QByteArray Class

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

Header: #include <QByteArray>
qmake: QT += core

Note: All functions in this class are reentrant.

Public Types

enum Base64Option { Base64Encoding, Base64UrlEncoding, KeepTrailingEquals, OmitTrailingEquals }
flags Base64Options
typedef const_iterator
typedef const_reverse_iterator
typedef iterator
typedef reverse_iterator

Public Functions

QByteArray(int size, char ch)
QByteArray(const char *data, int size = -1)
QByteArray &operator=(const QByteArray &other)
QByteArray &append(char ch)
QByteArray &append(const char *str)
QByteArray &append(const char *str, int len)
QByteArray &append(const QByteArray &ba)
void chop(int n)
int count(const QByteArray &ba) const
int count(char ch) const
int count(const char *str) const
bool endsWith(const QByteArray &ba) const
bool endsWith(char ch) const
bool endsWith(const char *str) const
QByteArray &fill(char ch, int size = -1)
int indexOf(char ch, int from = 0) const
int indexOf(const QByteArray &ba, int from = 0) const
QByteArray &insert(int i, char ch)
QByteArray &insert(int i, const char *str)
QByteArray &insert(int i, const char *str, int len)
QByteArray &insert(int i, const QByteArray &ba)
bool isLower() const
bool isUpper() const
int lastIndexOf(char ch, int from = -1) const
QByteArray left(int len) const
QByteArray leftJustified(int width, char fill = ' ', bool truncate = false) const
QByteArray mid(int pos, int len = -1) const
QByteArray &prepend(char ch)
QByteArray &prepend(const char *str)
QByteArray &prepend(const char *str, int len)
QByteArray &prepend(const QByteArray &ba)
QByteArray &remove(int pos, int len)
QByteArray repeated(int times) const
QByteArray &replace(int pos, int len, const QByteArray &after)
QByteArray &replace(char before, const QByteArray &after)
QByteArray &replace(const QByteArray &before, const QByteArray &after)
QByteArray &replace(char before, char after)
void resize(int size)
QByteArray right(int len) const
QByteArray rightJustified(int width, char fill = ' ', bool truncate = false) const
QByteArray &setNum(qlonglong n, int base = 10)
QByteArray &setNum(qulonglong n, int base = 10)
QByteArray &setNum(double n, char f = 'g', int prec = 6)
QByteArray &setRawData(const char *data, uint size)
QList<QByteArray> split(char sep) const
bool startsWith(const QByteArray &ba) const
bool startsWith(char ch) const
bool startsWith(const char *str) const
QByteArray toBase64() const
QByteArray toBase64(QByteArray::Base64Options options) const
CFDataRef toCFData() const
double toDouble(bool *ok = nullptr) const
float toFloat(bool *ok = nullptr) const
QByteArray toHex() const
QByteArray toHex(char separator) const
int toInt(bool *ok = nullptr, int base = 10) const
long toLong(bool *ok = nullptr, int base = 10) const
qlonglong toLongLong(bool *ok = nullptr, int base = 10) const
NSData *toNSData() const
QByteArray toPercentEncoding(const QByteArray &exclude = QByteArray(), const QByteArray &include = QByteArray(), char percent = '%') const
CFDataRef toRawCFData() const
NSData *toRawNSData() const
short toShort(bool *ok = nullptr, int base = 10) const
uint toUInt(bool *ok = nullptr, int base = 10) const
ulong toULong(bool *ok = nullptr, int base = 10) const
qulonglong toULongLong(bool *ok = nullptr, int base = 10) const
ushort toUShort(bool *ok = nullptr, int base = 10) const
void truncate(int pos)
QByteArray &operator=(const char *str)

