root/usr.bin/patch/patch.c
/*      $OpenBSD: patch.c,v 1.79 2026/04/03 12:58:40 kirill Exp $       */

/*
 * patch - a program to apply diffs to original files
 * 
 * Copyright 1986, Larry Wall
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following condition is met:
 * 1. Redistributions of source code must retain the above copyright notice,
 * this condition and the following disclaimer.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
 * 
 * -C option added in 1998, original code by Marc Espie, based on FreeBSD
 * behaviour
 */

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>

#include <ctype.h>
#include <getopt.h>
#include <libgen.h>
#include <limits.h>
#include <paths.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#include "common.h"
#include "util.h"
#include "pch.h"
#include "inp.h"
#include "backupfile.h"
#include "ed.h"

mode_t          filemode = 0644;

char            *buf;                   /* general purpose buffer */
size_t           bufsz;                 /* general purpose buffer size */

bool            using_plan_a = true;    /* try to keep everything in memory */
bool            out_of_mem = false;     /* ran out of memory in plan a */

#define MAXFILEC 2

char            *filearg[MAXFILEC];
bool            ok_to_create_file = false;
char            *outname = NULL;
char            *origprae = NULL;
char            *TMPOUTNAME;
char            *TMPINNAME;
char            *TMPREJNAME;
char            *TMPPATNAME;
bool            toutkeep = false;
bool            trejkeep = false;
bool            warn_on_invalid_line;
bool            last_line_missing_eol;

#ifdef DEBUGGING
int             debug = 0;
#endif

bool            force = false;
bool            batch = false;
bool            verbose = true;
bool            reverse = false;
bool            noreverse = false;
bool            skip_rest_of_patch = false;
int             strippath = 957;
bool            canonicalize = false;
bool            check_only = false;
int             diff_type = 0;
char            *revision = NULL;       /* prerequisite revision, if any */
LINENUM         input_lines = 0;        /* how long is input file in lines */
int             posix = 0;              /* strict POSIX mode? */

static void     reinitialize_almost_everything(void);
static void     get_some_switches(void);
static LINENUM  locate_hunk(LINENUM);
static void     abort_context_hunk(void);
static void     rej_line(int, LINENUM);
static void     abort_hunk(void);
static void     apply_hunk(LINENUM);
static void     init_output(const char *);
static void     init_reject(const char *);
static void     copy_till(LINENUM, bool);
static void     spew_output(void);
static void     dump_line(LINENUM, bool);
static bool     patch_match(LINENUM, LINENUM, LINENUM);
static bool     similar(const char *, const char *, ssize_t);
static __dead void usage(void);

/* true if -E was specified on command line.  */
static bool     remove_empty_files = false;

/* true if -R was specified on command line.  */
static bool     reverse_flag_specified = false;

static bool     Vflag = false;

/* buffer holding the name of the rejected patch file. */
static char     rejname[PATH_MAX];

/* how many input lines have been irretractibly output */
static LINENUM  last_frozen_line = 0;

static int      Argc;           /* guess */
static char     **Argv;
static int      Argc_last;      /* for restarting plan_b */
static char     **Argv_last;

static FILE     *ofp = NULL;    /* output file pointer */
static FILE     *rejfp = NULL;  /* reject file pointer */

static int      filec = 0;      /* how many file arguments? */
static LINENUM  last_offset = 0;
static LINENUM  maxfuzz = 2;

/* patch using ifdef, ifndef, etc. */
static bool             do_defines = false;
/* #ifdef xyzzy */
static char             if_defined[128];
/* #ifndef xyzzy */
static char             not_defined[128];
/* #else */
static const char       else_defined[] = "#else\n";
/* #endif xyzzy */
static char             end_defined[128];


/* Apply a set of diffs as appropriate. */

int
main(int argc, char *argv[])
{
        int     error = 0, hunk, failed, i, fd;
        bool    patch_seen;
        LINENUM where = 0, newwhere, fuzz, mymaxfuzz;
        const   char *tmpdir;
        char    *v;

        if (pledge("stdio rpath wpath cpath fattr unveil", NULL) == -1) {
                perror("pledge");
                my_exit(2);
        }

        bufsz = INITLINELEN;
        if ((buf = malloc(bufsz)) == NULL)
                pfatal("allocating input buffer");
        buf[0] = '\0';

        setvbuf(stdout, NULL, _IOLBF, 0);
        setvbuf(stderr, NULL, _IOLBF, 0);
        for (i = 0; i < MAXFILEC; i++)
                filearg[i] = NULL;

