coreutils/diff.c

/* vi: set sw=4 ts=4: */
/*
 * Mini diff implementation for busybox, adapted from OpenBSD diff.
 *
 * Copyright (C) 2006 by Robert Sullivan <cogito.ergo.cogito@hotmail.com>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
 */

/*
 * Copyright (c) 2003 Todd C. Miller <Todd.Miller@courtesan.com>
 *
 * Permission to
 * use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 *
 * Sponsored in part by the Defense Advanced Research Projects
 * Agency (DARPA) and Air Force Research Laboratory, Air Force
 * Materiel Command, USAF, under agreement number F39502-99-1-0512.
 */

#include <time.h>
#include <sys/types.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <ctype.h>
#include <errno.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <string.h>
#include <unistd.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <stddef.h>
#include <paths.h>
#include <dirent.h>
#include "busybox.h"

#define FSIZE_MAX 32768

/*
 * Output flags
 */
#define D_HEADER        1        /* Print a header/footer between files */
#define D_EMPTY1        2        /* Treat first file as empty (/dev/null) */
#define D_EMPTY2        4        /* Treat second file as empty (/dev/null) */

/*
 * Status values for print_status() and diffreg() return values
 * Guide:
 * D_SAME - files are the same
 * D_DIFFER - files differ
 * D_BINARY - binary files differ
 * D_COMMON - subdirectory common to both dirs
 * D_ONLY - file only exists in one dir
 * D_MISMATCH1 - path1 a dir, path2 a file
 * D_MISMATCH2 - path1 a file, path2 a dir
 * D_ERROR - error occurred
 * D_SKIPPED1 - skipped path1 as it is a special file
 * D_SKIPPED2 - skipped path2 as it is a special file
 */

#define D_SAME		0
#define D_DIFFER	(1<<0)
#define D_BINARY	(1<<1)
#define D_COMMON	(1<<2)
#define D_ONLY		(1<<3)
#define D_MISMATCH1	(1<<4)
#define D_MISMATCH2	(1<<5)
#define D_ERROR		(1<<6)
#define D_SKIPPED1	(1<<7)
#define D_SKIPPED2	(1<<8)

/* Command line options */
static unsigned long cmd_flags;
#define FLAG_a	(1<<0)
#define FLAG_b	(1<<1)
#define FLAG_d  (1<<2)
#define FLAG_i	(1<<3)
#define FLAG_L	(1<<4)
#define FLAG_N	(1<<5)
#define FLAG_q	(1<<6)
#define FLAG_r	(1<<7)
#define FLAG_s	(1<<8)
#define FLAG_S	(1<<9)
#define FLAG_t	(1<<10)
#define FLAG_T	(1<<11)
#define FLAG_U	(1<<12)
#define	FLAG_w	(1<<13)

int context, status;
char *start, *label[2];
struct stat stb1, stb2;
char **dl;
int dl_count = 0;

struct cand {
        int x;
        int y;
        int pred;
};

struct line {
        int serial;
        int value;
} *file[2];

/*
 * The following struct is used to record change information
 * doing a "context" or "unified" diff.  (see routine "change" to
 * understand the highly mnemonic field names)
 */
struct context_vec {
        int a;                        /* start line in old file */
        int b;                        /* end line in old file */
        int c;                        /* start line in new file */
        int d;                        /* end line in new file */
};

static int  *J;                 /* will be overlaid on class */
static int  *class;             /* will be overlaid on file[0] */
static int  *klist;             /* will be overlaid on file[0] after class */
static int  *member;            /* will be overlaid on file[1] */
static int   clen;
static int   len[2];
static int   pref, suff;        /* length of prefix and suffix */
static int   slen[2];
static int   anychange;
static long *ixnew;             /* will be overlaid on file[1] */
static long *ixold;             /* will be overlaid on klist */
static struct cand *clist;      /* merely a free storage pot for candidates */
static int   clistlen;          /* the length of clist */
static struct line *sfile[2];   /* shortened by pruning common prefix/suffix */
static struct context_vec *context_vec_start;
static struct context_vec *context_vec_end;
static struct context_vec *context_vec_ptr;