Static Public Members

QByteArray fromBase64(const QByteArray &base64)
QByteArray fromBase64(const QByteArray &base64, QByteArray::Base64Options options)
QByteArray fromCFData(CFDataRef data)
QByteArray fromHex(const QByteArray &hexEncoded)
QByteArray fromNSData(const NSData *data)
QByteArray fromPercentEncoding(const QByteArray &input, char percent = '%')
QByteArray fromRawCFData(CFDataRef data)
QByteArray fromRawData(const char *data, int size)
QByteArray fromRawNSData(const NSData *data)
QByteArray number(int n, int base = 10)
QByteArray number(uint n, int base = 10)
QByteArray number(qlonglong n, int base = 10)
QByteArray number(qulonglong n, int base = 10)
QByteArray number(double n, char f = 'g', int prec = 6)
quint16 qChecksum(const char *data, uint len)
quint16 qChecksum(const char *data, uint len, Qt::ChecksumType standard)
QByteArray qCompress(const uchar *data, int nbytes, int compressionLevel = -1)
QByteArray qUncompress(const uchar *data, int nbytes)
int qsnprintf(char *str, size_t n, const char *fmt, ...)
int qstrcmp(const char *str1, const char *str2)
char *qstrcpy(char *dst, const char *src)
char *qstrdup(const char *src)
int qstricmp(const char *str1, const char *str2)
uint qstrlen(const char *str)
char *qstrncpy(char *dst, const char *src, uint len)
int qstrnicmp(const char *str1, const char *str2, uint len)
int qvsnprintf(char *str, size_t n, const char *fmt, va_list ap)
bool operator!=(const int &a1, const int &a2)
QDataStream &operator<<(QDataStream &out, const QByteArray &ba)
bool operator==(const int &a1, const int &a2)
QDataStream &operator>>(QDataStream &in, QByteArray &ba)

Macros

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 stores 16-bit Unicode characters, making it easy to store non-ASCII/non-Latin-1 characters in your application. Furthermore, QString is used throughout in the Qt API. The two main cases where QByteArray is appropriate are when you need to store raw binary data, and when memory conservation is critical (e.g., with Qt for Embedded Linux).

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


  QByteArray ba("Hello");

Although the size() is 5, the byte array also maintains an extra '\0' character 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 performance reasons you don't want to take a deep copy of the character data, use QByteArray::fromRawData() instead.)

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


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

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


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

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

To extract many bytes at a time, use left(), right(), or mid().

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


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

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

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

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

If you want to obtain the length of the data up to and excluding the first '\0' character, 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 character data, 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 a raw data. This '\0' byte is automatically provided by QByteArray and is not counted in size().

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


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

The replace() and remove() functions' first two arguments are the position from which to start erasing and the number of bytes that should be erased.

When you append() data to a non-empty array, the array will be reallocated and the new data copied to it. You can avoid this behavior by calling reserve(), which preallocates a certain amount of memory. You can also call capacity() to find out how much memory QByteArray actually allocated. Data appended to an empty array is not copied.

A frequent requirement is to remove whitespace characters from a byte array ('\n', '\t', ' ', etc.). If you want to remove whitespace from both ends of a QByteArray, use trimmed(). If you want to remove whitespace from both ends and replace multiple consecutive whitespaces with a single space character within the byte array, use simplified().

If you want to find all occurrences of a particular character or substring 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 character or substring if they find it; otherwise, they return -1. For example, here's a typical loop that finds all occurrences of a particular substring:


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

If you simply want to check whether a QByteArray contains a particular character or substring, use contains(). If you want to find out how many times a particular character or substring 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 characters and is very fast, but is not what a human would expect. QString::localeAwareCompare() is a better choice for sorting user-interface strings.

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


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

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

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

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

Notes on Locale

Number-String Conversions

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

8-bit Character Comparisons

In QByteArray, the notion of uppercase and lowercase and of which character is greater than or less than another character is locale dependent. This affects functions that support a case insensitive option or that compare or lowercase or uppercase their arguments. Case insensitive operations and comparisons will be accurate if both strings contain only ASCII characters. (If $LC_CTYPE is set, most Unix systems do "the right thing".) Functions that this affects include contains(), indexOf(), lastIndexOf(), operator<(), operator<=(), operator>(), operator>=(), isLower(), isUpper(), toLower() and toUpper().

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

See also QString and QBitArray.

Member Type Documentation

enum QByteArray::Base64Option
flags QByteArray::Base64Options

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

ConstantValueDescription
QByteArray::Base64Encoding0(default) The regular Base64 alphabet, called simply "base64"
QByteArray::Base64UrlEncoding1An alternate alphabet, called "base64url", which replaces two characters in the alphabet to be more friendly to URLs.
QByteArray::KeepTrailingEquals0(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::OmitTrailingEquals2Omits adding the padding equal signs at the end of the encoded data.

QByteArray::fromBase64() ignores the KeepTrailingEquals and OmitTrailingEquals options and will not flag errors in case they are missing or if there are too many of them.

