Libc-825.24.tar.gz

[apple/libc.git] / string / stpncpy.c

/*
 * Copyright (c) 2011 Apple, Inc. All rights reserved.
 *
 * @APPLE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this
 * file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_LICENSE_HEADER_END@
 */

#include <string.h>

char *
stpncpy(char * restrict dst, const char * restrict src, size_t maxlen) {
    const size_t srclen = strnlen(src, maxlen);
    if (srclen < maxlen) {
        //  The stpncpy() and strncpy() functions copy at most maxlen
        //  characters from src into dst.
        memcpy(dst, src, srclen);
        //  If src is less than maxlen characters long, the remainder
        //  of dst is filled with '\0' characters.
        memset(dst+srclen, 0, maxlen-srclen);
        //  The stpcpy() and stpncpy() functions return a pointer to the
        //  terminating '\0' character of dst.
        return dst+srclen;
    } else {
        //  The stpncpy() and strncpy() functions copy at most maxlen
        //  characters from src into dst.
        memcpy(dst, src, maxlen);
        //  If stpncpy() does not terminate dst with a NUL character, it
        //  instead returns a pointer to src[maxlen] (which does not
        //  necessarily refer to a valid memory location.)
        return dst+maxlen;
    }
}