/**************************************************************************** ** ** QMemArray class documentation ** ** Copyright (C) 1992-2008 Trolltech ASA. 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Licensees holding valid Qt ** Commercial licenses may use this file in accordance with the Qt ** Commercial License Agreement provided with the Software. ** ** This file is provided "AS IS" with NO WARRANTY OF ANY KIND, ** INCLUDING THE WARRANTIES OF DESIGN, MERCHANTABILITY AND FITNESS FOR ** A PARTICULAR PURPOSE. Trolltech reserves all rights not granted ** herein. ** **********************************************************************/ /***************************************************************************** QMemArray documentation *****************************************************************************/ /*! \class QMemArray qmemarray.h \reentrant \brief The QMemArray class is a template class that provides arrays of simple types. \ingroup tools QMemArray is implemented as a template class. Define a template instance QMemArray\ to create an array that contains X items. QMemArray stores the array elements directly in the array. It can only deal with simple types (i.e. C++ types, structs, and classes that have no constructors, destructors, or virtual functions). QMemArray uses bitwise operations to copy and compare array elements. The QPtrVector collection class is also a kind of array. Like most \link collection.html collection classes\endlink, it uses pointers to the contained items. QMemArray uses \link shclass.html explicit sharing\endlink with a reference count. If more than one array shares common data and one of the arrays is modified, all the arrays are modified. 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. 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 \link shclass.html implicitly shared\endlink. Example: \code #include #include QMemArray fib( int num ) // returns fibonacci array { Q_ASSERT( num > 2 ); QMemArray 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 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; } \endcode Program output: \code 0: 1 1: 1 2: 2 3: 3 4: 5 5: 8 1 is found 2 times 5 is found at index 4 \endcode 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: \code // MyStruct may be padded to 4 or 8 bytes struct MyStruct { short i; // 2 bytes char c; // 1 byte }; QMemArray 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 \endcode 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. 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. \sa \link shclass.html Shared Classes\endlink */ /*! \enum QMemArray::Iterator A QMemArray iterator. \sa begin() end() */ /*! \enum QMemArray::ConstIterator A const QMemArray iterator. \sa begin() end() */ /*! \enum QMemArray::ValueType \internal */ /*! \fn QMemArray::QMemArray() Constructs a null array. \sa isNull() */ /*! \fn QMemArray::QMemArray( int size ) Constructs an array with room for \a size elements. Makes a null array if \a size == 0. The elements are left uninitialized. \sa resize(), isNull() */ /*! \fn QMemArray::QMemArray( const QMemArray &a ) Constructs a shallow copy of \a a. \sa assign() */ /*! \fn QMemArray::QMemArray( int, int ) Constructs an array \e{without allocating} array space. The arguments should be (0, 0). Use at your own risk. */ /*! \fn QMemArray::~QMemArray() Dereferences the array data and deletes it if this was the last reference. */ /*! \fn QMemArray &QMemArray::operator=( const QMemArray &a ) Assigns a shallow copy of \a a to this array and returns a reference to this array. Equivalent to assign( a ). */ /*! \fn type *QMemArray::data() const Returns a pointer to the actual array data. The array is a null array if data() == 0 (null pointer). \sa isNull() */ /*! \fn uint QMemArray::nrefs() const Returns the reference count for the shared array data. This reference count is always greater than zero. */ /*! \fn uint QMemArray::size() const Returns the size of the array (maximum number of elements). The array is a null array if size() == 0. \sa isNull(), resize() */ /*! \fn uint QMemArray::count() const Returns the same as size(). \sa size() */ /*! \fn bool QMemArray::isEmpty() const Returns TRUE if the array is empty; otherwise returns FALSE. isEmpty() is equivalent to isNull() for QMemArray (unlike QString). */ /*! \fn bool QMemArray::isNull() const Returns TRUE if the array is null; otherwise returns FALSE. A null array has size() == 0 and data() == 0. */ /*! \fn bool QMemArray::resize( uint size, Optimization optim ) Resizes (expands or shrinks) the array to \a size elements. The array becomes a null array if \a size == 0. Returns TRUE if successful, or FALSE if the memory cannot be allocated. New elements are not initialized. \a optim is either \c QGArray::MemOptim (the default) or \c QGArray::SpeedOptim. Note: By default, \c SpeedOptim is not available for general use since it is only available if Qt is built in a particular configuration. \sa size() */ /*! \fn bool QMemArray::resize( uint size ) \overload Resizes (expands or shrinks) the array to \a size elements. The array becomes a null array if \a size == 0. Returns TRUE