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diff.c
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C/C++ Source or Header
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1990-07-19
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6KB
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346 lines
/* diff - print differences between 2 files Author: Erik Baalbergen */
/* Poor man's implementation of diff(1)
- no options available
- may give more output than other diffs, due to the straight-forward algorithm
- runs out of memory if the differing chunks become too large
- input line length should not exceed LINELEN; longer lines are truncated,
while only the first LINELEN characters are compared
- Bug fixes by Rick Thomas Sept. 1989
Please report bugs and suggestions to erikb@cs.vu.nl
*/
#include <stdio.h>
#define LINELEN 128
FILE *fopen();
char *prog;
int diffs = 0;
main(argc, argv)
char **argv;
{
FILE *fp1 = NULL, *fp2 = NULL;
prog = *argv++;
if (argc != 3) fatal("Usage: %s file1 file2", prog);
if (strcmp(argv[0], "-") == 0)
fp1 = stdin;
else if (strcmp(argv[1], "-") == 0)
fp2 = stdin;
if (fp1 == NULL && (fp1 = fopen(argv[0], "r")) == NULL)
fatal("can't read %s", argv[0]);
if (fp2 == NULL && (fp2 = fopen(argv[1], "r")) == NULL)
fatal("can't read %s", argv[1]);
diff(fp1, fp2);
exit(diffs > 0);
}
fatal(fmt, s)
char *fmt, *s;
{
fprintf(stderr, "%s: ", prog);
fprintf(stderr, fmt, s);
fprintf(stderr, "\n");
exit(2);
}
/* The line module */
char *malloc();
char *fgets();
struct line {
struct line *l_next;
char l_text[LINELEN + 2];
char l_eof;
};
struct line *freelist = 0;
#define stepup(ll) ( ((ll) && ((ll)->l_eof==0)) ? (ll)->l_next : (ll) )
struct line *
new_line()
{
register struct line *l;
if (l = freelist)
freelist = freelist->l_next;
else if ((l = (struct line *) malloc(sizeof(struct line))) == 0)
fatal("out of memory");
return l;
}
free_line(l)
register struct line *l;
{
l->l_next = freelist;
freelist = l;
}
int equal_line(l1, l2)
struct line *l1, *l2;
{
if (l1 == 0 || l2 == 0)
return(0);
else if (l1->l_eof || l2->l_eof)
return(l1->l_eof == l2->l_eof);
else
return(strcmp(l1->l_text, l2->l_text) == 0);
}
int equal_3(l1, l2)
struct line *l1, *l2;
{
register int i, ansr;
ansr = 1;
#ifdef DEBUG
if (l1 == 0)
fprintf(stderr, "\t(null)\n");
else if (l1->l_eof)
fprintf(stderr, "\t(eof)\n");
else
fprintf(stderr, "\t%s", l1->l_text);
if (l2 == 0)
fprintf(stderr, "\t(null)\n");
else if (l2->l_eof)
fprintf(stderr, "\t(eof)\n");
else
fprintf(stderr, "\t%s", l2->l_text);
#endif
for (i = 0; i < 3; ++i) {
if (!equal_line(l1, l2)) {
ansr = 0;
break;
}
l1 = stepup(l1);
l2 = stepup(l2);
}
#ifdef DEBUG
fprintf(stderr, "\t%d\n", ansr);
#endif
return(ansr);
}
struct line *
read_line(fp)
FILE *fp;
{
register struct line *l = new_line();
register char *p;
register int c;
(p = &(l->l_text[LINELEN]))[1] = '\377';
l->l_eof = 0;
if (fgets(l->l_text, LINELEN + 2, fp) == NULL) {
l->l_eof = 1;
l->l_text[0] = 0;
} else if ((p[1] & 0377) != 0377 && *p != '\n') {