static void print_only(const char *path, size_t dirlen, const char *entry)
{
        if (dirlen > 1)
                dirlen--;
        printf("Only in %.*s: %s\n", (int)dirlen, path, entry);
}

static void print_status(int val, char *path1, char *path2, char *entry)
{
	const char * const _entry = entry ? entry : "";
	char *_path1 = entry ? concat_path_file(path1, _entry) : path1;
	char *_path2 = entry ? concat_path_file(path2, _entry) : path2;
        switch (val) {
        case D_ONLY:
                print_only(path1, strlen(path1), entry);
                break;
        case D_COMMON:
                printf("Common subdirectories: %s and %s\n", _path1, _path2);
                break;
        case D_BINARY:
                printf("Binary files %s and %s differ\n", _path1, _path2);
                break;
        case D_DIFFER:
                if (cmd_flags & FLAG_q)
                        printf("Files %s and %s differ\n", _path1, _path2);
                break;
        case D_SAME:
                if (cmd_flags & FLAG_s)
                        printf("Files %s and %s are identical\n", _path1, _path2);
                break;
        case D_MISMATCH1:
                printf("File %s is a directory while file %s is a regular file\n",
                    _path1, _path2);
                break;
        case D_MISMATCH2:
                printf("File %s is a regular file while file %s is a directory\n",
                    _path1, _path2);
                break;
        case D_SKIPPED1:
                printf("File %s is not a regular file or directory and was skipped\n",
                    _path1);
                break;
        case D_SKIPPED2:
                printf("File %s is not a regular file or directory and was skipped\n",
                    _path2);
                break;
        }
		if (entry) {
			free(_path1);
			free(_path2);
		}
}

/*
 * Hash function taken from Robert Sedgewick, Algorithms in C, 3d ed., p 578.
 */
static int readhash(FILE *f)
{
        int i, t, space;
        int sum;

        sum = 1;
        space = 0;
        if (!(cmd_flags & FLAG_b) && !(cmd_flags & FLAG_w)) {
                if (FLAG_i)
                        for (i = 0; (t = getc(f)) != '\n'; i++) {
                                if (t == EOF) {
                                        if (i == 0)
                                                return (0);
                                        break;
                                }
                                sum = sum * 127 + t;
                        }
                else
                        for (i = 0; (t = getc(f)) != '\n'; i++) {
                                if (t == EOF) {
                                        if (i == 0)
                                                return (0);
                                        break;
                                }
                                sum = sum * 127 + t;
                        }
        } else {
                for (i = 0;;) {
                        switch (t = getc(f)) {
                        case '\t':
                        case '\r':
                        case '\v':
                        case '\f':
                        case ' ':
                                space++;
                                continue;
                        default:
                                if (space && !(cmd_flags & FLAG_w)) {
                                        i++;
                                        space = 0;
                                }
                                sum = sum * 127 + t;
                                i++;
                                continue;
                        case EOF:
                                if (i == 0)
                                        return (0);
                                /* FALLTHROUGH */
                        case '\n':
                                break;
                        }
                        break;
                }
        }
        /*
         * There is a remote possibility that we end up with a zero sum.
         * Zero is used as an EOF marker, so return 1 instead.
         */
        return (sum == 0 ? 1 : sum);
}



/*
 * Check to see if the given files differ.
 * Returns 0 if they are the same, 1 if different, and -1 on error.
 */
static int files_differ(FILE *f1, FILE *f2, int flags)
{
        char buf1[BUFSIZ], buf2[BUFSIZ];
        size_t i, j;

        if ((flags & (D_EMPTY1|D_EMPTY2)) || stb1.st_size != stb2.st_size ||
            (stb1.st_mode & S_IFMT) != (stb2.st_mode & S_IFMT))
                return (1);
        while(1) {
                i = fread(buf1, 1, sizeof(buf1), f1);
                j = fread(buf2, 1, sizeof(buf2), f2);
                if (i != j)
                        return (1);
                if (i == 0 && j == 0) {
                        if (ferror(f1) || ferror(f2))
                                return (1);
                        return (0);
                }
                if (memcmp(buf1, buf2, i) != 0)
                        return (1);
        }
}