        /* Cons up the names of the temporary files.  */
        if ((tmpdir = getenv("TMPDIR")) == NULL || *tmpdir == '\0')
                tmpdir = _PATH_TMP;
        for (i = strlen(tmpdir) - 1; i > 0 && tmpdir[i] == '/'; i--)
                ;
        i++;
        if (asprintf(&TMPOUTNAME, "%.*s/patchoXXXXXXXXXX", i, tmpdir) == -1)
                fatal("cannot allocate memory");
        if ((fd = mkstemp(TMPOUTNAME)) == -1)
                pfatal("can't create %s", TMPOUTNAME);
        close(fd);

        if (asprintf(&TMPINNAME, "%.*s/patchiXXXXXXXXXX", i, tmpdir) == -1)
                fatal("cannot allocate memory");
        if ((fd = mkstemp(TMPINNAME)) == -1)
                pfatal("can't create %s", TMPINNAME);
        close(fd);

        if (asprintf(&TMPREJNAME, "%.*s/patchrXXXXXXXXXX", i, tmpdir) == -1)
                fatal("cannot allocate memory");
        if ((fd = mkstemp(TMPREJNAME)) == -1)
                pfatal("can't create %s", TMPREJNAME);
        close(fd);

        if (asprintf(&TMPPATNAME, "%.*s/patchpXXXXXXXXXX", i, tmpdir) == -1)
                fatal("cannot allocate memory");
        if ((fd = mkstemp(TMPPATNAME)) == -1)
                pfatal("can't create %s", TMPPATNAME);
        close(fd);

        v = getenv("SIMPLE_BACKUP_SUFFIX");
        if (v)
                simple_backup_suffix = v;
        else
                simple_backup_suffix = ORIGEXT;

        /* parse switches */
        Argc = argc;
        Argv = argv;
        get_some_switches();
        if (unveil(tmpdir, "rwc") == -1) {
                perror("unveil");
                my_exit(2);
        }
        if (outname != NULL)
                if (unveil(outname, "rwc") == -1) {
                        perror("unveil");
                        my_exit(2);
                }
        if (filearg[0] != NULL) {
                char *origdir;

                if (unveil(filearg[0], "rwc") == -1) {
                        perror("unveil");
                        my_exit(2);
                }
                if ((origdir = dirname(filearg[0])) == NULL) {
                        perror("dirname");
                        my_exit(2);
                }
                if (unveil(origdir, "rwc") == -1) {
                        perror("unveil");
                        my_exit(2);
                }
        } else {
                if (unveil(".", "rwc") == -1) {
                        perror("unveil");
                        my_exit(2);
                }
        }
        if (filearg[1] != NULL)
                if (unveil(filearg[1], "r") == -1) {
                        perror("unveil");
                        my_exit(2);
                }
        if (!force && !batch)
                if (unveil(_PATH_TTY, "r") == -1) {
                        perror("unveil");
                        my_exit(2);
                }
        if (*rejname != '\0')
                if (unveil(rejname, "rwc") == -1) {
                        perror("unveil");
                        my_exit(2);
                }
        if (pledge("stdio rpath wpath cpath fattr", NULL) == -1) {
                perror("pledge");
                my_exit(2);
        }

        if (!Vflag) {
                if ((v = getenv("PATCH_VERSION_CONTROL")) == NULL)
                        v = getenv("VERSION_CONTROL");
                if (v != NULL || !posix)
                        backup_type = get_version(v);   /* OK to pass NULL. */
        }

        /* make sure we clean up /tmp in case of disaster */
        set_signals(0);

        patch_seen = false;
        for (open_patch_file(filearg[1]); there_is_another_patch();
            reinitialize_almost_everything()) {
                /* for each patch in patch file */

                patch_seen = true;

                warn_on_invalid_line = true;

                if (outname == NULL)
                        outname = xstrdup(filearg[0]);

                /* initialize the patched file */
                if (!skip_rest_of_patch)
                        init_output(TMPOUTNAME);

                /* initialize reject file */
                init_reject(TMPREJNAME);

                /* find out where all the lines are */
                if (!skip_rest_of_patch)
                        scan_input(filearg[0]);

                /* for ed script just up and do it and exit */
                if (diff_type == ED_DIFF) {
                        do_ed_script();
                        if (ofp)
                                fclose(ofp);
                        ofp = NULL;
                        if (rejfp)
                                fclose(rejfp);
                        rejfp = NULL;
                        continue;
                }

