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pch.c

/* reading patches */

/* $Id: pch.c,v 1.45 2003/07/02 22:19:21 eggert Exp $ */

/* Copyright (C) 1986, 1987, 1988 Larry Wall

   Copyright (C) 1990, 1991, 1992, 1993, 1997, 1998, 1999, 2000, 2001,
   2002, 2003 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; see the file COPYING.
   If not, write to the Free Software Foundation,
   59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

#define XTERN extern
#include <common.h>
#include <backupfile.h>
#include <dirname.h>
#include <inp.h>
#include <quotearg.h>
#include <util.h>
#undef XTERN
#define XTERN
#include <pch.h>

#define INITHUNKMAX 125             /* initial dynamic allocation size */

/* Patch (diff listing) abstract type. */

static FILE *pfp;             /* patch file pointer */
static int p_says_nonexistent[2];   /* [0] for old file, [1] for new:
            0 for existent and nonempty,
            1 for existent and probably (but not necessarily) empty,
            2 for nonexistent */
static int p_rfc934_nesting;        /* RFC 934 nesting level */
static time_t p_timestamp[2];       /* timestamps in patch headers */
static off_t p_filesize;            /* size of the patch file */
static LINENUM p_first;             /* 1st line number */
static LINENUM p_newfirst;          /* 1st line number of replacement */
static LINENUM p_ptrn_lines;        /* # lines in pattern */
static LINENUM p_repl_lines;        /* # lines in replacement text */
static LINENUM p_end = -1;          /* last line in hunk */
static LINENUM p_max;               /* max allowed value of p_end */
static LINENUM p_prefix_context;    /* # of prefix context lines */
static LINENUM p_suffix_context;    /* # of suffix context lines */
static LINENUM p_input_line;        /* current line # from patch file */
static char **p_line;               /* the text of the hunk */
static size_t *p_len;               /* line length including \n if any */
static char *p_Char;                /* +, -, and ! */
static LINENUM hunkmax = INITHUNKMAX;     /* size of above arrays */
static int p_indent;                /* indent to patch */
static bool p_strip_trailing_cr;    /* true if stripping trailing \r */
static bool p_pass_comments_through;      /* true if not ignoring # lines */
static file_offset p_base;          /* where to intuit this time */
static LINENUM p_bline;             /* line # of p_base */
static file_offset p_start;         /* where intuit found a patch */
static LINENUM p_sline;             /* and the line number for it */
static LINENUM p_hunk_beg;          /* line number of current hunk */
static LINENUM p_efake = -1;        /* end of faked up lines--don't free */
static LINENUM p_bfake = -1;        /* beg of faked up lines */

enum nametype { OLD, NEW, INDEX, NONE };

static char *scan_linenum (char *, LINENUM *);
static enum diff intuit_diff_type (void);
static enum nametype best_name (char * const *, int const *);
static int prefix_components (char *, bool);
static size_t pget_line (int, int, bool, bool);
static size_t get_line (void);
static bool incomplete_line (void);
static bool grow_hunkmax (void);
static void malformed (void) __attribute__ ((noreturn));
static void next_intuit_at (file_offset, LINENUM);
static void skip_to (file_offset, LINENUM);
static char get_ed_command_letter (char const *);

/* Prepare to look for the next patch in the patch file. */

void
re_patch (void)
{
    p_first = 0;
    p_newfirst = 0;
    p_ptrn_lines = 0;
    p_repl_lines = 0;
    p_end = -1;
    p_max = 0;
    p_indent = 0;
    p_strip_trailing_cr = false;
}

/* Open the patch file at the beginning of time. */

void
open_patch_file (char const *filename)
{
    file_offset file_pos = 0;
    struct stat st;
    if (!filename || !*filename || strEQ (filename, "-"))
      {
      file_offset stdin_pos;
#if HAVE_SETMODE_DOS
      if (binary_transput)
        {
          if (isatty (STDIN_FILENO))
            fatal ("cannot read binary data from tty on this platform");
          setmode (STDIN_FILENO, O_BINARY);
        }
#endif
      if (fstat (STDIN_FILENO, &st) != 0)
        pfatal ("fstat");
      if (S_ISREG (st.st_mode) && (stdin_pos = file_tell (stdin)) != -1)
        {
          pfp = stdin;
          file_pos = stdin_pos;
        }
      else
        {
          size_t charsread;
          int exclusive = TMPPATNAME_needs_removal ? 0 : O_EXCL;
          TMPPATNAME_needs_removal = 1;
          pfp = fdopen (create_file (TMPPATNAME,
                               O_RDWR | O_BINARY | exclusive,
                               (mode_t) 0),
                    "w+b");
          if (!pfp)
            pfatal ("Can't open stream for file %s", quotearg (TMPPATNAME));
          for (st.st_size = 0;
             (charsread = fread (buf, 1, bufsize, stdin)) != 0;
             st.st_size += charsread)
            if (fwrite (buf, 1, charsread, pfp) != charsread)
            write_fatal ();
          if (ferror (stdin) || fclose (stdin) != 0)
            read_fatal ();
          if (fflush (pfp) != 0
            || file_seek (pfp, (file_offset) 0, SEEK_SET) != 0)
            write_fatal ();
        }
      }
    else
      {
      pfp = fopen (filename, binary_transput ? "rb" : "r");
      if (!pfp)
        pfatal ("Can't open patch file %s", quotearg (filename));
      if (fstat (fileno (pfp), &st) != 0)
        pfatal ("fstat");
      }
    p_filesize = st.st_size;
    if (p_filesize != (file_offset) p_filesize)
      fatal ("patch file is too long");
    next_intuit_at (file_pos, (LINENUM) 1);
    set_hunkmax();
}

/* Make sure our dynamically realloced tables are malloced to begin with. */

void
set_hunkmax (void)
{
    if (!p_line)
      p_line = (char **) malloc (hunkmax * sizeof *p_line);
    if (!p_len)
      p_len = (size_t *) malloc (hunkmax * sizeof *p_len);
    if (!p_Char)
      p_Char = malloc (hunkmax * sizeof *p_Char);
}

/* Enlarge the arrays containing the current hunk of patch. */

static bool
grow_hunkmax (void)
{
    hunkmax *= 2;
    assert (p_line && p_len && p_Char);
    if ((p_line = (char **) realloc (p_line, hunkmax * sizeof (*p_line)))
      && (p_len = (size_t *) realloc (p_len, hunkmax * sizeof (*p_len)))
      && (p_Char = realloc (p_Char, hunkmax * sizeof (*p_Char))))
      return true;
    if (!using_plan_a)
      memory_fatal ();
    /* Don't free previous values of p_line etc.,
       since some broken implementations free them for us.
       Whatever is null will be allocated again from within plan_a (),
       of all places.  */
    return false;
}