static void prepare(int i, FILE *fd, off_t filesize)
{
        struct line *p;
        int h;
        size_t j, sz;

        rewind(fd);

        sz = (filesize <= FSIZE_MAX ? filesize : FSIZE_MAX) / 25;
        if (sz < 100)
                sz = 100;

        p = xmalloc((sz + 3) * sizeof(struct line));
        for (j = 0; (h = readhash(fd));) {
                if (j == sz) {
                        sz = sz * 3 / 2;
                        p = xrealloc(p, (sz + 3) * sizeof(struct line));
                }
                p[++j].value = h;
        }
        len[i] = j;
        file[i] = p;
}

static void prune(void)
{
        int 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;
        }
}

static void equiv(struct line *a, int n, struct line *b, int m, int *c)
{
        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;
}

static int isqrt(int n) {
	int y, x = 1;
	if (n == 0) return(0);

	do {
		y = x;
		x = n / x;
		x += y;
		x /= 2;
	} while ((x - y) > 1 || (x - y) < -1);

	return (x);
}

static int newcand(int x, int y, int pred)
{
        struct cand *q;

        if (clen == clistlen) {
                clistlen = clistlen * 11 / 10;
                clist = xrealloc(clist, clistlen * sizeof(struct cand));
        }
        q = clist + clen;
        q->x = x;
        q->y = y;
        q->pred = pred;
        return (clen++);
}


static int search(int *c, int k, int y)
{
        int i, j, l, t;

        if (clist[c[k]].y < y)        /* quick look for typical case */
                return (k + 1);
        i = 0;
        j = k + 1;
        while (1) {
                l = i + j;
                if ((l >>= 1) <= i)
                        break;
                t = clist[c[l]].y;
                if (t > y)
                        j = l;
                else if (t < y)
                        i = l;
                else
                        return (l);
        }
        return (l + 1);
}


static int stone(int *a, int n, int *b, int *c)
{
        int i, k, y, j, l;
        int oldc, tc, oldl;
        u_int numtries;
#if ENABLE_FEATURE_DIFF_MINIMAL
		const u_int bound = (cmd_flags & FLAG_d) ? UINT_MAX : MAX(256, isqrt(n));
#else
		const u_int bound = MAX(256, isqrt(n));
#endif
        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];
                numtries = 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;
                                numtries++;
                        } else {
                                c[l] = newcand(i, y, oldc);
                                k++;
                                break;
                        }
                } while ((y = b[++j]) > 0 && numtries < bound);
        }
        return (k);
}

static void unravel(int p)
{
        struct cand *q;
        int i;

        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;
}


static void unsort(struct line *f, int l, int *b)
{
        int *a, i;

        a = xmalloc((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(a);
}

static int skipline(FILE *f)
{
        int i, c;

        for (i = 1; (c = getc(f)) != '\n' && c != EOF; i++)
                continue;
        return (i);
}


/*
 * 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
 */
static void check(FILE *f1, FILE *f2)
{
        int i, j, jackpot, c, d;
        long ctold, ctnew;

