V7M/src/cmd/diff3.c
#include <stdio.h>
#
/* diff3 - 3-way differential file comparison*/
/* diff3 [-e] d13 d23 f1 f2 f3
*
* d13 = diff report on f1 vs f3
* d23 = diff report on f2 vs f3
* f1, f2, f3 the 3 files
*/
struct range {int from,to; };
/* from is first in range of changed lines
* to is last+1
* from=to=line after point of insertion
* for added lines
*/
struct diff {struct range old, new;};
#define NC 200
/* de is used to gather editing scripts,
* that are later spewed out in reverse order.
* its first element must be all zero
* the "new" component of de contains line positions
* or byte positions depending on when you look(!?)
*/
struct diff d13[NC];
struct diff d23[NC];
struct diff de[NC];
char line[256];
FILE *fp[3];
int linct[3] = {0,0,0};
/* the number of the last-read line in each file
* is kept in cline[0-2]
*/
int cline[3];
/* the latest known correspondence between line
* numbers of the 3 files is stored in last[1-3]
*/
int last[4];
int eflag;
int debug = 0;
main(argc,argv)
char **argv;
{
register i,m,n;
if(*argv[1]=='-') {
switch(argv[1][1]) {
default:
eflag = 3;
break;
case '3':
eflag = 2;
break;
case 'x':
eflag = 1;
}
argv++;
argc--;
}
if(argc<6) {
fprintf(stderr,"diff3: arg count\n");
exit(1);
}
m = readin(argv[1],d13);
n = readin(argv[2],d23);
for(i=0;i<=2;i++)
if((fp[i] = fopen(argv[i+3],"r")) == NULL) {
printf("diff3: can't open %s\n",argv[i+3]);
exit(1);
}
merge(m,n);
}
/*pick up the line numbers of allcahnges from
* one change file
* (this puts the numbers in a vector, which is not
* strictly necessary, since the vector is processed
* in one sequential pass. The vector could be optimized
* out of existence)
*/
readin(name,dd)
char *name;
struct diff *dd;
{
register i;
int a,b,c,d;
char kind;
char *p;
fp[0] = fopen(name,"r");
for(i=0;getchange(fp[0]);i++) {
if(i>=NC) {
fprintf(stderr,"diff3: too many changes\n");
exit(0);
}
p = line;
a = b = number(&p);
if(*p==',') {
p++;
b = number(&p);
}
kind = *p++;
c = d = number(&p);
if(*p==',') {
p++;
d = number(&p);
}
if(kind=='a')
a++;
if(kind=='d')
c++;
b++;
d++;
dd[i].old.from = a;
dd[i].old.to = b;
dd[i].new.from = c;
dd[i].new.to = d;
}
dd[i].old.from = dd[i-1].old.to;
dd[i].new.from = dd[i-1].new.to;
fclose(fp[0]);
return(i);
}
number(lc)
char **lc;
{
register nn;
nn = 0;
while(digit(**lc))
nn = nn*10 + *(*lc)++ - '0';
return(nn);
}
digit(c)
{
return(c>='0'&&c<='9');
}
getchange(b)
FILE *b;
{
while(getline(b))
if(digit(line[0]))
return(1);
return(0);
}
getline(b)
FILE *b;
{
register i, c;
for(i=0;i<sizeof(line)-1;i++) {
c = getc(b);
if(c==EOF)
break;
line[i] = c;
if(c=='\n') {
line[++i] = 0;
return(i);
}
}
return(0);
}
merge(m1,m2)
{
register struct diff *d1, *d2, *d3;
int dup;
int j;
int t1,t2;
d1 = d13;
d2 = d23;
j = 0;
for(;(t1 = d1<d13+m1) | (t2 = d2<d23+m2);) {
if(debug) {
printf("%d,%d=%d,%d %d,%d=%d,%d\n",
d1->old.from,d1->old.to,
d1->new.from,d1->new.to,
d2->old.from,d2->old.to,
d2->new.from,d2->new.to);
}
/* first file is different from others*/
if(!t2||t1&&d1->new.to < d2->new.from) {
/* stuff peculiar to 1st file */
if(eflag==0) {
separate("1");
change(1,&d1->old,0);
keep(2,&d1->old,&d1->new);
change(3,&d1->new,0);
}
d1++;
continue;
}
/* second file is different from others*/
if(!t1||t2&&d2->new.to < d1->new.from) {
if(eflag==0) {
separate("2");
keep(1,&d2->old,&d2->new);
change(2,&d2->old,0);
change(3,&d2->new,0);
}
d2++;
continue;
}
/* merge overlapping changes in first file
* this happens after extension see below*/
if(d1+1<d13+m1 &&
d1->new.to>=d1[1].new.from) {
d1[1].old.from = d1->old.from;
d1[1].new.from = d1->new.from;
d1++;
continue;
}
/* merge overlapping changes in second*/
if(d2+1<d23+m2 &&
d2->new.to>=d2[1].new.from) {