/* True if the remainder of the patch file contains a diff of some sort. */

bool
there_is_another_patch (void)
{
    if (p_base != 0 && p_base >= p_filesize) {
      if (verbosity == VERBOSE)
          say ("done\n");
      return false;
    }
    if (verbosity == VERBOSE)
      say ("Hmm...");
    diff_type = intuit_diff_type();
    if (diff_type == NO_DIFF) {
      if (verbosity == VERBOSE)
        say (p_base
             ? "  Ignoring the trailing garbage.\ndone\n"
             : "  I can't seem to find a patch in there anywhere.\n");
      if (! p_base && p_filesize)
        fatal ("Only garbage was found in the patch input.");
      return false;
    }
    if (skip_rest_of_patch)
      {
      Fseek (pfp, p_start, SEEK_SET);
      p_input_line = p_sline - 1;
      return true;
      }
    if (verbosity == VERBOSE)
      say ("  %sooks like %s to me...\n",
          (p_base == 0 ? "L" : "The next patch l"),
          diff_type == UNI_DIFF ? "a unified diff" :
          diff_type == CONTEXT_DIFF ? "a context diff" :
          diff_type == NEW_CONTEXT_DIFF ? "a new-style context diff" :
          diff_type == NORMAL_DIFF ? "a normal diff" :
          "an ed script" );

    if (verbosity != SILENT)
      {
      if (p_indent)
        say ("(Patch is indented %d space%s.)\n", p_indent, p_indent==1?"":"s");
      if (p_strip_trailing_cr)
        say ("(Stripping trailing CRs from patch.)\n");
      if (! inname)
        {
          char numbuf[LINENUM_LENGTH_BOUND + 1];
          say ("can't find file to patch at input line %s\n",
             format_linenum (numbuf, p_sline));
          if (diff_type != ED_DIFF)
            say (strippath == -1
               ? "Perhaps you should have used the -p or --strip option?\n"
               : "Perhaps you used the wrong -p or --strip option?\n");
        }
      }

    skip_to(p_start,p_sline);
    while (!inname) {
      if (force | batch) {
          say ("No file to patch.  Skipping patch.\n");
          skip_rest_of_patch = true;
          return true;
      }
      ask ("File to patch: ");
      inname = fetchname (buf, 0, (time_t *) 0);
      if (inname)
        {
          if (stat (inname, &instat) == 0)
            {
            inerrno = 0;
            invc = -1;
            }
          else
            {
            perror (inname);
            fflush (stderr);
            free (inname);
            inname = 0;
            }
        }
      if (!inname) {
          ask ("Skip this patch? [y] ");
          if (*buf != 'n') {
            if (verbosity != SILENT)
                say ("Skipping patch.\n");
            skip_rest_of_patch = true;
            return true;
          }
      }
    }
    return true;
}

/* Determine what kind of diff is in the remaining part of the patch file. */

static enum diff
intuit_diff_type (void)
{
    register file_offset this_line = 0;
    register file_offset first_command_line = -1;
    char first_ed_command_letter = 0;
    LINENUM fcl_line = 0; /* Pacify `gcc -W'.  */
    register bool this_is_a_command = false;
    register bool stars_this_line = false;
    enum nametype i;
    char *name[3];
    struct stat st[3];
    int stat_errno[3];
    int version_controlled[3];
    register enum diff retval;

    name[OLD] = name[NEW] = name[INDEX] = 0;
    version_controlled[OLD] = -1;
    version_controlled[NEW] = -1;
    version_controlled[INDEX] = -1;
    p_rfc934_nesting = 0;
    p_timestamp[OLD] = p_timestamp[NEW] = (time_t) -1;
    p_says_nonexistent[OLD] = p_says_nonexistent[NEW] = 0;
    Fseek (pfp, p_base, SEEK_SET);
    p_input_line = p_bline - 1;
    for (;;) {
      register char *s;
      register char *t;
      register file_offset previous_line = this_line;
      register bool last_line_was_command = this_is_a_command;
      register bool stars_last_line = stars_this_line;
      register int indent = 0;
      char ed_command_letter;
      bool strip_trailing_cr;
      size_t chars_read;

      this_line = file_tell (pfp);
      chars_read = pget_line (0, 0, false, false);
      if (chars_read == (size_t) -1)
        memory_fatal ();
      if (! chars_read) {
          if (first_ed_command_letter) {
                              /* nothing but deletes!? */
            p_start = first_command_line;
            p_sline = fcl_line;
            retval = ED_DIFF;
            goto scan_exit;
          }
          else {
            p_start = this_line;
            p_sline = p_input_line;
            return NO_DIFF;
          }
      }
      strip_trailing_cr = 2 <= chars_read && buf[chars_read - 2] == '\r';
      for (s = buf; *s == ' ' || *s == '\t' || *s == 'X'; s++) {
          if (*s == '\t')
            indent = (indent + 8) & ~7;
          else
            indent++;
      }
      for (t = s;  ISDIGIT (*t) || *t == ',';  t++)
        continue;
      this_is_a_command = (ISDIGIT (*s) &&
        (*t == 'd' || *t == 'c' || *t == 'a') );
      if (first_command_line < 0
          && ((ed_command_letter = get_ed_command_letter (s))
            || this_is_a_command)) {
          first_command_line = this_line;
          first_ed_command_letter = ed_command_letter;
          fcl_line = p_input_line;
          p_indent = indent;        /* assume this for now */
          p_strip_trailing_cr = strip_trailing_cr;
      }
      if (!stars_last_line && strnEQ(s, "*** ", 4))
          name[OLD] = fetchname (s+4, strippath, &p_timestamp[OLD]);
      else if (strnEQ(s, "+++ ", 4))
        {
          /* Swap with NEW below.  */
          name[OLD] = fetchname (s+4, strippath, &p_timestamp[OLD]);
          p_strip_trailing_cr = strip_trailing_cr;
        }
      else if (strnEQ(s, "Index:", 6))
        {
          name[INDEX] = fetchname (s+6, strippath, (time_t *) 0);
          p_strip_trailing_cr = strip_trailing_cr;
        }
      else if (strnEQ(s, "Prereq:", 7)) {
          for (t = s + 7;  ISSPACE ((unsigned char) *t);  t++)
            continue;
          revision = t;
          for (t = revision;  *t;  t++)
            if (ISSPACE ((unsigned char) *t))
            {
              char const *u;
              for (u = t + 1;  ISSPACE ((unsigned char) *u);  u++)
                continue;
              if (*u)
                {
                  char numbuf[LINENUM_LENGTH_BOUND + 1];
                  say ("Prereq: with multiple words at line %s of patch\n",
                     format_linenum (numbuf, this_line));
                }
              break;
            }
          if (t == revision)
            revision = 0;
          else {
            char oldc = *t;
            *t = '\0';
            revision = savestr (revision);
            *t = oldc;
          }
      } else
        {
          for (t = s;  t[0] == '-' && t[1] == ' ';  t += 2)
            continue;
          if (strnEQ(t, "--- ", 4))
            {
            time_t timestamp = (time_t) -1;
            name[NEW] = fetchname (t+4, strippath, &timestamp);
            if (timestamp != (time_t) -1)
              {
                p_timestamp[NEW] = timestamp;
                p_rfc934_nesting = (t - s) >> 1;
              }
            p_strip_trailing_cr = strip_trailing_cr;
            }
        }
      if ((diff_type == NO_DIFF || diff_type == ED_DIFF) &&
        first_command_line >= 0 &&
        strEQ(s, ".\n") ) {
          p_start = first_command_line;
          p_sline = fcl_line;
          retval = ED_DIFF;
          goto scan_exit;
      }
      if ((diff_type == NO_DIFF || diff_type == UNI_DIFF)
          && strnEQ(s, "@@ -", 4)) {