        rewind(f1);
        rewind(f2);
        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(f1);
                        continue;
                }
                while (j < J[i]) {
                        ixnew[j] = ctnew += skipline(f2);
                        j++;
                }
                if ((cmd_flags & FLAG_b) || (cmd_flags & FLAG_w) || (cmd_flags & FLAG_i)) {
                        while (1) {
                                c = getc(f1);
                                d = getc(f2);
                                /*
                                 * GNU diff ignores a missing newline
                                 * in one file if bflag || wflag.
                                 */
                                if (((cmd_flags & FLAG_b) || (cmd_flags & FLAG_w)) &&
                                    ((c == EOF && d == '\n') ||
                                    (c == '\n' && d == EOF))) {
                                        break;
                                }
                                ctold++;
                                ctnew++;
                                if ((cmd_flags & FLAG_b) && isspace(c) && isspace(d)) {
                                        do {
                                                if (c == '\n')
                                                        break;
                                                ctold++;
                                        } while (isspace(c = getc(f1)));
                                        do {
                                                if (d == '\n')
                                                        break;
                                                ctnew++;
                                        } while (isspace(d = getc(f2)));
                                } else if (cmd_flags & FLAG_w) {
                                        while (isspace(c) && c != '\n') {
                                                c = getc(f1);
                                                ctold++;
                                        }
                                        while (isspace(d) && d != '\n') {
                                                d = getc(f2);
                                                ctnew++;
                                        }
                                }
                                if (c != d) {
                                        jackpot++;
                                        J[i] = 0;
                                        if (c != '\n' && c != EOF)
                                                ctold += skipline(f1);
                                        if (d != '\n' && c != EOF)
                                                ctnew += skipline(f2);
                                        break;
                                }
                                if (c == '\n' || c == EOF)
                                        break;
                        }
                } else {
                        while (1) {
                                ctold++;
                                ctnew++;
                                if ((c = getc(f1)) != (d = getc(f2))) {
                                        J[i] = 0;
                                        if (c != '\n' && c != EOF)
                                                ctold += skipline(f1);
                                        if (d != '\n' && c != EOF)
                                                ctnew += skipline(f2);
                                        break;
                                }
                                if (c == '\n' || c == EOF)
                                        break;
                        }
                }
                ixold[i] = ctold;
                ixnew[j] = ctnew;
                j++;
        }
        for (; j <= len[1]; j++)
                ixnew[j] = ctnew += skipline(f2);
}

/* shellsort CACM #201 */
static void sort(struct line *a, int n)
{
        struct line *ai, *aim, w;
        int j, m = 0, k;

        if (n == 0)
                return;
        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;
                        }
                }
        }
}


static void uni_range(int a, int b)
{
        if (a < b)
                printf("%d,%d", a, b - a + 1);
        else if (a == b)
                printf("%d", b);
        else
                printf("%d,0", b);
}

static int fetch(long *f, int a, int b, FILE *lb, int ch)
{
        int i, j, c, lastc, col, nc;

        if (a > b)
                return (0);
        for (i = a; i <= b; i++) {
                fseek(lb, f[i - 1], SEEK_SET);
                nc = f[i] - f[i - 1];
                if (ch != '\0') {
                        putchar(ch);
                        if (cmd_flags & FLAG_T)
                                putchar('\t');
                }
                col = 0;
                for (j = 0, lastc = '\0'; j < nc; j++, lastc = c) {
                        if ((c = getc(lb)) == EOF) {
                                puts("\n\\ No newline at end of file");
                                return (0);
                        }
                        if (c == '\t' && (cmd_flags & FLAG_t)) {
                                do {
                                        putchar(' ');
                                } while (++col & 7);
                        } else {
                                putchar(c);
                                col++;
                        }
                }
        }
        return (0);
}

static int asciifile(FILE *f)
{
#if ENABLE_FEATURE_DIFF_BINARY
	unsigned char buf[BUFSIZ];
	int i, cnt;
#endif

	if ((cmd_flags & FLAG_a) || f == NULL)
		return (1);

#if ENABLE_FEATURE_DIFF_BINARY
	rewind(f);
	cnt = fread(buf, 1, sizeof(buf), f);
	for (i = 0; i < cnt; i++) {
		if (!isprint(buf[i]) && !isspace(buf[i])) {
			return (0);
		}
	}
#endif
	return (1);
}

/* dump accumulated "unified" diff changes */
static void dump_unified_vec(FILE *f1, FILE *f2)
{
	struct context_vec *cvp = context_vec_start;
        int lowa, upb, lowc, upd;
        int a, b, c, d;
        char ch;

        if (context_vec_start > context_vec_ptr)
                return;

        b = d = 0;                /* gcc */
        lowa = MAX(1, cvp->a - context);
        upb = MIN(len[0], context_vec_ptr->b + context);
        lowc = MAX(1, cvp->c - context);
        upd = MIN(len[1], context_vec_ptr->d + context);

        fputs("@@ -", stdout);
        uni_range(lowa, upb);
        fputs(" +", stdout);
        uni_range(lowc, upd);
        fputs(" @@", stdout);
        putchar('\n');

