memchr.c

来自「the vxworks system kernel souce packeg.t」· C语言 代码 · 共 59 行

/* memchr.c - search memory for a character, string */

/* Copyright 1992-1993 Wind River Systems, Inc. */

/*
modification history
--------------------
01c,25feb93,jdi  documentation cleanup for 5.1.
01b,20sep92,smb  documentation additions
01a,08jul92,smb  written and documented.
*/

/*
DESCRIPTION

INCLUDE FILES: string.h

SEE ALSO: American National Standard X3.159-1989

NOMANUAL
*/

#include "vxWorks.h"
#include "string.h"

/*******************************************************************************
*
* memchr - search a block of memory for a character (ANSI)
*
* This routine searches for the first element of an array of `unsigned char',
* beginning at the address <m> with size <n>, that equals <c> converted to
* an `unsigned char'.
*
* INCLUDE FILES: string.h
*
* RETURNS: If successful, it returns the address of the matching element;
* otherwise, it returns a null pointer.
*/

void * memchr
    (
    const void * m,		/* block of memory */
    int 	 c,		/* character to search for */
    size_t 	 n		/* size of memory to search */
    )
    {
    uchar_t *p = (uchar_t *) CHAR_FROM_CONST(m);

    if (n != 0)
	do 
	    {
	    if (*p++ == (unsigned char) c)
		return (VOID_FROM_CONST(p - 1));

	    } while (--n != 0);

    return (NULL);
    }