V9/cmd/diff/diffreg.c
static char sccsid[] = "@(#)diffreg.c 4.1 10/9/80";
#include "diff.h"
/*
* diff - compare two files.
*/
/*
* Uses an algorithm due to Harold Stone, which finds
* a pair of longest identical subsequences in the two
* files.
*
* The major goal is to generate the match vector J.
* J[i] is the index of the line in file1 corresponding
* to line i file0. J[i] = 0 if there is no
* such line in file1.
*
* Lines are hashed so as to work in core. All potential
* matches are located by sorting the lines of each file
* on the hash (called ``value''). In particular, this
* collects the equivalence classes in file1 together.
* Subroutine equiv replaces the value of each line in
* file0 by the index of the first element of its
* matching equivalence in (the reordered) file1.
* To save space equiv squeezes file1 into a single
* array member in which the equivalence classes
* are simply concatenated, except that their first
* members are flagged by changing sign.
*
* Next the indices that point into member are unsorted into
* array class according to the original order of file0.
*
* The cleverness lies in routine stone. This marches
* through the lines of file0, developing a vector klist
* of "k-candidates". At step i a k-candidate is a matched
* pair of lines x,y (x in file0 y in file1) such that
* there is a common subsequence of length k
* between the first i lines of file0 and the first y
* lines of file1, but there is no such subsequence for
* any smaller y. x is the earliest possible mate to y
* that occurs in such a subsequence.
*
* Whenever any of the members of the equivalence class of
* lines in file1 matable to a line in file0 has serial number
* less than the y of some k-candidate, that k-candidate
* with the smallest such y is replaced. The new
* k-candidate is chained (via pred) to the current
* k-1 candidate so that the actual subsequence can
* be recovered. When a member has serial number greater
* that the y of all k-candidates, the klist is extended.
* At the end, the longest subsequence is pulled out
* and placed in the array J by unravel
*
* With J in hand, the matches there recorded are
* check'ed against reality to assure that no spurious
* matches have crept in due to hashing. If they have,
* they are broken, and "jackpot" is recorded--a harmless
* matter except that a true match for a spuriously
* mated line may now be unnecessarily reported as a change.
*
* Much of the complexity of the program comes simply
* from trying to minimize core utilization and
* maximize the range of doable problems by dynamically
* allocating what is needed and reusing what is not.
* The core requirements for problems larger than somewhat
* are (in words) 2*length(file0) + length(file1) +
* 3*(number of k-candidates installed), typically about
* 6n words for files of length n.
*/
#define prints(s) fputs(s,stdout)
FILE *input[2];
FILE *fopen();
struct cand {
int x;
int y;
int pred;
} cand;
struct line {
int serial;
int value;
} *file[2], line;
int len[2];
struct line *sfile[2]; /* shortened by pruning common prefix and suffix */
int slen[2];
int pref, suff; /* length of prefix and suffix */
int *class; /* will be overlaid on file[0] */
int *member; /* will be overlaid on file[1] */
int *klist; /* will be overlaid on file[0] after class */
struct cand *clist; /* merely a free storage pot for candidates */
int clen = 0;
int *J; /* will be overlaid on class */
long *ixold; /* will be overlaid on klist */
long *ixnew; /* will be overlaid on file[1] */
diffreg()
{
register int k;
if (hflag) {
diffargv[0] = "diffh";