        /*
         * Output changes in "unified" diff format--the old and new lines
         * are printed together.
         */
        for (; cvp <= context_vec_ptr; cvp++) {
                a = cvp->a;
                b = cvp->b;
                c = cvp->c;
                d = cvp->d;

                /*
                 * c: both new and old changes
                 * d: only changes in the old file
                 * a: only changes in the new file
                 */
                if (a <= b && c <= d)
                        ch = 'c';
                else
                        ch = (a <= b) ? 'd' : 'a';
#if 0
                switch (ch) {
                case 'c':
                        fetch(ixold, lowa, a - 1, f1, ' ');
                        fetch(ixold, a, b, f1, '-');
                        fetch(ixnew, c, d, f2, '+');
                        break;
                case 'd':
                        fetch(ixold, lowa, a - 1, f1, ' ');
                        fetch(ixold, a, b, f1, '-');
                        break;
                case 'a':
                        fetch(ixnew, lowc, c - 1, f2, ' ');
                        fetch(ixnew, c, d, f2, '+');
                        break;
                }
#else
                if (ch == 'c' || ch == 'd') {
                        fetch(ixold, lowa, a - 1, f1, ' ');
                        fetch(ixold, a, b, f1, '-');
				}
                if (ch == 'a')
                        fetch(ixnew, lowc, c - 1, f2, ' ');
                if (ch == 'c' || ch == 'a')
                        fetch(ixnew, c, d, f2, '+');
#endif
                lowa = b + 1;
                lowc = d + 1;
        }
        fetch(ixnew, d + 1, upd, f2, ' ');

        context_vec_ptr = context_vec_start - 1;
}


static void print_header(const char *file1, const char *file2)
{
        if (label[0] != NULL)
                printf("%s %s\n", "---",
                    label[0]);
        else
                printf("%s %s\t%s", "---",
                    file1, ctime(&stb1.st_mtime));
        if (label[1] != NULL)
                printf("%s %s\n", "+++",
                    label[1]);
        else
                printf("%s %s\t%s", "+++",
                    file2, ctime(&stb2.st_mtime));
}



/*
 * 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.
 */
static void change(char *file1, FILE *f1, char *file2, FILE *f2, int a, int b, int c, int d)
{
	static size_t max_context = 64;

        if (a > b && c > d)	return;
	if (cmd_flags & FLAG_q) return;
	
        /*
        * Allocate change records as needed.
        */
                if (context_vec_ptr == context_vec_end - 1) {
                        ptrdiff_t offset = context_vec_ptr - context_vec_start;
                        max_context <<= 1;
                        context_vec_start = xrealloc(context_vec_start,
                            max_context * sizeof(struct context_vec));
                        context_vec_end = context_vec_start + max_context;
                        context_vec_ptr = context_vec_start + offset;
                }
                if (anychange == 0) {
                        /*
                         * Print the context/unidiff header first time through.
                         */
                        print_header(file1, file2);
                        anychange = 1;
                } else if (a > context_vec_ptr->b + (2 * context) + 1 &&
                    c > context_vec_ptr->d + (2 * context) + 1) {
                        /*
                         * If this change is more than 'context' lines from the
                         * previous change, dump the record and reset it.
                         */
                    	dump_unified_vec(f1, f2);
                }
                context_vec_ptr++;
                context_vec_ptr->a = a;
                context_vec_ptr->b = b;
                context_vec_ptr->c = c;
                context_vec_ptr->d = d;
                return;
        
}


static void output(char *file1, FILE *f1, char *file2, FILE *f2)
{

		/* Note that j0 and j1 can't be used as they are defined in math.h.
		 * This also allows the rather amusing variable 'j00'... */
		int m, i0, i1, j00, j01;

        rewind(f1);
        rewind(f2);
        m = len[0];
        J[0] = 0;
        J[m + 1] = len[1] + 1;
        for (i0 = 1; i0 <= m; i0 = i1 + 1) {
                        while (i0 <= m && J[i0] == J[i0 - 1] + 1)
                                i0++;
                        j00 = J[i0 - 1] + 1;
                        i1 = i0 - 1;
                        while (i1 < m && J[i1 + 1] == 0)
                                i1++;
                        j01 = J[i1 + 1] - 1;
                        J[i1] = j01;
                        change(file1, f1, file2, f2, i0, i1, j00, j01);
        }
        if (m == 0) {
                change(file1, f1, file2, f2, 1, 0, 1, len[1]);
	}
	if (anychange != 0) {
        	dump_unified_vec(f1, f2);
        }
}

