/* GLIB - Library of useful routines for C programming
 *
 * gconvert.c: Convert between character sets using iconv
 * Copyright Red Hat Inc., 2000
 * Authors: Havoc Pennington <hp@redhat.com>, Owen Taylor <otaylor@redhat.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"
#include "glibconfig.h"

#ifndef G_OS_WIN32
#include <iconv.h>
#endif
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>

#ifdef G_OS_WIN32
#include "win_iconv.c"
#endif

#ifdef G_PLATFORM_WIN32
#define STRICT
#include <windows.h>
#undef STRICT
#endif

#include "gconvert.h"

#include "gcharsetprivate.h"
#include "gslist.h"
#include "gstrfuncs.h"
#include "gtestutils.h"
#include "gthread.h"
#include "gunicode.h"
#include "gfileutils.h"

#include "glibintl.h"

#if defined(USE_LIBICONV_GNU) && !defined (_LIBICONV_H)
#error GNU libiconv in use but included iconv.h not from libiconv
#endif
#if !defined(USE_LIBICONV_GNU) && defined (_LIBICONV_H) \
     && !defined (__APPLE_CC__) && !defined (__LP_64__)
#error GNU libiconv not in use but included iconv.h is from libiconv
#endif


/**
 * SECTION:conversions
 * @title: Character Set Conversion
 * @short_description: convert strings between different character sets
 *
 * The g_convert() family of function wraps the functionality of iconv().
 * In addition to pure character set conversions, GLib has functions to
 * deal with the extra complications of encodings for file names.
 *
 * ## File Name Encodings
 *
 * Historically, UNIX has not had a defined encoding for file names:
 * a file name is valid as long as it does not have path separators
 * in it ("/"). However, displaying file names may require conversion:
 * from the character set in which they were created, to the character
 * set in which the application operates. Consider the Spanish file name
 * "Presentacion.sxi". If the application which created it uses
 * ISO-8859-1 for its encoding,
 * |[
 * Character:  P  r  e  s  e  n  t  a  c  i  o  n  .  s  x  i
 * Hex code:   50 72 65 73 65 6e 74 61 63 69 f3 6e 2e 73 78 69
 * ]|
 * However, if the application use UTF-8, the actual file name on
 * disk would look like this:
 * |[
 * Character:  P  r  e  s  e  n  t  a  c  i  o  n  .  s  x  i
 * Hex code:   50 72 65 73 65 6e 74 61 63 69 c3 b3 6e 2e 73 78 69
 * ]|
 * Glib uses UTF-8 for its strings, and GUI toolkits like GTK+ that use
 * GLib do the same thing. If you get a file name from the file system,
 * for example, from readdir() or from g_dir_read_name(), and you wish
 * to display the file name to the user, you  will need to convert it
 * into UTF-8. The opposite case is when the user types the name of a
 * file they wish to save: the toolkit will give you that string in
 * UTF-8 encoding, and you will need to convert it to the character
 * set used for file names before you can create the file with open()
 * or fopen().
 *
 * By default, GLib assumes that file names on disk are in UTF-8
 * encoding. This is a valid assumption for file systems which
 * were created relatively recently: most applications use UTF-8
 * encoding for their strings, and that is also what they use for
 * the file names they create. However, older file systems may
 * still contain file names created in "older" encodings, such as
 * ISO-8859-1. In this case, for compatibility reasons, you may want
 * to instruct GLib to use that particular encoding for file names
 * rather than UTF-8. You can do this by specifying the encoding for
 * file names in the [`G_FILENAME_ENCODING`][G_FILENAME_ENCODING]
 * environment variable. For example, if your installation uses
 * ISO-8859-1 for file names, you can put this in your `~/.profile`:
 * |[
 * export G_FILENAME_ENCODING=ISO-8859-1
 * ]|
 * GLib provides the functions g_filename_to_utf8() and
 * g_filename_from_utf8() to perform the necessary conversions.
 * These functions convert file names from the encoding specified
 * in `G_FILENAME_ENCODING` to UTF-8 and vice-versa. This
 * [diagram][file-name-encodings-diagram] illustrates how
 * these functions are used to convert between UTF-8 and the
 * encoding for file names in the file system.
 *
 * ## Conversion between file name encodings # {#file-name-encodings-diagram)
 *
 * ![](file-name-encodings.png)
 *
 * ## Checklist for Application Writers
 *
 * This section is a practical summary of the detailed
 * things to do to make sure your applications process file
 * name encodings correctly.
 *
 * 1. If you get a file name from the file system from a function
 *    such as readdir() or gtk_file_chooser_get_filename(), you do
 *    not need to do any conversion to pass that file name to
 *    functions like open(), rename(), or fopen() -- those are "raw"
 *    file names which the file system understands.
 *
 * 2. If you need to display a file name, convert it to UTF-8 first
 *    by using g_filename_to_utf8(). If conversion fails, display a
 *    string like "Unknown file name". Do not convert this string back
 *    into the encoding used for file names if you wish to pass it to
 *    the file system; use the original file name instead.
 *
 *    For example, the document window of a word processor could display
 *    "Unknown file name" in its title bar but still let the user save
 *    the file, as it would keep the raw file name internally. This
 *    can happen if the user has not set the `G_FILENAME_ENCODING`
 *    environment variable even though he has files whose names are
 *    not encoded in UTF-8.
 *
 * 3. If your user interface lets the user type a file name for saving
 *    or renaming, convert it to the encoding used for file names in
 *    the file system by using g_filename_from_utf8(). Pass the converted
 *    file name to functions like fopen(). If conversion fails, ask the
 *    user to enter a different file name. This can happen if the user
 *    types Japanese characters when `G_FILENAME_ENCODING` is set to
 *    `ISO-8859-1`, for example.
 */

/* We try to terminate strings in unknown charsets with this many zero bytes
 * to ensure that multibyte strings really are nul-terminated when we return
 * them from g_convert() and friends.
 */
#define NUL_TERMINATOR_LENGTH 4

