QMemArray(3qt)

📦 version 3.3.8b, in fedora 43, fedora 44

💖 QMemArray 💖

okay bestie, this is the manual page for QMemArray(3qt) — she's a template class that provides arrays of simple types, and yes she's been here since forever, and yes she still slays ✨

✨ NAME ✨

QMemArray — Template class that provides arrays of simple types

🦋 SYNOPSIS 🦋

Okay so first things first: all the functions in this class are reentrant when Qt is built with thread support. </p> (yes that stray tag is literally in the original, we don't gatekeep 🙈)

#include <qmemarray.h>

Inherited by QByteArray and QPointArray. Passing the genes down fr fr 💅

🌸 Public Members 🌸

typedef type * Iterator
typedef const type * ConstIterator
QMemArray ()
QMemArray ( int size )
QMemArray ( const QMemArray<type> & a )
~QMemArray ()
QMemArray<type> & operator= ( const QMemArray<type> & a )
type * data () const
uint nrefs () const
uint size () const
uint count () const
bool isEmpty () const
bool isNull () const
bool resize ( uint size )
bool resize ( uint size, Optimization optim )
bool truncate ( uint pos )
bool fill ( const type & v, int size = -1 )
virtual void detach ()
QMemArray<type> copy () const
QMemArray<type> & assign ( const QMemArray<type> & a )
QMemArray<type> & assign ( const type * data, uint size )
QMemArray<type> & duplicate ( const QMemArray<type> & a )
QMemArray<type> & duplicate ( const type * data, uint size )
QMemArray<type> & setRawData ( const type * data, uint size )
void resetRawData ( const type * data, uint size )
int find ( const type & v, uint index = 0 ) const
int contains ( const type & v ) const
void sort ()
int bsearch ( const type & v ) const
type & operator[] ( int index ) const
type & at ( uint index ) const
operator const type * () const
bool operator== ( const QMemArray<type> & a ) const
bool operator!= ( const QMemArray<type> & a ) const
Iterator begin ()
Iterator end ()
ConstIterator begin () const
ConstIterator end () const

🎀 Protected Members 🎀

QMemArray ( int, int )

Q_UINT16 qChecksum ( const char * data, uint len )
QDataStream & operator<< ( QDataStream & s, const QByteArray & a )
QDataStream & operator>> ( QDataStream & s, QByteArray & a )

💅 DESCRIPTION 💅

The QMemArray class is a template class that provides arrays of simple types. That's the whole vibe. Simple types only, no drama 👑

QMemArray is implemented as a template class. Define a template instance QMemArray<X> to create an array that contains X items.

Now, the tea: QMemArray stores the array elements directly in the array. She can only deal with simple types — like, C++ types, structs, and classes that have no constructors, no destructors, and no virtual functions. QMemArray uses bitwise operations to copy and compare array elements. Bitwise. She's not reading your constructors, she's just copying bytes, okay? 😭

The QPtrVector collection class is also a kind of array. Like most collection classes, it uses pointers to the contained items. Different energy, still valid 💜

QMemArray uses explicit sharing with a reference count. And bestie, listen — if more than one array shares common data and one of the arrays is modified, all the arrays are modified. That's not a bug, that's the design, and it will humble you if you forget it 🙈

The benefit of sharing is that a program does not need to duplicate data when it is not required, which results in lower memory use and less copying of data. So like, efficient. Iconic. Lowkey genius ✨

An alternative to QMemArray is QValueVector. The QValueVector class also provides an array of objects, but can deal with objects that have constructors (specifically a copy constructor and a default constructor). QValueVector provides an STL-compatible syntax and is implicitly shared. So if you need actual constructors, that's your girl 🌸

Example:

#include <qmemarray.h>
#include <stdio.h>
QMemArray<int> fib( int num ) // returns fibonacci array
{
    Q_ASSERT( num > 2 );
    QMemArray<int> f( num ); // array of ints
    f[0] = f[1] = 1;
    for ( int i = 2; i < num; i++ )
        f[i] = f[i-1] + f[i-2];
    return f;
}
int main()
{
    QMemArray<int> a = fib( 6 ); // get first 6 fibonaccis
    for ( int i = 0; i < a.size(); i++ )
        qDebug( "%d: %d", i, a[i] );
    qDebug( "1 is found %d times", a.contains(1) );
    qDebug( "5 is found at index %d", a.find(5) );
    return 0;
}

Program output:

