/*
 * regsub @(#)regsub.c	1.3 of 2 April 86
 *
 * 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.
 */

/*
 * CHANGED, 14-Jan-93, by J.Harper,
 * added #ifdef __STDC__ prototype sections so I can use registerized
 * arguments
 *
 * also, I added the regsublen() function for safety & general usefulness
 * (regsub() has no checks for overstepping its dest string)
 */

#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

#ifdef __STDC__
#include <string.h>
void	regerror(char *);
#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;

    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';
}

/*
 * - regsublen - dummy regsub() returning length of contructed string,
 * including terminating '\0'
 */
int
regsublen(prog, source)
    regexp	   *prog;
    char	   *source;
{
    register char  *src;
    register char   c;
    register int    no;
    register int    dstlen = 1;

    if (prog == NULL || source == NULL) {
	regerror("NULL parm to regsublen");
	return(0);
    }
    if (UCHARAT(prog->program) != MAGIC) {
	regerror("damaged regexp fed to regsublen");
	return(0);
    }
    src = source;
    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++;
	    dstlen++;
	} else if (prog->startp[no] != NULL && prog->endp[no] != NULL) {
	    dstlen += prog->endp[no] - prog->startp[no];
	}
    }
    return(dstlen);
}