G_DEFINE_QUARK (g_convert_error, g_convert_error)

static gboolean
try_conversion (const char *to_codeset,
        const char *from_codeset,
        iconv_t    *cd)
{
  *cd = iconv_open (to_codeset, from_codeset);

  if (*cd == (iconv_t)-1 && errno == EINVAL)
    return FALSE;
  else
    return TRUE;
}

static gboolean
try_to_aliases (const char **to_aliases,
        const char  *from_codeset,
        iconv_t     *cd)
{
  if (to_aliases)
    {
      const char **p = to_aliases;
      while (*p)
    {
      if (try_conversion (*p, from_codeset, cd))
        return TRUE;

      p++;
    }
    }

  return FALSE;
}

/**
 * g_iconv_open: (skip)
 * @to_codeset: destination codeset
 * @from_codeset: source codeset
 *
 * Same as the standard UNIX routine iconv_open(), but
 * may be implemented via libiconv on UNIX flavors that lack
 * a native implementation.
 *
 * GLib provides g_convert() and g_locale_to_utf8() which are likely
 * more convenient than the raw iconv wrappers.
 *
 * Returns: a "conversion descriptor", or (GIConv)-1 if
 *  opening the converter failed.
 **/
GIConv
g_iconv_open (const gchar  *to_codeset,
          const gchar  *from_codeset)
{
  iconv_t cd;

  if (!try_conversion (to_codeset, from_codeset, &cd))
    {
      const char **to_aliases = _g_charset_get_aliases (to_codeset);
      const char **from_aliases = _g_charset_get_aliases (from_codeset);

      if (from_aliases)
    {
      const char **p = from_aliases;
      while (*p)
        {
          if (try_conversion (to_codeset, *p, &cd))
        goto out;

          if (try_to_aliases (to_aliases, *p, &cd))
        goto out;

          p++;
        }
    }

      if (try_to_aliases (to_aliases, from_codeset, &cd))
    goto out;
    }

 out:
  return (cd == (iconv_t)-1) ? (GIConv)-1 : (GIConv)cd;
}

/**
 * g_iconv: (skip)
 * @converter: conversion descriptor from g_iconv_open()
 * @inbuf: bytes to convert
 * @inbytes_left: inout parameter, bytes remaining to convert in @inbuf
 * @outbuf: converted output bytes
 * @outbytes_left: inout parameter, bytes available to fill in @outbuf
 *
 * Same as the standard UNIX routine iconv(), but
 * may be implemented via libiconv on UNIX flavors that lack
 * a native implementation.
 *
 * GLib provides g_convert() and g_locale_to_utf8() which are likely
 * more convenient than the raw iconv wrappers.
 *
 * Note that the behaviour of iconv() for characters which are valid in the
 * input character set, but which have no representation in the output character
 * set, is implementation defined. This function may return success (with a
 * positive number of non-reversible conversions as replacement characters were
 * used), or it may return -1 and set an error such as %EILSEQ, in such a
 * situation.
 *
 * Returns: count of non-reversible conversions, or -1 on error
 **/
gsize
g_iconv (GIConv   converter,
     gchar  **inbuf,
     gsize   *inbytes_left,
     gchar  **outbuf,
     gsize   *outbytes_left)
{
  iconv_t cd = (iconv_t)converter;

  return iconv (cd, inbuf, inbytes_left, outbuf, outbytes_left);
}

/**
 * g_iconv_close: (skip)
 * @converter: a conversion descriptor from g_iconv_open()
 *
 * Same as the standard UNIX routine iconv_close(), but
 * may be implemented via libiconv on UNIX flavors that lack
 * a native implementation. Should be called to clean up
 * the conversion descriptor from g_iconv_open() when
 * you are done converting things.
 *
 * GLib provides g_convert() and g_locale_to_utf8() which are likely
 * more convenient than the raw iconv wrappers.
 *
 * Returns: -1 on error, 0 on success
 **/
gint
g_iconv_close (GIConv converter)
{
  iconv_t cd = (iconv_t)converter;

  return iconv_close (cd);
}

static GIConv
open_converter (const gchar *to_codeset,
        const gchar *from_codeset,
        GError     **error)
{
  GIConv cd;

  cd = g_iconv_open (to_codeset, from_codeset);

  if (cd == (GIConv) -1)
    {
      /* Something went wrong.  */
      if (error)
    {
      if (errno == EINVAL)
        g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_NO_CONVERSION,
             _("Conversion from character set '%s' to '%s' is not supported"),
             from_codeset, to_codeset);
      else
        g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_FAILED,
             _("Could not open converter from '%s' to '%s'"),
             from_codeset, to_codeset);
    }
    }

  return cd;
}

static int
close_converter (GIConv cd)
{
  if (cd == (GIConv) -1)
    return 0;

  return g_iconv_close (cd);
}

/**
 * g_convert_with_iconv: (skip)
 * @str:           (array length=len) (element-type guint8):
 *                 the string to convert.
 * @len:           the length of the string in bytes, or -1 if the string is
 *                 nul-terminated (Note that some encodings may allow nul
 *                 bytes to occur inside strings. In that case, using -1
 *                 for the @len parameter is unsafe)
 * @converter:     conversion descriptor from g_iconv_open()
 * @bytes_read:    (out) (optional): location to store the number of bytes in
 *                 the input string that were successfully converted, or %NULL.
 *                 Even if the conversion was successful, this may be
 *                 less than @len if there were partial characters
 *                 at the end of the input. If the error
 *                 #G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value
 *                 stored will be the byte offset after the last valid
 *                 input sequence.
 * @bytes_written: (out) (optional): the number of bytes stored in
 *                 the output buffer (not including the terminating nul).
 * @error:         location to store the error occurring, or %NULL to ignore
 *                 errors. Any of the errors in #GConvertError may occur.
 *
 * Converts a string from one character set to another.
 *
 * Note that you should use g_iconv() for streaming conversions.
 * Despite the fact that @bytes_read can return information about partial
 * characters, the g_convert_... functions are not generally suitable
 * for streaming. If the underlying converter maintains internal state,
 * then this won't be preserved across successive calls to g_convert(),
 * g_convert_with_iconv() or g_convert_with_fallback(). (An example of
 * this is the GNU C converter for CP1255 which does not emit a base
 * character until it knows that the next character is not a mark that
 * could combine with the base character.)
 *
 * Characters which are valid in the input character set, but which have no
 * representation in the output character set will result in a
 * %G_CONVERT_ERROR_ILLEGAL_SEQUENCE error. This is in contrast to the iconv()
 * specification, which leaves this behaviour implementation defined. Note that
 * this is the same error code as is returned for an invalid byte sequence in
 * the input character set. To get defined behaviour for conversion of
 * unrepresentable characters, use g_convert_with_fallback().
 *
 * Returns: (array length=bytes_written) (element-type guint8) (transfer full):
 *               If the conversion was successful, a newly allocated buffer
 *               containing the converted string, which must be freed with
 *               g_free(). Otherwise %NULL and @error will be set.
 **/
gchar*
g_convert_with_iconv (const gchar *str,
              gssize       len,
              GIConv       converter,
              gsize       *bytes_read,
              gsize       *bytes_written,
              GError     **error)
{
  gchar *dest;
  gchar *outp;
  const gchar *p;
  gsize inbytes_remaining;
  gsize outbytes_remaining;
  gsize err;
  gsize outbuf_size;
  gboolean have_error = FALSE;
  gboolean done = FALSE;
  gboolean reset = FALSE;

  g_return_val_if_fail (converter != (GIConv) -1, NULL);

  if (len < 0)
    len = strlen (str);

  p = str;
  inbytes_remaining = len;
  outbuf_size = len + NUL_TERMINATOR_LENGTH;

  outbytes_remaining = outbuf_size - NUL_TERMINATOR_LENGTH;
  outp = dest = g_malloc (outbuf_size);

  while (!done && !have_error)
    {
      if (reset)
        err = g_iconv (converter, NULL, &inbytes_remaining, &outp, &outbytes_remaining);
      else
        err = g_iconv (converter, (char **)&p, &inbytes_remaining, &outp, &outbytes_remaining);