d2[1].old.from = d2->old.from;
d2[1].new.from = d2->new.from;
d2++;
continue;
}
/* stuff peculiar to third file or different in all*/
if(d1->new.from==d2->new.from&&
d1->new.to==d2->new.to) {
dup = duplicate(&d1->old,&d2->old);
/* dup=0 means all files differ
* dup =1 meands files 1&2 identical*/
if(eflag==0) {
separate(dup?"3":"");
change(1,&d1->old,dup);
change(2,&d2->old,0);
d3 = d1->old.to>d1->old.from?d1:d2;
change(3,&d3->new,0);
} else
j = edit(d1,dup,j);
d1++;
d2++;
continue;
}
/* overlapping changes from file1 & 2
* extend changes appropriately to
* make them coincide*/
if(d1->new.from<d2->new.from) {
d2->old.from -= d2->new.from-d1->new.from;
d2->new.from = d1->new.from;
}
else if(d2->new.from<d1->new.from) {
d1->old.from -= d1->new.from-d2->new.from;
d1->new.from = d2->new.from;
}
if(d1->new.to >d2->new.to) {
d2->old.to += d1->new.to - d2->new.to;
d2->new.to = d1->new.to;
}
else if(d2->new.to >d1->new.to) {
d1->old.to += d2->new.to - d1->new.to;
d1->new.to = d2->new.to;
}
}
if(eflag)
edscript(j);
}
separate(s)
char *s;
{
printf("====%s\n",s);
}
/* the range of ines rold.from thru rold.to in file i
* is to be changed. it is to be printed only if
* it does not duplicate something to be printed later
*/
change(i,rold,dup)
struct range *rold;
{
printf("%d:",i);
last[i] = rold->to;
prange(rold);
if(dup)
return;
if(debug)
return;
i--;
skip(i,rold->from,(char *)0);
skip(i,rold->to," ");
}
/* print the range of line numbers, rold.from thru rold.to
* as n1,n2 or n1
*/
prange(rold)
struct range *rold;
{
if(rold->to<=rold->from)
printf("%da\n",rold->from-1);
else {
printf("%d",rold->from);
if(rold->to > rold->from+1)
printf(",%d",rold->to-1);
printf("c\n");
}
}
/* no difference was reported by diff between file 1(or 2)
* and file 3, and an artificial dummy difference (trange)
* must be ginned up to correspond to the change reported
* in the other file
*/
keep(i,rold,rnew)
struct range *rold, *rnew;
{
register delta;
struct range trange;
delta = last[3] - last[i];
trange.from = rnew->from - delta;
trange.to = rnew->to - delta;
change(i,&trange,1);
}
/* skip to just befor line number from in file i
* if "pr" is nonzero, print all skipped stuff
* w with string pr as a prefix
*/
skip(i,from,pr)
char *pr;
{
register j,n;
for(n=0;cline[i]<from-1;n+=j) {
if((j=getline(fp[i]))==0)
trouble();
if(pr)
printf("%s%s",pr,line);
cline[i]++;
}
return(n);
}
/* return 1 or 0 according as the old range
* (in file 1) contains exactly the same data
* as the new range (in file 2)
*/
duplicate(r1,r2)
struct range *r1, *r2;
{
register c,d;
register nchar;
int nline;
if(r1->to-r1->from != r2->to-r2->from)
return(0);
skip(0,r1->from,(char *)0);
skip(1,r2->from,(char *)0);
nchar = 0;
for(nline=0;nline<r1->to-r1->from;nline++) {
do {
c = getc(fp[0]);
d = getc(fp[1]);
if(c== -1||d== -1)
trouble();
nchar++;
if(c!=d) {
repos(nchar);
return;
}
} while(c!= '\n');
}
repos(nchar);
return(1);
}
repos(nchar)
{
register i;
for(i=0;i<2;i++)
fseek(fp[i], (long)-nchar, 1);
}
trouble()
{
fprintf(stderr,"diff3: logic error\n");
abort();
}
/* collect an editing script for later regurgitation
*/
edit(diff,dup,j)
struct diff *diff;
{
if(((dup+1)&eflag)==0)
return(j);
j++;
de[j].old.from = diff->old.from;
de[j].old.to = diff->old.to;
de[j].new.from = de[j-1].new.to
+skip(2,diff->new.from,(char *)0);
de[j].new.to = de[j].new.from
+skip(2,diff->new.to,(char *)0);
return(j);
}
/* regurgitate */
edscript(n)
{
register j,k;
char block[512];
for(n=n;n>0;n--) {
prange(&de[n].old);
fseek(fp[2], (long)de[n].new.from, 0);
for(k=de[n].new.to-de[n].new.from;k>0;k-= j) {
j = k>512?512:k;
if(fread(block,1,j,fp[2])!=j)
trouble();
fwrite(block, 1, j, stdout);
}
printf(".\n");
}
}