          /* `name' and `p_timestamp' are backwards; swap them.  */
          time_t ti = p_timestamp[OLD];
          p_timestamp[OLD] = p_timestamp[NEW];
          p_timestamp[NEW] = ti;
          t = name[OLD];
          name[OLD] = name[NEW];
          name[NEW] = t;

          s += 4;
          if (s[0] == '0' && !ISDIGIT (s[1]))
            p_says_nonexistent[OLD] = 1 + ! p_timestamp[OLD];
          while (*s != ' ' && *s != '\n')
            s++;
          while (*s == ' ')
            s++;
          if (s[0] == '+' && s[1] == '0' && !ISDIGIT (s[2]))
            p_says_nonexistent[NEW] = 1 + ! p_timestamp[NEW];
          p_indent = indent;
          p_start = this_line;
          p_sline = p_input_line;
          retval = UNI_DIFF;
          if (! ((name[OLD] || ! p_timestamp[OLD])
               && (name[NEW] || ! p_timestamp[NEW]))
            && ! name[INDEX])
            {
            char numbuf[LINENUM_LENGTH_BOUND + 1];
            say ("missing header for unified diff at line %s of patch\n",
                 format_linenum (numbuf, p_sline));
            }
          goto scan_exit;
      }
      stars_this_line = strnEQ(s, "********", 8);
      if ((diff_type == NO_DIFF
           || diff_type == CONTEXT_DIFF
           || diff_type == NEW_CONTEXT_DIFF)
          && stars_last_line && strnEQ (s, "*** ", 4)) {
          s += 4;
          if (s[0] == '0' && !ISDIGIT (s[1]))
            p_says_nonexistent[OLD] = 1 + ! p_timestamp[OLD];
          /* if this is a new context diff the character just before */
          /* the newline is a '*'. */
          while (*s != '\n')
            s++;
          p_indent = indent;
          p_strip_trailing_cr = strip_trailing_cr;
          p_start = previous_line;
          p_sline = p_input_line - 1;
          retval = (*(s-1) == '*' ? NEW_CONTEXT_DIFF : CONTEXT_DIFF);

          {
            /* Scan the first hunk to see whether the file contents
             appear to have been deleted.  */
            file_offset saved_p_base = p_base;
            LINENUM saved_p_bline = p_bline;
            Fseek (pfp, previous_line, SEEK_SET);
            p_input_line -= 2;
            if (another_hunk (retval, false)
              && ! p_repl_lines && p_newfirst == 1)
            p_says_nonexistent[NEW] = 1 + ! p_timestamp[NEW];
            next_intuit_at (saved_p_base, saved_p_bline);
          }

          if (! ((name[OLD] || ! p_timestamp[OLD])
               && (name[NEW] || ! p_timestamp[NEW]))
            && ! name[INDEX])
            {
            char numbuf[LINENUM_LENGTH_BOUND + 1];
            say ("missing header for context diff at line %s of patch\n",
                 format_linenum (numbuf, p_sline));
            }
          goto scan_exit;
      }
      if ((diff_type == NO_DIFF || diff_type == NORMAL_DIFF) &&
        last_line_was_command &&
        (strnEQ(s, "< ", 2) || strnEQ(s, "> ", 2)) ) {
          p_start = previous_line;
          p_sline = p_input_line - 1;
          p_indent = indent;
          p_strip_trailing_cr = strip_trailing_cr;
          retval = NORMAL_DIFF;
          goto scan_exit;
      }
    }

  scan_exit:

    /* To intuit `inname', the name of the file to patch,
       use the algorithm specified by POSIX 1003.1-2001 XCU lines 25680-26599
       (with some modifications if posixly_correct is zero):

       - Take the old and new names from the context header if present,
       and take the index name from the `Index:' line if present and
       if either the old and new names are both absent
       or posixly_correct is nonzero.
       Consider the file names to be in the order (old, new, index).
       - If some named files exist, use the first one if posixly_correct
       is nonzero, the best one otherwise.
       - If patch_get is nonzero, and no named files exist,
       but an RCS or SCCS master file exists,
       use the first named file with an RCS or SCCS master.
       - If no named files exist, no RCS or SCCS master was found,
       some names are given, posixly_correct is zero,
       and the patch appears to create a file, then use the best name
       requiring the creation of the fewest directories.
       - Otherwise, report failure by setting `inname' to 0;
       this causes our invoker to ask the user for a file name.  */

    i = NONE;

    if (!inname)
      {
      enum nametype i0 = NONE;

      if (! posixly_correct && (name[OLD] || name[NEW]) && name[INDEX])
        {
          free (name[INDEX]);
          name[INDEX] = 0;
        }

      for (i = OLD;  i <= INDEX;  i++)
        if (name[i])
          {
            if (i0 != NONE && strcmp (name[i0], name[i]) == 0)
            {
              /* It's the same name as before; reuse stat results.  */
              stat_errno[i] = stat_errno[i0];
              if (! stat_errno[i])
                st[i] = st[i0];
            }
            else if (stat (name[i], &st[i]) != 0)
            stat_errno[i] = errno;
            else
            {
              stat_errno[i] = 0;
              if (posixly_correct)
                break;
            }
            i0 = i;
          }

      if (! posixly_correct)
        {
          bool is_empty;

          i = best_name (name, stat_errno);

          if (i == NONE && patch_get)
            {
            enum nametype nope = NONE;

            for (i = OLD;  i <= INDEX;  i++)
              if (name[i])
                {
                  char const *cs;
                  char *getbuf;
                  char *diffbuf;
                  bool readonly = (outfile
                               && strcmp (outfile, name[i]) != 0);

                  if (nope == NONE || strcmp (name[nope], name[i]) != 0)
                  {
                    cs = (version_controller
                          (name[i], readonly, (struct stat *) 0,
                         &getbuf, &diffbuf));
                    version_controlled[i] = !! cs;
                    if (cs)
                      {
                        if (version_get (name[i], cs, false, readonly,
                                     getbuf, &st[i]))
                        stat_errno[i] = 0;
                        else
                        version_controlled[i] = 0;

                        free (getbuf);
                        if (diffbuf)
                        free (diffbuf);

                        if (! stat_errno[i])
                        break;
                      }
                  }

                  nope = i;
                }
            }

          is_empty = i == NONE || st[i].st_size == 0;
          if ((! is_empty) < p_says_nonexistent[reverse ^ is_empty])
            {
            assert (i0 != NONE);
            reverse ^=
              ok_to_reverse
                ("The next patch%s would %s the file %s,\nwhich %s!",
                 reverse ? ", when reversed," : "",
                 (i == NONE ? "delete"
                  : st[i].st_size == 0 ? "empty out"
                  : "create"),
                 quotearg (name[i == NONE || st[i].st_size == 0 ? i0 : i]),
                 (i == NONE ? "does not exist"
                  : st[i].st_size == 0 ? "is already empty"
                  : "already exists"));
            }

          if (i == NONE && p_says_nonexistent[reverse])
            {
            int newdirs[3];
            int newdirs_min = INT_MAX;
            int distance_from_minimum[3];

            for (i = OLD;  i <= INDEX;  i++)
              if (name[i])
                {
                  newdirs[i] = (prefix_components (name[i], false)
                            - prefix_components (name[i], true));
                  if (newdirs[i] < newdirs_min)
                  newdirs_min = newdirs[i];
                }

            for (i = OLD;  i <= INDEX;  i++)
              if (name[i])
                distance_from_minimum[i] = newdirs[i] - newdirs_min;

            i = best_name (name, distance_from_minimum);
            }
        }
      }

    if (i == NONE)
      inerrno = -1;
    else
      {
      inname = name[i];
      name[i] = 0;
      inerrno = stat_errno[i];
      invc = version_controlled[i];
      instat = st[i];
      }

    for (i = OLD;  i <= INDEX;  i++)
      if (name[i])
      free (name[i]);

    return retval;
}

/* Count the path name components in FILENAME's prefix.
   If CHECKDIRS is true, count only existing directories.  */
static int
prefix_components (char *filename, bool checkdirs)
{
  int count = 0;
  struct stat stat_buf;
  int stat_result;
  char *f = filename + FILESYSTEM_PREFIX_LEN (filename);

  if (*f)
    while (*++f)
      if (ISSLASH (f[0]) && ! ISSLASH (f[-1]))
      {
        if (checkdirs)
          {
            *f = '\0';
            stat_result = stat (filename, &stat_buf);
            *f = '/';
            if (! (stat_result == 0 && S_ISDIR (stat_buf.st_mode)))
            break;
          }

        count++;
      }

  return count;
}

/* Return the index of the best of NAME[OLD], NAME[NEW], and NAME[INDEX].
   Ignore null names, and ignore NAME[i] if IGNORE[i] is nonzero.
   Return NONE if all names are ignored.  */
static enum nametype
best_name (char *const *name, int const *ignore)
{
  enum nametype i;
  int components[3];
  int components_min = INT_MAX;
  size_t basename_len[3];
  size_t basename_len_min = SIZE_MAX;
  size_t len[3];
  size_t len_min = SIZE_MAX;

  for (i = OLD;  i <= INDEX;  i++)
    if (name[i] && !ignore[i])
      {
      /* Take the names with the fewest prefix components.  */
      components[i] = prefix_components (name[i], false);
      if (components_min < components[i])
        continue;
      components_min = components[i];