      if (err == (gsize) -1)
    {
      switch (errno)
        {
        case EINVAL:
          /* Incomplete text, do not report an error */
          done = TRUE;
          break;
        case E2BIG:
          {
        gsize used = outp - dest;

        outbuf_size *= 2;
        dest = g_realloc (dest, outbuf_size);

        outp = dest + used;
        outbytes_remaining = outbuf_size - used - NUL_TERMINATOR_LENGTH;
          }
          break;
        case EILSEQ:
              g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                                   _("Invalid byte sequence in conversion input"));
          have_error = TRUE;
          break;
        default:
              {
                int errsv = errno;

                g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_FAILED,
                             _("Error during conversion: %s"),
                             g_strerror (errsv));
              }
          have_error = TRUE;
          break;
        }
    }
      else if (err > 0)
        {
          /* @err gives the number of replacement characters used. */
          g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                               _("Unrepresentable character in conversion input"));
          have_error = TRUE;
        }
      else
    {
      if (!reset)
        {
          /* call g_iconv with NULL inbuf to cleanup shift state */
          reset = TRUE;
          inbytes_remaining = 0;
        }
      else
        done = TRUE;
    }
    }

  memset (outp, 0, NUL_TERMINATOR_LENGTH);

  if (bytes_read)
    *bytes_read = p - str;
  else
    {
      if ((p - str) != len)
    {
          if (!have_error)
            {
              g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_PARTIAL_INPUT,
                                   _("Partial character sequence at end of input"));
              have_error = TRUE;
            }
    }
    }

  if (bytes_written)
    *bytes_written = outp - dest;   /* Doesn't include '\0' */

  if (have_error)
    {
      g_free (dest);
      return NULL;
    }
  else
    return dest;
}

/**
 * g_convert:
 * @str:           (array length=len) (element-type guint8):
 *                 the string to convert.
 * @len:           the length of the string in bytes, or -1 if the string is
 *                 nul-terminated (Note that some encodings may allow nul
 *                 bytes to occur inside strings. In that case, using -1
 *                 for the @len parameter is unsafe)
 * @to_codeset:    name of character set into which to convert @str
 * @from_codeset:  character set of @str.
 * @bytes_read:    (out) (optional): location to store the number of bytes in
 *                 the input string that were successfully converted, or %NULL.
 *                 Even if the conversion was successful, this may be
 *                 less than @len if there were partial characters
 *                 at the end of the input. If the error
 *                 #G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value
 *                 stored will be the byte offset after the last valid
 *                 input sequence.
 * @bytes_written: (out) (optional): the number of bytes stored in
 *                 the output buffer (not including the terminating nul).
 * @error:         location to store the error occurring, or %NULL to ignore
 *                 errors. Any of the errors in #GConvertError may occur.
 *
 * Converts a string from one character set to another.
 *
 * Note that you should use g_iconv() for streaming conversions.
 * Despite the fact that @bytes_read can return information about partial
 * characters, the g_convert_... functions are not generally suitable
 * for streaming. If the underlying converter maintains internal state,
 * then this won't be preserved across successive calls to g_convert(),
 * g_convert_with_iconv() or g_convert_with_fallback(). (An example of
 * this is the GNU C converter for CP1255 which does not emit a base
 * character until it knows that the next character is not a mark that
 * could combine with the base character.)
 *
 * Using extensions such as "//TRANSLIT" may not work (or may not work
 * well) on many platforms.  Consider using g_str_to_ascii() instead.
 *
 * Returns: (array length=bytes_written) (element-type guint8) (transfer full):
 *          If the conversion was successful, a newly allocated buffer
 *          containing the converted string, which must be freed with g_free().
 *          Otherwise %NULL and @error will be set.
 **/
gchar*
g_convert (const gchar *str,
           gssize       len,
           const gchar *to_codeset,
           const gchar *from_codeset,
           gsize       *bytes_read,
       gsize       *bytes_written,
       GError     **error)
{
  gchar *res;
  GIConv cd;

  g_return_val_if_fail (str != NULL, NULL);
  g_return_val_if_fail (to_codeset != NULL, NULL);
  g_return_val_if_fail (from_codeset != NULL, NULL);

  cd = open_converter (to_codeset, from_codeset, error);

  if (cd == (GIConv) -1)
    {
      if (bytes_read)
        *bytes_read = 0;

      if (bytes_written)
        *bytes_written = 0;

      return NULL;
    }

  res = g_convert_with_iconv (str, len, cd,
                  bytes_read, bytes_written,
                  error);

  close_converter (cd);

  return res;
}

/**
 * g_convert_with_fallback:
 * @str:          (array length=len) (element-type guint8):
 *                the string to convert.
 * @len:          the length of the string in bytes, or -1 if the string is
 *                 nul-terminated (Note that some encodings may allow nul
 *                 bytes to occur inside strings. In that case, using -1
 *                 for the @len parameter is unsafe)
 * @to_codeset:   name of character set into which to convert @str
 * @from_codeset: character set of @str.
 * @fallback:     UTF-8 string to use in place of characters not
 *                present in the target encoding. (The string must be
 *                representable in the target encoding).
 *                If %NULL, characters not in the target encoding will
 *                be represented as Unicode escapes \uxxxx or \Uxxxxyyyy.
 * @bytes_read:   (out) (optional): location to store the number of bytes in
 *                the input string that were successfully converted, or %NULL.
 *                Even if the conversion was successful, this may be
 *                less than @len if there were partial characters
 *                at the end of the input.
 * @bytes_written: (out) (optional): the number of bytes stored in
 *                 the output buffer (not including the terminating nul).
 * @error:        location to store the error occurring, or %NULL to ignore
 *                errors. Any of the errors in #GConvertError may occur.
 *
 * Converts a string from one character set to another, possibly
 * including fallback sequences for characters not representable
 * in the output. Note that it is not guaranteed that the specification
 * for the fallback sequences in @fallback will be honored. Some
 * systems may do an approximate conversion from @from_codeset
 * to @to_codeset in their iconv() functions,
 * in which case GLib will simply return that approximate conversion.
 *
 * Note that you should use g_iconv() for streaming conversions.
 * Despite the fact that @bytes_read can return information about partial
 * characters, the g_convert_... functions are not generally suitable
 * for streaming. If the underlying converter maintains internal state,
 * then this won't be preserved across successive calls to g_convert(),
 * g_convert_with_iconv() or g_convert_with_fallback(). (An example of
 * this is the GNU C converter for CP1255 which does not emit a base
 * character until it knows that the next character is not a mark that
 * could combine with the base character.)
 *
 * Returns: (array length=bytes_written) (element-type guint8) (transfer full):
 *          If the conversion was successful, a newly allocated buffer
 *          containing the converted string, which must be freed with g_free().
 *          Otherwise %NULL and @error will be set.
 **/
gchar*
g_convert_with_fallback (const gchar *str,
             gssize       len,
             const gchar *to_codeset,
             const gchar *from_codeset,
             const gchar *fallback,
             gsize       *bytes_read,
             gsize       *bytes_written,
             GError     **error)
{
  gchar *utf8;
  gchar *dest;
  gchar *outp;
  const gchar *insert_str = NULL;
  const gchar *p;
  gsize inbytes_remaining;
  const gchar *save_p = NULL;
  gsize save_inbytes = 0;
  gsize outbytes_remaining;
  gsize err;
  GIConv cd;
  gsize outbuf_size;
  gboolean have_error = FALSE;
  gboolean done = FALSE;