0: 1
1: 1
2: 2
3: 3
4: 5
5: 8
1 is found 2 times
5 is found at index 4

Okay now the important warning, no cap. Note concerning the use of QMemArray for manipulating structs or classes: Compilers will often pad the size of structs of odd sizes up to the nearest word boundary. This will then be the size QMemArray will use for its bitwise element comparisons. Because the remaining bytes will typically be uninitialized, this can cause find() etc. to fail to find the element. Example:

// MyStruct may be padded to 4 or 8 bytes
struct MyStruct
{
    short i; // 2 bytes
    char c;  // 1 byte
};
QMemArray<MyStruct> a(1);
a[0].i = 5;
a[0].c = 't';
MyStruct x;
x.i = '5';
x.c = 't';
int i = a.find( x ); // may return -1 if the pad bytes differ

To work around this, make sure that you use a struct where sizeof() returns the same as the sum of the sizes of the members either by changing the types of the struct members or by adding dummy members. Dummy members are literally the padding's therapist 🫶

QMemArray data can be traversed by iterators (see begin() and end()). The number of items is returned by count(). The array can be resized with resize() and filled using fill().

You can make a shallow copy of the array with assign() (or operator=()) and a deep copy with duplicate().

Search for values in the array with find() and contains(). For sorted arrays (see sort()) you can search using bsearch().

You can set the data directly using setRawData() and resetRawData(), although this requires care. Like, care care. Not vibes-only care. Actual care 😭

See also Shared Classes and Non-GUI Classes.

🧚 Member Type Documentation 🧚

`QMemArray::ConstIterator`

A const QMemArray iterator.

`QMemArray::Iterator`

A QMemArray iterator.

📚 MEMBER FUNCTION DOCUMENTATION 📚

`QMemArray::QMemArray ( int, int )` [protected]

Constructs an array without allocating array space. The arguments should be (0, 0). Use at your own risk. That's it. That's the documentation. She's telling you to be careful and she means it 💀

`QMemArray::QMemArray ()`

Constructs a null array.

`QMemArray::QMemArray ( int size )`

Constructs an array with room for size elements. Makes a null array if size == 0.

The elements are left uninitialized. So don't come crying when they're garbage, bestie, that's the deal ✨

`QMemArray::QMemArray ( const QMemArray<type> & a )`

Constructs a shallow copy of a.

`QMemArray::~QMemArray ()`

Dereferences the array data and deletes it if this was the last reference. Last one out, turns off the lights 💅

`QMemArray<type> & QMemArray::assign ( const QMemArray<type> & a )`

Shallow copy. Dereferences the current array and references the data contained in a instead. Returns a reference to this array.

`QMemArray<type> & QMemArray::assign ( const type * data, uint size )`

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Shallow copy. Dereferences the current array and references the array data data, which contains size elements. Returns a reference to this array.

Do not delete data later; QMemArray will call free() on it at the right time.

`type & QMemArray::at ( uint index ) const`

Returns a reference to the element at position index in the array.

This can be used to both read and set an element. Two-for-one, we love a multitasker 💖

`Iterator QMemArray::begin ()`

Returns an iterator pointing at the beginning of this array. This iterator can be used in the same way as the iterators of QValueList and QMap, for example.

`ConstIterator QMemArray::begin () const`

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Returns a const iterator pointing at the beginning of this array. This iterator can be used in the same way as the iterators of QValueList and QMap, for example.

`int QMemArray::bsearch ( const type & v ) const`

In a sorted array (as sorted by sort()), finds the first occurrence of v by using a binary search. For a sorted array this is generally much faster than find(), which does a linear search.

Returns the position of v, or -1 if v could not be found.

`int QMemArray::contains ( const type & v ) const`

Returns the number of times v occurs in the array.

`QMemArray<type> QMemArray::copy () const`

Returns a deep copy of this array.

`uint QMemArray::count () const`

Returns the same as size().

`type * QMemArray::data () const`

Returns a pointer to the actual array data.

The array is a null array if data() == 0 (null pointer).

`void QMemArray::detach ()` [virtual]

Detaches this array from shared array data; i.e. it makes a private, deep copy of the data.

Copying will be performed only if the reference count is greater than one.

`QMemArray<type> & QMemArray::duplicate ( const QMemArray<type> & a )`

Deep copy. Dereferences the current array and obtains a copy of the data contained in a instead. Returns a reference to this array.

`QMemArray<type> & QMemArray::duplicate ( const type * data, uint size )`

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Deep copy. Dereferences the current array and obtains a copy of the array data data instead. Returns a reference to this array. The size of the array is given by size.

