swab.c

C标准库源代码,能提高对C的理解,不错的哦

/***
*swab.c - block copy, while swapping even/odd bytes
*
*       Copyright (c) 1989-1997, Microsoft Corporation. All rights reserved.
*
*Purpose:
*       This module contains the routine _swab() which swaps the odd/even
*       bytes of words during a block copy.
*
*******************************************************************************/

#include <cruntime.h>
#include <stdlib.h>

/***
*void _swab(srcptr, dstptr, nbytes) - swap ODD/EVEN bytes during word move
*
*Purpose:
*       This routine copys a block of words and swaps the odd and even
*       bytes.  nbytes must be > 0, otherwise nothing is copied.  If
*       nbytes is odd, then only (nbytes-1) bytes are copied.
*
*Entry:
*       srcptr = pointer to the source block
*       dstptr = pointer to the destination block
*       nbytes = number of bytes to swap
*
*Returns:
*       None.
*
*Exceptions:
*
*******************************************************************************/

void __cdecl _swab (
        char *src,
        char *dest,
        int nbytes
        )
{
        char b1, b2;

        while (nbytes > 1) {
                b1 = *src++;
                b2 = *src++;
                *dest++ = b2;
                *dest++ = b1;
                nbytes -= 2;
        }
}