  GError *local_error = NULL;

  g_return_val_if_fail (str != NULL, NULL);
  g_return_val_if_fail (to_codeset != NULL, NULL);
  g_return_val_if_fail (from_codeset != NULL, NULL);

  if (len < 0)
    len = strlen (str);

  /* Try an exact conversion; we only proceed if this fails
   * due to an illegal sequence in the input string.
   */
  dest = g_convert (str, len, to_codeset, from_codeset,
            bytes_read, bytes_written, &local_error);
  if (!local_error)
    return dest;

  if (!g_error_matches (local_error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE))
    {
      g_propagate_error (error, local_error);
      return NULL;
    }
  else
    g_error_free (local_error);

  local_error = NULL;

  /* No go; to proceed, we need a converter from "UTF-8" to
   * to_codeset, and the string as UTF-8.
   */
  cd = open_converter (to_codeset, "UTF-8", error);
  if (cd == (GIConv) -1)
    {
      if (bytes_read)
        *bytes_read = 0;

      if (bytes_written)
        *bytes_written = 0;

      return NULL;
    }

  utf8 = g_convert (str, len, "UTF-8", from_codeset,
            bytes_read, &inbytes_remaining, error);
  if (!utf8)
    {
      close_converter (cd);
      if (bytes_written)
        *bytes_written = 0;
      return NULL;
    }

  /* Now the heart of the code. We loop through the UTF-8 string, and
   * whenever we hit an offending character, we form fallback, convert
   * the fallback to the target codeset, and then go back to
   * converting the original string after finishing with the fallback.
   *
   * The variables save_p and save_inbytes store the input state
   * for the original string while we are converting the fallback
   */
  p = utf8;

  outbuf_size = len + NUL_TERMINATOR_LENGTH;
  outbytes_remaining = outbuf_size - NUL_TERMINATOR_LENGTH;
  outp = dest = g_malloc (outbuf_size);

  while (!done && !have_error)
    {
      gsize inbytes_tmp = inbytes_remaining;
      err = g_iconv (cd, (char **)&p, &inbytes_tmp, &outp, &outbytes_remaining);
      inbytes_remaining = inbytes_tmp;

      if (err == (gsize) -1)
    {
      switch (errno)
        {
        case EINVAL:
          g_assert_not_reached();
          break;
        case E2BIG:
          {
        gsize used = outp - dest;

        outbuf_size *= 2;
        dest = g_realloc (dest, outbuf_size);

        outp = dest + used;
        outbytes_remaining = outbuf_size - used - NUL_TERMINATOR_LENGTH;

        break;
          }
        case EILSEQ:
          if (save_p)
        {
          /* Error converting fallback string - fatal
           */
          g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                   _("Cannot convert fallback '%s' to codeset '%s'"),
                   insert_str, to_codeset);
          have_error = TRUE;
          break;
        }
          else if (p)
        {
          if (!fallback)
            {
              gunichar ch = g_utf8_get_char (p);
              insert_str = g_strdup_printf (ch < 0x10000 ? "\\u%04x" : "\\U%08x",
                            ch);
            }
          else
            insert_str = fallback;

          save_p = g_utf8_next_char (p);
          save_inbytes = inbytes_remaining - (save_p - p);
          p = insert_str;
          inbytes_remaining = strlen (p);
          break;
        }
          /* fall thru if p is NULL */
        default:
              {
                int errsv = errno;

                g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_FAILED,
                             _("Error during conversion: %s"),
                             g_strerror (errsv));
              }

          have_error = TRUE;
          break;
        }
    }
      else
    {
      if (save_p)
        {
          if (!fallback)
        g_free ((gchar *)insert_str);
          p = save_p;
          inbytes_remaining = save_inbytes;
          save_p = NULL;
        }
      else if (p)
        {
          /* call g_iconv with NULL inbuf to cleanup shift state */
          p = NULL;
          inbytes_remaining = 0;
        }
      else
        done = TRUE;
    }
    }

  /* Cleanup
   */
  memset (outp, 0, NUL_TERMINATOR_LENGTH);

  close_converter (cd);

  if (bytes_written)
    *bytes_written = outp - dest;   /* Doesn't include '\0' */

  g_free (utf8);

  if (have_error)
    {
      if (save_p && !fallback)
    g_free ((gchar *)insert_str);
      g_free (dest);
      return NULL;
    }
  else
    return dest;
}

/*
 * g_locale_to_utf8
 *
 *
 */

/*
 * Validate @string as UTF-8. @len can be negative if @string is
 * nul-terminated, or a non-negative value in bytes. If @string ends in an
 * incomplete sequence, or contains any illegal sequences or nul codepoints,
 * %NULL will be returned and the error set to
 * %G_CONVERT_ERROR_ILLEGAL_SEQUENCE.
 * On success, @bytes_read and @bytes_written, if provided, will be set to
 * the number of bytes in @string up to @len or the terminating nul byte.
 * On error, @bytes_read will be set to the byte offset after the last valid
 * and non-nul UTF-8 sequence in @string, and @bytes_written will be set to 0.
 */
static gchar *
strdup_len (const gchar *string,
        gssize       len,
        gsize       *bytes_read,
        gsize       *bytes_written,
        GError     **error)
{
  gsize real_len;
  const gchar *end_valid;

  if (!g_utf8_validate (string, len, &end_valid))
    {
      if (bytes_read)
    *bytes_read = end_valid - string;
      if (bytes_written)
    *bytes_written = 0;

      g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                           _("Invalid byte sequence in conversion input"));
      return NULL;
    }

  real_len = end_valid - string;

  if (bytes_read)
    *bytes_read = real_len;
  if (bytes_written)
    *bytes_written = real_len;

  return g_strndup (string, real_len);
}

typedef enum
{
  CONVERT_CHECK_NO_NULS_IN_INPUT  = 1 << 0,
  CONVERT_CHECK_NO_NULS_IN_OUTPUT = 1 << 1
} ConvertCheckFlags;

