Xref: utzoo comp.sources.d:7058 comp.sources.bugs:2971 alt.sources.patches:36
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From: djm@eng.umd.edu (David J. MacKenzie)
Newsgroups: comp.sources.d,comp.sources.bugs,alt.sources.patches
Subject: Re: compress 4.1 file deletion fixes
Message-ID: <DJM.91Jun28142309@rift.eng.umd.edu>
Date: 28 Jun 91 19:23:09 GMT
References: <csm-v20i064=compress.133807@sparky.imd.sterling.com>
	<1991Jun26.221030.23987@motcad.portal.com>
	<DJM.91Jun27022257@egypt.eng.umd.edu>
	<1991Jun28.153802.22464@agate.berkeley.edu>
Organization: Project GLUE, University of Maryland
Lines: 81

> Pardon the ignorance, but what kind of diff format is the one above?
> Larry Wall's patch doesn't seem to recognise it.

Sorry, I forgot to mention it.  It's a unified diff, produced by GNU
diff 1.15.  It's like context format except that it omits duplicate
context lines to save space.  If you can anonymous ftp,
prep.ai.mit.edu:pub/gnu/patch-2.0.12u4.tar.Z is a version of patch
that recognizes unified diffs.  If not, here is a short program called
unipatch that converts unified diffs to context diffs.  It came from
comp.sources.misc "v14i070: Unified context diff tools" plus a patch
in comp.sources.bugs.  You'll likely be seeing more unified diffs on
the net as time goes on, so it's worth while having programs that can
deal with them.


/*
A filter to turn a unidiff into a degenerate context diff (no '!'s)
for patch. Author: davison@dri.com (uunet!drivax!davison).
*/
#include <stdio.h>
#define ERR(a) {fputs(a,stderr);exit(1);}
struct Ln {
	struct Ln *lk;
	char t;
	char s[1];
} r,*h,*ln;
char *malloc();
main()
{
char bf[2048],*cp,ch;
long os,ol,ns,nl,ne,lncnt=0;
for(;;){
 for(;;){
	if(!fgets(bf,sizeof bf,stdin)) exit(0);
	lncnt++;
	if(!strncmp(bf,"@@ -",4)) break;
	if(!strncmp(bf,"+++ ",4)) printf("***%s",bf+3);
	else fputs(bf,stdout);
 }
 if(sscanf(bf+4,"%ld,%ld +%ld,%ld %c",&os,&ol,&ns,&nl,&ch)!=5||ch!='@')
	goto bad;
 r.lk=0, h= &r, ne=ns+nl-1;
 printf("***************\n*** %ld,%ld ****\n",os,os+ol-(os>0));
 while(ol||nl){
	if(!fgets(bf,sizeof bf,stdin)){
		if(nl>2) ERR("Unexpected end of file.\n");
		strcpy(bf," \n");
	}
	lncnt++;
	if(*bf=='\t'||*bf=='\n')
		ch=' ', cp=bf;
	else
		ch= *bf, cp=bf+1;
	switch(ch){
	case'-':if(!ol--) goto bad;
		printf("- %s",cp);
		break;
	case'=':ch=' ';
	case' ':if(!ol--) goto bad;
		printf("  %s",cp);
	case'+':if(!nl--) goto bad;
		ln = (struct Ln*)malloc(sizeof(*ln)+strlen(cp));
		if(!ln) ERR("Out of memory!\n");
		ln->lk=0, ln->t=ch, strcpy(ln->s,cp);
		h->lk=ln, h=ln;
		break;
	default:
	bad:	fprintf(stderr,"Malformed unidiff at line %ld: ",lncnt);
		ERR(bf);
	}
 }
 printf("--- %ld,%ld ----\n",ns,ne);
 for(ln=r.lk;ln;ln=h){
	printf("%c %s",ln->t,ln->s);
	h=ln->lk;
	free(ln);
 }
}
}
--
David J. MacKenzie <djm@eng.umd.edu> <djm@ai.mit.edu>