/*      $OpenBSD: diff.c,v 1.40 2019/06/28 13:35:03 deraadt Exp $       */
/*
 * Copyright (C) Caldera International Inc.  2001-2002.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code and documentation must retain the above
 *    copyright notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed or owned by Caldera
 *      International, Inc.
 * 4. Neither the name of Caldera International, Inc. nor the names of other
 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
 *
 * USE OF THE SOFTWARE PROVIDED FOR UNDER THIS LICENSE BY CALDERA
 * INTERNATIONAL, INC. AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL CALDERA INTERNATIONAL, INC. BE LIABLE FOR ANY DIRECT,
 * INDIRECT INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */
/*-
 * Copyright (c) 1991, 1993
 *      The Regents of the University of California.  All rights reserved.
 * Copyright (c) 2004 Jean-Francois Brousseau.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 *      @(#)diffreg.c   8.1 (Berkeley) 6/6/93
 */

#include <sys/stat.h>

#include <ctype.h>
#include <err.h>
#include <stdarg.h>
#include <stdint.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>

#include "buf.h"
#include "diff.h"
#include "xmalloc.h"

#define MINIMUM(a, b)   (((a) < (b)) ? (a) : (b))
#define MAXIMUM(a, b)   (((a) > (b)) ? (a) : (b))

/*
 * 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.
 */

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 when
 * 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 void      output(FILE *, FILE *, int);
static void      check(FILE *, FILE *, int);
static void      range(int, int, char *);
static void      uni_range(int, int);
static void      dump_context_vec(FILE *, FILE *, int);
static void      dump_unified_vec(FILE *, FILE *, int);
static void      prepare(int, FILE *, off_t, int);
static void      prune(void);
static void      equiv(struct line *, int, struct line *, int, int *);
static void      unravel(int);
static void      unsort(struct line *, int, int *);
static void      change(FILE *, FILE *, int, int, int, int, int);
static void      sort(struct line *, int);
static int       ignoreline(char *);
static int       asciifile(FILE *);
static void      fetch(long *, int, int, FILE *, int, int, int);
static int       newcand(int, int, int);
static int       search(int *, int, int);
static int       skipline(FILE *);
static int       isqrt(int);
static int       stone(int *, int, int *, int *, int);
static int       readhash(FILE *, int);
static int       files_differ(FILE *, FILE *);
static char     *match_function(const long *, int, FILE *);
static char     *preadline(int, size_t, off_t);


int diff_context = 3;
int diff_format = D_NORMAL;
char *diff_file = NULL;
RCSNUM *diff_rev1 = NULL;
RCSNUM *diff_rev2 = NULL;
char diffargs[512]; /* XXX */
static struct stat stb1, stb2;
static char *ifdefname;
regex_t *diff_ignore_re;

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   inifdef;           /* whether or not we are in a #ifdef block */
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 u_char *chrtran;         /* translation table for case-folding */
static struct context_vec *context_vec_start;
static struct context_vec *context_vec_end;
static struct context_vec *context_vec_ptr;

#define FUNCTION_CONTEXT_SIZE   55
static char lastbuf[FUNCTION_CONTEXT_SIZE];
static int lastline;
static int lastmatchline;
BUF  *diffbuf = NULL;


/*
 * chrtran points to one of 2 translation tables: cup2low if folding upper to
 * lower case clow2low if not folding case
 */
u_char clow2low[256] = {
        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a,
        0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15,
        0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
        0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b,
        0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36,
        0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x40, 0x41,
        0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a, 0x4b, 0x4c,
        0x4d, 0x4e, 0x4f, 0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57,
        0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f, 0x60, 0x61, 0x62,
        0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d,
        0x6e, 0x6f, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
        0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, 0x80, 0x81, 0x82, 0x83,
        0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e,
        0x8f, 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99,
        0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f, 0xa0, 0xa1, 0xa2, 0xa3, 0xa4,
        0xa5, 0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
        0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba,
        0xbb, 0xbc, 0xbd, 0xbe, 0xbf, 0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5,
        0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf, 0xd0,
        0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xdb,
        0xdc, 0xdd, 0xde, 0xdf, 0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6,
        0xe7, 0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef, 0xf0, 0xf1,
        0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9, 0xfa, 0xfb, 0xfc,
        0xfd, 0xfe, 0xff
};