/*
 * Convert from @string in the encoding identified by @from_codeset,
 * returning a string in the encoding identifed by @to_codeset.
 * @len can be negative if @string is nul-terminated, or a non-negative
 * value in bytes. Flags defined in #ConvertCheckFlags can be set in @flags
 * to check the input, the output, or both, for embedded nul bytes.
 * On success, @bytes_read, if provided, will be set to the number of bytes
 * in @string up to @len or the terminating nul byte, and @bytes_written, if
 * provided, will be set to the number of output bytes written into the
 * returned buffer, excluding the terminating nul sequence.
 * On error, @bytes_read will be set to the byte offset after the last valid
 * sequence in @string, and @bytes_written will be set to 0.
 */
static gchar *
convert_checked (const gchar      *string,
                 gssize            len,
                 const gchar      *to_codeset,
                 const gchar      *from_codeset,
                 ConvertCheckFlags flags,
                 gsize            *bytes_read,
                 gsize            *bytes_written,
                 GError          **error)
{
  gchar *out;
  gsize outbytes;

  if ((flags & CONVERT_CHECK_NO_NULS_IN_INPUT) && len > 0)
    {
      const gchar *early_nul = memchr (string, '\0', len);
      if (early_nul != NULL)
        {
          if (bytes_read)
            *bytes_read = early_nul - string;
          if (bytes_written)
            *bytes_written = 0;

          g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                               _("Embedded NUL byte in conversion input"));
          return NULL;
        }
    }

  out = g_convert (string, len, to_codeset, from_codeset,
                   bytes_read, &outbytes, error);
  if (out == NULL)
    {
      if (bytes_written)
        *bytes_written = 0;
      return NULL;
    }

  if ((flags & CONVERT_CHECK_NO_NULS_IN_OUTPUT)
      && memchr (out, '\0', outbytes) != NULL)
    {
      g_free (out);
      if (bytes_written)
        *bytes_written = 0;
      g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_EMBEDDED_NUL,
                           _("Embedded NUL byte in conversion output"));
      return NULL;
    }

  if (bytes_written)
    *bytes_written = outbytes;
  return out;
}

/**
 * g_locale_to_utf8:
 * @opsysstring:   (array length=len) (element-type guint8): a string in the
 *                 encoding of the current locale. On Windows
 *                 this means the system codepage.
 * @len:           the length of the string, or -1 if the string is
 *                 nul-terminated (Note that some encodings may allow nul
 *                 bytes to occur inside strings. In that case, using -1
 *                 for the @len parameter is unsafe)
 * @bytes_read: (out) (optional): location to store the number of bytes in the
 *                 input string that were successfully converted, or %NULL.
 *                 Even if the conversion was successful, this may be
 *                 less than @len if there were partial characters
 *                 at the end of the input. If the error
 *                 %G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value
 *                 stored will be the byte offset after the last valid
 *                 input sequence.
 * @bytes_written: (out) (optional): the number of bytes stored in the output
 *                 buffer (not including the terminating nul).
 * @error:         location to store the error occurring, or %NULL to ignore
 *                 errors. Any of the errors in #GConvertError may occur.
 *
 * Converts a string which is in the encoding used for strings by
 * the C runtime (usually the same as that used by the operating
 * system) in the [current locale][setlocale] into a UTF-8 string.
 *
 * If the source encoding is not UTF-8 and the conversion output contains a
 * nul character, the error %G_CONVERT_ERROR_EMBEDDED_NUL is set and the
 * function returns %NULL.
 * If the source encoding is UTF-8, an embedded nul character is treated with
 * the %G_CONVERT_ERROR_ILLEGAL_SEQUENCE error for backward compatibility with
 * earlier versions of this library. Use g_convert() to produce output that
 * may contain embedded nul characters.
 *
 * Returns: (type utf8): The converted string, or %NULL on an error.
 **/
gchar *
g_locale_to_utf8 (const gchar  *opsysstring,
          gssize        len,
          gsize        *bytes_read,
          gsize        *bytes_written,
          GError      **error)
{
  const char *charset;

  if (g_get_charset (&charset))
    return strdup_len (opsysstring, len, bytes_read, bytes_written, error);
  else
    return convert_checked (opsysstring, len, "UTF-8", charset,
                            CONVERT_CHECK_NO_NULS_IN_OUTPUT,
                            bytes_read, bytes_written, error);
}

/**
 * g_locale_from_utf8:
 * @utf8string:    a UTF-8 encoded string
 * @len:           the length of the string, or -1 if the string is
 *                 nul-terminated.
 * @bytes_read: (out) (optional): location to store the number of bytes in the
 *                 input string that were successfully converted, or %NULL.
 *                 Even if the conversion was successful, this may be
 *                 less than @len if there were partial characters
 *                 at the end of the input. If the error
 *                 %G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value
 *                 stored will be the byte offset after the last valid
 *                 input sequence.
 * @bytes_written: (out) (optional): the number of bytes stored in the output
 *                 buffer (not including the terminating nul).
 * @error:         location to store the error occurring, or %NULL to ignore
 *                 errors. Any of the errors in #GConvertError may occur.
 *
 * Converts a string from UTF-8 to the encoding used for strings by
 * the C runtime (usually the same as that used by the operating
 * system) in the [current locale][setlocale]. On Windows this means
 * the system codepage.
 *
 * The input string shall not contain nul characters even if the @len
 * argument is positive. A nul character found inside the string will result
 * in error %G_CONVERT_ERROR_ILLEGAL_SEQUENCE. Use g_convert() to convert
 * input that may contain embedded nul characters.
 *
 * Returns: (array length=bytes_written) (element-type guint8) (transfer full):
 *          A newly-allocated buffer containing the converted string,
 *          or %NULL on an error, and error will be set.
 **/
gchar *
g_locale_from_utf8 (const gchar *utf8string,
            gssize       len,
            gsize       *bytes_read,
            gsize       *bytes_written,
            GError     **error)
{
  const gchar *charset;

  if (g_get_charset (&charset))
    return strdup_len (utf8string, len, bytes_read, bytes_written, error);
  else
    return convert_checked (utf8string, len, charset, "UTF-8",
                            CONVERT_CHECK_NO_NULS_IN_INPUT,
                            bytes_read, bytes_written, error);
}

#ifndef G_PLATFORM_WIN32

typedef struct _GFilenameCharsetCache GFilenameCharsetCache;

struct _GFilenameCharsetCache {
  gboolean is_utf8;
  gchar *charset;
  gchar **filename_charsets;
};

static void
filename_charset_cache_free (gpointer data)
{
  GFilenameCharsetCache *cache = data;
  g_free (cache->charset);
  g_strfreev (cache->filename_charsets);
  g_free (cache);
}