                /* from here on, open no standard i/o files, because malloc */
                /* might misfire and we can't catch it easily */

                /* apply each hunk of patch */
                hunk = 0;
                failed = 0;
                out_of_mem = false;
                while (another_hunk()) {
                        hunk++;
                        fuzz = 0;
                        mymaxfuzz = pch_context();
                        if (maxfuzz < mymaxfuzz)
                                mymaxfuzz = maxfuzz;
                        if (!skip_rest_of_patch) {
                                do {
                                        where = locate_hunk(fuzz);
                                        if ((hunk == 1 && where == 0 && !force) ||
                                            (where == 1 && pch_ptrn_lines() == 0 && !force)) {
                                                /* dwim for reversed patch? */
                                                if (!pch_swap()) {
                                                        if (fuzz == 0)
                                                                say("Not enough memory to try swapped hunk!  Assuming unswapped.\n");
                                                        continue;
                                                }
                                                reverse = !reverse;
                                                /* try again */
                                                where = locate_hunk(fuzz);
                                                if (where == 0) {
                                                        /* didn't find it swapped */
                                                        if (!pch_swap())
                                                                /* put it back to normal */
                                                                fatal("lost hunk on alloc error!\n");
                                                        reverse = !reverse;

                                                        /* restore position if this patch creates a file */
                                                        if (pch_ptrn_lines() == 0)
                                                                where = 1;
                                                } else if (noreverse) {
                                                        if (!pch_swap())
                                                                /* put it back to normal */
                                                                fatal("lost hunk on alloc error!\n");
                                                        reverse = !reverse;
                                                        say("Ignoring previously applied (or reversed) patch.\n");
                                                        skip_rest_of_patch = true;
                                                } else if (batch) {
                                                        if (verbose)
                                                                say("%seversed (or previously applied) patch detected!  %s -R.",
                                                                    reverse ? "R" : "Unr",
                                                                    reverse ? "Assuming" : "Ignoring");
                                                } else {
                                                        ask("%seversed (or previously applied) patch detected!  %s -R? [y] ",
                                                            reverse ? "R" : "Unr",
                                                            reverse ? "Assume" : "Ignore");
                                                        if (*buf == 'n') {
                                                                ask("Apply anyway? [n] ");
                                                                if (*buf != 'y')
                                                                        skip_rest_of_patch = true;
                                                                where = 0;
                                                                reverse = !reverse;
                                                                if (!pch_swap())
                                                                        /* put it back to normal */
                                                                        fatal("lost hunk on alloc error!\n");
                                                        }
                                                }
                                        }
                                } while (!skip_rest_of_patch && where == 0 &&
                                    ++fuzz <= mymaxfuzz);

                                if (skip_rest_of_patch) {       /* just got decided */
                                        fclose(ofp);
                                        ofp = NULL;
                                }
                        }
                        newwhere = pch_newfirst() + last_offset;
                        if (skip_rest_of_patch) {
                                abort_hunk();
                                failed++;
                                if (verbose)
                                        say("Hunk #%d ignored at %ld.\n",
                                            hunk, newwhere);
                        } else if (where == 0) {
                                abort_hunk();
                                failed++;
                                if (verbose)
                                        say("Hunk #%d failed at %ld.\n",
                                            hunk, newwhere);
                        } else {
                                apply_hunk(where);
                                if (verbose) {
                                        say("Hunk #%d succeeded at %ld",
                                            hunk, newwhere);
                                        if (fuzz != 0)
                                                say(" with fuzz %ld", fuzz);
                                        if (last_offset)
                                                say(" (offset %ld line%s)",
                                                    last_offset,
                                                    last_offset == 1L ? "" : "s");
                                        say(".\n");
                                }
                        }
                }

                if (out_of_mem && using_plan_a) {
                        Argc = Argc_last;
                        Argv = Argv_last;
                        say("\n\nRan out of memory using Plan A--trying again...\n\n");
                        if (ofp)
                                fclose(ofp);
                        ofp = NULL;
                        if (rejfp)
                                fclose(rejfp);
                        rejfp = NULL;
                        continue;
                }
                if (hunk == 0)
                        fatal("Internal error: hunk should not be 0\n");

                /* finish spewing out the new file */
                if (!skip_rest_of_patch)
                        spew_output();

                /* and put the output where desired */
                ignore_signals();
                if (!skip_rest_of_patch) {
                        struct stat     statbuf;
                        char    *realout = outname;