if successful, i.e. if the memory can be allocated; otherwise returns FALSE. New elements are not initialized. \sa size() */ /*! \fn bool QMemArray::truncate( uint pos ) Truncates the array at position \a pos. Returns TRUE if successful, i.e. if the memory can be allocated; otherwise returns FALSE. Equivalent to resize(\a pos). \sa resize() */ /*! \fn bool QMemArray::fill( const type &v, int size ) Fills the array with the value \a v. If \a size is specified as different from -1, then the array will be resized before being filled. Returns TRUE if successful, i.e. if \a size is -1, or \a size is != -1 and the memory can be allocated; otherwise returns FALSE. \sa resize() */ /*! \fn void QMemArray::detach() 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 \link nrefs() reference count\endlink is greater than one. \sa copy() */ /*! \fn QMemArray QMemArray::copy() const Returns a deep copy of this array. \sa detach(), duplicate() */ /*! \fn QMemArray &QMemArray::assign( const QMemArray &a ) Shallow copy. Dereferences the current array and references the data contained in \a a instead. Returns a reference to this array. \sa operator=() */ /*! \fn QMemArray &QMemArray::assign( const type *data, uint size ) \overload Shallow copy. Dereferences the current array and references the array data \a data, which contains \a size elements. Returns a reference to this array. Do not delete \a data later; QMemArray will call free() on it at the right time. */ /*! \fn QMemArray &QMemArray::duplicate( const QMemArray &a ) Deep copy. Dereferences the current array and obtains a copy of the data contained in \a a instead. Returns a reference to this array. \sa copy() */ /*! \fn QMemArray &QMemArray::duplicate( const type *data, uint size ) \overload Deep copy. Dereferences the current array and obtains a copy of the array data \a data instead. Returns a reference to this array. The size of the array is given by \a size. \sa copy() */ /*! \fn QMemArray &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 \a data and the new array size to \a size. Do not attempt to resize or re-assign the array data when raw data has been set. Call resetRawData(\a data, \a size) to reset the array. Setting raw data is useful because it sets QMemArray data without allocating memory or copying data. Example I (intended use): \code 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 >> ; // read raw bindata a.resetRawData( bindata, sizeof(bindata) ); // finished \endcode Example II (you don't want to do this): \code 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 \endcode \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. \sa resetRawData() */ /*! \fn void QMemArray::resetRawData( const type *data, uint size ) Removes internal references to the raw data that was set using setRawData(). This means that QMemArray no longer has access to the \a data, so you are free to manipulate \a data as you wish. You can now use the QMemArray without affecting the original \a data, for example by calling setRawData() with a pointer to some other data. The arguments must be the \a data and length, \a size, that were passed to setRawData(). This is for consistency checking. \sa setRawData() */ /*! \fn int QMemArray::find( const type &v, uint index ) const Finds the first occurrence of \a v, starting at position \a index. Returns the position of \a v, or -1 if \a v could not be found. \sa contains() */ /*! \fn int QMemArray::contains( const type &v ) const Returns the number of times \a v occurs in the array. \sa find() */ /*! \fn void QMemArray::sort() Sorts the array elements in ascending order, using bitwise comparison (memcmp()). \sa bsearch() */ /*! \fn int QMemArray::bsearch( const type &v ) const In a sorted array (as sorted by sort()), finds the first occurrence of \a 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 \a v, or -1 if \a v could not be found. \sa sort(), find() */ /*! \fn type &QMemArray::operator[]( int index ) const Returns a reference to the element at position \a index in the array. This can be used to both read and set an element. Equivalent to at(). \sa at() */ /*! \fn type &QMemArray::at( uint index ) const Returns a reference to the element at position \a index in the array. This can be used to both read and set an element. \sa operator[]() */ /*! \fn QMemArray::operator const type *() const Cast operator. Returns a pointer to the array. \sa data() */ /*! \fn bool QMemArray::operator==( const QMemArray &a ) const Returns TRUE if this array is equal to \a a; otherwise returns FALSE. The two arrays are compared bitwise. \sa operator!=() */ /*! \fn bool QMemArray::operator!=( const QMemArray &a ) const Returns TRUE if this array is different from \a a; otherwise returns FALSE. The two arrays are compared bitwise. \sa operator==() */ /*! \fn 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. */ /*! \fn 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. */ /*! \fn ConstIterator QMemArray::begin() const \overload 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. */ /*! \fn ConstIterator QMemArray::end() const \overload 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. */