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regsub.c revision 1.1 
      1 /*
      2  * regsub
      3  *
      4  *	Copyright (c) 1986 by University of Toronto.
      5  *	Written by Henry Spencer.  Not derived from licensed software.
      6  *
      7  *	Permission is granted to anyone to use this software for any
      8  *	purpose on any computer system, and to redistribute it freely,
      9  *	subject to the following restrictions:
     10  *
     11  *	1. The author is not responsible for the consequences of use of
     12  *		this software, no matter how awful, even if they arise
     13  *		from defects in it.
     14  *
     15  *	2. The origin of this software must not be misrepresented, either
     16  *		by explicit claim or by omission.
     17  *
     18  *	3. Altered versions must be plainly marked as such, and must not
     19  *		be misrepresented as being the original software.
     20  */
     21 #include <regexp.h>
     22 #include <stdio.h>
     23 #include <string.h>
     24 #include "regmagic.h"
     25 
     26 #ifndef CHARBITS
     27 #define	UCHARAT(p)	((int)*(unsigned char *)(p))
     28 #else
     29 #define	UCHARAT(p)	((int)*(p)&CHARBITS)
     30 #endif
     31 
     32 /*
     33  - regsub - perform substitutions after a regexp match
     34  */
     35 void
     36 regsub(prog, source, dest)
     37 const regexp *prog;
     38 const char *source;
     39 char *dest;
     40 {
     41 	register char *src;
     42 	register char *dst;
     43 	register char c;
     44 	register int no;
     45 	register int len;
     46 	extern char *strncpy();
     47 
     48 	if (prog == NULL || source == NULL || dest == NULL) {
     49 		regerror("NULL parm to regsub");
     50 		return;
     51 	}
     52 	if (UCHARAT(prog->program) != MAGIC) {
     53 		regerror("damaged regexp fed to regsub");
     54 		return;
     55 	}
     56 
     57 	src = (char *)source;
     58 	dst = dest;
     59 	while ((c = *src++) != '\0') {
     60 		if (c == '&')
     61 			no = 0;
     62 		else if (c == '\\' && '0' <= *src && *src <= '9')
     63 			no = *src++ - '0';
     64 		else
     65 			no = -1;
     66  		if (no < 0) {	/* Ordinary character. */
     67  			if (c == '\\' && (*src == '\\' || *src == '&'))
     68  				c = *src++;
     69  			*dst++ = c;
     70  		} else if (prog->startp[no] != NULL && prog->endp[no] != NULL) {
     71 			len = prog->endp[no] - prog->startp[no];
     72 			(void) strncpy(dst, prog->startp[no], len);
     73 			dst += len;
     74 			if (len != 0 && *(dst-1) == '\0') {	/* strncpy hit NUL. */
     75 				regerror("damaged match string");
     76 				return;
     77 			}
     78 		}
     79 	}
     80 	*dst++ = '\0';
     81 }
     82