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.

typedef QByteArray::const_iterator

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

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

typedef QByteArray::const_reverse_iterator

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

This typedef was introduced in Qt 5.6.

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

typedef QByteArray::iterator

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

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

typedef QByteArray::reverse_iterator

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

This typedef was introduced in Qt 5.6.

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

Member Function Documentation

QByteArray::QByteArray(int size, char ch)

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

See also fill().

QByteArray::QByteArray(const char *data, int 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 nul-terminated string and its length is determined dynamically. The terminating nul-character is not considered part of the byte array.

QByteArray makes a deep copy of the string data.

See also fromRawData().

QByteArray &QByteArray::operator=(const QByteArray &other)

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

QByteArray &QByteArray::append(char ch)

This is an overloaded function.

Appends the character ch to this byte array.

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

This is an overloaded function.

Appends the string str to this byte array.

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

This function overloads append().

Appends the first len characters of the string str to this byte array and returns a reference to this byte array.

If len is negative, the length of the string 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(const QByteArray &ba)

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

Example:


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

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

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

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

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

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

void QByteArray::chop(int n)

Removes n bytes from the end of the byte array.

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

Example:


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

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

int QByteArray::count(const QByteArray &ba) const

Returns the number of (potentially overlapping) occurrences of byte array ba in this byte array.

See also contains() and indexOf().

int QByteArray::count(char ch) const

This is an overloaded function.

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

See also contains() and indexOf().

int QByteArray::count(const char *str) const

This is an overloaded function.

Returns the number of (potentially overlapping) occurrences of string str in the byte array.

bool QByteArray::endsWith(const QByteArray &ba) const

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

Example:


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

See also startsWith() and right().

bool QByteArray::endsWith(char ch) const

This is an overloaded function.

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

bool QByteArray::endsWith(const char *str) const

This is an overloaded function.

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

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

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

Example:


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

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

See also resize().

[static] QByteArray QByteArray::fromBase64(const QByteArray &base64)

Returns a decoded copy of the Base64 array base64. Input is not checked for validity; invalid characters in the input are skipped, enabling the decoding process to continue with subsequent characters.

For example:


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

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

See also toBase64().

[static] QByteArray QByteArray::fromBase64(const QByteArray &base64, QByteArray::Base64Options options)

This is an overloaded function.

Returns a decoded copy of the Base64 array base64, using the alphabet defined by options. Input is not checked for validity; invalid characters in the input are skipped, enabling the decoding process to continue with subsequent characters.

For example:


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

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

This function was introduced in Qt 5.2.

See also toBase64().

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

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

This function was introduced in Qt 5.3.

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

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

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

For example:


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

See also toHex().

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

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

This function was introduced in Qt 5.3.

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

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

Returns a decoded copy of the URI/URL-style percent-encoded input. The percent parameter allows you to replace the '%' character for another (for instance, '_' or '=').

For example:


  QByteArray text = QByteArray::fromPercentEncoding("Qt%20is%20great%33");
  text.data();            // returns "Qt is great!"

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

This function was introduced in Qt 4.4.

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

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

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

The data's bytes are not copied.

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

This function was introduced in Qt 5.3.

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

[static] QByteArray QByteArray::fromRawData(const char *data, int size)

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

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

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


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

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

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

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

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

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

The data's bytes are not copied.

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

This function was introduced in Qt 5.3.

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

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

This is an overloaded function.

Returns the index position of the first occurrence of the character ch in the byte array, searching forward from index position from. Returns -1 if ch could not be found.

Example:


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

See also lastIndexOf() and contains().

int QByteArray::indexOf(const QByteArray &ba, int from = 0) const

Returns the index position of the first occurrence of the byte array ba in this byte array, searching forward from index position from. Returns -1 if ba could not be found.

Example:


  QByteArray x("sticky question");
  QByteArray 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

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

QByteArray &QByteArray::insert(int i, char ch)

This is an overloaded function.

Inserts character ch at index position i in the byte array. If i is greater than size(), the array is first extended using resize().

QByteArray &QByteArray::insert(int i, const char *str)

This is an overloaded function.

Inserts the string str at position i in the byte array.

If i is greater than size(), the array is first extended using resize().

QByteArray &QByteArray::insert(int i, const char *str, int len)

This is an overloaded function.

Inserts len bytes of the string str at position i in the byte array.

If i is greater than size(), the array is first extended using resize().

This function was introduced in Qt 4.6.