/**
 * g_get_filename_charsets:
 * @filename_charsets: (out) (transfer none) (array zero-terminated=1):
 *    return location for the %NULL-terminated list of encoding names
 *
 * Determines the preferred character sets used for filenames.
 * The first character set from the @charsets is the filename encoding, the
 * subsequent character sets are used when trying to generate a displayable
 * representation of a filename, see g_filename_display_name().
 *
 * On Unix, the character sets are determined by consulting the
 * environment variables `G_FILENAME_ENCODING` and `G_BROKEN_FILENAMES`.
 * On Windows, the character set used in the GLib API is always UTF-8
 * and said environment variables have no effect.
 *
 * `G_FILENAME_ENCODING` may be set to a comma-separated list of
 * character set names. The special token "\@locale" is taken
 * to  mean the character set for the [current locale][setlocale].
 * If `G_FILENAME_ENCODING` is not set, but `G_BROKEN_FILENAMES` is,
 * the character set of the current locale is taken as the filename
 * encoding. If neither environment variable  is set, UTF-8 is taken
 * as the filename encoding, but the character set of the current locale
 * is also put in the list of encodings.
 *
 * The returned @charsets belong to GLib and must not be freed.
 *
 * Note that on Unix, regardless of the locale character set or
 * `G_FILENAME_ENCODING` value, the actual file names present
 * on a system might be in any random encoding or just gibberish.
 *
 * Returns: %TRUE if the filename encoding is UTF-8.
 *
 * Since: 2.6
 */
gboolean
g_get_filename_charsets (const gchar ***filename_charsets)
{
  static GPrivate cache_private = G_PRIVATE_INIT (filename_charset_cache_free);
  GFilenameCharsetCache *cache = g_private_get (&cache_private);
  const gchar *charset;

  if (!cache)
    {
      cache = g_new0 (GFilenameCharsetCache, 1);
      g_private_set (&cache_private, cache);
    }

  g_get_charset (&charset);

  if (!(cache->charset && strcmp (cache->charset, charset) == 0))
    {
      const gchar *new_charset;
      gchar *p;
      gint i;

      g_free (cache->charset);
      g_strfreev (cache->filename_charsets);
      cache->charset = g_strdup (charset);

      p = getenv ("G_FILENAME_ENCODING");
      if (p != NULL && p[0] != '\0')
    {
      cache->filename_charsets = g_strsplit (p, ",", 0);
      cache->is_utf8 = (strcmp (cache->filename_charsets[0], "UTF-8") == 0);

      for (i = 0; cache->filename_charsets[i]; i++)
        {
          if (strcmp ("@locale", cache->filename_charsets[i]) == 0)
        {
          g_get_charset (&new_charset);
          g_free (cache->filename_charsets[i]);
          cache->filename_charsets[i] = g_strdup (new_charset);
        }
        }
    }
      else if (getenv ("G_BROKEN_FILENAMES") != NULL)
    {
      cache->filename_charsets = g_new0 (gchar *, 2);
      cache->is_utf8 = g_get_charset (&new_charset);
      cache->filename_charsets[0] = g_strdup (new_charset);
    }
      else
    {
      cache->filename_charsets = g_new0 (gchar *, 3);
      cache->is_utf8 = TRUE;
      cache->filename_charsets[0] = g_strdup ("UTF-8");
      if (!g_get_charset (&new_charset))
        cache->filename_charsets[1] = g_strdup (new_charset);
    }
    }

  if (filename_charsets)
    *filename_charsets = (const gchar **)cache->filename_charsets;

  return cache->is_utf8;
}

#else /* G_PLATFORM_WIN32 */

gboolean
g_get_filename_charsets (const gchar ***filename_charsets)
{
  static const gchar *charsets[] = {
    "UTF-8",
    NULL
  };

#ifdef G_OS_WIN32
  /* On Windows GLib pretends that the filename charset is UTF-8 */
  if (filename_charsets)
    *filename_charsets = charsets;

  return TRUE;
#else
  gboolean result;

  /* Cygwin works like before */
  result = g_get_charset (&(charsets[0]));

  if (filename_charsets)
    *filename_charsets = charsets;

  return result;
#endif
}

#endif /* G_PLATFORM_WIN32 */

static gboolean
get_filename_charset (const gchar **filename_charset)
{
  const gchar **charsets;
  gboolean is_utf8;

  is_utf8 = g_get_filename_charsets (&charsets);

  if (filename_charset)
    *filename_charset = charsets[0];

  return is_utf8;
}

/**
 * g_filename_to_utf8:
 * @opsysstring: (type filename): a string in the encoding for filenames
 * @len:           the length of the string, or -1 if the string is
 *                 nul-terminated (Note that some encodings may allow nul
 *                 bytes to occur inside strings. In that case, using -1
 *                 for the @len parameter is unsafe)
 * @bytes_read: (out) (optional): location to store the number of bytes in the
 *                 input string that were successfully converted, or %NULL.
 *                 Even if the conversion was successful, this may be
 *                 less than @len if there were partial characters
 *                 at the end of the input. If the error
 *                 %G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value
 *                 stored will be the byte offset after the last valid
 *                 input sequence.
 * @bytes_written: (out) (optional): the number of bytes stored in the output
 *                 buffer (not including the terminating nul).
 * @error:         location to store the error occurring, or %NULL to ignore
 *                 errors. Any of the errors in #GConvertError may occur.
 *
 * Converts a string which is in the encoding used by GLib for
 * filenames into a UTF-8 string. Note that on Windows GLib uses UTF-8
 * for filenames; on other platforms, this function indirectly depends on
 * the [current locale][setlocale].
 *
 * The input string shall not contain nul characters even if the @len
 * argument is positive. A nul character found inside the string will result
 * in error %G_CONVERT_ERROR_ILLEGAL_SEQUENCE.
 * If the source encoding is not UTF-8 and the conversion output contains a
 * nul character, the error %G_CONVERT_ERROR_EMBEDDED_NUL is set and the
 * function returns %NULL. Use g_convert() to produce output that
 * may contain embedded nul characters.
 *
 * Returns: (type utf8): The converted string, or %NULL on an error.
 **/
gchar*
g_filename_to_utf8 (const gchar *opsysstring,
            gssize       len,
            gsize       *bytes_read,
            gsize       *bytes_written,
            GError     **error)
{
  const gchar *charset;

  g_return_val_if_fail (opsysstring != NULL, NULL);

  if (get_filename_charset (&charset))
    return strdup_len (opsysstring, len, bytes_read, bytes_written, error);
  else
    return convert_checked (opsysstring, len, "UTF-8", charset,
                            CONVERT_CHECK_NO_NULS_IN_INPUT |
                            CONVERT_CHECK_NO_NULS_IN_OUTPUT,
                            bytes_read, bytes_written, error);
}