`Iterator QMemArray::end ()`

Returns an iterator pointing behind the last element of this array. This iterator can be used in the same way as the iterators of QValueList and QMap, for example.

`ConstIterator QMemArray::end () const`

This is an overloaded member function, provided for convenience. It behaves essentially like the above function.

Returns a const iterator pointing behind the last element of this array. This iterator can be used in the same way as the iterators of QValueList and QMap, for example.

`bool QMemArray::fill ( const type & v, int size = -1 )`

Fills the array with the value v. If size is specified as different from -1, then the array will be resized before being filled.

Returns TRUE if successful, i.e. if size is -1, or size is != -1 and the memory can be allocated; otherwise returns FALSE.

`int QMemArray::find ( const type & v, uint index = 0 ) const`

Finds the first occurrence of v, starting at position index.

Returns the position of v, or -1 if v could not be found.

`bool QMemArray::isEmpty () const`

Returns TRUE if the array is empty; otherwise returns FALSE.

isEmpty() is equivalent to isNull() for QMemArray (unlike QString). Yes, she's built different. Noted. Recorded. Iconic 🌈

`bool QMemArray::isNull () const`

Returns TRUE if the array is null, and FALSE if it's not, bestie. That's it, that's the whole job. 💅

A null array means size() == 0 and data() == 0. Both. Like, empty AND pointing at nothing. The full void vibe. 🕳️

`uint QMemArray::nrefs () const`

Hands you back the reference count for the shared array data — as in, how many little besties are currently holding hands with this same chunk of memory. 🫶

Fun fact: this reference count is always greater than zero. Never zero. Not once. ✨

`QMemArray::operator const type * () const`

Cast operator, queen. Returns a pointer to the array. 👑

`bool QMemArray::operator!= ( const QMemArray<type> & a ) const`

Returns TRUE if this array is different from a, otherwise FALSE. Not me comparing arrays with my whole chest. 💀

The two arrays are compared bitwise, jsyk.

`QMemArray<type> & QMemArray::operator= ( const QMemArray<type> & a )`

Assigns a shallow copy of a to this array and returns a reference to this array. 🎀

Lowkey it's exactly the same as assign( a ). Like, identical. No notes.

`bool QMemArray::operator== ( const QMemArray<type> & a ) const`

Returns TRUE if this array is equal to a, otherwise FALSE. Twin energy. 👯

The two arrays are compared bitwise.

`type & QMemArray::operator[] ( int index ) const`

Gives you a reference to the element sitting at position index in the array. 🔍

You can use this to read an element and to set one — it's giving both-directions. Equivalent to at().

`void QMemArray::resetRawData ( const type * data, uint size )`

Okay so, remember that raw data you set up with setRawData()? This is the part where you let it go. 🕊️ It removes the internal references to it, which means QMemArray has no access to that data anymore — so you're free to do literally whatever you want with it, bestie, it's yours. ✨

You can now use the QMemArray without affecting the original data, for example by calling setRawData() with a pointer to some other data.

The arguments must be the data and length, size, that were passed to setRawData(). That's for consistency checking — it's checking your work, respectfully. 📝

`bool QMemArray::resize ( uint size, Optimization optim )`

Resizes (expands or shrinks) the array to size elements. The array becomes a null array if size == 0. Poof. Gone. 🫥

Returns TRUE if successful, or FALSE if the memory cannot be allocated.

Heads up: new elements are not initialized. Not even a little. 🙈

optim is either QGArray::MemOptim (the default) or QGArray::SpeedOptim.

Note: By default, SpeedOptim is not available for general use since it is only available if Qt is built in a particular configuration. So don't come for me if it's not there. 😭

`bool QMemArray::resize ( uint size )`

This is an overloaded member function, provided for convenience. It behaves essentially like the above function. Same energy, fewer arguments. 💅

Resizes (expands or shrinks) the array to size elements. The array becomes a null array if size == 0.

Returns TRUE if successful, i.e. if the memory can be allocated; otherwise returns FALSE.

And again, for the people in the back: new elements are not initialized. 🫠

`QMemArray<type> & QMemArray::setRawData ( const type * data, uint size )`

Sets raw data and returns a reference to the array. 🎯

Dereferences the current array and sets the new array data to data and the new array size to size. And listen — do not attempt to resize or re-assign the array data when raw data has been set. Do not. I'm serious. 😤 Call resetRawData(data, size) to reset the array.