u_char cup2low[256] = {
        0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a,
        0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12, 0x13, 0x14, 0x15,
        0x16, 0x17, 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20,
        0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b,
        0x2c, 0x2d, 0x2e, 0x2f, 0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36,
        0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x60, 0x61,
        0x62, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c,
        0x6d, 0x6e, 0x6f, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
        0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, 0x60, 0x61, 0x62,
        0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d,
        0x6e, 0x6f, 0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78,
        0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, 0x80, 0x81, 0x82, 0x83,
        0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e,
        0x8f, 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99,
        0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f, 0xa0, 0xa1, 0xa2, 0xa3, 0xa4,
        0xa5, 0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
        0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba,
        0xbb, 0xbc, 0xbd, 0xbe, 0xbf, 0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5,
        0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf, 0xd0,
        0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xdb,
        0xdc, 0xdd, 0xde, 0xdf, 0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6,
        0xe7, 0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef, 0xf0, 0xf1,
        0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9, 0xfa, 0xfb, 0xfc,
        0xfd, 0xfe, 0xff
};

int
diffreg(const char *file1, const char *file2, BUF *out, int flags)
{
        FILE *f1, *f2;
        int i, rval;

        f1 = f2 = NULL;
        rval = D_SAME;
        anychange = 0;
        lastline = 0;
        lastmatchline = 0;
        context_vec_ptr = context_vec_start - 1;
        if (flags & D_IGNORECASE)
                chrtran = cup2low;
        else
                chrtran = clow2low;
        if (out != NULL)
                diffbuf = out;

        f1 = fopen(file1, "r");
        if (f1 == NULL) {
                warn("%s", file1);
                goto closem;
        }

        f2 = fopen(file2, "r");
        if (f2 == NULL) {
                warn("%s", file2);
                goto closem;
        }

        if (fstat(fileno(f1), &stb1) == -1) {
                warn("%s", file1);
                goto closem;
        }

        if (fstat(fileno(f2), &stb2) == -1) {
                warn("%s", file2);
                goto closem;
        }

        switch (files_differ(f1, f2)) {
        case 1:
                break;
        case -1:
                rval = D_ERROR;
                /* FALLTHROUGH */
        case 0:
                goto closem;
        default:
                errx(D_ERROR, "files_differ: invalid case");
        }

        if ((flags & D_FORCEASCII) == 0 &&
            (!asciifile(f1) || !asciifile(f2))) {
                rval = D_ERROR;
                goto closem;
        }

        prepare(0, f1, stb1.st_size, flags);
        prepare(1, f2, stb2.st_size, flags);

        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 = xreallocarray(member, slen[1] + 2, sizeof(*member));

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

        klist = xcalloc(slen[0] + 2, sizeof(*klist));
        clen = 0;
        clistlen = 100;
        clist = xcalloc(clistlen, sizeof(*clist));
        i = stone(class, slen[0], member, klist, flags);
        free(member);
        free(class);

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

        ixold = xreallocarray(ixold, len[0] + 2, sizeof(*ixold));
        ixnew = xreallocarray(ixnew, len[1] + 2, sizeof(*ixnew));
        check(f1, f2, flags);
        output(f1, f2, flags);

closem:
        if (anychange) {
                if (rval == D_SAME)
                        rval = D_DIFFER;
        }
        if (f1 != NULL)
                fclose(f1);
        if (f2 != NULL)
                fclose(f2);

        return (rval);
}

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

        if (stb1.st_size != stb2.st_size)
                return (1);
        for (;;) {
                i = fread(buf1, 1, sizeof(buf1), f1);
                j = fread(buf2, 1, sizeof(buf2), f2);
                if ((!i && ferror(f1)) || (!j && ferror(f2)))
                        return (-1);
                if (i != j)
                        return (1);
                if (i == 0)
                        return (0);
                if (memcmp(buf1, buf2, i) != 0)
                        return (1);
        }
}