                        if (!check_only) {
                                if (move_file(TMPOUTNAME, outname) < 0) {
                                        toutkeep = true;
                                        realout = TMPOUTNAME;
                                        chmod(TMPOUTNAME, filemode);
                                } else
                                        chmod(outname, filemode);

                                if (remove_empty_files &&
                                    stat(realout, &statbuf) == 0 &&
                                    statbuf.st_size == 0) {
                                        if (verbose)
                                                say("Removing %s (empty after patching).\n",
                                                    realout);
                                        unlink(realout);
                                }
                        }
                }
                fclose(rejfp);
                rejfp = NULL;
                if (failed) {
                        error = 1;
                        if (*rejname == '\0') {
                                if (strlcpy(rejname, outname,
                                    sizeof(rejname)) >= sizeof(rejname))
                                        fatal("filename %s is too long\n", outname);
                                if (strlcat(rejname, REJEXT,
                                    sizeof(rejname)) >= sizeof(rejname))
                                        fatal("filename %s is too long\n", outname);
                        }
                        if (!check_only)
                                say("%d out of %d hunks %s--saving rejects to %s\n",
                                    failed, hunk, skip_rest_of_patch ? "ignored" : "failed", rejname);
                        else
                                say("%d out of %d hunks %s\n",
                                    failed, hunk, skip_rest_of_patch ? "ignored" : "failed");
                        if (!check_only && move_file(TMPREJNAME, rejname) < 0)
                                trejkeep = true;
                }
                set_signals(1);
        }

        if (!patch_seen)
                error = 2;

        my_exit(error);
        /* NOTREACHED */
}

/* Prepare to find the next patch to do in the patch file. */

static void
reinitialize_almost_everything(void)
{
        re_patch();
        re_input();

        input_lines = 0;
        last_frozen_line = 0;

        filec = 0;
        if (!out_of_mem) {
                free(filearg[0]);
                filearg[0] = NULL;
        }

        free(outname);
        outname = NULL;

        last_offset = 0;
        diff_type = 0;

        free(revision);
        revision = NULL;

        reverse = reverse_flag_specified;
        skip_rest_of_patch = false;

        get_some_switches();
}

/* Process switches and filenames. */

static void
get_some_switches(void)
{
        const char *options = "b::B:cCd:D:eEfF:i:lnNo:p:r:RstuvV:x:z:";
        static struct option longopts[] = {
                {"backup",              no_argument,            0,      'b'},
                {"batch",               no_argument,            0,      't'},
                {"check",               no_argument,            0,      'C'},
                {"context",             no_argument,            0,      'c'},
                {"debug",               required_argument,      0,      'x'},
                {"directory",           required_argument,      0,      'd'},
                {"dry-run",             no_argument,            0,      'C'},
                {"ed",                  no_argument,            0,      'e'},
                {"force",               no_argument,            0,      'f'},
                {"forward",             no_argument,            0,      'N'},
                {"fuzz",                required_argument,      0,      'F'},
                {"ifdef",               required_argument,      0,      'D'},
                {"input",               required_argument,      0,      'i'},
                {"ignore-whitespace",   no_argument,            0,      'l'},
                {"normal",              no_argument,            0,      'n'},
                {"output",              required_argument,      0,      'o'},
                {"prefix",              required_argument,      0,      'B'},
                {"quiet",               no_argument,            0,      's'},
                {"reject-file",         required_argument,      0,      'r'},
                {"remove-empty-files",  no_argument,            0,      'E'},
                {"reverse",             no_argument,            0,      'R'},
                {"silent",              no_argument,            0,      's'},
                {"strip",               required_argument,      0,      'p'},
                {"suffix",              required_argument,      0,      'z'},
                {"unified",             no_argument,            0,      'u'},
                {"version",             no_argument,            0,      'v'},
                {"version-control",     required_argument,      0,      'V'},
                {"posix",               no_argument,            &posix, 1},
                {NULL,                  0,                      0,      0}
        };
        int ch;
        const char *errstr;