QByteArray &QByteArray::insert(int i, const QByteArray &ba)

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

Example:


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

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

bool QByteArray::isLower() const

Returns true if this byte array contains only lowercase letters, otherwise returns false. The byte array is interpreted as a Latin-1 encoded string.

This function was introduced in Qt 5.12.

See also isUpper() and toLower().

bool QByteArray::isUpper() const

Returns true if this byte array contains only uppercase letters, otherwise returns false. The byte array is interpreted as a Latin-1 encoded string.

This function was introduced in Qt 5.12.

See also isLower() and toUpper().

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

This is an overloaded function.

Returns the index position of the last occurrence of character ch in the byte array, searching backward from index position from. If from is -1 (the default), the search starts at the last (size() - 1) byte. Returns -1 if ch could not be found.

Example:


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

See also indexOf() and contains().

QByteArray QByteArray::left(int len) const

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

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

Example:


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

See also startsWith(), right(), mid(), chopped(), chop(), and truncate().

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

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

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

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

Example:


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

See also rightJustified().

QByteArray QByteArray::mid(int pos, int len = -1) const

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

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.

Example:


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

See also left(), right(), chopped(), chop(), and truncate().

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

Returns a byte array containing the string equivalent of the number n to base base (10 by default). The base can be any value between 2 and 36.

Example:


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

Note: The format of the number is not localized; the default C locale is used irrespective of the user's locale.

See also setNum() and toInt().

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

This is an overloaded function.

See also toUInt().

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

This is an overloaded function.

See also toLongLong().

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

This is an overloaded function.

See also toULongLong().

[static] QByteArray QByteArray::number(double n, char f = 'g', int prec = 6)

This is an overloaded function.

Returns a byte array that contains the printed value of n, formatted in format f with precision prec.

Argument n is formatted according to the f format specified, which is g by default, and can be any of the following:

FormatMeaning
eformat as [-]9.9e[+|-]999
Eformat as [-]9.9E[+|-]999
fformat as [-]9.9
guse e or f format, whichever is the most concise
Guse E or f format, whichever is the most concise

With 'e', 'E', and 'f', prec is the number of digits after the decimal point. With 'g' and 'G', prec is the maximum number of significant digits (trailing zeroes are omitted).


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

Note: The format of the number is not localized; the default C locale is used irrespective of the user's locale.

See also toDouble().

QByteArray &QByteArray::prepend(char ch)

This is an overloaded function.

Prepends the character ch to this byte array.

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

This is an overloaded function.

Prepends the string str to this byte array.

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

This is an overloaded function.

Prepends len bytes of the string str to this byte array.

This function was introduced in Qt 4.6.

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

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

Example:


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

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

Note: QByteArray is an implicitly shared class. Consequently, if you prepend 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 prepended to is not empty, a deep copy of the data is performed, taking linear time.

See also append() and insert().

QByteArray &QByteArray::remove(int pos, int len)

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

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

Example:


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

See also insert() and replace().

QByteArray QByteArray::repeated(int times) const

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

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

Example:


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

This function was introduced in Qt 4.5.

QByteArray &QByteArray::replace(int pos, int len, const QByteArray &after)

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

Example:


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

See also insert() and remove().

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

This is an overloaded function.

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

QByteArray &QByteArray::replace(const QByteArray &before, const QByteArray &after)

This is an overloaded function.

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

Example:


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

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

This is an overloaded function.

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

void QByteArray::resize(int 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 are removed from the end.

See also size() and truncate().

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

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

Example:


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

See also endsWith(), left(), mid(), chopped(), chop(), and truncate().

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

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

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

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

Example:


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

See also leftJustified().

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

This is an overloaded function.

See also toLongLong().

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

This is an overloaded function.

See also toULongLong().

QByteArray &QByteArray::setNum(double n, char f = 'g', int prec = 6)

This is an overloaded function.

Sets the byte array to the printed value of n, formatted in format f with precision prec, and returns a reference to the byte array.

The format f can be any of the following:

FormatMeaning
eformat as [-]9.9e[+|-]999
Eformat as [-]9.9E[+|-]999
fformat as [-]9.9
guse e or f format, whichever is the most concise
Guse E or f format, whichever is the most concise

With 'e', 'E', and 'f', prec is the number of digits after the decimal point. With 'g' and 'G', prec is the maximum number of significant digits (trailing zeroes are omitted).