      /* Of those, take the names with the shortest basename.  */
      basename_len[i] = strlen (base_name (name[i]));
      if (basename_len_min < basename_len[i])
        continue;
      basename_len_min = basename_len[i];

      /* Of those, take the shortest names.  */
      len[i] = strlen (name[i]);
      if (len_min < len[i])
        continue;
      len_min = len[i];
      }

  /* Of those, take the first name.  */
  for (i = OLD;  i <= INDEX;  i++)
    if (name[i] && !ignore[i]
      && components[i] == components_min
      && basename_len[i] == basename_len_min
      && len[i] == len_min)
      break;

  return i;
}

/* Remember where this patch ends so we know where to start up again. */

static void
next_intuit_at (file_offset file_pos, LINENUM file_line)
{
    p_base = file_pos;
    p_bline = file_line;
}

/* Basically a verbose fseek() to the actual diff listing. */

static void
skip_to (file_offset file_pos, LINENUM file_line)
{
    register FILE *i = pfp;
    register FILE *o = stdout;
    register int c;

    assert(p_base <= file_pos);
    if ((verbosity == VERBOSE || !inname) && p_base < file_pos) {
      Fseek (i, p_base, SEEK_SET);
      say ("The text leading up to this was:\n--------------------------\n");

      while (file_tell (i) < file_pos)
        {
          putc ('|', o);
          do
            {
            if ((c = getc (i)) == EOF)
              read_fatal ();
            putc (c, o);
            }
          while (c != '\n');
        }

      say ("--------------------------\n");
    }
    else
      Fseek (i, file_pos, SEEK_SET);
    p_input_line = file_line - 1;
}

/* Make this a function for better debugging.  */
static void
malformed (void)
{
    char numbuf[LINENUM_LENGTH_BOUND + 1];
    fatal ("malformed patch at line %s: %s",
         format_linenum (numbuf, p_input_line), buf);
            /* about as informative as "Syntax error" in C */
}

/* Parse a line number from a string.
   Return the address of the first char after the number.  */
static char *
scan_linenum (char *s0, LINENUM *linenum)
{
  char *s;
  LINENUM n = 0;
  bool overflow = false;
  char numbuf[LINENUM_LENGTH_BOUND + 1];

  for (s = s0;  ISDIGIT (*s);  s++)
    {
      LINENUM new_n = 10 * n + (*s - '0');
      overflow |= new_n / 10 != n;
      n = new_n;
    }

  if (s == s0)
    fatal ("missing line number at line %s: %s",
         format_linenum (numbuf, p_input_line), buf);

  if (overflow)
    fatal ("line number %.*s is too large at line %s: %s",
         (int) (s - s0), s0, format_linenum (numbuf, p_input_line), buf);

  *linenum = n;
  return s;
}

/* 1 if there is more of the current diff listing to process;
   0 if not; -1 if ran out of memory. */

int
another_hunk (enum diff difftype, bool rev)
{
    register char *s;
    register LINENUM context = 0;
    register size_t chars_read;
    char numbuf0[LINENUM_LENGTH_BOUND + 1];
    char numbuf1[LINENUM_LENGTH_BOUND + 1];
    char numbuf2[LINENUM_LENGTH_BOUND + 1];
    char numbuf3[LINENUM_LENGTH_BOUND + 1];

    while (p_end >= 0) {
      if (p_end == p_efake)
          p_end = p_bfake;          /* don't free twice */
      else
          free(p_line[p_end]);
      p_end--;
    }
    assert(p_end == -1);
    p_efake = -1;

    p_max = hunkmax;                /* gets reduced when --- found */
    if (difftype == CONTEXT_DIFF || difftype == NEW_CONTEXT_DIFF) {
      file_offset line_beginning = file_tell (pfp);
                              /* file pos of the current line */
      LINENUM repl_beginning = 0;   /* index of --- line */
      register LINENUM fillcnt = 0; /* #lines of missing ptrn or repl */
      register LINENUM fillsrc;     /* index of first line to copy */
      register LINENUM filldst;     /* index of first missing line */
      bool ptrn_spaces_eaten = false;     /* ptrn was slightly misformed */
      bool some_context = false;    /* (perhaps internal) context seen */
      register bool repl_could_be_missing = true;
      bool ptrn_missing = false;    /* The pattern was missing.  */
      bool repl_missing = false;    /* Likewise for replacement.  */
      file_offset repl_backtrack_position = 0;
                              /* file pos of first repl line */
      LINENUM repl_patch_line;      /* input line number for same */
      LINENUM repl_context;         /* context for same */
      LINENUM ptrn_prefix_context = -1; /* lines in pattern prefix context */
      LINENUM ptrn_suffix_context = -1; /* lines in pattern suffix context */
      LINENUM repl_prefix_context = -1; /* lines in replac. prefix context */
      LINENUM ptrn_copiable = 0;    /* # of copiable lines in ptrn */
      LINENUM repl_copiable = 0;    /* Likewise for replacement.  */

      /* Pacify `gcc -Wall'.  */
      fillsrc = filldst = repl_patch_line = repl_context = 0;

