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Annotation of researchv10no/cmd/f2c/safstrncpy.c, revision 1.1

1.1     ! root        1: /****************************************************************
        !             2: Copyright 1990 by AT&T Bell Laboratories and Bellcore.
        !             3: 
        !             4: Permission to use, copy, modify, and distribute this software
        !             5: and its documentation for any purpose and without fee is hereby
        !             6: granted, provided that the above copyright notice appear in all
        !             7: copies and that both that the copyright notice and this
        !             8: permission notice and warranty disclaimer appear in supporting
        !             9: documentation, and that the names of AT&T Bell Laboratories or
        !            10: Bellcore or any of their entities not be used in advertising or
        !            11: publicity pertaining to distribution of the software without
        !            12: specific, written prior permission.
        !            13: 
        !            14: AT&T and Bellcore disclaim all warranties with regard to this
        !            15: software, including all implied warranties of merchantability
        !            16: and fitness.  In no event shall AT&T or Bellcore be liable for
        !            17: any special, indirect or consequential damages or any damages
        !            18: whatsoever resulting from loss of use, data or profits, whether
        !            19: in an action of contract, negligence or other tortious action,
        !            20: arising out of or in connection with the use or performance of
        !            21: this software.
        !            22: ****************************************************************/
        !            23: 
        !            24: /* safe_strncpy
        !            25: 
        !            26:        Copies at most   max_length   characters, stopping at the first   \0
        !            27:    character in   source.   The algorithm correctly handles overlapping
        !            28:    buffer areas. */
        !            29: 
        !            30: #include <stdio.h>
        !            31: #ifndef NULL
        !            32: /* ANSI C */
        !            33: #include <stddef.h>
        !            34: #endif
        !            35: 
        !            36: char *safe_strncpy (dest, source, max_length)
        !            37: char *dest, *source;
        !            38: int max_length;
        !            39: {
        !            40: 
        !            41: /* There are several conditions to be considered in determining buffer
        !            42:    area overlap:
        !            43: 
        !            44:    Buffer Overlap?             Picture         Direction In Which To Copy
        !            45: ---------------------------------------------------------------------------
        !            46: 1. dest == source         | dest/src |           no copy necessary
        !            47:                           ============
        !            48: 
        !            49: 2. tail of dest against          |   dest | | src   |    left to right
        !            50:    head of source        ---------===--------
        !            51: 
        !            52: 3. head of dest against          |   src | | dest   |    right to left
        !            53:    tail of source        --------===---------
        !            54: 
        !            55: 4. no overlap  |src| |dest|   or   |dest| |src|  either direction
        !            56:                ----- ------        ------ -----
        !            57: */
        !            58: 
        !            59:     register char *ret_val = dest;
        !            60:     register int real_length;
        !            61: 
        !            62:     if (source == NULL || dest == NULL)
        !            63:        return NULL;
        !            64: 
        !            65: /* Compute the actual length of the text to be copied */
        !            66: 
        !            67:     for (real_length = 0; real_length < max_length && source[real_length];
        !            68:            real_length++);
        !            69: 
        !            70: /* Account for condition 3,  dest head v. source tail */
        !            71: 
        !            72:     if (source + real_length >= dest && source < dest)
        !            73:        for (; real_length >= 0; real_length--)
        !            74:            dest[real_length] = source[real_length];
        !            75: 
        !            76: /* Account for conditions 2 and 4,  dest tail v. source head  or no overlap */
        !            77: 
        !            78:     else if (source != dest)
        !            79:        for (; real_length >= 0; real_length--)
        !            80:            *dest++ = *source++;
        !            81: 
        !            82: /* Implicitly handle condition 1, by not performing the copy */
        !            83: 
        !            84:     return ret_val;
        !            85: } /* safe_strncpy */
        !            86: 

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