execv(diffh, diffargv);
fprintf(stderr, "diff: ");
perror(diffh);
done();
}
dummy = malloc(1);
if ((stb1.st_mode & S_IFMT) == S_IFDIR)
file1 = splice(file1, file2);
else if ((stb2.st_mode & S_IFMT) == S_IFDIR)
file2 = splice(file2, file1);
else if (!strcmp(file1, "-")) {
if (!strcmp(file2, "-")) {
fprintf(stderr, "diff: can't specify - -\n");
done();
}
file1 = copytemp();
} else if (!strcmp(file2, "-"))
file2 = copytemp();
prepare(0, file1);
prepare(1, file2);
prune();
sort(sfile[0],slen[0]);
sort(sfile[1],slen[1]);
member = (int *)file[1];
equiv(sfile[0], slen[0], sfile[1], slen[1], member);
member = (int *)ralloc((char *)member,(slen[1]+2)*sizeof(int));
class = (int *)file[0];
unsort(sfile[0], slen[0], class);
class = (int *)ralloc((char *)class,(slen[0]+2)*sizeof(int));
klist = (int *)talloc((slen[0]+2)*sizeof(int));
clist = (struct cand *)talloc(sizeof(cand));
k = stone(class, slen[0], member, klist);
free((char *)member);
free((char *)class);
J = (int *)talloc((len[0]+2)*sizeof(int));
unravel(klist[k]);
free((char *)clist);
free((char *)klist);
ixold = (long *)talloc((len[0]+2)*sizeof(long));
ixnew = (long *)talloc((len[1]+2)*sizeof(long));
check();
output();
status = anychange;
if (opt == D_CONTEXT && anychange == 0)
printf("No differences encountered\n");
done();
}
char *
copytemp()
{
char buf[BUFSIZ];
register int i, f;
signal(SIGHUP,done);
signal(SIGINT,done);
signal(SIGPIPE,done);
signal(SIGTERM,done);
tempfile = mktemp("/tmp/dXXXXX");
f = creat(tempfile,0600);
if (f < 0) {
fprintf(stderr, "diff: ");
perror(tempfile);
done();
}
while ((i = read(0,buf,BUFSIZ)) > 0)
if (write(f,buf,i) != i) {
fprintf(stderr, "diff: ");
perror(tempfile);
done();
}
close(f);
return (tempfile);
}
char *
splice(dir, file)
char *dir, *file;
{
char *tail;
char buf[BUFSIZ];
if (!strcmp(file, "-")) {
fprintf(stderr, "diff: can't specify - with other arg directory\n");
done();
}
tail = strrchr(file, '/');
if (tail == 0)
tail = file;
else
tail++;
sprintf(buf, "%s/%s", dir, tail);
return (savestr(buf));
}
prepare(i, arg)
char *arg;
{
register struct line *p;
register j,h;
if((input[i] = fopen(arg,"r")) == NULL){
fprintf(stderr, "diff: ");
perror(arg);
done();
}
p = (struct line *)talloc(3*sizeof(line));
for(j=0; h=readhash(input[i]);) {
p = (struct line *)ralloc((char *)p,(++j+3)*sizeof(line));
p[j].value = h;
}
len[i] = j;
file[i] = p;
fclose(input[i]);
}
prune()
{
register i,j;
for(pref=0;pref<len[0]&&pref<len[1]&&
file[0][pref+1].value==file[1][pref+1].value;
pref++ ) ;
for(suff=0;suff<len[0]-pref&&suff<len[1]-pref&&
file[0][len[0]-suff].value==file[1][len[1]-suff].value;
suff++) ;
for(j=0;j<2;j++) {
sfile[j] = file[j]+pref;
slen[j] = len[j]-pref-suff;
for(i=0;i<=slen[j];i++)
sfile[j][i].serial = i;
}
}
equiv(a,n,b,m,c)
struct line *a, *b;
int *c;
{
register int i, j;
i = j = 1;
while(i<=n && j<=m) {
if(a[i].value <b[j].value)
a[i++].value = 0;
else if(a[i].value == b[j].value)
a[i++].value = j;
else
j++;
}
while(i <= n)
a[i++].value = 0;
b[m+1].value = 0;
j = 0;
while(++j <= m) {
c[j] = -b[j].serial;
while(b[j+1].value == b[j].value) {
j++;
c[j] = b[j].serial;
}
}
c[j] = -1;
}
stone(a,n,b,c)
int *a;
int *b;
int *c;
{
register int i, k,y;
int j, l;
int oldc, tc;
int oldl;
k = 0;
c[0] = newcand(0,0,0);
for(i=1; i<=n; i++) {
j = a[i];
if(j==0)
continue;
y = -b[j];
oldl = 0;
oldc = c[0];
do {
if(y <= clist[oldc].y)
continue;
l = search(c, k, y);
if(l!=oldl+1)
oldc = c[l-1];
if(l<=k) {
if(clist[c[l]].y <= y)
continue;
tc = c[l];
c[l] = newcand(i,y,oldc);
oldc = tc;
oldl = l;
} else {
c[l] = newcand(i,y,oldc);
k++;
break;
}