Setting raw data is useful because it sets QMemArray data without allocating memory or copying data. Iconic, efficient, slay. ✨

Example I (intended use):

static char bindata[] = { 231, 1, 44, ... };
QByteArray  a;
a.setRawData( bindata, sizeof(bindata) );   // a points to bindata
QDataStream s( a, IO_ReadOnly );            // open on a's data
s >> <something>;                           // read raw bindata
a.resetRawData( bindata, sizeof(bindata) ); // finished

Example II (you don't want to do this):

static char bindata[] = { 231, 1, 44, ... };
QByteArray  a, b;
a.setRawData( bindata, sizeof(bindata) );   // a points to bindata
a.resize( 8 );                              // will crash
b = a;                                      // will crash
a[2] = 123;                                 // might crash
// forget to resetRawData: will crash

Like, look at Example II and tell me that's not a horror movie. 💀💀💀

Warning: If you do not call resetRawData(), QMemArray will attempt to deallocate or reallocate the raw data, which might not be too good. Be careful. Fr fr, be careful. 🙏

`uint QMemArray::size () const`

Returns the size of the array (the maximum number of elements). 📏

The array is a null array if size() == 0.

`void QMemArray::sort ()`

Sorts the array elements in ascending order, using bitwise comparison (memcmp()). 🔤✨

`bool QMemArray::truncate ( uint pos )`

Truncates the array at position pos. Snip snip. ✂️

Returns TRUE if successful, i.e. if the memory can be allocated; otherwise returns FALSE.

Equivalent to resize(pos).

`QDataStream & operator<< ( QDataStream & s, const QByteArray & a )`

Writes byte array a to the stream s and returns a reference to the stream. Out it goes, bestie. 📤

See also Format of the QDataStream operators.

`QDataStream & operator>> ( QDataStream & s, QByteArray & a )`

Reads a byte array into a from the stream s and returns a reference to the stream. In it comes. 📥

See also Format of the QDataStream operators.

`Q_UINT16 qChecksum ( const char * data, uint len )`

Returns the CRC-16 checksum of len bytes starting at data. 🧮

The checksum is independent of the byte order (endianness). So no matter which way your bytes are facing, same answer. Equal opportunity checksum. 💜

👀 SEE ALSO 👀

©️ COPYRIGHT

✍️ AUTHOR

Generated automatically from the source code. No human wrote this one, bestie, the machine did. 🤖✨

🐛 BUGS

If you find a bug in Qt, please report it as described in http://doc.trolltech.com/bughowto.html. Good bug reports help us to help you. Thank you. 🫶

The definitive Qt documentation is provided in HTML format; it is located at $QTDIR/doc/html and can be read using Qt Assistant or with a web browser. This man page is provided as a convenience for those users who prefer man pages, although this format is not officially supported by Trolltech.

If you find errors in this manual page, please report them to qt-bugs@trolltech.com. Please include the name of the manual page (qmemarray.3qt) and the Qt version (3.3.8). Help a girl out. 🙏💖

And that's a wrap on QMemArray(3qt), bestie! 🎀 This one came to you courtesy of Trolltech AS, dated 2 February 2007, and it's the Qt 3.3.8 era — vintage, honestly. Go forth and manage your memory arrays responsibly, and remember: call resetRawData(). Periodt. 💅✨

📦 where this page comes from

fedora 43: qt3-devel-docs 3.3.8b-102.fc43 · QPL-1.0 OR GPL-2.0-only OR GPL-3.0-only
fedora 44: qt3-devel-docs 3.3.8b-103.fc44 · QPL-1.0 OR GPL-2.0-only OR GPL-3.0-only
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-10-14: a language model's rewrite of the original, under its terms

QMemArray(3qt)

💖 QMemArray 💖

✨ NAME ✨

🦋 SYNOPSIS 🦋

🌸 Public Members 🌸

🎀 Protected Members 🎀

🌈 RELATED FUNCTION DOCUMENTATION 🌈

💅 DESCRIPTION 💅

🧚 Member Type Documentation 🧚

QMemArray::ConstIterator

QMemArray::Iterator

📚 MEMBER FUNCTION DOCUMENTATION 📚

QMemArray::QMemArray ( int, int ) [protected]

QMemArray::QMemArray ()

QMemArray::QMemArray ( int size )

QMemArray::QMemArray ( const QMemArray<type> & a )

QMemArray::~QMemArray ()

