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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  
#include  
#include  
#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) 
const regexp *prog; 
const 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 = (char *)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'; 
}