/*
 *      The following code 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
 *      checked 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.
 */

static int diffreg(char *ofile1, char *ofile2, int flags)
{
        char *file1 = ofile1;
        char *file2 = ofile2;
        FILE *f1 = NULL;
        FILE *f2 = NULL;
        int rval = D_SAME;
        int i;

        anychange = 0;
        context_vec_ptr = context_vec_start - 1;
                
        if (S_ISDIR(stb1.st_mode) != S_ISDIR(stb2.st_mode))
                return (S_ISDIR(stb1.st_mode) ? D_MISMATCH1 : D_MISMATCH2);
        if (strcmp(file1, "-") == 0 && strcmp(file2, "-") == 0)
                goto closem;

        if (flags & D_EMPTY1)
                f1 = bb_xfopen(_PATH_DEVNULL, "r");
        else {
                if (strcmp(file1, "-") == 0)
                        f1 = stdin;
                else
                        f1 = bb_xfopen(file1, "r");
        }

        if (flags & D_EMPTY2)
                f2 = bb_xfopen(_PATH_DEVNULL, "r");
        else {
                if (strcmp(file2, "-") == 0)
                        f2 = stdin;
                else
                        f2 = bb_xfopen(file2, "r");
        }
	
	if ((i=files_differ(f1, f2, flags)) == 0)
                goto closem;
	else if (i != 1) {/* 1 == ok */
                /* error */
                status |= 2;
                goto closem;
        }

        if (!asciifile(f1) || !asciifile(f2)) {
                rval = D_BINARY;
                status |= 1;
                goto closem;
        }

        prepare(0, f1, stb1.st_size);
        prepare(1, f2, stb2.st_size);
        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 = xrealloc(member, (slen[1] + 2) * sizeof(int));

        class = (int *)file[0];
        unsort(sfile[0], slen[0], class);
        class = xrealloc(class, (slen[0] + 2) * sizeof(int));

        klist = xmalloc((slen[0] + 2) * sizeof(int));
        clen = 0;
        clistlen = 100;
        clist = xmalloc(clistlen * sizeof(struct cand));
        i = stone(class, slen[0], member, klist);
        free(member);
        free(class);

        J = xrealloc(J, (len[0] + 2) * sizeof(int));
        unravel(klist[i]);
        free(clist);
        free(klist);

        ixold = xrealloc(ixold, (len[0] + 2) * sizeof(long));
        ixnew = xrealloc(ixnew, (len[1] + 2) * sizeof(long));
        check(f1, f2);
        output(file1, f1, file2, f2);

closem:
        if (anychange) {
		status |= 1;
                if (rval == D_SAME)
                        rval = D_DIFFER;
        }
        if (f1 != NULL)
                fclose(f1);
        if (f2 != NULL)
                fclose(f2);
        if (file1 != ofile1)
                free(file1);
        if (file2 != ofile2)
                free(file2);
	return (rval);
}

#if ENABLE_FEATURE_DIFF_DIR
static void do_diff (char *dir1, char *path1, char *dir2, char *path2) {
	
	int flags = D_HEADER;
	int val;
	
	char *fullpath1 = bb_xasprintf("%s/%s", dir1, path1);
	char *fullpath2 = bb_xasprintf("%s/%s", dir2, path2);

	if (stat(fullpath1, &stb1) != 0) {
		flags |= D_EMPTY1;
		memset(&stb1, 0, sizeof(stb1));
		fullpath1 = bb_xasprintf("%s/%s", dir1, path2);
	}
	if (stat(fullpath2, &stb2) != 0) {
		flags |= D_EMPTY2;
		memset(&stb2, 0, sizeof(stb2));
		stb2.st_mode = stb1.st_mode;
		fullpath2 = bb_xasprintf("%s/%s", dir2, path1);
	}

	if (stb1.st_mode == 0)
		stb1.st_mode = stb2.st_mode;
	