} while((y=b[++j]) > 0);
}
return(k);
}
newcand(x,y,pred)
{
register struct cand *q;
clist = (struct cand *)ralloc((char *)clist,++clen*sizeof(cand));
q = clist + clen -1;
q->x = x;
q->y = y;
q->pred = pred;
return(clen-1);
}
search(c, k, y)
int *c;
{
register int i, j, l;
int t;
if(clist[c[k]].y<y) /*quick look for typical case*/
return(k+1);
i = 0;
j = k+1;
while((l=(i+j)/2) > i) {
t = clist[c[l]].y;
if(t > y)
j = l;
else if(t < y)
i = l;
else
return(l);
}
return(l+1);
}
unravel(p)
{
register int i;
register struct cand *q;
for(i=0; i<=len[0]; i++)
J[i] = i<=pref ? i:
i>len[0]-suff ? i+len[1]-len[0]:
0;
for(q=clist+p;q->y!=0;q=clist+q->pred)
J[q->x+pref] = q->y+pref;
}
/* check does double duty:
1. ferret out any fortuitous correspondences due
to confounding by hashing (which result in "jackpot")
2. collect random access indexes to the two files */
check()
{
register int i, j;
int jackpot;
long ctold, ctnew;
char c,d;
input[0] = fopen(file1,"r");
input[1] = fopen(file2,"r");
j = 1;
ixold[0] = ixnew[0] = 0;
jackpot = 0;
ctold = ctnew = 0;
for(i=1;i<=len[0];i++) {
if(J[i]==0) {
ixold[i] = ctold += skipline(0);
continue;
}
while(j<J[i]) {
ixnew[j] = ctnew += skipline(1);
j++;
}
for(;;) {
c = getc(input[0]);
d = getc(input[1]);
ctold++;
ctnew++;
if(bflag && isspace(c) && isspace(d)) {
do {
if(c=='\n') break;
ctold++;
} while(isspace(c=getc(input[0])));
do {
if(d=='\n') break;
ctnew++;
} while(isspace(d=getc(input[1])));
}
if(c!=d) {
jackpot++;
J[i] = 0;
if(c!='\n')
ctold += skipline(0);
if(d!='\n')
ctnew += skipline(1);
break;
}
if(c=='\n')
break;
}
ixold[i] = ctold;
ixnew[j] = ctnew;
j++;
}
for(;j<=len[1];j++) {
ixnew[j] = ctnew += skipline(1);
}
fclose(input[0]);
fclose(input[1]);
/*
if(jackpot)
fprintf(stderr, "jackpot\n");
*/
}
sort(a,n) /*shellsort CACM #201*/
struct line *a;
{
struct line w;
register int j,m;
struct line *ai;
register struct line *aim;
int k;
for(j=1;j<=n;j*= 2)
m = 2*j - 1;
for(m/=2;m!=0;m/=2) {
k = n-m;
for(j=1;j<=k;j++) {
for(ai = &a[j]; ai > a; ai -= m) {
aim = &ai[m];
if(aim < ai)
break; /*wraparound*/
if(aim->value > ai[0].value ||
aim->value == ai[0].value &&
aim->serial > ai[0].serial)
break;
w.value = ai[0].value;
ai[0].value = aim->value;
aim->value = w.value;
w.serial = ai[0].serial;
ai[0].serial = aim->serial;
aim->serial = w.serial;
}
}
}
}
unsort(f, l, b)
struct line *f;
int *b;
{
register int *a;
register int i;
a = (int *)talloc((l+1)*sizeof(int));
for(i=1;i<=l;i++)
a[f[i].serial] = f[i].value;
for(i=1;i<=l;i++)
b[i] = a[i];
free((char *)a);
}
skipline(f)
{
register i;
for(i=1;getc(input[f])!='\n';i++) ;
return(i);
}
output()
{
int m;
register int i0, i1, j1;
int j0;
input[0] = fopen(file1,"r");
input[1] = fopen(file2,"r");
m = len[0];
J[0] = 0;
J[m+1] = len[1]+1;
if(opt!=D_EDIT) for(i0=1;i0<=m;i0=i1+1) {
while(i0<=m&&J[i0]==J[i0-1]+1) i0++;
j0 = J[i0-1]+1;
i1 = i0-1;
while(i1<m&&J[i1+1]==0) i1++;
j1 = J[i1+1]-1;
J[i1] = j1;
change(i0,i1,j0,j1);
} else for(i0=m;i0>=1;i0=i1-1) {
while(i0>=1&&J[i0]==J[i0+1]-1&&J[i0]!=0) i0--;
j0 = J[i0+1]-1;
i1 = i0+1;
while(i1>1&&J[i1-1]==0) i1--;
j1 = J[i1-1]+1;
J[i1] = j1;
change(i1,i0,j1,j0);
}
if(m==0)
change(1,0,1,len[1]);
if (opt==D_IFDEF) {
for (;;) {
#define c i0
c = getc(input[0]);
if (c < 0)
return;
putchar(c);
}
#undef c
}
}
/* indicate that there is a difference between lines a and b of the from file
to get to lines c to d of the to file.
If a is greater then b then there are no lines in the from file involved
and this means that there were lines appended (beginning at b).
If c is greater than d then there are lines missing from the to file.
