The Q3MemArray class is a template class that provides arrays of simple types. 更多...
| 头： | #include <Q3MemArray> |
| typedef | ConstIterator |
| typedef | Iterator |
| Q3MemArray () | |
| Q3MemArray (int size ) | |
| Q3MemArray (const Q3MemArray<type> & a ) | |
| Q3MemArray (const QVector<type> & vector ) | |
| ~Q3MemArray () | |
| Q3MemArray<type> & | assign (const Q3MemArray<type> & a ) |
| Q3MemArray<type> & | assign (const type * data , uint size ) |
| type & | at (uint index ) const |
| 迭代器 | begin () |
| ConstIterator | begin () const |
| int | bsearch (const type & v ) const |
| int | contains (const type & v ) const |
| Q3MemArray<type> | copy () const |
| uint | count () const |
| type * | data () const |
| Q3MemArray<type> & | duplicate (const Q3MemArray<type> & a ) |
| Q3MemArray<type> & | duplicate (const type * data , uint size ) |
| 迭代器 | end () |
| ConstIterator | end () const |
| bool | fill (const type & v , int size = -1) |
| int | find (const type & v , uint index = 0) const |
| bool | isEmpty () const |
| bool | isNull () const |
| uint | nrefs () const |
| void | resetRawData (const type * data , uint size ) |
| bool | resize (uint size , Optimization optim ) |
| bool | resize (uint size ) |
| Q3MemArray<type> & | setRawData (const type * data , uint size ) |
| uint | size () const |
| void | sort () |
| bool | truncate (uint pos ) |
| operator QVector<type> () const | |
| operator const type * () const | |
| bool | operator!= (const Q3MemArray<type> & a ) const |
| Q3MemArray<type> & | operator= (const Q3MemArray<type> & a ) |
| bool | operator== (const Q3MemArray<type> & a ) const |
| type & | operator[] (int index ) const |
| virtual void | detach () |
| Q3MemArray (int arg1 , int arg2 ) |
The Q3MemArray class is a template class that provides arrays of simple types.
Q3MemArray is implemented as a template class. Define a template instance Q3MemArray <X> to create an array that contains X items.
Q3MemArray 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). Q3MemArray uses bitwise operations to copy and compare array elements.
The Q3PtrVector collection class is also a kind of array. Like most old Qt collection classes, it uses pointers to the contained items.
Q3MemArray uses explicit sharing 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.
范例：
#include <q3memarray.h> #include <stdio.h> Q3MemArray<int> fib( int num ) // returns fibonacci array { Q_ASSERT( num > 2 ); Q3MemArray<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() { Q3MemArray<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
Note concerning the use of Q3MemArray 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 Q3MemArray 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 }; Q3MemArray<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.
Q3MemArray data can be traversed by iterators (see begin () 和 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 () 和 contains (). For sorted arrays (see sort ()) you can search using bsearch ().
You can set the data directly using setRawData () 和 resetRawData (), although this requires care.
A const Q3MemArray iterator.
A Q3MemArray iterator.
[protected]
Q3MemArray::
Q3MemArray
(
int
arg1
,
int
arg2
)
Constructs an array without allocating array space. The arguments arg1 and arg2 should be zero. Use at your own risk.
Constructs a null array.
另请参阅 isNull ().
Constructs an array with room for size elements. Makes a null array if size == 0.
The elements are left uninitialized.
Constructs a shallow copy of a .
另请参阅 assign ().
构造副本为 vector .
Dereferences the array data and deletes it if this was the last reference.
Shallow copy. Dereferences the current array and references the data contained in a instead. Returns a reference to this array.
另请参阅 operator= ().
这是重载函数。
Shallow copy. Dereferences the current array and references the array data data , which contains size elements. Returns a reference to this array.
不要删除 data later; Q3MemArray will call free() on it at the right time.
Returns a reference to the element at position index in the array.
This can be used to both read and set an element.
另请参阅 operator[] ().
Returns an iterator pointing at the beginning of this array. This iterator can be used in the same way as the iterators of Q3ValueList and QMap ，例如。
这是重载函数。
Returns a const iterator pointing at the beginning of this array. This iterator can be used in the same way as the iterators of Q3ValueList and QMap ，例如。
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 ，或 -1 若 v could not be found.
Returns the number of times v occurs in the array.
另请参阅 find ().
Returns a deep copy of this array.
另请参阅 detach () 和 duplicate ().
Returns the same as size ().
另请参阅 size ().
Returns a pointer to the actual array data.
The array is a null array if data() == 0 (null pointer).
另请参阅 isNull ().
[虚拟]
void
Q3MemArray::
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 reference count is greater than one.
另请参阅 copy ().
Deep copy. Dereferences the current array and obtains a copy of the data contained in a instead. Returns a reference to this array.
另请参阅 copy ().
这是重载函数。
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 .
另请参阅 copy ().
Returns an iterator pointing behind the last element of this array. This iterator can be used in the same way as the iterators of Q3ValueList and QMap ，例如。
这是重载函数。
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 Q3ValueList and QMap ，例如。
Fills the array with the value v 。若 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.
另请参阅 resize ().
Finds the first occurrence of v , starting at position index .
Returns the position of v ，或 -1 若 v could not be found.
另请参阅 contains ().
Returns TRUE if the array is empty; otherwise returns FALSE.
isEmpty() is equivalent to isNull () 对于 Q3MemArray (unlike QString ).
Returns TRUE if the array is null; otherwise returns FALSE.
A null array has size () == 0 and data () == 0.
Returns the reference count for the shared array data. This reference count is always greater than zero.
Removes internal references to the raw data that was set using setRawData (). This means that Q3MemArray no longer has access to the data , so you are free to manipulate data as you wish. You can now use the Q3MemArray 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 (). This is for consistency checking.
另请参阅 setRawData ().
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 are not initialized.
optim
is either
MemOptim
(默认) 或
SpeedOptim
. When optimizing for speed rather than memory consumption, the array uses a smart grow and shrink algorithm that might allocate more memory than is actually needed for
size
elements. This speeds up subsequent resize operations, for example when appending many elements to an array, since the space has already been allocated.
另请参阅 size ().
这是重载函数。
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.
New elements are not initialized.
另请参阅 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 ( data , size ) to reset the array.
Setting raw data is useful because it sets Q3MemArray 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, ... }; 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
警告： If you do not call resetRawData (), Q3MemArray will attempt to deallocate or reallocate the raw data, which might not be too good. Be careful.
另请参阅 resetRawData ().
Returns the size of the array (maximum number of elements).
The array is a null array if size() == 0.
Sorts the array elements in ascending order, using bitwise comparison (memcmp()).
另请参阅 bsearch ().
Truncates the array at position pos .
Returns TRUE if successful, i.e. if the memory can be allocated; otherwise returns FALSE.
Equivalent to resize( pos ).
另请参阅 resize ().
Automatically converts the Q3MemArray <type> into a QVector <type>.
Cast operator. Returns a pointer to the array.
另请参阅 data ().
Returns TRUE if this array is different from a ; otherwise returns FALSE.
The two arrays are compared bitwise.
另请参阅 operator== ().
Assigns a shallow copy of a to this array and returns a reference to this array.
Equivalent to assign( a ).
Returns TRUE if this array is equal to a ; otherwise returns FALSE.
The two arrays are compared bitwise.
另请参阅 operator!= ().
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 ().
另请参阅 at ().