Note: The format of the number is not localized; the default C locale is used irrespective of the user's locale.

See also toDouble().

QByteArray &QByteArray::setRawData(const char *data, uint 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.

This function was introduced in Qt 4.7.

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

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.

bool QByteArray::startsWith(const QByteArray &ba) const

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

Example:


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

See also endsWith() and left().

bool QByteArray::startsWith(char ch) const

This is an overloaded function.

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

bool QByteArray::startsWith(const char *str) const

This is an overloaded function.

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

QByteArray QByteArray::toBase64() const

Returns a copy of the byte array, encoded as Base64.


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

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

See also fromBase64().

QByteArray QByteArray::toBase64(QByteArray::Base64Options options) const

This is an overloaded function.

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


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

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

This function was introduced in Qt 5.2.

See also fromBase64().

CFDataRef QByteArray::toCFData() const

Creates a CFData from a QByteArray. The caller owns the CFData object and is responsible for releasing it.

This function was introduced in Qt 5.3.

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

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

Returns the byte array converted to a double value.

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

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


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

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

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

Note: The conversion of the number is performed in the default C locale, irrespective of the user's locale.

This function ignores leading and trailing whitespace.

See also number().

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

Returns the byte array converted to a float value.

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

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


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

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

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

Note: The conversion of the number is performed in the default C locale, irrespective of the user's locale.

This function ignores leading and trailing whitespace.

See also number().

QByteArray QByteArray::toHex() const

Returns a hex encoded copy of the byte array. The hex encoding uses the numbers 0-9 and the letters a-f.

See also fromHex().

QByteArray QByteArray::toHex(char separator) const

This is an overloaded function.

Returns a hex encoded copy of the byte array. The hex encoding uses the numbers 0-9 and the letters a-f.

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

Example:


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

This function was introduced in Qt 5.9.

See also fromHex().

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

Returns the byte array converted to an int using base base, which is 10 by default and must be between 2 and 36, or 0.

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; if it begins with "0", it is assumed to be octal; otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

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


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

Note: The conversion of the number is performed in the default C locale, irrespective of the user's locale.

See also number().

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

Returns the byte array converted to a long int using base base, which is 10 by default and must be between 2 and 36, or 0.

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; if it begins with "0", it is assumed to be octal; otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

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


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

Note: The conversion of the number is performed in the default C locale, irrespective of the user's locale.

This function was introduced in Qt 4.1.

See also number().

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

Returns the byte array converted to a long long using base base, which is 10 by default and must be between 2 and 36, or 0.

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; if it begins with "0", it is assumed to be octal; otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

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

Note: The conversion of the number is performed in the default C locale, irrespective of the user's locale.

See also number().

NSData *QByteArray::toNSData() const

Creates a NSData from a QByteArray. The NSData object is autoreleased.

This function was introduced in Qt 5.3.

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

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

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

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

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

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

Example:


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

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

This function was introduced in Qt 4.4.

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

CFDataRef QByteArray::toRawCFData() const

Constructs a CFData that uses the bytes of the QByteArray.

The QByteArray's bytes are not copied.

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

This function was introduced in Qt 5.3.

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

NSData *QByteArray::toRawNSData() const

Constructs a NSData that uses the bytes of the QByteArray.

The QByteArray's bytes are not copied.

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

This function was introduced in Qt 5.3.

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

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

Returns the byte array converted to a short using base base, which is 10 by default and must be between 2 and 36, or 0.

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; if it begins with "0", it is assumed to be octal; otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

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

Note: The conversion of the number is performed in the default C locale, irrespective of the user's locale.

See also number().

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

Returns the byte array converted to an unsigned int using base base, which is 10 by default and must be between 2 and 36, or 0.

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; if it begins with "0", it is assumed to be octal; otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

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

Note: The conversion of the number is performed in the default C locale, irrespective of the user's locale.

See also number().

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

Returns the byte array converted to an unsigned long int using base base, which is 10 by default and must be between 2 and 36, or 0.

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; if it begins with "0", it is assumed to be octal; otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

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

Note: The conversion of the number is performed in the default C locale, irrespective of the user's locale.

This function was introduced in Qt 4.1.

See also number().

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

Returns the byte array converted to an unsigned long long using base base, which is 10 by default and must be between 2 and 36, or 0.

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; if it begins with "0", it is assumed to be octal; otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

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

Note: The conversion of the number is performed in the default C locale, irrespective of the user's locale.

