PWB1/sys/source/s1/diff.c
#
/* diff - differential file comparison
*
* 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 lenght 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.
*/
#include <stdio.h>
#define WORD 0177777L
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]*/
int opt; /* -1,0,1 = -e,normal,-f */
int bflag;
char *tempfile; /*used when comparing against std input*/
char *mktemp();
char *dummy; /*used in resetting storage search ptr*/
done(code) int code;
{
unlink(tempfile);
exit(code);
}
donesig()
{
unlink(tempfile);
exit(5);
}
char *talloc(n)
{
extern char *alloc();
register p;
p = alloc(n);
if(p!=-1)
return(p);
noroom();
}
char *ralloc(p,n) /*compacting reallocation */
char *p;
{
register q;
free(p);
free(dummy);
dummy = alloc(1);
q = realloc(p,n);
if(q==-1 || q==0)
noroom();
return(q);
}
noroom()
{
mesg("Out of space.\n");
done(1);
}
mesg(s)
char *s;
{
while(*s)
write(2,s++,1);
}
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 = talloc((l+1)*sizeof(a[0]));
for(i=1;i<=l;i++)
a[f[i].serial] = f[i].value;
for(i=1;i<=l;i++)
b[i] = a[i];
free(a);
}
filename(pa1, pa2)
char **pa1, **pa2;
{
register char *a1, *b1, *a2;
int buf[256];
int i, f;
a1 = *pa1;
a2 = *pa2;
if(stat(a1,buf)!=-1&&(buf[2]&040000)!=0) {
b1 = *pa1 = alloc(100);
while(*b1++ = *a1++) ;
b1[-1] = '/';
a1 = b1;
while(*a1++ = *a2++)
if(*a2 && *a2!='/' && a2[-1]=='/')
a1 = b1;
}
else if(a1[0]=='-'&&a1[1]==0&&tempfile==0) {
signal(2,donesig);
*pa1 = tempfile = mktemp("/tmp/dXXXXX");
if((f=creat(tempfile,0600)) < 0) {
mesg("Cannot creat");
mesg(tempfile);
mesg("\n");
done(2);
}
while((i=read(0,buf,512))>0)
write(f,buf,i);
close(f);
}
}
prepare(i, arg)
char *arg;
{
register struct line *p;
register j,h;
if((input[i] = fopen(arg,"r")) == NULL){
mesg("Cannot open ");
mesg(arg);
mesg("\n");
done(3);
}
p = talloc(3*sizeof(line));
for(j=0; h=readhash(input[i]);) {
p = ralloc(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;
}
main(argc, argv)
char **argv;
{
register int k;
if(argc>3 && *argv[1]=='-') {
argc--;
argv++;
while(*++*argv) {
switch(**argv) {
case 'e':
opt = -1;
break;
case 'f':
opt = 1;
break;
case 'b':
bflag = 1;
break;
}
}
}
if(argc!=3) {
mesg("Arg count\n");
done(4);
}
dummy = alloc(1);
filename(&argv[1], &argv[2]);
filename(&argv[2], &argv[1]);
prepare(0, argv[1]);
prepare(1, argv[2]);
prune();
sort(sfile[0],slen[0]);
sort(sfile[1],slen[1]);
member = file[1];
equiv(sfile[0], slen[0], sfile[1], slen[1], member);
member = ralloc(member,(slen[1]+2)*sizeof(*member));
class = file[0];
unsort(sfile[0], slen[0], class);
class = ralloc(class,(slen[0]+2)*sizeof(*class));
klist = talloc((slen[0]+2)*sizeof(*klist));
clist = talloc(sizeof(cand));
k = stone(class, slen[0], member, klist);
free(member);
free(class);
J = talloc((len[0]+2)*sizeof(*J));
unravel(klist[k]);
free(clist);
free(klist);
ixold = talloc((len[0]+2)*sizeof(*ixold));
ixnew = talloc((len[1]+2)*sizeof(*ixnew));
check(argv);
output(argv);
done(0);
}
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 = ralloc(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 counfounding by hashing (which result in "jackpot")
2. collect random access indexes to the two files */
check(argv)
char **argv;
{
register int i, j;
int jackpot;
long ctold, ctnew;
char c,d;
input[0] = fopen(argv[1],"r");
input[1] = fopen(argv[2],"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 && blank(c) && blank(d)) {
do {
if(c=='\n') break;
ctold++;
} while(blank(c=getc(input[0])));
do {
if(d=='\n') break;
ctnew++;
} while(blank(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)
mesg("Jackpot\n");
}
skipline(f)
{
register i;
for(i=1;getc(input[f])!='\n';i++) ;
return(i);
}
blank(c)
char c;
{
switch(c) {
case '\t':
case ' ':
case '\n':
return(1);
}
return(0);
}
output(argv)
char **argv;
{
int m;
register int i0, i1, j1;
int j0;
input[0] = fopen(argv[1],"r");
input[1] = fopen(argv[2],"r");
m = len[0];
J[0] = 0;
J[m+1] = len[1]+1;
if(opt!=-1) 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]);
flush();
}
change(a,b,c,d)
{
if(a>b&&c>d) return;
if(opt!=1) {
range(a,b,",");
putchar(a>b?'a':c>d?'d':'c');
if(opt!=-1) range(c,d,",");
} else {
putchar(a>b?'a':c>d?'d':'c');
range(a,b," ");
}
putchar('\n');
if(opt==0) {
fetch(ixold,a,b,input[0],"< ");
if(a<=b&&c<=d) prints("---\n");
}
fetch(ixnew,c,d,input[1],opt==0?"> ":"");
if(opt!=0&&c<=d) prints(".\n");
}
range(a,b,separator)
char *separator;
{
if(a>b) printn(b);
if(a<=b) printn(a);
if(a<b) {
prints(separator);
printn(b);
}
}
fetch(f,a,b,lb,s)
long *f;
FILE *lb;
char *s;
{
register int i, j;
register int nc;
for(i=a;i<=b;i++) {
fseek(lb,f[i-1],0);
nc = f[i]-f[i-1];
prints(s);
for(j=0;j<nc;j++)
putchar(getc(lb));
}
}
/* 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 shift;
register space;
register t;
struct { int hi, lo; };
sum = 1;
space = 0;
if(!bflag) for(shift=0;(t=getc(f))!='\n';shift=+7) {
if(t==-1)
return(0);
sum =+ (t+0L) << (shift=& 017);
}
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 =+ (t+0L) <<(shift=& 017);
shift =+ 7;
continue;
case '\n':
break;
}
break;
}
sum = (sum.lo&WORD) + sum.hi;
return(sum.lo+sum.hi);
}
prints(s)
register char *s;
{
while(*s)
putchar(*s++);
}
printn(n)
register n;
{
if(n>9) printn(n/10);
putchar(n%10 + '0');
}