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/*

 * regsub

 *

 *      Copyright (c) 1986 by University of Toronto.

 *      Written by Henry Spencer.  Not derived from licensed software.

 *

 *      Permission is granted to anyone to use this software for any

 *      purpose on any computer system, and to redistribute it freely,

 *      subject to the following restrictions:

 *

 *      1. The author is not responsible for the consequences of use of

 *              this software, no matter how awful, even if they arise

 *              from defects in it.

 *

 *      2. The origin of this software must not be misrepresented, either

 *              by explicit claim or by omission.

 *

 *      3. Altered versions must be plainly marked as such, and must not

 *              be misrepresented as being the original software.

 */

#include <stdio.h>

#include <regexp.h>

#include "regmagic.h"

#ifndef CHARBITS

#define UCHARAT(p)      ((int)*(unsigned char *)(p))

#else

#define UCHARAT(p)      ((int)*(p)&CHARBITS)

#endif

/*

 - regsub - perform substitutions after a regexp match

 */

void

regsub(prog, source, dest)

regexp *prog;

char *source;

char *dest;

{

        register char *src;

        register char *dst;

        register char c;

        register int no;

        register int len;

        extern char *strncpy();

        if (prog == NULL || source == NULL || dest == NULL) {

                regerror("NULL parm to regsub");

                return;

        }

        if (UCHARAT(prog->program) != MAGIC) {

                regerror("damaged regexp fed to regsub");

                return;

        }

        src = source;

        dst = dest;

        while ((c = *src++) != '\0') {

                if (c == '&')

                        no = 0;

                else if (c == '\\' && '0' <= *src && *src <= '9')

                        no = *src++ - '0';

                else

                        no = -1;

                if (no < 0) {    /* Ordinary character. */

                        if (c == '\\' && (*src == '\\' || *src == '&'))

                                c = *src++;

                        *dst++ = c;

                } else if (prog->startp[no] != NULL && prog->endp[no] != NULL) {

                        len = prog->endp[no] - prog->startp[no];

                        (void) strncpy(dst, prog->startp[no], len);

                        dst += len;

                        if (len != 0 && *(dst-1) == '\0') {

                                                        /* strncpy hit NUL. */

                                regerror("damaged match string");

                                return;

                        }

                }

        }

        *dst++ = '\0';

}