        rejname[0] = '\0';
        Argc_last = Argc;
        Argv_last = Argv;
        if (!Argc)
                return;
        optreset = optind = 1;
        while ((ch = getopt_long(Argc, Argv, options, longopts, NULL)) != -1) {
                switch (ch) {
                case 'b':
                        if (backup_type == none)
                                backup_type = numbered_existing;
                        if (optarg == NULL)
                                break;
                        if (verbose)
                                say("Warning, the ``-b suffix'' option has been"
                                    " obsoleted by the -z option.\n");
                        /* FALLTHROUGH */
                case 'z':
                        /* must directly follow 'b' case for backwards compat */
                        simple_backup_suffix = xstrdup(optarg);
                        break;
                case 'B':
                        origprae = xstrdup(optarg);
                        break;
                case 'c':
                        diff_type = CONTEXT_DIFF;
                        break;
                case 'C':
                        check_only = true;
                        break;
                case 'd':
                        if (chdir(optarg) == -1)
                                pfatal("can't cd to %s", optarg);
                        break;
                case 'D':
                        do_defines = true;
                        if (!isalpha((unsigned char)*optarg) && *optarg != '_')
                                fatal("argument to -D is not an identifier\n");
                        snprintf(if_defined, sizeof if_defined,
                            "#ifdef %s\n", optarg);
                        snprintf(not_defined, sizeof not_defined,
                            "#ifndef %s\n", optarg);
                        snprintf(end_defined, sizeof end_defined,
                            "#endif /* %s */\n", optarg);
                        break;
                case 'e':
                        diff_type = ED_DIFF;
                        break;
                case 'E':
                        remove_empty_files = true;
                        break;
                case 'f':
                        force = true;
                        break;
                case 'F':
                        maxfuzz = strtonum(optarg, 0, INT_MAX, &errstr);
                        if (errstr != NULL)
                                fatal("maximum fuzz is %s: %s\n",
                                    errstr, optarg);
                        break;
                case 'i':
                        if (++filec == MAXFILEC)
                                fatal("too many file arguments\n");
                        filearg[filec] = xstrdup(optarg);
                        break;
                case 'l':
                        canonicalize = true;
                        break;
                case 'n':
                        diff_type = NORMAL_DIFF;
                        break;
                case 'N':
                        noreverse = true;
                        break;
                case 'o':
                        outname = xstrdup(optarg);
                        break;
                case 'p':
                        strippath = strtonum(optarg, 0, INT_MAX, &errstr);
                        if (errstr != NULL)
                                fatal("strip count is %s: %s\n",
                                    errstr, optarg);
                        break;
                case 'r':
                        if (strlcpy(rejname, optarg,
                            sizeof(rejname)) >= sizeof(rejname))
                                fatal("argument for -r is too long\n");
                        break;
                case 'R':
                        reverse = true;
                        reverse_flag_specified = true;
                        break;
                case 's':
                        verbose = false;
                        break;
                case 't':
                        batch = true;
                        break;
                case 'u':
                        diff_type = UNI_DIFF;
                        break;
                case 'v':
                        version();
                        break;
                case 'V':
                        backup_type = get_version(optarg);
                        Vflag = true;
                        break;
#ifdef DEBUGGING
                case 'x':
                        debug = strtonum(optarg, 0, INT_MAX, &errstr);
                        if (errstr != NULL)
                                fatal("debug number is %s: %s\n",
                                    errstr, optarg);
                        break;
#endif
                default:
                        if (ch != '\0')
                                usage();
                        break;
                }
        }
        Argc -= optind;
        Argv += optind;

        if (Argc > 0) {
                filearg[0] = xstrdup(*Argv++);
                Argc--;
                while (Argc > 0) {
                        if (++filec == MAXFILEC)
                                fatal("too many file arguments\n");
                        filearg[filec] = xstrdup(*Argv++);
                        Argc--;
                }
        }

        if (getenv("POSIXLY_CORRECT") != NULL)
                posix = 1;
}

static __dead void
usage(void)
{
        fprintf(stderr,
"usage: patch [-bCcEeflNnRstuv] [-B backup-prefix] [-D symbol] [-d directory]\n"
"             [-F max-fuzz] [-i patchfile] [-o out-file] [-p strip-count]\n"
"             [-r rej-name] [-V t | nil | never | none] [-x number]\n"
"             [-z backup-ext] [--posix] [origfile [patchfile]]\n"
"       patch <patchfile\n");
        my_exit(2);
}

