xnu-2422.1.72.tar.gz

[apple/xnu.git] / libsyscall / mach / mig_strncpy.c

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/* 
 * Mach Operating System
 * Copyright (c) 1991,1990,1989 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
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 *  Pittsburgh PA 15213-3890
 * 
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 */
/*
 * mig_strncpy.c - by Joshua Block
 *
 * mig_strncpy -- Bounded string copy.  Does what the library routine strncpy
 * OUGHT to do:  Copies the (null terminated) string in src into dest, a 
 * buffer of length len.  Assures that the copy is still null terminated
 * and doesn't overflow the buffer, truncating the copy if necessary.
 *
 * Parameters:
 * 
 *     dest - Pointer to destination buffer.
 * 
 *     src - Pointer to source string.
 * 
 *     len - Length of destination buffer.
 *
 * Result:
 *	length of string copied, INCLUDING the trailing 0.
 */
#include <mach/mig_errors.h>

int
mig_strncpy(
    char *dest,
    const char *src,
    int len)
{
    int i;

    if (len <= 0) {
		return 0;
	}

    for (i = 1; i < len; i++) {
		if (!(*dest++ = *src++)) {
			return i;
		}
	}

    *dest = '\0';
    return i;
}