calloc.c

C标准库源代码

/***
*calloc.c - allocate storage for an array from the heap
*
*       Copyright (c) 1989-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
*       Defines the calloc() function.
*
*******************************************************************************/

#ifdef WINHEAP

#include <malloc.h>
#include <string.h>
#include <winheap.h>
#include <windows.h>
#include <internal.h>
#include <mtdll.h>
#include <dbgint.h>

/***
*void *calloc(size_t num, size_t size) - allocate storage for an array from
*       the heap
*
*Purpose:
*       Allocate a block of memory from heap big enough for an array of num
*       elements of size bytes each, initialize all bytes in the block to 0
*       and return a pointer to it.
*
*Entry:
*       size_t num  - number of elements in the array
*       size_t size - size of each element
*
*Exit:
*       Success:  void pointer to allocated block
*       Failure:  NULL
*
*Uses:
*
*Exceptions:
*
*******************************************************************************/

void * __cdecl _calloc_base (size_t num, size_t size)
{
    size_t  size_sbh;
    void *  pvReturn;

    size_sbh = size = size * num;


    /* round up to the nearest paragraph */
    if (size <= _HEAP_MAXREQ)
    {
        if (size == 0)
            size = 1;
        size = (size + BYTES_PER_PARA - 1) & ~(BYTES_PER_PARA - 1);
    }

    for (;;)
    {
        pvReturn = NULL;

        if (size <= _HEAP_MAXREQ)
        {
            if (size_sbh <= __sbh_threshold)
            {
                //  Allocate the block from the small-block heap and
                //  initialize it with zeros.
                _mlock(_HEAP_LOCK);
                pvReturn = __sbh_alloc_block(size_sbh);
                _munlock(_HEAP_LOCK);

                if (pvReturn != NULL)
                    memset(pvReturn, 0, size_sbh);
            }

            if (pvReturn == NULL)
                pvReturn = HeapAlloc(_crtheap, HEAP_ZERO_MEMORY, size);
        }

        if (pvReturn || _newmode == 0)
            return pvReturn;

        /* call installed new handler */
        if (!_callnewh(size))
            return NULL;

        /* new handler was successful -- try to allocate again */
    }

}

#else  /* WINHEAP */


#include <cruntime.h>
#include <heap.h>
#include <malloc.h>
#include <mtdll.h>
#include <stddef.h>
#include <dbgint.h>

/***
*void *calloc(size_t num, size_t size) - allocate storage for an array from
*       the heap
*
*Purpose:
*       Allocate a block of memory from heap big enough for an array of num
*       elements of size bytes each, initialize all bytes in the block to 0
*       and return a pointer to it.
*
*Entry:
*       size_t num  - number of elements in the array
*       size_t size - size of each element
*
*Exit:
*       Success:  void pointer to allocated block block
*       Failure:  NULL
*
*Uses:
*
*Exceptions:
*
*******************************************************************************/

void * __cdecl _calloc_base (
        size_t num,
        size_t size
        )
{
        void *retp;
        REG1 size_t *startptr;
        REG2 size_t *lastptr;

        /* try to malloc the requested space
         */
        retp = _malloc_base(size *= num);

        /* if malloc() succeeded, initialize the allocated space to zeros.
         * note the assumptions that the size of the allocation block is an
         * integral number of sizeof(size_t) bytes and that (size_t)0 is
         * sizeof(size_t) bytes of 0.
         */
        if ( retp != NULL ) {
            startptr = (size_t *)retp;
            lastptr = startptr + ((size + sizeof(size_t) - 1) /
            sizeof(size_t));
            while ( startptr < lastptr )
                *(startptr++) = 0;
        }

        return retp;
}

#endif  /* WINHEAP */