10] QByteArray QByteArray::chopped(qsizetype len) const▲

See Also▲

void QByteArray::clear()▲

See Also▲

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

See Also▲

QByteArray::const_iterator QByteArray::constBegin() const▲

See Also▲

const char *QByteArray::constData() const▲

See Also▲

QByteArray::const_iterator QByteArray::constEnd() const▲

See Also▲

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

See Also▲

bool QByteArray::contains(char ch) const▲

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

See Also▲

qsizetype QByteArray::count(char ch) const▲

const char QByteArray::operator const char () const▲