      chars_read = get_line ();
      if (chars_read == (size_t) -1
          || chars_read <= 8
          || strncmp (buf, "********", 8) != 0) {
          next_intuit_at(line_beginning,p_input_line);
          return chars_read == (size_t) -1 ? -1 : 0;
      }
      p_hunk_beg = p_input_line + 1;
      while (p_end < p_max) {
          chars_read = get_line ();
          if (chars_read == (size_t) -1)
            return -1;
          if (!chars_read) {
            if (repl_beginning && repl_could_be_missing) {
                repl_missing = true;
                goto hunk_done;
            }
            if (p_max - p_end < 4) {
                strcpy (buf, "  \n");  /* assume blank lines got chopped */
                chars_read = 3;
            } else {
                fatal ("unexpected end of file in patch");
            }
          }
          p_end++;
          if (p_end == hunkmax)
            fatal ("unterminated hunk starting at line %s; giving up at line %s: %s",
                 format_linenum (numbuf0, pch_hunk_beg ()),
                 format_linenum (numbuf1, p_input_line), buf);
          assert(p_end < hunkmax);
          p_Char[p_end] = *buf;
          p_len[p_end] = 0;
          p_line[p_end] = 0;
          switch (*buf) {
          case '*':
            if (strnEQ(buf, "********", 8)) {
                if (repl_beginning && repl_could_be_missing) {
                  repl_missing = true;
                  goto hunk_done;
                }
                else
                  fatal ("unexpected end of hunk at line %s",
                       format_linenum (numbuf0, p_input_line));
            }
            if (p_end != 0) {
                if (repl_beginning && repl_could_be_missing) {
                  repl_missing = true;
                  goto hunk_done;
                }
                fatal ("unexpected `***' at line %s: %s",
                     format_linenum (numbuf0, p_input_line), buf);
            }
            context = 0;
            p_len[p_end] = strlen (buf);
            if (! (p_line[p_end] = savestr (buf))) {
                p_end--;
                return -1;
            }
            for (s = buf;  *s && !ISDIGIT (*s);  s++)
              continue;
            if (strnEQ(s,"0,0",3))
                remove_prefix (s, 2);
            s = scan_linenum (s, &p_first);
            if (*s == ',') {
                while (*s && !ISDIGIT (*s))
                  s++;
                scan_linenum (s, &p_ptrn_lines);
                p_ptrn_lines += 1 - p_first;
            }
            else if (p_first)
                p_ptrn_lines = 1;
            else {
                p_ptrn_lines = 0;
                p_first = 1;
            }
            p_max = p_ptrn_lines + 6;     /* we need this much at least */
            while (p_max >= hunkmax)
                if (! grow_hunkmax ())
                  return -1;
            p_max = hunkmax;
            break;
          case '-':
            if (buf[1] != '-')
              goto change_line;
            if (ptrn_prefix_context == -1)
              ptrn_prefix_context = context;
            ptrn_suffix_context = context;
            if (repl_beginning
                || (p_end
                  != p_ptrn_lines + 1 + (p_Char[p_end - 1] == '\n')))
              {
                if (p_end == 1)
                  {
                  /* `Old' lines were omitted.  Set up to fill
                     them in from `new' context lines.  */
                  ptrn_missing = true;
                  p_end = p_ptrn_lines + 1;
                  ptrn_prefix_context = ptrn_suffix_context = -1;
                  fillsrc = p_end + 1;
                  filldst = 1;
                  fillcnt = p_ptrn_lines;
                  }
                else if (! repl_beginning)
                  fatal ("%s `---' at line %s; check line numbers at line %s",
                       (p_end <= p_ptrn_lines
                        ? "Premature"
                        : "Overdue"),
                       format_linenum (numbuf0, p_input_line),
                       format_linenum (numbuf1, p_hunk_beg));
                else if (! repl_could_be_missing)
                  fatal ("duplicate `---' at line %s; check line numbers at line %s",
                       format_linenum (numbuf0, p_input_line),
                       format_linenum (numbuf1,
                                   p_hunk_beg + repl_beginning));
                else
                  {
                  repl_missing = true;
                  goto hunk_done;
                  }
              }
            repl_beginning = p_end;
            repl_backtrack_position = file_tell (pfp);
            repl_patch_line = p_input_line;
            repl_context = context;
            p_len[p_end] = strlen (buf);
            if (! (p_line[p_end] = savestr (buf)))
              {
                p_end--;
                return -1;
              }
            p_Char[p_end] = '=';
            for (s = buf;  *s && ! ISDIGIT (*s);  s++)
              continue;
            s = scan_linenum (s, &p_newfirst);
            if (*s == ',')
              {
                do
                  {
                  if (!*++s)
                    malformed ();
                  }
                while (! ISDIGIT (*s));
                scan_linenum (s, &p_repl_lines);
                p_repl_lines += 1 - p_newfirst;
              }
            else if (p_newfirst)
              p_repl_lines = 1;
            else
              {
                p_repl_lines = 0;
                p_newfirst = 1;
              }
            p_max = p_repl_lines + p_end;
            while (p_max >= hunkmax)
              if (! grow_hunkmax ())
                return -1;
            if (p_repl_lines != ptrn_copiable
                && (p_prefix_context != 0
                  || context != 0
                  || p_repl_lines != 1))
              repl_could_be_missing = false;
            context = 0;
            break;
          case '+':  case '!':
            repl_could_be_missing = false;
            change_line:
            s = buf + 1;
            chars_read--;
            if (*s == '\n' && canonicalize) {
                strcpy (s, " \n");
                chars_read = 2;
            }
            if (*s == ' ' || *s == '\t') {
                s++;
                chars_read--;
            } else if (repl_beginning && repl_could_be_missing) {
                repl_missing = true;
                goto hunk_done;
            }
            if (! repl_beginning)
              {
                if (ptrn_prefix_context == -1)
                  ptrn_prefix_context = context;
              }
            else
              {
                if (repl_prefix_context == -1)
                  repl_prefix_context = context;
              }
            chars_read -=
              (1 < chars_read
               && p_end == (repl_beginning ? p_max : p_ptrn_lines)
               && incomplete_line ());
            p_len[p_end] = chars_read;
            if (! (p_line[p_end] = savebuf (s, chars_read))) {
                p_end--;
                return -1;
            }
            context = 0;
            break;
          case '\t': case '\n':     /* assume spaces got eaten */
            s = buf;
            if (*buf == '\t') {
                s++;
                chars_read--;
            }
            if (repl_beginning && repl_could_be_missing &&
                (!ptrn_spaces_eaten || difftype == NEW_CONTEXT_DIFF) ) {
                repl_missing = true;
                goto hunk_done;
            }
            chars_read -=
              (1 < chars_read
               && p_end == (repl_beginning ? p_max : p_ptrn_lines)
               && incomplete_line ());
            p_len[p_end] = chars_read;
            if (! (p_line[p_end] = savebuf (buf, chars_read))) {
                p_end--;
                return -1;
            }
            if (p_end != p_ptrn_lines + 1) {
                ptrn_spaces_eaten |= (repl_beginning != 0);
                some_context = true;
                context++;
                if (repl_beginning)
                  repl_copiable++;
                else
                  ptrn_copiable++;
                p_Char[p_end] = ' ';
            }
            break;
          case ' ':
            s = buf + 1;
            chars_read--;
            if (*s == '\n' && canonicalize) {
                strcpy (s, "\n");
                chars_read = 2;
            }
            if (*s == ' ' || *s == '\t') {
                s++;
                chars_read--;
            } else if (repl_beginning && repl_could_be_missing) {
                repl_missing = true;
                goto hunk_done;
            }
            some_context = true;
            context++;
            if (repl_beginning)
                repl_copiable++;
            else
                ptrn_copiable++;
            chars_read -=
              (1 < chars_read
               && p_end == (repl_beginning ? p_max : p_ptrn_lines)
               && incomplete_line ());
            p_len[p_end] = chars_read;
            if (! (p_line[p_end] = savebuf (buf + 2, chars_read))) {
                p_end--;
                return -1;
            }
            break;
          default:
            if (repl_beginning && repl_could_be_missing) {
                repl_missing = true;
                goto hunk_done;
            }
            malformed ();
          }
      }

    hunk_done:
      if (p_end >=0 && !repl_beginning)
        fatal ("no `---' found in patch at line %s",
             format_linenum (numbuf0, pch_hunk_beg ()));

      if (repl_missing) {

          /* reset state back to just after --- */
          p_input_line = repl_patch_line;
          context = repl_context;
          for (p_end--; p_end > repl_beginning; p_end--)
            free(p_line[p_end]);
          Fseek (pfp, repl_backtrack_position, SEEK_SET);

          /* redundant 'new' context lines were omitted - set */
          /* up to fill them in from the old file context */
          fillsrc = 1;
          filldst = repl_beginning+1;
          fillcnt = p_repl_lines;
          p_end = p_max;
      }
      else if (! ptrn_missing && ptrn_copiable != repl_copiable)
        fatal ("context mangled in hunk at line %s",
             format_linenum (numbuf0, p_hunk_beg));
      else if (!some_context && fillcnt == 1) {
          /* the first hunk was a null hunk with no context */
          /* and we were expecting one line -- fix it up. */
          while (filldst < p_end) {
            p_line[filldst] = p_line[filldst+1];
            p_Char[filldst] = p_Char[filldst+1];
            p_len[filldst] = p_len[filldst+1];
            filldst++;
          }
#if 0
          repl_beginning--;         /* this doesn't need to be fixed */
#endif
          p_end--;
          p_first++;                /* do append rather than insert */
          fillcnt = 0;
          p_ptrn_lines = 0;
      }

      p_prefix_context = ((repl_prefix_context == -1
                       || (ptrn_prefix_context != -1
                         && ptrn_prefix_context < repl_prefix_context))
                      ? ptrn_prefix_context : repl_prefix_context);
      p_suffix_context = ((ptrn_suffix_context != -1
                       && ptrn_suffix_context < context)
                      ? ptrn_suffix_context : context);
      assert (p_prefix_context != -1 && p_suffix_context != -1);

      if (difftype == CONTEXT_DIFF
          && (fillcnt
            || (p_first > 1
                && p_prefix_context + p_suffix_context < ptrn_copiable))) {
          if (verbosity == VERBOSE)
            say ("%s\n%s\n%s\n",
"(Fascinating -- this is really a new-style context diff but without",
"the telltale extra asterisks on the *** line that usually indicate",
"the new style...)");
          diff_type = difftype = NEW_CONTEXT_DIFF;
      }