while ((c = fgetc(fp)) != '\n' && c != EOF) {
}
*p++ = '\n';
*p = '\0';
}
l->l_next = 0;
return l;
}
/* File window handler */
struct f {
struct line *f_bwin, *f_ewin;
struct line *f_aside;
int f_linecnt; /* line number in file of last advanced line */
FILE *f_fp;
};
advance(f)
register struct f *f;
{
register struct line *l;
if (l = f->f_bwin) {
if (f->f_ewin == l)
f->f_bwin = f->f_ewin = 0;
else
f->f_bwin = l->l_next;
free_line(l);
(f->f_linecnt)++;
}
}
aside(f, l)
struct f *f;
struct line *l;
{
register struct line *ll;
if (l == 0) return;
if (ll = l->l_next) {
while (ll->l_next) ll = ll->l_next;
ll->l_next = f->f_aside;
f->f_aside = l->l_next;
l->l_next = 0;
f->f_ewin = l;
}
}
struct line *
next(f)
register struct f *f;
{
register struct line *l;
if (l = f->f_aside) {
f->f_aside = l->l_next;
l->l_next = 0;
} else
l = read_line(f->f_fp);
if (l) {
if (f->f_bwin == 0)
f->f_bwin = f->f_ewin = l;
else {
if (f->f_ewin->l_eof && l->l_eof) {
free_line(l);
return(f->f_ewin);
}
f->f_ewin->l_next = l;
f->f_ewin = l;
}
}
return l;
}
init_f(f, fp)
register struct f *f;
FILE *fp;
{
f->f_bwin = f->f_ewin = f->f_aside = 0;
f->f_linecnt = 0;
f->f_fp = fp;
}
update(f, s)
register struct f *f;
char *s;
{
while (f->f_bwin && f->f_bwin != f->f_ewin) {
printf("%s%s", s, f->f_bwin->l_text);
advance(f);
}
}
/* Diff procedure */
diff(fp1, fp2)
FILE *fp1, *fp2;
{
struct f f1, f2;
struct line *l1, *s1, *b1, *l2, *s2, *b2;
register struct line *ll;
init_f(&f1, fp1);
init_f(&f2, fp2);
l1 = next(&f1);
l2 = next(&f2);
while ((l1->l_eof == 0) || (l2->l_eof == 0)) {
if (equal_line(l1, l2)) {
equal:
advance(&f1);
advance(&f2);
l1 = next(&f1);
l2 = next(&f2);
continue;
}
s1 = b1 = l1;
s2 = b2 = l2;
/* Read several more lines */
next(&f1);
next(&f1);
next(&f2);
next(&f2);
/* Start searching */
search:
next(&f2);
ll = s1;
do {
if (equal_3(ll, b2)) {
l1 = ll;
l2 = b2;
aside(&f1, ll);
aside(&f2, b2);
differ(&f1, &f2);
goto equal;
}
if (ll->l_eof) break;
ll = stepup(ll);
} while (ll);
b2 = stepup(b2);
next(&f1);
ll = s2;
do {
if (equal_3(b1, ll)) {
l1 = b1;
l2 = ll;
aside(&f2, ll);
aside(&f1, b1);
differ(&f1, &f2);
goto equal;
}
if (ll->l_eof) break;
ll = stepup(ll);
} while (ll);
b1 = stepup(b1);
goto search;
}
/* Both of the files reached EOF */
}
differ(f1, f2)
register struct f *f1, *f2;
{
int cnt1 = f1->f_linecnt, len1 = wlen(f1), cnt2 = f2->f_linecnt, len2 = wlen(f2);
if ((len1 = wlen(f1)) || (len2 = wlen(f2))) {
if (len1 == 0) {
printf("%da", cnt1);
range(cnt2 + 1, cnt2 + len2);
} else if (len2 == 0) {
range(cnt1 + 1, cnt1 + len1);
printf("d%d", cnt2);
} else {
range(cnt1 + 1, cnt1 + len1);
putchar('c');
range(cnt2 + 1, cnt2 + len2);
}
putchar('\n');
if (len1) update(f1, "< ");
if (len1 && len2) printf("---\n");
if (len2) update(f2, "> ");
diffs++;
}
}
wlen(f)
struct f *f;
{
register cnt = 0;
register struct line *l = f->f_bwin, *e = f->f_ewin;
while (l && l != e) {
cnt++;
l = l->l_next;
}
return cnt;
}
range(a, b)
{
printf(((a == b) ? "%d" : "%d,%d"), a, b);
}