/**
 * g_filename_from_utf8:
 * @utf8string:    (type utf8): a UTF-8 encoded string.
 * @len:           the length of the string, or -1 if the string is
 *                 nul-terminated.
 * @bytes_read:    (out) (optional): location to store the number of bytes in
 *                 the input string that were successfully converted, or %NULL.
 *                 Even if the conversion was successful, this may be
 *                 less than @len if there were partial characters
 *                 at the end of the input. If the error
 *                 %G_CONVERT_ERROR_ILLEGAL_SEQUENCE occurs, the value
 *                 stored will be the byte offset after the last valid
 *                 input sequence.
 * @bytes_written: (out) (optional): the number of bytes stored in
 *                 the output buffer (not including the terminating nul).
 * @error:         location to store the error occurring, or %NULL to ignore
 *                 errors. Any of the errors in #GConvertError may occur.
 *
 * Converts a string from UTF-8 to the encoding GLib uses for
 * filenames. Note that on Windows GLib uses UTF-8 for filenames;
 * on other platforms, this function indirectly depends on the
 * [current locale][setlocale].
 *
 * The input string shall not contain nul characters even if the @len
 * argument is positive. A nul character found inside the string will result
 * in error %G_CONVERT_ERROR_ILLEGAL_SEQUENCE. If the filename encoding is
 * not UTF-8 and the conversion output contains a nul character, the error
 * %G_CONVERT_ERROR_EMBEDDED_NUL is set and the function returns %NULL.
 *
 * Returns: (type filename):
 *               The converted string, or %NULL on an error.
 **/
gchar*
g_filename_from_utf8 (const gchar *utf8string,
              gssize       len,
              gsize       *bytes_read,
              gsize       *bytes_written,
              GError     **error)
{
  const gchar *charset;

  if (get_filename_charset (&charset))
    return strdup_len (utf8string, len, bytes_read, bytes_written, error);
  else
    return convert_checked (utf8string, len, charset, "UTF-8",
                            CONVERT_CHECK_NO_NULS_IN_INPUT |
                            CONVERT_CHECK_NO_NULS_IN_OUTPUT,
                            bytes_read, bytes_written, error);
}

/* Test of haystack has the needle prefix, comparing case
 * insensitive. haystack may be UTF-8, but needle must
 * contain only ascii. */
static gboolean
has_case_prefix (const gchar *haystack, const gchar *needle)
{
  const gchar *h, *n;

  /* Eat one character at a time. */
  h = haystack;
  n = needle;

  while (*n && *h &&
     g_ascii_tolower (*n) == g_ascii_tolower (*h))
    {
      n++;
      h++;
    }

  return *n == '\0';
}

typedef enum {
  UNSAFE_ALL        = 0x1,  /* Escape all unsafe characters   */
  UNSAFE_ALLOW_PLUS = 0x2,  /* Allows '+'  */
  UNSAFE_PATH       = 0x8,  /* Allows '/', '&', '=', ':', '@', '+', '$' and ',' */
  UNSAFE_HOST       = 0x10, /* Allows '/' and ':' and '@' */
  UNSAFE_SLASHES    = 0x20  /* Allows all characters except for '/' and '%' */
} UnsafeCharacterSet;

static const guchar acceptable[96] = {
  /* A table of the ASCII chars from space (32) to DEL (127) */
  /*      !    "    #    $    %    &    '    (    )    *    +    ,    -    .    / */
  0x00,0x3F,0x20,0x20,0x28,0x00,0x2C,0x3F,0x3F,0x3F,0x3F,0x2A,0x28,0x3F,0x3F,0x1C,
  /* 0    1    2    3    4    5    6    7    8    9    :    ;    <    =    >    ? */
  0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x38,0x20,0x20,0x2C,0x20,0x20,
  /* @    A    B    C    D    E    F    G    H    I    J    K    L    M    N    O */
  0x38,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,
  /* P    Q    R    S    T    U    V    W    X    Y    Z    [    \    ]    ^    _ */
  0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x20,0x20,0x20,0x20,0x3F,
  /* `    a    b    c    d    e    f    g    h    i    j    k    l    m    n    o */
  0x20,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,
  /* p    q    r    s    t    u    v    w    x    y    z    {    |    }    ~  DEL */
  0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x3F,0x20,0x20,0x20,0x3F,0x20
};

static const gchar hex[16] = "0123456789ABCDEF";

/* Note: This escape function works on file: URIs, but if you want to
 * escape something else, please read RFC-2396 */
static gchar *
g_escape_uri_string (const gchar *string,
             UnsafeCharacterSet mask)
{
#define ACCEPTABLE(a) ((a)>=32 && (a)<128 && (acceptable[(a)-32] & use_mask))

  const gchar *p;
  gchar *q;
  gchar *result;
  int c;
  gint unacceptable;
  UnsafeCharacterSet use_mask;

  g_return_val_if_fail (mask == UNSAFE_ALL
            || mask == UNSAFE_ALLOW_PLUS
            || mask == UNSAFE_PATH
            || mask == UNSAFE_HOST
            || mask == UNSAFE_SLASHES, NULL);

  unacceptable = 0;
  use_mask = mask;
  for (p = string; *p != '\0'; p++)
    {
      c = (guchar) *p;
      if (!ACCEPTABLE (c))
    unacceptable++;
    }

  result = g_malloc (p - string + unacceptable * 2 + 1);

  use_mask = mask;
  for (q = result, p = string; *p != '\0'; p++)
    {
      c = (guchar) *p;

      if (!ACCEPTABLE (c))
    {
      *q++ = '%'; /* means hex coming */
      *q++ = hex[c >> 4];
      *q++ = hex[c & 15];
    }
      else
    *q++ = *p;
    }

  *q = '\0';

  return result;
}


static gchar *
g_escape_file_uri (const gchar *hostname,
           const gchar *pathname)
{
  char *escaped_hostname = NULL;
  char *escaped_path;
  char *res;

#ifdef G_OS_WIN32
  char *p, *backslash;

  /* Turn backslashes into forward slashes. That's what Netscape
   * does, and they are actually more or less equivalent in Windows.
   */

  pathname = g_strdup (pathname);
  p = (char *) pathname;

  while ((backslash = strchr (p, '\\')) != NULL)
    {
      *backslash = '/';
      p = backslash + 1;
    }
#endif

  if (hostname && *hostname != '\0')
    {
      escaped_hostname = g_escape_uri_string (hostname, UNSAFE_HOST);
    }

  escaped_path = g_escape_uri_string (pathname, UNSAFE_PATH);

  res = g_strconcat ("file://",
             (escaped_hostname) ? escaped_hostname : "",
             (*escaped_path != '/') ? "/" : "",
             escaped_path,
             NULL);

#ifdef G_OS_WIN32
  g_free ((char *) pathname);
#endif

  g_free (escaped_hostname);
  g_free (escaped_path);

  return res;
}

static int
unescape_character (const char *scanner)
{
  int first_digit;
  int second_digit;

  first_digit = g_ascii_xdigit_value (scanner[0]);
  if (first_digit < 0)
    return -1;

  second_digit = g_ascii_xdigit_value (scanner[1]);
  if (second_digit < 0)
    return -1;

  return (first_digit << 4) | second_digit;
}

static gchar *
g_unescape_uri_string (const char *escaped,
               int         len,
               const char *illegal_escaped_characters,
               gboolean    ascii_must_not_be_escaped)
{
  const gchar *in, *in_end;
  gchar *out, *result;
  int c;

  if (escaped == NULL)
    return NULL;

  if (len < 0)
    len = strlen (escaped);

  result = g_malloc (len + 1);

  out = result;
  for (in = escaped, in_end = escaped + len; in < in_end; in++)
    {
      c = *in;

      if (c == '%')
    {
      /* catch partial escape sequences past the end of the substring */
      if (in + 3 > in_end)
        break;

      c = unescape_character (in + 1);