      /* if there were omitted context lines, fill them in now */
      if (fillcnt) {
          p_bfake = filldst;        /* remember where not to free() */
          p_efake = filldst + fillcnt - 1;
          while (fillcnt-- > 0) {
            while (fillsrc <= p_end && fillsrc != repl_beginning
                   && p_Char[fillsrc] != ' ')
                fillsrc++;
            if (p_end < fillsrc || fillsrc == repl_beginning)
              {
                fatal ("replacement text or line numbers mangled in hunk at line %s",
                     format_linenum (numbuf0, p_hunk_beg));
              }
            p_line[filldst] = p_line[fillsrc];
            p_Char[filldst] = p_Char[fillsrc];
            p_len[filldst] = p_len[fillsrc];
            fillsrc++; filldst++;
          }
          while (fillsrc <= p_end && fillsrc != repl_beginning)
            {
            if (p_Char[fillsrc] == ' ')
              fatal ("replacement text or line numbers mangled in hunk at line %s",
                   format_linenum (numbuf0, p_hunk_beg));
            fillsrc++;
            }
          if (debug & 64)
            printf ("fillsrc %s, filldst %s, rb %s, e+1 %s\n",
                  format_linenum (numbuf0, fillsrc),
                  format_linenum (numbuf1, filldst),
                  format_linenum (numbuf2, repl_beginning),
                  format_linenum (numbuf3, p_end + 1));
          assert(fillsrc==p_end+1 || fillsrc==repl_beginning);
          assert(filldst==p_end+1 || filldst==repl_beginning);
      }
    }
    else if (difftype == UNI_DIFF) {
      file_offset line_beginning = file_tell (pfp);
                              /* file pos of the current line */
      register LINENUM fillsrc;     /* index of old lines */
      register LINENUM filldst;     /* index of new lines */
      char ch = '\0';

      chars_read = get_line ();
      if (chars_read == (size_t) -1
          || chars_read <= 4
          || strncmp (buf, "@@ -", 4) != 0) {
          next_intuit_at(line_beginning,p_input_line);
          return chars_read == (size_t) -1 ? -1 : 0;
      }
      s = scan_linenum (buf + 4, &p_first);
      if (*s == ',')
          s = scan_linenum (s + 1, &p_ptrn_lines);
      else
          p_ptrn_lines = 1;
      if (*s == ' ') s++;
      if (*s != '+')
          malformed ();
      s = scan_linenum (s + 1, &p_newfirst);
      if (*s == ',')
          s = scan_linenum (s + 1, &p_repl_lines);
      else
          p_repl_lines = 1;
      if (*s == ' ') s++;
      if (*s != '@')
          malformed ();
      if (!p_ptrn_lines)
          p_first++;                /* do append rather than insert */
      if (!p_repl_lines)
          p_newfirst++;
      p_max = p_ptrn_lines + p_repl_lines + 1;
      while (p_max >= hunkmax)
          if (! grow_hunkmax ())
            return -1;
      fillsrc = 1;
      filldst = fillsrc + p_ptrn_lines;
      p_end = filldst + p_repl_lines;
      sprintf (buf, "*** %s,%s ****\n",
             format_linenum (numbuf0, p_first),
             format_linenum (numbuf1, p_first + p_ptrn_lines - 1));
      p_len[0] = strlen (buf);
      if (! (p_line[0] = savestr (buf))) {
          p_end = -1;
          return -1;
      }
      p_Char[0] = '*';
      sprintf (buf, "--- %s,%s ----\n",
             format_linenum (numbuf0, p_newfirst),
             format_linenum (numbuf1, p_newfirst + p_repl_lines - 1));
      p_len[filldst] = strlen (buf);
      if (! (p_line[filldst] = savestr (buf))) {
          p_end = 0;
          return -1;
      }
      p_Char[filldst++] = '=';
      p_prefix_context = -1;
      p_hunk_beg = p_input_line + 1;
      while (fillsrc <= p_ptrn_lines || filldst <= p_end) {
          chars_read = get_line ();
          if (!chars_read) {
            if (p_max - filldst < 3) {
                strcpy (buf, " \n");  /* assume blank lines got chopped */
                chars_read = 2;
            } else {
                fatal ("unexpected end of file in patch");
            }
          }
          if (chars_read == (size_t) -1)
            s = 0;
          else if (*buf == '\t' || *buf == '\n') {
            ch = ' ';         /* assume the space got eaten */
            s = savebuf (buf, chars_read);
          }
          else {
            ch = *buf;
            s = savebuf (buf+1, --chars_read);
          }
          if (!s) {
            while (--filldst > p_ptrn_lines)
                free(p_line[filldst]);
            p_end = fillsrc-1;
            return -1;
          }
          switch (ch) {
          case '-':
            if (fillsrc > p_ptrn_lines) {
                free(s);
                p_end = filldst-1;
                malformed ();
            }
            chars_read -= fillsrc == p_ptrn_lines && incomplete_line ();
            p_Char[fillsrc] = ch;
            p_line[fillsrc] = s;
            p_len[fillsrc++] = chars_read;
            break;
          case '=':
            ch = ' ';
            /* FALL THROUGH */
          case ' ':
            if (fillsrc > p_ptrn_lines) {
                free(s);
                while (--filldst > p_ptrn_lines)
                  free(p_line[filldst]);
                p_end = fillsrc-1;
                malformed ();
            }
            context++;
            chars_read -= fillsrc == p_ptrn_lines && incomplete_line ();
            p_Char[fillsrc] = ch;
            p_line[fillsrc] = s;
            p_len[fillsrc++] = chars_read;
            s = savebuf (s, chars_read);
            if (!s) {
                while (--filldst > p_ptrn_lines)
                  free(p_line[filldst]);
                p_end = fillsrc-1;
                return -1;
            }
            /* FALL THROUGH */
          case '+':
            if (filldst > p_end) {
                free(s);
                while (--filldst > p_ptrn_lines)
                  free(p_line[filldst]);
                p_end = fillsrc-1;
                malformed ();
            }
            chars_read -= filldst == p_end && incomplete_line ();
            p_Char[filldst] = ch;
            p_line[filldst] = s;
            p_len[filldst++] = chars_read;
            break;
          default:
            p_end = filldst;
            malformed ();
          }
          if (ch != ' ') {
            if (p_prefix_context == -1)
                p_prefix_context = context;
            context = 0;
          }
      }/* while */
      if (p_prefix_context == -1)
        malformed ();
      p_suffix_context = context;
    }
    else {                    /* normal diff--fake it up */
      char hunk_type;
      register int i;
      LINENUM min, max;
      file_offset line_beginning = file_tell (pfp);

