memmem.c

/* memmem.c -- replacement memmem() routine
 *
 * Copyright (c) 1994-2012 Carnegie Mellon University.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The name "Carnegie Mellon University" must not be used to
 *    endorse or promote products derived from this software without
 *    prior written permission. For permission or any legal
 *    details, please contact
 *      Carnegie Mellon University
 *      Center for Technology Transfer and Enterprise Creation
 *      4615 Forbes Avenue
 *      Suite 302
 *      Pittsburgh, PA  15213
 *      (412) 268-7393, fax: (412) 268-7395
 *      innovation@andrew.cmu.edu
 *
 * 4. Redistributions of any form whatsoever must retain the following
 *    acknowledgment:
 *    "This product includes software developed by Computing Services
 *     at Carnegie Mellon University (http://www.cmu.edu/computing/)."
 *
 * CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
 * THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
 * AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
 * FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
 * AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
 * OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#include <config.h>
#ifdef HAVE_STRING_H
#include <string.h>
#endif

/*
 * Search for a needle 'vm' of length 'mlen' in
 * haystack 'vb' of length 'len' and return the
 * pointer to the first occurrence or NULL.
 * Does not handle mlen=0.
 */
void *memmem(const void *vb, size_t len,
             const void *vm, size_t mlen)
{
    /* use unsigned char* not void* so ptr arithmetic works portably */
    const unsigned char *b = vb;
    const unsigned char *end = b+len;
    const unsigned char *m = vm;
    const unsigned char *p;

    while (b < end) {
        p = memchr(b, *m, end-b);
        if (!p) return NULL;
        if (p + mlen > end) return NULL;
        if (!memcmp(p, m, mlen)) return (void *)p;
        b = p+1;
    }
    return NULL;
}