	if (S_ISDIR(stb1.st_mode) && S_ISDIR(stb2.st_mode)) {
		printf("Common subdirectories: %s and %s\n", fullpath1, fullpath2);
		return;
	}

	if (!S_ISREG(stb1.st_mode) && !S_ISDIR(stb1.st_mode))
		val = D_SKIPPED1;
	else if (!S_ISREG(stb2.st_mode) && !S_ISDIR(stb2.st_mode))
		val = D_SKIPPED2;
	else
		val = diffreg(fullpath1, fullpath2, flags);
	
	print_status(val, fullpath1, fullpath2, NULL);
}
#endif

#if ENABLE_FEATURE_DIFF_DIR
static int dir_strcmp(const void *p1, const void *p2) {
	return strcmp(*(char * const *)p1, *(char * const *)p2);
}

/* This function adds a filename to dl, the directory listing. */

static int add_to_dirlist (const char *filename,
		struct stat ATTRIBUTE_UNUSED *sb, void *userdata) {
	dl_count++;
	dl = xrealloc(dl, dl_count * sizeof(char *));
	dl[dl_count - 1] = bb_xstrdup(filename);
	if (cmd_flags & FLAG_r) {
		int *pp = (int *) userdata;
		int path_len = *pp + 1;
		dl[dl_count - 1] = &(dl[dl_count - 1])[path_len];
	}
	return TRUE;
}

/* This returns a sorted directory listing. */
static char **get_dir(char *path) {

	int i;
	char **retval;

	/* If -r has been set, then the recursive_action function will be
	 * used. Unfortunately, this outputs the root directory along with
	 * the recursed paths, so use void *userdata to specify the string
	 * length of the root directory. It can then be removed in
	 * add_to_dirlist. */

	int path_len = strlen(path);
	void *userdata = &path_len;

	/* Reset dl_count - there's no need to free dl as bb_xrealloc does
	 * the job nicely. */
	dl_count = 0;

	/* Now fill dl with a listing. */
	if (cmd_flags & FLAG_r)
		recursive_action(path, TRUE, TRUE, FALSE, add_to_dirlist, NULL, userdata);
	else {
		DIR *dp;
		struct dirent *ep;
		if ((dp = opendir(path)) == NULL)
			bb_error_msg("Error reading directory");
		while ((ep = readdir(dp))) {
			if ((!strcmp(ep->d_name, "..")) || (!strcmp(ep->d_name, ".")))
				continue;
			add_to_dirlist(ep->d_name, NULL, NULL);
		}
		closedir(dp);
	}

	/* Sort dl alphabetically. */
	qsort(dl, dl_count, sizeof(char *), dir_strcmp);

	/* Copy dl so that we can return it. */
	retval = xmalloc(dl_count * sizeof(char *));
	for (i = 0; i < dl_count; i++)
		retval[i] = bb_xstrdup(dl[i]);

	return retval;
}

static void diffdir (char *p1, char *p2) {
	
	char **dirlist1, **dirlist2;
	char *dp1, *dp2;
	int dirlist1_count, dirlist2_count;
	int pos;

	/* Check for trailing slashes. */
	
	if (p1[strlen(p1) - 1] == '/')
		p1[strlen(p1) - 1] = '\0';
	if (p2[strlen(p2) - 1] == '/')
		p2[strlen(p2) - 1] = '\0';
	
	/* Get directory listings for p1 and p2. */
	
	dirlist1 = get_dir(p1);
	dirlist1_count = dl_count;
	dirlist1[dirlist1_count] = NULL;
	dirlist2 = get_dir(p2);
	dirlist2_count = dl_count;
	dirlist2[dirlist2_count] = NULL;
	
	/* If -S was set, find the starting point. */
	if (start) {
		while (*dirlist1 != NULL && strcmp(*dirlist1, start) < 0)
			dirlist1++;
		while (*dirlist2 != NULL && strcmp(*dirlist2, start) < 0)
			dirlist2++;
		if ((*dirlist1 == NULL) || (*dirlist2 == NULL))
			bb_error_msg("Invalid argument to -S");
	}
	