      p_prefix_context = p_suffix_context = 0;
      chars_read = get_line ();
      if (chars_read == (size_t) -1 || !chars_read || !ISDIGIT (*buf)) {
          next_intuit_at(line_beginning,p_input_line);
          return chars_read == (size_t) -1 ? -1 : 0;
      }
      s = scan_linenum (buf, &p_first);
      if (*s == ',') {
          s = scan_linenum (s + 1, &p_ptrn_lines);
          p_ptrn_lines += 1 - p_first;
      }
      else
          p_ptrn_lines = (*s != 'a');
      hunk_type = *s;
      if (hunk_type == 'a')
          p_first++;                /* do append rather than insert */
      s = scan_linenum (s + 1, &min);
      if (*s == ',')
          scan_linenum (s + 1, &max);
      else
          max = min;
      if (hunk_type == 'd')
          min++;
      p_end = p_ptrn_lines + 1 + max - min + 1;
      while (p_end >= hunkmax)
        if (! grow_hunkmax ())
          {
            p_end = -1;
            return -1;
          }
      p_newfirst = min;
      p_repl_lines = max - min + 1;
      sprintf (buf, "*** %s,%s\n",
             format_linenum (numbuf0, p_first),
             format_linenum (numbuf1, p_first + p_ptrn_lines - 1));
      p_len[0] = strlen (buf);
      if (! (p_line[0] = savestr (buf))) {
          p_end = -1;
          return -1;
      }
      p_Char[0] = '*';
      for (i=1; i<=p_ptrn_lines; i++) {
          chars_read = get_line ();
          if (chars_read == (size_t) -1)
            {
            p_end = i - 1;
            return -1;
            }
          if (!chars_read)
            fatal ("unexpected end of file in patch at line %s",
                 format_linenum (numbuf0, p_input_line));
          if (buf[0] != '<' || (buf[1] != ' ' && buf[1] != '\t'))
            fatal ("`<' expected at line %s of patch",
                 format_linenum (numbuf0, p_input_line));
          chars_read -= 2 + (i == p_ptrn_lines && incomplete_line ());
          p_len[i] = chars_read;
          if (! (p_line[i] = savebuf (buf + 2, chars_read))) {
            p_end = i-1;
            return -1;
          }
          p_Char[i] = '-';
      }
      if (hunk_type == 'c') {
          chars_read = get_line ();
          if (chars_read == (size_t) -1)
            {
            p_end = i - 1;
            return -1;
            }
          if (! chars_read)
            fatal ("unexpected end of file in patch at line %s",
                 format_linenum (numbuf0, p_input_line));
          if (*buf != '-')
            fatal ("`---' expected at line %s of patch",
                 format_linenum (numbuf0, p_input_line));
      }
      sprintf (buf, "--- %s,%s\n",
             format_linenum (numbuf0, min),
             format_linenum (numbuf1, max));
      p_len[i] = strlen (buf);
      if (! (p_line[i] = savestr (buf))) {
          p_end = i-1;
          return -1;
      }
      p_Char[i] = '=';
      for (i++; i<=p_end; i++) {
          chars_read = get_line ();
          if (chars_read == (size_t) -1)
            {
            p_end = i - 1;
            return -1;
            }
          if (!chars_read)
            fatal ("unexpected end of file in patch at line %s",
                 format_linenum (numbuf0, p_input_line));
          if (buf[0] != '>' || (buf[1] != ' ' && buf[1] != '\t'))
            fatal ("`>' expected at line %s of patch",
                 format_linenum (numbuf0, p_input_line));
          chars_read -= 2 + (i == p_end && incomplete_line ());
          p_len[i] = chars_read;
          if (! (p_line[i] = savebuf (buf + 2, chars_read))) {
            p_end = i-1;
            return -1;
          }
          p_Char[i] = '+';
      }
    }
    if (rev)                        /* backwards patch? */
      if (!pch_swap())
          say ("Not enough memory to swap next hunk!\n");
    if (debug & 2) {
      LINENUM i;
      char special;

      for (i=0; i <= p_end; i++) {
          if (i == p_ptrn_lines)
            special = '^';
          else
            special = ' ';
          fprintf (stderr, "%s %c %c ", format_linenum (numbuf0, i),
                 p_Char[i], special);
          pch_write_line (i, stderr);
          fflush (stderr);
      }
    }
    if (p_end+1 < hunkmax)    /* paranoia reigns supreme... */
      p_Char[p_end+1] = '^';  /* add a stopper for apply_hunk */
    return 1;
}

static size_t
get_line (void)
{
   return pget_line (p_indent, p_rfc934_nesting, p_strip_trailing_cr,
                 p_pass_comments_through);
}

/* Input a line from the patch file, worrying about indentation.
   Strip up to INDENT characters' worth of leading indentation.
   Then remove up to RFC934_NESTING instances of leading "- ".
   If STRIP_TRAILING_CR is true, remove any trailing carriage-return.
   Unless PASS_COMMENTS_THROUGH is true, ignore any resulting lines
   that begin with '#'; they're comments.
   Ignore any partial lines at end of input, but warn about them.
   Succeed if a line was read; it is terminated by "\n\0" for convenience.
   Return the number of characters read, including '\n' but not '\0'.
   Return -1 if we ran out of memory.  */

static size_t
pget_line (int indent, int rfc934_nesting, bool strip_trailing_cr,
         bool pass_comments_through)
{
  register FILE *fp = pfp;
  register int c;
  register int i;
  register char *b;
  register size_t s;

  do
    {
      i = 0;
      for (;;)
      {
        c = getc (fp);
        if (c == EOF)
          {
            if (ferror (fp))
            read_fatal ();
            return 0;
          }
        if (indent <= i)
          break;
        if (c == ' ' || c == 'X')
          i++;
        else if (c == '\t')
          i = (i + 8) & ~7;
        else
          break;
      }

      i = 0;
      b = buf;

      while (c == '-' && 0 <= --rfc934_nesting)
      {
        c = getc (fp);
        if (c == EOF)
          goto patch_ends_in_middle_of_line;
        if (c != ' ')
          {
            i = 1;
            b[0] = '-';
            break;
          }
        c = getc (fp);
        if (c == EOF)
          goto patch_ends_in_middle_of_line;
      }

      s = bufsize;

      for (;;)
      {
        if (i == s - 1)
          {
            s *= 2;
            b = realloc (b, s);
            if (!b)
            {
              if (!using_plan_a)
                memory_fatal ();
              return (size_t) -1;
            }
            buf = b;
            bufsize = s;
          }
        b[i++] = c;
        if (c == '\n')
          break;
        c = getc (fp);
        if (c == EOF)
          goto patch_ends_in_middle_of_line;
      }

      p_input_line++;
    }
  while (*b == '#' && !pass_comments_through);

  if (strip_trailing_cr && 2 <= i && b[i - 2] == '\r')
    b[i-- - 2] = '\n';
  b[i] = '\0';
  return i;

 patch_ends_in_middle_of_line:
  if (ferror (fp))
    read_fatal ();
  say ("patch unexpectedly ends in middle of line\n");
  return 0;
}

static bool
incomplete_line (void)
{
  register FILE *fp = pfp;
  register int c;
  register file_offset line_beginning = file_tell (fp);

  if (getc (fp) == '\\')
    {
      while ((c = getc (fp)) != '\n'  &&  c != EOF)
      continue;
      return true;
    }
  else
    {
      /* We don't trust ungetc.  */
      Fseek (pfp, line_beginning, SEEK_SET);
      return false;
    }
}

/* Reverse the old and new portions of the current hunk. */

bool
pch_swap (void)
{
    char **tp_line;           /* the text of the hunk */
    size_t *tp_len;           /* length of each line */
    char *tp_char;            /* +, -, and ! */
    register LINENUM i;
    register LINENUM n;
    bool blankline = false;
    register char *s;

    i = p_first;
    p_first = p_newfirst;
    p_newfirst = i;

    /* make a scratch copy */

    tp_line = p_line;
    tp_len = p_len;
    tp_char = p_Char;
    p_line = 0;   /* force set_hunkmax to allocate again */
    p_len = 0;
    p_Char = 0;
    set_hunkmax();
    if (!p_line || !p_len || !p_Char) {
      if (p_line)
        free (p_line);
      p_line = tp_line;
      if (p_len)
        free (p_len);
      p_len = tp_len;
      if (p_Char)
        free (p_Char);
      p_Char = tp_char;
      return false;           /* not enough memory to swap hunk! */
    }

