[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
 *  Carnegie Mellon University
 *  Pittsburgh PA 15213-3890
 *
 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */
/*
 * 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;
}

/*
 * mig_strncpy_zerofill -- 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. If the string in src is smaller
 * than given length len, it will zero fill the remaining bytes in dest.
 *
 * 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.
 */
int
mig_strncpy_zerofill(
        char *dest,
        const char *src,
        int len)
{
        int i;
        boolean_t terminated = FALSE;
        int retval = 0;

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

        if (src == 0) {
                terminated = TRUE;
        }

        for (i = 1; i < len; i++) {
                if (!terminated) {
                        if (!(*dest++ = *src++)) {
                                retval = i;
                                terminated = TRUE;
                        }
                } else {
                        *dest++ = '\0';
                }
        }

        *dest = '\0';
        if (!terminated) {
                retval = i;
        }

        return retval;
}