See also number().

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

Returns the byte array converted to an unsigned short using base base, which is 10 by default and must be between 2 and 36, or 0.

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; if it begins with "0", it is assumed to be octal; otherwise it is assumed to be decimal.

Returns 0 if the conversion fails.

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

Note: The conversion of the number is performed in the default C locale, irrespective of the user's locale.

See also number().

void QByteArray::truncate(int pos)

Truncates the byte array at index position pos.

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

Example:


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

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

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

This is an overloaded function.

Assigns str to this byte array.

Related Non-Members

quint16 QByteArray::qChecksum(const char *data, uint len)

Returns the CRC-16 checksum of the first len bytes of data.

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

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

quint16 QByteArray::qChecksum(const char *data, uint len, Qt::ChecksumType standard)

Returns the CRC-16 checksum of the first len bytes of data.

The checksum is independent of the byte order (endianness) and will be calculated accorded to the algorithm published in standard.

Note: 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 QByteArray::qCompress(const uchar *data, int 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 QByteArray::qUncompress(const uchar *data, int nbytes)

This is an overloaded function.

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

int QByteArray::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.

Warning: 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.

See also qvsnprintf() and QString::asprintf().

int QByteArray::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.

Special case 1: Returns 0 if str1 and str2 are both nullptr.

Special case 2: Returns an arbitrary non-zero value if str1 is nullptr or str2 is nullptr (but not both).

See also qstrncmp(), qstricmp(), qstrnicmp(), 8-bit Character Comparisons, and QByteArray::compare().

char *QByteArray::qstrcpy(char *dst, const char *src)

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

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

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

See also qstrncpy().

char *QByteArray::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 QByteArray::qstricmp(const char *str1, const char *str2)

A safe stricmp() function.

Compares str1 and str2 ignoring the case of the characters. The encoding of the strings is assumed to be Latin-1.

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.

Special case 1: Returns 0 if str1 and str2 are both nullptr.

Special case 2: Returns a random non-zero value if str1 is nullptr or str2 is nullptr (but not both).

See also qstrcmp(), qstrncmp(), qstrnicmp(), 8-bit Character Comparisons, and QByteArray::compare().

uint QByteArray::qstrlen(const char *str)

A safe strlen() function.

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

See also qstrnlen().

char *QByteArray::qstrncpy(char *dst, const char *src, uint 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.

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

Note: When compiling with Visual C++ compiler version 14.00 (Visual C++ 2005) or later, internally the function strncpy_s will be used.

See also qstrcpy().

int QByteArray::qstrnicmp(const char *str1, const char *str2, uint len)

A safe strnicmp() function.

Compares at most len bytes of str1 and str2 ignoring the case of the characters. The encoding of the strings is assumed to be Latin-1.

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.

Special case 1: Returns 0 if str1 and str2 are both nullptr.

Special case 2: Returns a random non-zero value if str1 is nullptr or str2 is nullptr (but not both).

See also qstrcmp(), qstrncmp(), qstricmp(), 8-bit Character Comparisons, and QByteArray::compare().

int QByteArray::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.

Warning: 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.

See also qsnprintf() and QString::asprintf().

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

Returns false if v1 and v2 are equal; otherwise returns true.

Warning: To make this function work with a custom type registered with qRegisterMetaType(), its comparison operator must be registered using QMetaType::registerComparators().

This function was introduced in Qt 5.0.

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

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

See also Serializing Qt Data Types.

bool QByteArray::operator==(const int &a1, const int &a2)

Returns true if v1 and v2 are equal; otherwise returns false.

If v1 and v2 have the same type(), the type's equality operator is used for comparison. If not, it is attempted to convert() v2 to the same type as v1. See canConvert() for a list of possible conversions.

The result of the function is not affected by the result of QVariant::isNull, which means that two values can be equal even if one of them is null and another is not.

Warning: To make this function work with a custom type registered with qRegisterMetaType(), its comparison operator must be registered using QMetaType::registerComparators().

This function was introduced in Qt 5.0.

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

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

See also Serializing Qt Data Types.

Macro Documentation

QByteArray::QByteArrayLiteral(ba)

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

For instance:


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

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

See also QStringLiteral.

QByteArray::QT_NO_CAST_FROM_BYTEARRAY

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

See also QT_NO_CAST_TO_ASCII and QT_NO_CAST_FROM_ASCII.