/*
 * Attempt to find the right place to apply this hunk of patch.
 */
static LINENUM
locate_hunk(LINENUM fuzz)
{
        LINENUM first_guess = pch_first() + last_offset;
        LINENUM offset;
        LINENUM pat_lines = pch_ptrn_lines();
        LINENUM max_pos_offset = input_lines - first_guess - pat_lines + 1;
        LINENUM max_neg_offset = first_guess - last_frozen_line - 1 + pch_context();

        if (pat_lines == 0) {           /* null range matches always */
                if (verbose && fuzz == 0 && (diff_type == CONTEXT_DIFF
                    || diff_type == NEW_CONTEXT_DIFF
                    || diff_type == UNI_DIFF)) {
                        say("Empty context always matches.\n");
                }
                if (first_guess == 0)
                        return 1;
                return (first_guess);
        }
        if (max_neg_offset >= first_guess)      /* do not try lines < 0 */
                max_neg_offset = first_guess - 1;
        if (first_guess <= input_lines && patch_match(first_guess, 0, fuzz))
                return first_guess;
        for (offset = 1; ; offset++) {
                bool    check_after = (offset <= max_pos_offset);
                bool    check_before = (offset <= max_neg_offset);

                if (check_after && patch_match(first_guess, offset, fuzz)) {
#ifdef DEBUGGING
                        if (debug & 1)
                                say("Offset changing from %ld to %ld\n",
                                    last_offset, offset);
#endif
                        last_offset = offset;
                        return first_guess + offset;
                } else if (check_before && patch_match(first_guess, -offset, fuzz)) {
#ifdef DEBUGGING
                        if (debug & 1)
                                say("Offset changing from %ld to %ld\n",
                                    last_offset, -offset);
#endif
                        last_offset = -offset;
                        return first_guess - offset;
                } else if (!check_before && !check_after)
                        return 0;
        }
}

/* We did not find the pattern, dump out the hunk so they can handle it. */

static void
abort_context_hunk(void)
{
        LINENUM i;
        const LINENUM   pat_end = pch_end();
        /*
         * add in last_offset to guess the same as the previous successful
         * hunk
         */
        const LINENUM   oldfirst = pch_first() + last_offset;
        const LINENUM   newfirst = pch_newfirst() + last_offset;
        const LINENUM   oldlast = oldfirst + pch_ptrn_lines() - 1;
        const LINENUM   newlast = newfirst + pch_repl_lines() - 1;
        const char      *stars = (diff_type >= NEW_CONTEXT_DIFF ? " ****" : "");
        const char      *minuses = (diff_type >= NEW_CONTEXT_DIFF ? " ----" : " -----");

        fprintf(rejfp, "***************\n");
        for (i = 0; i <= pat_end; i++) {
                switch (pch_char(i)) {
                case '*':
                        if (oldlast < oldfirst)
                                fprintf(rejfp, "*** 0%s\n", stars);
                        else if (oldlast == oldfirst)
                                fprintf(rejfp, "*** %ld%s\n", oldfirst, stars);
                        else
                                fprintf(rejfp, "*** %ld,%ld%s\n", oldfirst,
                                    oldlast, stars);
                        break;
                case '=':
                        if (newlast < newfirst)
                                fprintf(rejfp, "--- 0%s\n", minuses);
                        else if (newlast == newfirst)
                                fprintf(rejfp, "--- %ld%s\n", newfirst, minuses);
                        else
                                fprintf(rejfp, "--- %ld,%ld%s\n", newfirst,
                                    newlast, minuses);
                        break;
                case '\n':
                        fprintf(rejfp, "%s", pfetch(i));
                        break;
                case ' ':
                case '-':
                case '+':
                case '!':
                        fprintf(rejfp, "%c %s", pch_char(i), pfetch(i));
                        break;
                default:
                        fatal("fatal internal error in abort_context_hunk\n");
                }
        }
}

static void
rej_line(int ch, LINENUM i)
{
        size_t len;
        const char *line = pfetch(i);

        len = strlen(line);

        fprintf(rejfp, "%c%s", ch, line);
        if (len == 0 || line[len-1] != '\n')
                fprintf(rejfp, "\n\\ No newline at end of file\n");
}

static void
abort_hunk(void)
{
        LINENUM         i, j, split;
        int             ch1, ch2;
        const LINENUM   pat_end = pch_end();
        const LINENUM   oldfirst = pch_first() + last_offset;
        const LINENUM   newfirst = pch_newfirst() + last_offset;