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

        rewind(fd);

        sz = ((uintmax_t)filesize <= SIZE_MAX ? (size_t)filesize : SIZE_MAX) / 25;
        if (sz < 100)
                sz = 100;

        p = xcalloc(sz + 3, sizeof(*p));
        for (j = 0; (h = readhash(fd, flags));) {
                if ((size_t)j == sz) {
                        sz = sz * 3 / 2;
                        p = xreallocarray(p, sz + 3, sizeof(*p));
                }
                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;
}

/* Code taken from ping.c */
static int
isqrt(int n)
{
        int y, x = 1;

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

        do { /* newton was a stinker */
                y = x;
                x = n / x;
                x += y;
                x /= 2;
        } while ((x - y) > 1 || (x - y) < -1);

        return (x);
}

static int
stone(int *a, int n, int *b, int *c, int flags)
{
        int i, k, y, j, l;
        int oldc, tc, oldl, sq;
        u_int numtries, bound;

        if (flags & D_MINIMAL)
                bound = UINT_MAX;
        else {
                sq = isqrt(n);
                bound = MAXIMUM(256, sq);
        }

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

        if (clen == clistlen) {
                clistlen = clistlen * 11 / 10;
                clist = xreallocarray(clist, clistlen, sizeof(*clist));
        }
        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;
        for (;;) {
                l = (i + j) / 2;
                if (l <= 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 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;
}

/*
 * 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 flags)
{
        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 (flags & (D_FOLDBLANKS|D_IGNOREBLANKS|D_IGNORECASE)) {
                        for (;;) {
                                c = getc(f1);
                                d = getc(f2);
                                /*
                                 * GNU diff ignores a missing newline
                                 * in one file for -b or -w.
                                 */
                                if ((flags & (D_FOLDBLANKS|D_IGNOREBLANKS)) &&
                                    ((c == EOF && d == '\n') ||
                                    (c == '\n' && d == EOF))) {
                                        break;
                                }
                                ctold++;
                                ctnew++;
                                if ((flags & D_FOLDBLANKS) && 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 ((flags & D_IGNOREBLANKS)) {
                                        while (isspace(c) && c != '\n') {
                                                c = getc(f1);
                                                ctold++;
                                        }
                                        while (isspace(d) && d != '\n') {
                                                d = getc(f2);
                                                ctnew++;
                                        }
                                }
                                if (chrtran[c] != chrtran[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 {
                        for (;;) {
                                ctold++;
                                ctnew++;
                                if ((c = getc(f1)) != (d = getc(f2))) {
                                        /* 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;
                        }
                }
                ixold[i] = ctold;
                ixnew[j] = ctnew;
                j++;
        }
        for (; j <= len[1]; j++)
                ixnew[j] = ctnew += skipline(f2);
        /*
         * if (jackpot)
         *      fprintf(stderr, "jackpot\n");
         */
}

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

        a = xcalloc(l + 1, sizeof(*a));
        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);
}

static void
output(FILE *f1, FILE *f2, int flags)
{
        int m, i0, i1, j0, j1;

        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++;
                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(f1, f2, i0, i1, j0, j1, flags);
        }
        if (m == 0)
                change(f1, f2, 1, 0, 1, len[1], flags);
        if (diff_format == D_IFDEF) {
                for (;;) {
#define c i0
                        if ((c = getc(f1)) == EOF)
                                return;
                        diff_output("%c", c);
                }
#undef c
        }
        if (anychange != 0) {
                if (diff_format == D_CONTEXT)
                        dump_context_vec(f1, f2, flags);
                else if (diff_format == D_UNIFIED)
                        dump_unified_vec(f1, f2, flags);
        }
}

static void
range(int a, int b, char *separator)
{
        diff_output("%d", a > b ? b : a);
        if (a < b)
                diff_output("%s%d", separator, b);
}

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

static char *
preadline(int fd, size_t rlen, off_t off)
{
        char *line;
        ssize_t nr;

        line = xmalloc(rlen + 1);
        if ((nr = pread(fd, line, rlen, off)) == -1)
                err(D_ERROR, "preadline");
        line[nr] = '\0';
        return (line);
}

static int
ignoreline(char *line)
{
        int ret;

        ret = regexec(diff_ignore_re, line, 0, NULL, 0);
        free(line);
        return (ret == 0);      /* if it matched, it should be ignored. */
}