QMemArray<type> & QMemArray::assign ( const QMemArray<type> & a )

QMemArray<type> & QMemArray::assign ( const type * data, uint size )

type & QMemArray::at ( uint index ) const

Iterator QMemArray::begin ()

ConstIterator QMemArray::begin () const

int QMemArray::bsearch ( const type & v ) const

int QMemArray::contains ( const type & v ) const

QMemArray<type> QMemArray::copy () const

uint QMemArray::count () const

type * QMemArray::data () const

void QMemArray::detach () [virtual]

QMemArray<type> & QMemArray::duplicate ( const QMemArray<type> & a )

QMemArray<type> & QMemArray::duplicate ( const type * data, uint size )

Iterator QMemArray::end ()

ConstIterator QMemArray::end () const

bool QMemArray::fill ( const type & v, int size = -1 )

int QMemArray::find ( const type & v, uint index = 0 ) const

bool QMemArray::isEmpty () const

bool QMemArray::isNull () const

uint QMemArray::nrefs () const

QMemArray::operator const type * () const

bool QMemArray::operator!= ( const QMemArray<type> & a ) const

QMemArray<type> & QMemArray::operator= ( const QMemArray<type> & a )

bool QMemArray::operator== ( const QMemArray<type> & a ) const

type & QMemArray::operator[] ( int index ) const

void QMemArray::resetRawData ( const type * data, uint size )

bool QMemArray::resize ( uint size, Optimization optim )

bool QMemArray::resize ( uint size )

QMemArray<type> & QMemArray::setRawData ( const type * data, uint size )

uint QMemArray::size () const

void QMemArray::sort ()

bool QMemArray::truncate ( uint pos )

🌈 RELATED FUNCTION DOCUMENTATION 🌈

QDataStream & operator<< ( QDataStream & s, const QByteArray & a )

QDataStream & operator>> ( QDataStream & s, QByteArray & a )

Q_UINT16 qChecksum ( const char * data, uint len )

👀 SEE ALSO 👀

©️ COPYRIGHT

✍️ AUTHOR

🐛 BUGS

`QMemArray::ConstIterator`

`QMemArray::Iterator`

`QMemArray::QMemArray ( int, int )` [protected]

`QMemArray::QMemArray ()`

`QMemArray::QMemArray ( int size )`

`QMemArray::QMemArray ( const QMemArray<type> & a )`

`QMemArray::~QMemArray ()`

`QMemArray<type> & QMemArray::assign ( const QMemArray<type> & a )`

`QMemArray<type> & QMemArray::assign ( const type * data, uint size )`

`type & QMemArray::at ( uint index ) const`

`Iterator QMemArray::begin ()`

`ConstIterator QMemArray::begin () const`

`int QMemArray::bsearch ( const type & v ) const`

`int QMemArray::contains ( const type & v ) const`

`QMemArray<type> QMemArray::copy () const`

`uint QMemArray::count () const`

`type * QMemArray::data () const`

`void QMemArray::detach ()` [virtual]

`QMemArray<type> & QMemArray::duplicate ( const QMemArray<type> & a )`

`QMemArray<type> & QMemArray::duplicate ( const type * data, uint size )`

`Iterator QMemArray::end ()`

`ConstIterator QMemArray::end () const`

`bool QMemArray::fill ( const type & v, int size = -1 )`

`int QMemArray::find ( const type & v, uint index = 0 ) const`

`bool QMemArray::isEmpty () const`

`bool QMemArray::isNull () const`

`uint QMemArray::nrefs () const`

`QMemArray::operator const type * () const`

`bool QMemArray::operator!= ( const QMemArray<type> & a ) const`

`QMemArray<type> & QMemArray::operator= ( const QMemArray<type> & a )`

`bool QMemArray::operator== ( const QMemArray<type> & a ) const`

`type & QMemArray::operator[] ( int index ) const`

`void QMemArray::resetRawData ( const type * data, uint size )`

`bool QMemArray::resize ( uint size, Optimization optim )`

`bool QMemArray::resize ( uint size )`

`QMemArray<type> & QMemArray::setRawData ( const type * data, uint size )`

`uint QMemArray::size () const`

`void QMemArray::sort ()`

`bool QMemArray::truncate ( uint pos )`

`QDataStream & operator<< ( QDataStream & s, const QByteArray & a )`

`QDataStream & operator>> ( QDataStream & s, QByteArray & a )`

`Q_UINT16 qChecksum ( const char * data, uint len )`