        if (diff_type != UNI_DIFF) {
                abort_context_hunk();
                return;
        }
        split = -1;
        for (i = 0; i <= pat_end; i++) {
                if (pch_char(i) == '=') {
                        split = i;
                        break;
                }
        }
        if (split == -1) {
                fprintf(rejfp, "malformed hunk: no split found\n");
                return;
        }
        i = 0;
        j = split + 1;
        fprintf(rejfp, "@@ -%ld,%ld +%ld,%ld @@\n",
            pch_ptrn_lines() ? oldfirst : 0,
            pch_ptrn_lines(), newfirst, pch_repl_lines());
        while (i < split || j <= pat_end) {
                ch1 = i < split ? pch_char(i) : -1;
                ch2 = j <= pat_end ? pch_char(j) : -1;
                if (ch1 == '-') {
                        rej_line('-', i);
                        i++;
                } else if (ch1 == ' ' && ch2 == ' ') {
                        rej_line(' ', i);
                        i++;
                        j++;
                } else if (ch1 == '!' && ch2 == '!') {
                        while (i < split && ch1 == '!') {
                                rej_line('-', i);
                                i++;
                                ch1 = i < split ? pch_char(i) : -1;
                        }
                        while (j <= pat_end && ch2 == '!') {
                                rej_line('+', j);
                                j++;
                                ch2 = j <= pat_end ? pch_char(j) : -1;
                        }
                } else if (ch1 == '*') {
                        i++;
                } else if (ch2 == '+' || ch2 == ' ') {
                        rej_line(ch2, j);
                        j++;
                } else {
                        fprintf(rejfp, "internal error on (%ld %ld %ld)\n",
                            i, split, j);
                        rej_line(ch1, i);
                        rej_line(ch2, j);
                        return;
                }
        }
}

/* We found where to apply it (we hope), so do it. */

static void
apply_hunk(LINENUM where)
{
        LINENUM         old = 1;
        const LINENUM   lastline = pch_ptrn_lines();
        LINENUM         new = lastline + 1;
#define OUTSIDE 0
#define IN_IFNDEF 1
#define IN_IFDEF 2
#define IN_ELSE 3
        int             def_state = OUTSIDE;
        const LINENUM   pat_end = pch_end();

        where--;
        while (pch_char(new) == '=' || pch_char(new) == '\n')
                new++;

        while (old <= lastline) {
                if (pch_char(old) == '-') {
                        copy_till(where + old - 1, false);
                        if (do_defines) {
                                if (def_state == OUTSIDE) {
                                        fputs(not_defined, ofp);
                                        def_state = IN_IFNDEF;
                                } else if (def_state == IN_IFDEF) {
                                        fputs(else_defined, ofp);
                                        def_state = IN_ELSE;
                                }
                                fputs(pfetch(old), ofp);
                        }
                        last_frozen_line++;
                        old++;
                } else if (new > pat_end) {
                        break;
                } else if (pch_char(new) == '+') {
                        copy_till(where + old - 1, false);
                        if (do_defines) {
                                if (def_state == IN_IFNDEF) {
                                        fputs(else_defined, ofp);
                                        def_state = IN_ELSE;
                                } else if (def_state == OUTSIDE) {
                                        fputs(if_defined, ofp);
                                        def_state = IN_IFDEF;
                                }
                        }
                        fputs(pfetch(new), ofp);
                        new++;
                } else if (pch_char(new) != pch_char(old)) {
                        say("Out-of-sync patch, lines %ld,%ld--mangled text or line numbers, maybe?\n",
                            pch_hunk_beg() + old,
                            pch_hunk_beg() + new);
#ifdef DEBUGGING
                        say("oldchar = '%c', newchar = '%c'\n",
                            pch_char(old), pch_char(new));
#endif
                        my_exit(2);
                } else if (pch_char(new) == '!') {
                        copy_till(where + old - 1, false);
                        if (do_defines) {
                                fputs(not_defined, ofp);
                                def_state = IN_IFNDEF;
                        }
                        while (pch_char(old) == '!') {
                                if (do_defines) {
                                        fputs(pfetch(old), ofp);
                                }
                                last_frozen_line++;
                                old++;
                        }
                        if (do_defines) {
                                fputs(else_defined, ofp);
                                def_state = IN_ELSE;
                        }
                        while (pch_char(new) == '!') {
                                fputs(pfetch(new), ofp);
                                new++;
                        }
                } else {
                        if (pch_char(new) != ' ')
                                fatal("Internal error: expected ' '\n");
                        old++;
                        new++;
                        if (do_defines && def_state != OUTSIDE) {
                                fputs(end_defined, ofp);
                                def_state = OUTSIDE;
                        }
                }
        }
        if (new <= pat_end && pch_char(new) == '+') {
                copy_till(where + old - 1, false);
                if (do_defines) {
                        if (def_state == OUTSIDE) {
                                fputs(if_defined, ofp);
                                def_state = IN_IFDEF;
                        } else if (def_state == IN_IFNDEF) {
                                fputs(else_defined, ofp);
                                def_state = IN_ELSE;
                        }
                }
                while (new <= pat_end && pch_char(new) == '+') {
                        fputs(pfetch(new), ofp);
                        new++;
                }
        }
        if (do_defines && def_state != OUTSIDE) {
                fputs(end_defined, ofp);
        }
}