/*
 * 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(FILE *f1, FILE *f2, int a, int b, int c, int d, int flags)
{
        static size_t max_context = 64;
        char buf[64];
        struct tm *t;
        int i;

        if (diff_format != D_IFDEF && a > b && c > d)
                return;
        if (diff_ignore_re != NULL) {
                char *line;
                /*
                 * All lines in the change, insert, or delete must
                 * match an ignore pattern for the change to be
                 * ignored.
                 */
                if (a <= b) {           /* Changes and deletes. */
                        for (i = a; i <= b; i++) {
                                line = preadline(fileno(f1),
                                    ixold[i] - ixold[i - 1], ixold[i - 1]);
                                if (!ignoreline(line))
                                        goto proceed;
                        }
                }
                if (a > b || c <= d) {  /* Changes and inserts. */
                        for (i = c; i <= d; i++) {
                                line = preadline(fileno(f2),
                                    ixnew[i] - ixnew[i - 1], ixnew[i - 1]);
                                if (!ignoreline(line))
                                        goto proceed;
                        }
                }
                return;
        }
proceed:
        if (diff_format == D_CONTEXT || diff_format == D_UNIFIED) {
                /*
                 * 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 = xreallocarray(context_vec_start,
                            max_context, sizeof(*context_vec_start));
                        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.
                         */
                        t = localtime(&stb1.st_mtime);
                        (void)strftime(buf, sizeof(buf),
                            "%Y/%m/%d %H:%M:%S", t);

                        diff_output("%s %s      %s",
                            diff_format == D_CONTEXT ? "***" : "---", diff_file,
                            buf);

                        if (diff_rev1 != NULL) {
                                rcsnum_tostr(diff_rev1, buf, sizeof(buf));
                                diff_output("\t%s", buf);
                        }

                        printf("\n");

                        t = localtime(&stb2.st_mtime);
                        (void)strftime(buf, sizeof(buf),
                            "%Y/%m/%d %H:%M:%S", t);

                        diff_output("%s %s      %s",
                            diff_format == D_CONTEXT ? "---" : "+++", diff_file,
                            buf);

                        if (diff_rev2 != NULL) {
                                rcsnum_tostr(diff_rev2, buf, sizeof(buf));
                                diff_output("\t%s", buf);
                        }

                        printf("\n");
                        anychange = 1;
                } else if (a > context_vec_ptr->b + (2 * diff_context) + 1 &&
                    c > context_vec_ptr->d + (2 * diff_context) + 1) {
                        /*
                         * If this change is more than 'diff_context' lines from the
                         * previous change, dump the record and reset it.
                         */
                        if (diff_format == D_CONTEXT)
                                dump_context_vec(f1, f2, flags);
                        else
                                dump_unified_vec(f1, f2, flags);
                }
                context_vec_ptr++;
                context_vec_ptr->a = a;
                context_vec_ptr->b = b;
                context_vec_ptr->c = c;
                context_vec_ptr->d = d;
                return;
        }
        if (anychange == 0)
                anychange = 1;
        switch (diff_format) {
        case D_BRIEF:
                return;
        case D_NORMAL:
                range(a, b, ",");
                diff_output("%c", a > b ? 'a' : c > d ? 'd' : 'c');
                if (diff_format == D_NORMAL)
                        range(c, d, ",");
                diff_output("\n");
                break;
        case D_RCSDIFF:
                if (a > b)
                        diff_output("a%d %d\n", b, d - c + 1);
                else {
                        diff_output("d%d %d\n", a, b - a + 1);

                        if (!(c > d))   /* add changed lines */
                                diff_output("a%d %d\n", b, d - c + 1);
                }
                break;
        }
        if (diff_format == D_NORMAL || diff_format == D_IFDEF) {
                fetch(ixold, a, b, f1, '<', 1, flags);
                if (a <= b && c <= d && diff_format == D_NORMAL)
                        diff_output("---\n");
        }
        fetch(ixnew, c, d, f2, diff_format == D_NORMAL ? '>' : '\0', 0, flags);
        if (inifdef) {
                diff_output("#endif /* %s */\n", ifdefname);
                inifdef = 0;
        }
}

