/* Read, sort and compare two directories.  Used for GNU DIFF.

   Copyright (C) 1988-1989, 1992-1995, 1998, 2001-2002, 2004, 2006-2007,

   2009-2013, 2015-2017 Free Software Foundation, Inc.

   This file is part of GNU DIFF.

   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 3 of the License, 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.  If not, see <http://www.gnu.org/licenses/>.  */

#include "diff.h"

#include <error.h>

#include <exclude.h>

#include <filenamecat.h>

#include <setjmp.h>

#include <xalloc.h>

/* Read the directory named by DIR and store into DIRDATA a sorted vector

   of filenames for its contents.  DIR->desc == -1 means this directory is

   known to be nonexistent, so set DIRDATA to an empty vector.

   Return -1 (setting errno) if error, 0 otherwise.  */

struct dirdata

{

  size_t nnames;	/* Number of names.  */

  char const **names;	/* Sorted names of files in dir, followed by 0.  */

  char *data;	/* Allocated storage for file names.  */

};

/* Whether file names in directories should be compared with

   locale-specific sorting.  */

static bool locale_specific_sorting;

/* Where to go if locale-specific sorting fails.  */

static jmp_buf failed_locale_specific_sorting;

static bool dir_loop (struct comparison const *, int);

/* Read a directory and get its vector of names.  */

static bool

dir_read (struct file_data const *dir, struct dirdata *dirdata)

{

  register struct dirent *next;

  register size_t i;

  /* Address of block containing the files that are described.  */

  char const **names;

  /* Number of files in directory.  */

  size_t nnames;

  /* Allocated and used storage for file name data.  */

  char *data;

  size_t data_alloc, data_used;

  dirdata->names = 0;

  dirdata->data = 0;

  nnames = 0;

  data = 0;

  if (dir->desc != -1)

    {

      /* Open the directory and check for errors.  */

      register DIR *reading = opendir (dir->name);

      if (!reading)

	return false;

      /* Initialize the table of filenames.  */

      data_alloc = 512;

      data_used = 0;

      dirdata->data = data = xmalloc (data_alloc);

      /* Read the directory entries, and insert the subfiles

	 into the 'data' table.  */

      while ((errno = 0, (next = readdir (reading)) != 0))

	{

	  char *d_name = next->d_name;

	  size_t d_size = _D_EXACT_NAMLEN (next) + 1;

	  /* Ignore "." and "..".  */

	  if (d_name[0] == '.'

	      && (d_name[1] == 0 || (d_name[1] == '.' && d_name[2] == 0)))

	    continue;

	  if (excluded_file_name (excluded, d_name))

	    continue;

	  while (data_alloc < data_used + d_size)

	    {

	      if (PTRDIFF_MAX / 2 <= data_alloc)

		xalloc_die ();

	      dirdata->data = data = xrealloc (data, data_alloc *= 2);

	    }

	  memcpy (data + data_used, d_name, d_size);

	  data_used += d_size;

	  nnames++;

	}

      if (errno)

	{

	  int e = errno;

	  closedir (reading);

	  errno = e;

	  return false;

	}

#if CLOSEDIR_VOID

      closedir (reading);

#else

      if (closedir (reading) != 0)

	return false;

#endif

    }

  /* Create the 'names' table from the 'data' table.  */

  if (PTRDIFF_MAX / sizeof *names - 1 <= nnames)

    xalloc_die ();

  dirdata->names = names = xmalloc ((nnames + 1) * sizeof *names);

  dirdata->nnames = nnames;

  for (i = 0;  i < nnames;  i++)

    {

      names[i] = data;

      data += strlen (data) + 1;

    }

  names[nnames] = 0;

  return true;

}

/* Compare strings in a locale-specific way, returning a value

   compatible with strcmp.  */

static int

compare_collated (char const *name1, char const *name2)

{

  int r;

  errno = 0;

  if (ignore_file_name_case)

    r = strcasecoll (name1, name2);

  else

    r = strcoll (name1, name2);

  if (errno)

    {

      error (0, errno, _("cannot compare file names '%s' and '%s'"),

	     name1, name2);

      longjmp (failed_locale_specific_sorting, 1);

    }

  return r;

}

/* Compare file names, returning a value compatible with strcmp.  */

static int

compare_names (char const *name1, char const *name2)

{

  if (locale_specific_sorting)

    {

      int diff = compare_collated (name1, name2);

      if (diff || ignore_file_name_case)

	return diff;

    }

  return file_name_cmp (name1, name2);

}

/* Compare names FILE1 and FILE2 when sorting a directory.

   Prefer filtered comparison, breaking ties with file_name_cmp.  */

static int

compare_names_for_qsort (void const *file1, void const *file2)

{

  char const *const *f1 = file1;

  char const *const *f2 = file2;

  char const *name1 = *f1;

  char const *name2 = *f2;

  if (locale_specific_sorting)

    {

      int diff = compare_collated (name1, name2);

      if (diff)

	return diff;

    }

  return file_name_cmp (name1, name2);

}

/* Compare the contents of two directories named in CMP.

   This is a top-level routine; it does everything necessary for diff

   on two directories.

   CMP->file[0].desc == -1 says directory CMP->file[0] doesn't exist,

   but pretend it is empty.  Likewise for CMP->file[1].

   HANDLE_FILE is a caller-provided subroutine called to handle each file.

   It gets three operands: CMP, name of file in dir 0, name of file in dir 1.

