QArray(3qt)QArray(3qt)NAME
QArray - Template class that provides arrays of simple
types
#include <qarray.h>
Inherits QGArray.
Inherited by QByteArray and QPointArray.
Public Members
QArray ()
QArray ( int size )
QArray ( const QArray<type> & a )
~QArray ()
QArray<type>& operator= ( const QArray<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 truncate ( uint pos )
bool fill ( const type & v, int size = -1 )
virtual void detach ()
QArray<type> copy () const
QArray<type>& assign ( const QArray<type> & a )
QArray<type>& assign ( const type * data, uint size )
QArray<type>& duplicate ( const QArray<type> & a )
QArray<type>& duplicate ( const type * data, uint size )
QArray<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 QArray<type> & a ) const
bool operator!= ( const QArray<type> & a ) const
Iterator begin ()
Iterator end ()
ConstIterator begin () const
ConstIterator end () const
Protected Members
QArray ( int, int )
DESCRIPTION
The QArray class is a template class that provides arrays
of simple types.
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QArray is implemented as a template class. Define a
template instance QArray<X> to create an array that
contains X items.
QArray 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. QArray uses bitwise operations to copy
and compare array elements.
The QVector collection class is also a kind of array. Like
most collection classes, it has pointers to the contained
items.
QArray uses explicit sharing with a reference count. If
more than one array share common data, and one array is
modified, all arrays will be modified.
The benefit of sharing is that a program does not need to
duplicate data when it is not required, which results in
less memory usage and less copying of data.
Example:
#include <qarray.h>
#include <stdio.h>
QArray<int> fib( int num ) // returns fibonacci array
{
ASSERT( num > 2 );
QArray<int> f( num ); // array of ints
f[0] = f[1] = 1; // initialize first two numbers
for ( int i=2; i<num; i++ )
f[i] = f[i-1] + f[i-2];
return f;
}
void main()
{
QArray<int> a = fib( 6 ); // get 6 first fibonaccis
int i;
for ( i=0; i<a.size(); i++ ) // print them
prinf( "%d: %d\n", i, a[i] );
printf( "1 is found %d time(s)\n", a.contains(1) );
printf( "5 is found at index %d\n", a.find(5) );
}
Program output:
0: 1
1: 1
2: 2
3: 3
4: 5
5: 8
1 is found 2 times
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5 is found at index 4
Note about using QArray 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 QArray will use for its bitwise element
comparisons. Since the remaining bytes will typically be
uninitialized, this can cause find() etc. to fail to find
the element. Example:
struct MyStruct
{
short i; // 2 bytes
char c; // 1 byte
}; // sizeof(MyStruct) may be padded to 4 bytes
QArray<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 workaround 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.
See also Shared Classes
MEMBER FUNCTION DOCUMENTATIONQArray::QArray ()
Constructs a null array.
See also isNull().
QArray::QArray ( const QArray<;type> & a )
Constructs a shallow copy of a.
See also assign().
QArray::QArray ( int size )
Constructs an array with room for size elements. Makes a
null array if size == 0.
Note that the elements are not initialized.
See also resize() and isNull().
QArray::QArray ( int, int ) [protected]
Constructs an array without allocating array space. The
arguments should be (0, 0). Use at own risk.
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Dereferences the array data and deletes it if this was the
last reference.
QArray::operator const type * () const
Cast operator. Returns a pointer to the array.
See also data().
QArray<;type> & QArray::assign ( const QArray<type> & a )
Shallow copy. Dereferences the current array and
references the data contained in a instead. Returns a
reference to this array.
See also operator=().
QArray<;type> & QArray::assign ( const type * data, uint size )
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, QArray takes care of that.
type & QArray::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.
See also operator[]().
ConstIterator QArray::begin () const
Returns a const iterator pointing at the beginning of this
array. This iterator can be used as the iterators of
QValueList and QMap for example. In fact it does not only
behave like a usual pointer: It is a pointer.
Iterator QArray::begin ()
Returns an iterator pointing at the beginning of this
array. This iterator can be used as the iterators of
QValueList and QMap for example. In fact it does not only
behave like a usual pointer: It is a pointer.
int QArray::bsearch ( const type & v ) const
In a sorted array, finds the first occurrence of v using
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.
See also sort() and find().
int QArray::contains ( const type & v ) const
Returns the number of times v occurs in the array.
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See also find().