/*
 * Open the new file.
 */
static void
init_output(const char *name)
{
        ofp = fopen(name, "w");
        if (ofp == NULL)
                pfatal("can't create %s", name);
}

/*
 * Open a file to put hunks we can't locate.
 */
static void
init_reject(const char *name)
{
        rejfp = fopen(name, "w");
        if (rejfp == NULL)
                pfatal("can't create %s", name);
}

/*
 * Copy input file to output, up to wherever hunk is to be applied.
 * If endoffile is true, treat the last line specially since it may
 * lack a newline.
 */
static void
copy_till(LINENUM lastline, bool endoffile)
{
        if (last_frozen_line > lastline)
                fatal("misordered hunks! output would be garbled\n");
        while (last_frozen_line < lastline) {
                if (++last_frozen_line == lastline && endoffile)
                        dump_line(last_frozen_line, !last_line_missing_eol);
                else
                        dump_line(last_frozen_line, true);
        }
}

/*
 * Finish copying the input file to the output file.
 */
static void
spew_output(void)
{
#ifdef DEBUGGING
        if (debug & 256)
                say("il=%ld lfl=%ld\n", input_lines, last_frozen_line);
#endif
        if (input_lines)
                copy_till(input_lines, true);   /* dump remainder of file */
        fclose(ofp);
        ofp = NULL;
}

/*
 * Copy one line from input to output.
 */
static void
dump_line(LINENUM line, bool write_newline)
{
        char    *s;

        s = ifetch(line, 0);
        if (s == NULL)
                return;
        /* Note: string is not NUL terminated. */
        for (; *s != '\n'; s++)
                putc(*s, ofp);
        if (write_newline)
                putc('\n', ofp);
}

/*
 * Does the patch pattern match at line base+offset?
 */
static bool
patch_match(LINENUM base, LINENUM offset, LINENUM fuzz)
{
        LINENUM         pline = 1 + fuzz;
        LINENUM         iline;
        LINENUM         pat_lines = pch_ptrn_lines() - fuzz;
        const char      *ilineptr;
        const char      *plineptr;
        ssize_t         plinelen;

        for (iline = base + offset + fuzz; pline <= pat_lines; pline++, iline++) {
                ilineptr = ifetch(iline, offset >= 0);
                if (ilineptr == NULL)
                        return false;
                plineptr = pfetch(pline);
                plinelen = pch_line_len(pline);
                if (canonicalize) {
                        if (!similar(ilineptr, plineptr, plinelen))
                                return false;
                } else if (strnNE(ilineptr, plineptr, plinelen))
                        return false;
                if (iline == input_lines) {
                        /*
                         * We are looking at the last line of the file.
                         * If the file has no eol, the patch line should
                         * not have one either and vice-versa. Note that
                         * plinelen > 0.
                         */
                        if (last_line_missing_eol) {
                                if (plineptr[plinelen - 1] == '\n')
                                        return false;
                        } else {
                                if (plineptr[plinelen - 1] != '\n')
                                        return false;
                        }
                }
        }
        return true;
}

/*
 * Do two lines match with canonicalized white space?
 */
static bool
similar(const char *a, const char *b, ssize_t len)
{
        while (len) {
                if (isspace((unsigned char)*b)) { /* whitespace (or \n) to match? */
                        if (!isspace((unsigned char)*a))
                                return false;   /* no corresponding whitespace */
                        while (len && isspace((unsigned char)*b) && *b != '\n')
                                b++, len--;     /* skip pattern whitespace */
                        while (isspace((unsigned char)*a) && *a != '\n')
                                a++;    /* skip target whitespace */
                        if (*a == '\n' || *b == '\n')
                                return (*a == *b);      /* should end in sync */
                } else if (*a++ != *b++)        /* match non-whitespace chars */
                        return false;
                else
                        len--;  /* probably not necessary */
        }
        return true;            /* actually, this is not reached */
        /* since there is always a \n */
}