    /* now turn the new into the old */

    i = p_ptrn_lines + 1;
    if (tp_char[i] == '\n') {       /* account for possible blank line */
      blankline = true;
      i++;
    }
    if (p_efake >= 0) {             /* fix non-freeable ptr range */
      if (p_efake <= i)
          n = p_end - i + 1;
      else
          n = -i;
      p_efake += n;
      p_bfake += n;
    }
    for (n=0; i <= p_end; i++,n++) {
      p_line[n] = tp_line[i];
      p_Char[n] = tp_char[i];
      if (p_Char[n] == '+')
          p_Char[n] = '-';
      p_len[n] = tp_len[i];
    }
    if (blankline) {
      i = p_ptrn_lines + 1;
      p_line[n] = tp_line[i];
      p_Char[n] = tp_char[i];
      p_len[n] = tp_len[i];
      n++;
    }
    assert(p_Char[0] == '=');
    p_Char[0] = '*';
    for (s=p_line[0]; *s; s++)
      if (*s == '-')
          *s = '*';

    /* now turn the old into the new */

    assert(tp_char[0] == '*');
    tp_char[0] = '=';
    for (s=tp_line[0]; *s; s++)
      if (*s == '*')
          *s = '-';
    for (i=0; n <= p_end; i++,n++) {
      p_line[n] = tp_line[i];
      p_Char[n] = tp_char[i];
      if (p_Char[n] == '-')
          p_Char[n] = '+';
      p_len[n] = tp_len[i];
    }
    assert(i == p_ptrn_lines + 1);
    i = p_ptrn_lines;
    p_ptrn_lines = p_repl_lines;
    p_repl_lines = i;
    if (tp_line)
      free (tp_line);
    if (tp_len)
      free (tp_len);
    if (tp_char)
      free (tp_char);
    return true;
}

/* Return whether file WHICH (false = old, true = new) appears to nonexistent.
   Return 1 for empty, 2 for nonexistent.  */

int
pch_says_nonexistent (bool which)
{
  return p_says_nonexistent[which];
}

/* Return timestamp of patch header for file WHICH (false = old, true = new),
   or -1 if there was no timestamp or an error in the timestamp.  */

time_t
pch_timestamp (bool which)
{
  return p_timestamp[which];
}

/* Return the specified line position in the old file of the old context. */

LINENUM
pch_first (void)
{
    return p_first;
}

/* Return the number of lines of old context. */

LINENUM
pch_ptrn_lines (void)
{
    return p_ptrn_lines;
}

/* Return the probable line position in the new file of the first line. */

LINENUM
pch_newfirst (void)
{
    return p_newfirst;
}

/* Return the number of lines in the replacement text including context. */

LINENUM
pch_repl_lines (void)
{
    return p_repl_lines;
}

/* Return the number of lines in the whole hunk. */

LINENUM
pch_end (void)
{
    return p_end;
}

/* Return the number of context lines before the first changed line. */

LINENUM
pch_prefix_context (void)
{
    return p_prefix_context;
}

/* Return the number of context lines after the last changed line. */

LINENUM
pch_suffix_context (void)
{
    return p_suffix_context;
}

/* Return the length of a particular patch line. */

size_t
pch_line_len (LINENUM line)
{
    return p_len[line];
}

/* Return the control character (+, -, *, !, etc) for a patch line. */

char
pch_char (LINENUM line)
{
    return p_Char[line];
}

/* Return a pointer to a particular patch line. */

char *
pfetch (LINENUM line)
{
    return p_line[line];
}

/* Output a patch line.  */

bool
pch_write_line (LINENUM line, FILE *file)
{
  bool after_newline = p_line[line][p_len[line] - 1] == '\n';
  if (! fwrite (p_line[line], sizeof (*p_line[line]), p_len[line], file))
    write_fatal ();
  return after_newline;
}

/* Return where in the patch file this hunk began, for error messages. */

LINENUM
pch_hunk_beg (void)
{
    return p_hunk_beg;
}

/* Is the newline-terminated line a valid `ed' command for patch
   input?  If so, return the command character; if not, return 0.
   This accepts accepts just a subset of the valid commands, but it's
   good enough in practice.  */

static char
get_ed_command_letter (char const *line)
{
  char const *p = line;
  char letter;
  bool pair = false;
  if (! ISDIGIT (*p))
    return 0;
  while (ISDIGIT (*++p))
    continue;
  if (*p == ',')
    {
      if (! ISDIGIT (*++p))
      return 0;
      while (ISDIGIT (*++p))
      continue;
      pair = true;
    }
  letter = *p++;

  switch (letter)
    {
    case 'a':
    case 'i':
      if (pair)
      return 0;
      break;

    case 'c':
    case 'd':
      break;

    case 's':
      if (strncmp (p, "/.//", 4) != 0)
      return 0;
      p += 4;
      break;

    default:
      return 0;
    }

  while (*p == ' ' || *p == '\t')
    p++;
  if (*p == '\n')
    return letter;
  return 0;
}

/* Apply an ed script by feeding ed itself. */

void
do_ed_script (FILE *ofp)
{
    static char const ed_program[] = ed_PROGRAM;

    register file_offset beginning_of_this_line;
    register FILE *pipefp = 0;
    register size_t chars_read;

    if (! dry_run && ! skip_rest_of_patch) {
      int exclusive = TMPOUTNAME_needs_removal ? 0 : O_EXCL;
      assert (! inerrno);
      TMPOUTNAME_needs_removal = 1;
      copy_file (inname, TMPOUTNAME, exclusive, instat.st_mode);
      sprintf (buf, "%s %s%s", ed_program, verbosity == VERBOSE ? "" : "- ",
             TMPOUTNAME);
      fflush (stdout);
      pipefp = popen(buf, binary_transput ? "wb" : "w");
      if (!pipefp)
        pfatal ("Can't open pipe to %s", quotearg (buf));
    }
    for (;;) {
      char ed_command_letter;
      beginning_of_this_line = file_tell (pfp);
      chars_read = get_line ();
      if (! chars_read) {
          next_intuit_at(beginning_of_this_line,p_input_line);
          break;
      }
      ed_command_letter = get_ed_command_letter (buf);
      if (ed_command_letter) {
          if (pipefp)
            if (! fwrite (buf, sizeof *buf, chars_read, pipefp))
                write_fatal ();
          if (ed_command_letter != 'd' && ed_command_letter != 's') {
              p_pass_comments_through = true;
            while ((chars_read = get_line ()) != 0) {
                if (pipefp)
                  if (! fwrite (buf, sizeof *buf, chars_read, pipefp))
                      write_fatal ();
                if (chars_read == 2  &&  strEQ (buf, ".\n"))
                  break;
            }
            p_pass_comments_through = false;
          }
      }
      else {
          next_intuit_at(beginning_of_this_line,p_input_line);
          break;
      }
    }
    if (!pipefp)
      return;
    if (fwrite ("w\nq\n", sizeof (char), (size_t) 4, pipefp) == 0
      || fflush (pipefp) != 0)
      write_fatal ();
    if (pclose (pipefp) != 0)
      fatal ("%s FAILED", ed_program);

    if (ofp)
      {
      FILE *ifp = fopen (TMPOUTNAME, binary_transput ? "rb" : "r");
      int c;
      if (!ifp)
        pfatal ("can't open `%s'", TMPOUTNAME);
      while ((c = getc (ifp)) != EOF)
        if (putc (c, ofp) == EOF)
          write_fatal ();
      if (ferror (ifp) || fclose (ifp) != 0)
        read_fatal ();
      }
}

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