QArray<;type> QArray::copy () const
Returns a deep copy of this array.
See also detach() and duplicate().
uint QArray::count () const
Returns the same as size().
See also size().
type * QArray::data () const
Returns a pointer to the actual array data.
The array is a null array if data() == 0 (null pointer).
See also isNull().
void QArray::detach () [virtual]
Detaches this array from shared array data, i.e. makes a
private, deep copy of the data.
Copying will only be performed if the reference count is
greater than one.
See also copy().
Reimplemented from QGArray.
QArray<;type> & QArray::duplicate ( const QArray<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.
See also copy().
QArray<;type> & QArray::duplicate ( const type * data, uint size )
Deep copy. Dereferences the current array and obtains a
copy of the array data data instead. Returns a reference
to this array.
See also copy().
ConstIterator QArray::end () const
Returns a const iterator pointing behind the last element
of this array. This iterator can be used as the iterators
of QValueList and QMap for example. In fact it does not
only behave like a usual pointer: It is a pointer.
Iterator QArray::end ()
Returns an iterator pointing behind the last element of
this array. This iterator can be used as the iterators of
QValueList and QMap for example. In fact it does not only
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behave like a usual pointer: It is a pointer.
bool QArray::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
filled.
Returns TRUE if successful, or FALSE if the memory cannot
be allocated (only when size != -1).
See also resize().
int QArray::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.
See also contains().
bool QArray::isEmpty () const
Returns TRUE if the array is empty, i.e. size() == 0,
otherwise FALSE.
isEmpty() is equivalent with isNull() for QArray. Note
that this is not the case for QCString::isEmpty().
bool QArray::isNull () const
Returns TRUE if the array is null, otherwise FALSE.
A null array has size() == 0 and data() == 0.
uint QArray::nrefs () const
Returns the reference count for the shared array data.
This reference count is always greater than zero.
bool QArray::operator!= ( const QArray<type> & a ) const
Returns TRUE if this array is different from a, otherwise
FALSE.
The two arrays are bitwise compared.
See also operator==().
QArray<;type> & QArray::operator= ( const QArray<type> & a )
Assigns a shallow copy of a to this array and returns a
reference to this array.
Equivalent to assign( a ).
bool QArray::operator== ( const QArray<type> & a ) const
Returns TRUE if this array is equal to a, otherwise FALSE.
The two arrays are bitwise compared.
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See also operator!=().
type & QArray::operator[] ( int 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.
Equivalent to at().
See also at().
void QArray::resetRawData ( const type * data, uint size )
Resets raw data that was set using setRawData().
The arguments must be the data and length that were passed
to setRawData(). This is for consistency checking.
See also setRawData().
bool QArray::resize ( uint size )
Resizes (expands or shrinks) the array to size elements.
The array becomes a null array if size == 0.
Returns TRUE if successful, or FALSE if the memory cannot
be allocated.
New elements will not be initialized.
See also size().
QArray<;type> & QArray::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. Do not attempt to
resize or re-assign the array data when raw data has been
set. Call resetRawData(d,len) to reset the array.
Setting raw data is useful because it sets QArray data
without allocating memory or copying data.
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, ... };
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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
Warning: If you do not call resetRawData(), QArray will
attempt to deallocate or reallocate the raw data, which
might not be too good. Be careful.
See also resetRawData().
uint QArray::size () const
Returns the size of the array (max number of elements).
The array is a null array if size() == 0.
See also isNull() and resize().
void QArray::sort ()
Sorts the array elements in ascending order, using bitwise
comparison (memcmp()).
See also bsearch().
bool QArray::truncate ( uint pos )
Truncates the array at position pos.
Returns TRUE if successful, or FALSE if the memory cannot
be allocated.
Equivalent to resize(pos).
See also resize().
SEE ALSO
http://doc.trolltech.com/qarray.html
http://www.trolltech.com/faq/tech.html
COPYRIGHT
Copyright 1992-2001 Trolltech AS,
http://www.trolltech.com. See the license file included
in the distribution for a complete license statement.
AUTHOR
Generated automatically from the source code.
BUGS
If you find a bug in Qt, please report it as described in
http://doc.trolltech.com/bughowto.html. Good bug reports
make our job much simpler. Thank you.
In case of content or formattting problems with this
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manual page, please report them to qt-bugs@trolltech.com.
Please include the name of the manual page (qarray.3qt)
and the Qt version (2.3.1).
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