BSD 4 release

[unix-history] / usr / src / 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("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 = rindex(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) {
               fprintf(stdout, "#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)
                       fprintf(stdout, "#else %s%s\n", oneflag && oldfile==1 ? "!" : "", ifdef2);
               else {
                       if (oneflag) {
                               /* There was only one ifdef given */
                               endifname = ifdef2;
                               if (oldfile)
                                       fprintf(stdout, "#ifndef %s\n", endifname);
                               else
                                       fprintf(stdout, "#ifdef %s\n", endifname);
                       }
                       else {
                               endifname = oldfile ? ifdef1 : ifdef2;
                               fprintf(stdout, "#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) {
               fprintf(stdout, "#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));
}