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

        /*
         * When doing #ifdef's, copy down to current line
         * if this is the first file, so that stuff makes it to output.
         */
        if (diff_format == 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++)
                        diff_output("%c", getc(lb));
        }
        if (a > b)
                return;
        if (diff_format == D_IFDEF) {
                if (inifdef) {
                        diff_output("#else /* %s%s */\n",
                            oldfile == 1 ? "!" : "", ifdefname);
                } else {
                        if (oldfile)
                                diff_output("#ifndef %s\n", ifdefname);
                        else
                                diff_output("#ifdef %s\n", ifdefname);
                }
                inifdef = 1 + oldfile;
        }
        for (i = a; i <= b; i++) {
                fseek(lb, f[i - 1], SEEK_SET);
                nc = f[i] - f[i - 1];
                if (diff_format != D_IFDEF && ch != '\0') {
                        diff_output("%c", ch);
                        if (diff_format != D_UNIFIED)
                                diff_output(" ");
                }
                col = 0;
                for (j = 0; j < nc; j++) {
                        if ((c = getc(lb)) == EOF) {
                                if (diff_format == D_RCSDIFF)
                                        warnx("No newline at end of file");
                                else
                                        diff_output("\n\\ No newline at end of "
                                            "file");
                                return;
                        }
                        if (c == '\t' && (flags & D_EXPANDTABS)) {
                                do {
                                        diff_output(" ");
                                } while (++col & 7);
                        } else {
                                diff_output("%c", c);
                                col++;
                        }
                }
        }
}

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

        sum = 1;
        space = 0;
        if ((flags & (D_FOLDBLANKS|D_IGNOREBLANKS)) == 0) {
                if (flags & D_IGNORECASE)
                        for (i = 0; (t = getc(f)) != '\n'; i++) {
                                if (t == EOF) {
                                        if (i == 0)
                                                return (0);
                                        break;
                                }
                                sum = sum * 127 + chrtran[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 && (flags & D_IGNOREBLANKS) == 0) {
                                        i++;
                                        space = 0;
                                }
                                sum = sum * 127 + chrtran[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);
}

static int
asciifile(FILE *f)
{
        unsigned char buf[BUFSIZ];
        size_t cnt;

        if (f == NULL)
                return (1);

        rewind(f);
        cnt = fread(buf, 1, sizeof(buf), f);
        return (memchr(buf, '\0', cnt) == NULL);
}

#define begins_with(s, pre) (strncmp(s, pre, sizeof(pre)-1) == 0)

static char *
match_function(const long *f, int pos, FILE *fp)
{
        unsigned char buf[FUNCTION_CONTEXT_SIZE];
        size_t nc;
        int last = lastline;
        char *state = NULL;

        lastline = pos;
        while (pos > last) {
                fseek(fp, f[pos - 1], SEEK_SET);
                nc = f[pos] - f[pos - 1];
                if (nc >= sizeof(buf))
                        nc = sizeof(buf) - 1;
                nc = fread(buf, 1, nc, fp);
                if (nc > 0) {
                        buf[nc] = '\0';
                        buf[strcspn(buf, "\n")] = '\0';
                        if (isalpha(buf[0]) || buf[0] == '_' || buf[0] == '$') {
                                if (begins_with(buf, "private:")) {
                                        if (!state)
                                                state = " (private)";
                                } else if (begins_with(buf, "protected:")) {
                                        if (!state)
                                                state = " (protected)";
                                } else if (begins_with(buf, "public:")) {
                                        if (!state)
                                                state = " (public)";
                                } else {
                                        if (strlcpy(lastbuf, buf,
                                            sizeof(lastbuf)) >= sizeof(lastbuf))
                                                errx(1,
                                                    "match_function: strlcpy");
                                        lastmatchline = pos;
                                        return lastbuf;
                                }
                        }
                }
                pos--;
        }
        return lastmatchline > 0 ? lastbuf : NULL;
}

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

        if (context_vec_start > context_vec_ptr)
                return;

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

        diff_output("***************");
        if ((flags & D_PROTOTYPE)) {
                f = match_function(ixold, lowa-1, f1);
                if (f != NULL)
                        diff_output(" %s", f);
        }
        diff_output("\n*** ");
        range(lowa, upb, ",");
        diff_output(" ****\n");

