Return the size of a memory block allocated in the heap.
| #include <malloc.h> | Required only for function declarations |
size_t _msize( void *memblock );
size_t _bmsize( __segment seg, void __based( void ) *memblock );
size_t _fmsize( void __far *memblock );
size_t _nmsize( void __near *memblock );
| memblock | Pointer to memory block | |
| seg | Based-heap segment selector |
The _msize family of functions returns the size, in bytes, of the memory block allocated by a call to the appropriate version of the calloc, malloc, or realloc functions.
In large data models (compact-, large-, and huge-model programs), _msize maps to _fmsize. In small data models (tiny-, small-, and medium-model programs), _msize maps to _nmsize.
The _nmsize function returns the size (in bytes) of the memory block allocated by a call to _nmalloc, and the _fmsize function returns the size (in bytes) of the memory block allocated by a call to _fmalloc or _frealloc. The _bmsize function returns the size of a block allocated in segment seg by a call to _bmalloc, _bcalloc, or _brealloc.
The location of the memory block is indicated below:
| Function | Data Segment |
| _msize | Depends on data model of program |
| _bmsize | Based heap segment specified by seg value |
| _fmsize | Far heap segment (outside default data segment) |
| _nmsize | Default data segment (inside near heap) |
All four functions return the size (in bytes) as an unsigned integer.
_msize
Standards:None
16-Bit:DOS, QWIN, WIN, WIN DLL
32-Bit:DOS32X
_bmsize, _fmsize, _nmsize
Standards:None
16-Bit:DOS, QWIN, WIN, WIN DLL
32-Bit:None
calloc functions, _expand functions, malloc functions, realloc functions
/* REALLOC.C: This program allocates a block of memory for buffer
* and then uses _msize to display the size of that block. Next, it
* uses realloc to expand the amount of memory used by buffer
* and then calls _msize again to display the new amount of
* memory allocated to buffer.
*/
#include <stdio.h>
#include <malloc.h>
#include <stdlib.h>
void main( void )
{
long *buffer;
size_t size;
if( (buffer = (long *)malloc( 1000 * sizeof( long ) )) == NULL )
exit( 1 );
size = _msize( buffer );
printf( "Size of block after malloc of 1000 longs: %u\n", size );
/* Reallocate and show new size: */
if( (buffer = realloc( buffer, size + (1000 * sizeof( long )) )) == NULL )
exit( 1 );
size = _msize( buffer );
printf( "Size of block after realloc of 1000 more longs: %u\n", size );
free( buffer );
exit( 0 );
}
Size of block after malloc of 1000 longs: 4000
Size of block after realloc of 1000 more longs: 8000