*/
change(a,b,c,d)
{
char ch;
int lowa,upb,lowc,upd;
struct stat stbuf;
if (opt != D_IFDEF && a>b && c>d)
return;
if (anychange == 0) {
anychange = 1;
if(opt == D_CONTEXT) {
printf("*** %s ", file1);
stat(file1, &stbuf);
printf("%s--- %s ",
ctime(&stbuf.st_mtime), file2);
stat(file2, &stbuf);
printf("%s", ctime(&stbuf.st_mtime));
}
}
if (a <= b && c <= d)
ch = 'c';
else
ch = (a <= b) ? 'd' : 'a';
if(opt == D_CONTEXT) {
lowa = max(1, a-context);
upb = min(len[0], b+context);
lowc = max(1, c-context);
upd = min(len[1], d+context);
/* print out from file */
printf("***************\n*** ");
range(lowa,upb,",");
printf("\n");
if (ch == 'a')
fetch(ixold,lowa,upb,input[0]," ");
else {
fetch(ixold,lowa,a-1,input[0]," ");
fetch(ixold,a,b,input[0],ch == 'c' ? "! " : "- ");
fetch(ixold,b+1,upb,input[0]," ");
}
putchar('\n');
printf("--- ");
range(lowc,upd,",");
printf(" -----\n");
if (ch == 'd')
fetch(ixnew,lowc,upd,input[1]," ");
else {
fetch(ixnew,lowc,c-1,input[1]," ");
fetch(ixnew,c,d,input[1],ch == 'c' ? "! " : "+ ");
fetch(ixnew,d+1,upd,input[1]," ");
}
return;
}
switch (opt) {
case D_NORMAL:
case D_EDIT:
range(a,b,",");
putchar(a>b?'a':c>d?'d':'c');
if(opt==D_NORMAL)
range(c,d,",");
putchar('\n');
break;
case D_REVERSE:
putchar(a>b?'a':c>d?'d':'c');
range(a,b," ");
putchar('\n');
break;
}
if(opt == D_NORMAL || opt == D_IFDEF) {
fetch(ixold,a,b,input[0],"< ", 1);
if(a<=b&&c<=d && opt == D_NORMAL)
prints("---\n");
}
fetch(ixnew,c,d,input[1],opt==D_NORMAL?"> ":"", 0);
if ((opt ==D_EDIT || opt == D_REVERSE) && c<=d)
prints(".\n");
if (inifdef) {
printf("#endif %s\n", endifname);
inifdef = 0;
}
}
range(a,b,separator)
char *separator;
{
printf("%d", a>b?b:a);
if(a<b) {
printf("%s%d", separator, b);
}
}
fetch(f,a,b,lb,s,oldfile)
long *f;
FILE *lb;
char *s;
{
register int i, j;
register int nc;
int oneflag = (*ifdef1!='\0') != (*ifdef2!='\0');
/*
* When doing #ifdef's, copy down to current line
* if this is the first file, so that stuff makes it to output.
*/
if (opt == D_IFDEF && oldfile){
long curpos = ftell(lb);
/* print through if append (a>b), else to (nb: 0 vs 1 orig) */
nc = f[a>b? b : a-1 ] - curpos;
for (i = 0; i < nc; i++)
putchar(getc(lb));
}
if (a > b)
return;
if (opt == D_IFDEF) {
if (inifdef)
printf("#else %s%s\n", oneflag && oldfile==1 ? "!" : "", ifdef2);
else {
if (oneflag) {
/* There was only one ifdef given */
endifname = ifdef2;
if (oldfile)
printf("#ifndef %s\n", endifname);
else
printf("#ifdef %s\n", endifname);
}
else {
endifname = oldfile ? ifdef1 : ifdef2;
printf("#ifdef %s\n", endifname);
}
}
inifdef = 1+oldfile;
}
for(i=a;i<=b;i++) {
fseek(lb,f[i-1],0);
nc = f[i]-f[i-1];
if (opt != D_IFDEF)
prints(s);
for(j=0;j<nc;j++)
putchar(getc(lb));
}
if (inifdef && !wantelses) {
printf("#endif %s\n", endifname);
inifdef = 0;
}
}
#define HALFLONG 16
#define low(x) (x&((1L<<HALFLONG)-1))
#define high(x) (x>>HALFLONG)
/*
* hashing has the effect of
* arranging line in 7-bit bytes and then
* summing 1-s complement in 16-bit hunks
*/
readhash(f)
FILE *f;
{
long sum;
register unsigned shift;
register space;
register t;
sum = 1;
space = 0;
if(!bflag) for(shift=0;(t=getc(f))!='\n';shift+=7) {
if(t==-1)
return(0);
sum += (long)t << (shift%=HALFLONG);
}
else for(shift=0;;) {
switch(t=getc(f)) {
case -1:
return(0);
case '\t':
case ' ':
space++;
continue;
default:
if(space) {
shift += 7;
space = 0;
}
sum += (long)t << (shift%=HALFLONG);
shift += 7;
continue;
case '\n':
break;
}
break;
}
sum = low(sum) + high(sum);
return((short)low(sum) + (short)high(sum));
}