   These names are relative to the original working directory.

   For a file that appears in only one of the dirs, one of the name-args

   to HANDLE_FILE is zero.

   Returns the maximum of all the values returned by HANDLE_FILE,

   or EXIT_TROUBLE if trouble is encountered in opening files.  */

int

diff_dirs (struct comparison const *cmp,

	   int (*handle_file) (struct comparison const *,

			       char const *, char const *))

{

  struct dirdata dirdata[2];

  int volatile val = EXIT_SUCCESS;

  int i;

  if ((cmp->file[0].desc == -1 || dir_loop (cmp, 0))

      && (cmp->file[1].desc == -1 || dir_loop (cmp, 1)))

    {

      error (0, 0, _("%s: recursive directory loop"),

	     cmp->file[cmp->file[0].desc == -1].name);

      return EXIT_TROUBLE;

    }

  /* Get contents of both dirs.  */

  for (i = 0; i < 2; i++)

    if (! dir_read (&cmp->file[i], &dirdata[i]))

      {

	perror_with_name (cmp->file[i].name);

	val = EXIT_TROUBLE;

      }

  if (val == EXIT_SUCCESS)

    {

      char const **volatile names[2];

      names[0] = dirdata[0].names;

      names[1] = dirdata[1].names;

      /* Use locale-specific sorting if possible, else native byte order.  */

      locale_specific_sorting = true;

      if (setjmp (failed_locale_specific_sorting))

	locale_specific_sorting = false;

      /* Sort the directories.  */

      for (i = 0; i < 2; i++)

	qsort (names[i], dirdata[i].nnames, sizeof *dirdata[i].names,

	       compare_names_for_qsort);

      /* If '-S name' was given, and this is the topmost level of comparison,

	 ignore all file names less than the specified starting name.  */

      if (starting_file && ! cmp->parent)

	{

	  while (*names[0] && compare_names (*names[0], starting_file) < 0)

	    names[0]++;

	  while (*names[1] && compare_names (*names[1], starting_file) < 0)

	    names[1]++;

	}

      /* Loop while files remain in one or both dirs.  */

      while (*names[0] || *names[1])

	{

	  /* Compare next name in dir 0 with next name in dir 1.

	     At the end of a dir,

	     pretend the "next name" in that dir is very large.  */

	  int nameorder = (!*names[0] ? 1 : !*names[1] ? -1

			   : compare_names (*names[0], *names[1]));

	  /* Prefer a file_name_cmp match if available.  This algorithm is

	     O(N**2), where N is the number of names in a directory

	     that compare_names says are all equal, but in practice N

	     is so small it's not worth tuning.  */

	  if (nameorder == 0 && ignore_file_name_case)

	    {

	      int raw_order = file_name_cmp (*names[0], *names[1]);

	      if (raw_order != 0)

		{

		  int greater_side = raw_order < 0;

		  int lesser_side = 1 - greater_side;

		  char const **lesser = names[lesser_side];

		  char const *greater_name = *names[greater_side];

		  char const **p;

		  for (p = lesser + 1;

		       *p && compare_names (*p, greater_name) == 0;

		       p++)

		    {

		      int c = file_name_cmp (*p, greater_name);

		      if (0 <= c)

			{

			  if (c == 0)

			    {

			      memmove (lesser + 1, lesser,

				       (char *) p - (char *) lesser);

			      *lesser = greater_name;

			    }

			  break;

			}

		    }

		}

	    }

	  int v1 = (*handle_file) (cmp,

				   0 < nameorder ? 0 : *names[0]++,

				   nameorder < 0 ? 0 : *names[1]++);

	  if (val < v1)

	    val = v1;

	}

    }

  for (i = 0; i < 2; i++)

    {

      free (dirdata[i].names);

      free (dirdata[i].data);

    }

  return val;

}

/* Return nonzero if CMP is looping recursively in argument I.  */

static bool _GL_ATTRIBUTE_PURE

dir_loop (struct comparison const *cmp, int i)

{

  struct comparison const *p = cmp;

  while ((p = p->parent))

    if (0 < same_file (&p->file[i].stat, &cmp->file[i].stat))

      return true;

  return false;

}

/* Find a matching filename in a directory.  */

char *

find_dir_file_pathname (char const *dir, char const *file)

{

  /* The 'IF_LINT (volatile)' works around what appears to be a bug in

     gcc 4.8.0 20120825; see

     <http://lists.gnu.org/archive/html/bug-diffutils/2012-08/msg00007.html>.

     */

  char const * IF_LINT (volatile) match = file;

  char *val;

  struct dirdata dirdata;

  dirdata.names = NULL;

  dirdata.data = NULL;

  if (ignore_file_name_case)

    {

      struct file_data filedata;

      filedata.name = dir;

      filedata.desc = 0;

      if (dir_read (&filedata, &dirdata))

	{

	  locale_specific_sorting = true;

	  if (setjmp (failed_locale_specific_sorting))

	    match = file; /* longjmp may mess up MATCH.  */

	  else

	    {

	      for (char const **p = dirdata.names; *p; p++)

		if (compare_names (*p, file) == 0)

		  {

		    if (file_name_cmp (*p, file) == 0)

		      {

			match = *p;

			break;

		      }

		    if (match == file)

		      match = *p;

		  }

	    }

	}

    }

  val = file_name_concat (dir, match, NULL);

  free (dirdata.names);

  free (dirdata.data);

  return val;

}