        /*
         * Output changes to the "old" file.  The first loop suppresses
         * output if there were no changes to the "old" file (we'll see
         * the "old" lines as context in the "new" list).
         */
        do_output = 0;
        for (; cvp <= context_vec_ptr; cvp++)
                if (cvp->a <= cvp->b) {
                        cvp = context_vec_start;
                        do_output++;
                        break;
                }
        if (do_output) {
                while (cvp <= context_vec_ptr) {
                        a = cvp->a;
                        b = cvp->b;
                        c = cvp->c;
                        d = cvp->d;

                        if (a <= b && c <= d)
                                ch = 'c';
                        else
                                ch = (a <= b) ? 'd' : 'a';

                        if (ch == 'a')
                                fetch(ixold, lowa, b, f1, ' ', 0, flags);
                        else {
                                fetch(ixold, lowa, a - 1, f1, ' ', 0, flags);
                                fetch(ixold, a, b, f1,
                                    ch == 'c' ? '!' : '-', 0, flags);
                        }
                        lowa = b + 1;
                        cvp++;
                }
                fetch(ixold, b + 1, upb, f1, ' ', 0, flags);
        }
        /* output changes to the "new" file */
        diff_output("--- ");
        range(lowc, upd, ",");
        diff_output(" ----\n");

        do_output = 0;
        for (cvp = context_vec_start; cvp <= context_vec_ptr; cvp++)
                if (cvp->c <= cvp->d) {
                        cvp = context_vec_start;
                        do_output++;
                        break;
                }
        if (do_output) {
                while (cvp <= context_vec_ptr) {
                        a = cvp->a;
                        b = cvp->b;
                        c = cvp->c;
                        d = cvp->d;

                        if (a <= b && c <= d)
                                ch = 'c';
                        else
                                ch = (a <= b) ? 'd' : 'a';

                        if (ch == 'd')
                                fetch(ixnew, lowc, d, f2, ' ', 0, flags);
                        else {
                                fetch(ixnew, lowc, c - 1, f2, ' ', 0, flags);
                                fetch(ixnew, c, d, f2,
                                    ch == 'c' ? '!' : '+', 0, flags);
                        }
                        lowc = d + 1;
                        cvp++;
                }
                fetch(ixnew, d + 1, upd, f2, ' ', 0, flags);
        }
        context_vec_ptr = context_vec_start - 1;
}

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

        if (context_vec_start > context_vec_ptr)
                return;

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

        diff_output("@@ -");
        uni_range(lowa, upb);
        diff_output(" +");
        uni_range(lowc, upd);
        diff_output(" @@");
        if ((flags & D_PROTOTYPE)) {
                f = match_function(ixold, lowa-1, f1);
                if (f != NULL)
                        diff_output(" %s", f);
        }
        diff_output("\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';

                switch (ch) {
                case 'c':
                        fetch(ixold, lowa, a - 1, f1, ' ', 0, flags);
                        fetch(ixold, a, b, f1, '-', 0, flags);
                        fetch(ixnew, c, d, f2, '+', 0, flags);
                        break;
                case 'd':
                        fetch(ixold, lowa, a - 1, f1, ' ', 0, flags);
                        fetch(ixold, a, b, f1, '-', 0, flags);
                        break;
                case 'a':
                        fetch(ixnew, lowc, c - 1, f2, ' ', 0, flags);
                        fetch(ixnew, c, d, f2, '+', 0, flags);
                        break;
                }
                lowa = b + 1;
                lowc = d + 1;
        }
        fetch(ixnew, d + 1, upd, f2, ' ', 0, flags);

        context_vec_ptr = context_vec_start - 1;
}

void
diff_output(const char *fmt, ...)
{
        va_list vap;
        int i;
        char *str;

        va_start(vap, fmt);
        i = vasprintf(&str, fmt, vap);
        va_end(vap);
        if (i == -1)
                err(1, "diff_output");
        if (diffbuf != NULL)
                buf_append(diffbuf, str, strlen(str));
        else
                printf("%s", str);
        free(str);
}