	/* Now that both dirlist1 and dirlist2 contain sorted directory
	 * listings, we can start to go through dirlist1. If both listings
	 * contain the same file, then do a normal diff. Otherwise, behaviour
	 * is determined by whether the -N flag is set. */	
	while (*dirlist1 != NULL || *dirlist2 != NULL) {
		dp1 = *dirlist1;
		dp2 = *dirlist2;
		pos = dp1 == NULL ? 1 : dp2 == NULL ? -1 : strcmp(dp1, dp2);
		if (pos == 0) {
			do_diff(p1, dp1, p2, dp2);
			dirlist1++;
			dirlist2++;
		}
		else if (pos < 0) {
			if (cmd_flags & FLAG_N)
				do_diff(p1, dp1, p2, NULL);
			else
				print_only(p1, strlen(p1) + 1, dp1);
			dirlist1++;
		}
		else {
			if (cmd_flags & FLAG_N)
				do_diff(p1, NULL, p2, dp2);
			else
				print_only(p2, strlen(p2) + 1, dp2);
			dirlist2++;
		}
	}
}
#endif



int diff_main(int argc, char **argv) {
	char *ep;
	int gotstdin = 0;

	char *U_opt;
	llist_t *L_arg = NULL;
	bb_opt_complementally = "L::";
	cmd_flags = bb_getopt_ulflags(argc, argv, "abdiL:NqrsS:tTU:wu", &L_arg, &start, &U_opt);

	if (cmd_flags & FLAG_L) {
		while (L_arg) {
			if (label[0] == NULL)
				label[0] = L_arg->data;
			else if (label[1] == NULL)
				label[1] = L_arg->data;
			else
				bb_show_usage();

			L_arg = L_arg->link;
		}

		/* If both label[0] and label[1] were set, they need to be swapped. */
		if (label[0] && label[1]) {
			char *tmp;
			tmp = label[1];
			label[1] = label[0];
			label[0] = tmp;
		}
	}

	context = 3;	/* This is the default number of lines of context. */
	if (cmd_flags & FLAG_U) {
		context = strtol(U_opt, &ep, 10);
		if (context == 0) {
			bb_error_msg("Invalid context length");
			bb_show_usage();
		}
	}
	argc -= optind;
        argv += optind;

        /*
         * Do sanity checks, fill in stb1 and stb2 and call the appropriate
         * driver routine.  Both drivers use the contents of stb1 and stb2.
         */
        if (argc < 2) {
		bb_error_msg("Missing filename");
		bb_show_usage();
	}
        if (strcmp(argv[0], "-") == 0) {
                fstat(STDIN_FILENO, &stb1);
                gotstdin = 1;
        } else if (stat(argv[0], &stb1) != 0)
                bb_perror_msg_and_die("Couldn't stat %s", argv[0]);
        if (strcmp(argv[1], "-") == 0) {
                fstat(STDIN_FILENO, &stb2);
                gotstdin = 1;
        } else if (stat(argv[1], &stb2) != 0)
                bb_perror_msg_and_die("Couldn't stat %s", argv[1]);
        if (gotstdin && (S_ISDIR(stb1.st_mode) || S_ISDIR(stb2.st_mode)))
                bb_error_msg_and_die("Can't compare - to a directory");
        if (S_ISDIR(stb1.st_mode) && S_ISDIR(stb2.st_mode)) {
#if ENABLE_FEATURE_DIFF_DIR
		diffdir(argv[0], argv[1]);
#else
		bb_error_msg_and_die("Directory comparison not supported");
#endif
	}
	else {
		if (S_ISDIR(stb1.st_mode)) {
			argv[0] = concat_path_file(argv[0], argv[1]);
			if (stat(argv[0], &stb1) < 0)
				bb_perror_msg_and_die("Couldn't stat %s", argv[0]);
		}
		if (S_ISDIR(stb2.st_mode)) {
			argv[1] = concat_path_file(argv[1], argv[0]);
			if (stat(argv[1], &stb2) < 0)
				bb_perror_msg_and_die("Couldn't stat %s", argv[1]);
		}
		print_status(diffreg(argv[0], argv[1], 0), argv[0], argv[1], NULL);
	}
	exit(status);
}