      /* catch bad escape sequences and NUL characters */
      if (c <= 0)
        break;

      /* catch escaped ASCII */
      if (ascii_must_not_be_escaped && c <= 0x7F)
        break;

      /* catch other illegal escaped characters */
      if (strchr (illegal_escaped_characters, c) != NULL)
        break;

      in += 2;
    }

      *out++ = c;
    }

  g_assert (out - result <= len);
  *out = '\0';

  if (in != in_end)
    {
      g_free (result);
      return NULL;
    }

  return result;
}

static gboolean
is_asciialphanum (gunichar c)
{
  return c <= 0x7F && g_ascii_isalnum (c);
}

static gboolean
is_asciialpha (gunichar c)
{
  return c <= 0x7F && g_ascii_isalpha (c);
}

/* allows an empty string */
static gboolean
hostname_validate (const char *hostname)
{
  const char *p;
  gunichar c, first_char, last_char;

  p = hostname;
  if (*p == '\0')
    return TRUE;
  do
    {
      /* read in a label */
      c = g_utf8_get_char (p);
      p = g_utf8_next_char (p);
      if (!is_asciialphanum (c))
    return FALSE;
      first_char = c;
      do
    {
      last_char = c;
      c = g_utf8_get_char (p);
      p = g_utf8_next_char (p);
    }
      while (is_asciialphanum (c) || c == '-');
      if (last_char == '-')
    return FALSE;

      /* if that was the last label, check that it was a toplabel */
      if (c == '\0' || (c == '.' && *p == '\0'))
    return is_asciialpha (first_char);
    }
  while (c == '.');
  return FALSE;
}

/**
 * g_filename_from_uri:
 * @uri: a uri describing a filename (escaped, encoded in ASCII).
 * @hostname: (out) (optional) (nullable): Location to store hostname for the URI.
 *            If there is no hostname in the URI, %NULL will be
 *            stored in this location.
 * @error: location to store the error occurring, or %NULL to ignore
 *         errors. Any of the errors in #GConvertError may occur.
 *
 * Converts an escaped ASCII-encoded URI to a local filename in the
 * encoding used for filenames.
 *
 * Returns: (type filename): a newly-allocated string holding
 *               the resulting filename, or %NULL on an error.
 **/
gchar *
g_filename_from_uri (const gchar *uri,
             gchar      **hostname,
             GError     **error)
{
  const char *path_part;
  const char *host_part;
  char *unescaped_hostname;
  char *result;
  char *filename;
  int offs;
#ifdef G_OS_WIN32
  char *p, *slash;
#endif

  if (hostname)
    *hostname = NULL;

  if (!has_case_prefix (uri, "file:/"))
    {
      g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_BAD_URI,
           _("The URI '%s' is not an absolute URI using the 'file' scheme"),
           uri);
      return NULL;
    }

  path_part = uri + strlen ("file:");

  if (strchr (path_part, '#') != NULL)
    {
      g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_BAD_URI,
           _("The local file URI '%s' may not include a '#'"),
           uri);
      return NULL;
    }

  if (has_case_prefix (path_part, "///"))
    path_part += 2;
  else if (has_case_prefix (path_part, "//"))
    {
      path_part += 2;
      host_part = path_part;

      path_part = strchr (path_part, '/');

      if (path_part == NULL)
    {
      g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_BAD_URI,
               _("The URI '%s' is invalid"),
               uri);
      return NULL;
    }

      unescaped_hostname = g_unescape_uri_string (host_part, path_part - host_part, "", TRUE);

      if (unescaped_hostname == NULL ||
      !hostname_validate (unescaped_hostname))
    {
      g_free (unescaped_hostname);
      g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_BAD_URI,
               _("The hostname of the URI '%s' is invalid"),
               uri);
      return NULL;
    }

      if (hostname)
    *hostname = unescaped_hostname;
      else
    g_free (unescaped_hostname);
    }

  filename = g_unescape_uri_string (path_part, -1, "/", FALSE);

  if (filename == NULL)
    {
      g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_BAD_URI,
           _("The URI '%s' contains invalidly escaped characters"),
           uri);
      return NULL;
    }

  offs = 0;
#ifdef G_OS_WIN32
  /* Drop localhost */
  if (hostname && *hostname != NULL &&
      g_ascii_strcasecmp (*hostname, "localhost") == 0)
    {
      g_free (*hostname);
      *hostname = NULL;
    }

  /* Turn slashes into backslashes, because that's the canonical spelling */
  p = filename;
  while ((slash = strchr (p, '/')) != NULL)
    {
      *slash = '\\';
      p = slash + 1;
    }

  /* Windows URIs with a drive letter can be like "file://host/c:/foo"
   * or "file://host/c|/foo" (some Netscape versions). In those cases, start
   * the filename from the drive letter.
   */
  if (g_ascii_isalpha (filename[1]))
    {
      if (filename[2] == ':')
    offs = 1;
      else if (filename[2] == '|')
    {
      filename[2] = ':';
      offs = 1;
    }
    }
#endif

  result = g_strdup (filename + offs);
  g_free (filename);

  return result;
}

/**
 * g_filename_to_uri:
 * @filename: (type filename): an absolute filename specified in the GLib file
 *     name encoding, which is the on-disk file name bytes on Unix, and UTF-8
 *     on Windows
 * @hostname: (nullable): A UTF-8 encoded hostname, or %NULL for none.
 * @error: location to store the error occurring, or %NULL to ignore
 *         errors. Any of the errors in #GConvertError may occur.
 *
 * Converts an absolute filename to an escaped ASCII-encoded URI, with the path
 * component following Section 3.3. of RFC 2396.
 *
 * Returns: a newly-allocated string holding the resulting
 *               URI, or %NULL on an error.
 **/
gchar *
g_filename_to_uri (const gchar *filename,
           const gchar *hostname,
           GError     **error)
{
  char *escaped_uri;

  g_return_val_if_fail (filename != NULL, NULL);

  if (!g_path_is_absolute (filename))
    {
      g_set_error (error, G_CONVERT_ERROR, G_CONVERT_ERROR_NOT_ABSOLUTE_PATH,
           _("The pathname '%s' is not an absolute path"),
           filename);
      return NULL;
    }

  if (hostname &&
      !(g_utf8_validate (hostname, -1, NULL)
    && hostname_validate (hostname)))
    {
      g_set_error_literal (error, G_CONVERT_ERROR, G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
                           _("Invalid hostname"));
      return NULL;
    }

#ifdef G_OS_WIN32
  /* Don't use localhost unnecessarily */
  if (hostname && g_ascii_strcasecmp (hostname, "localhost") == 0)
    hostname = NULL;
#endif

  escaped_uri = g_escape_file_uri (hostname, filename);

  return escaped_uri;
}

/**
 * g_uri_list_extract_uris:
 * @uri_list: an URI list
 *
 * Splits an URI list conforming to the text/uri-list
 * mime type defined in RFC 2483 into individual URIs,
 * discarding any comments. The URIs are not validated.
 *
 * Returns: (transfer full): a newly allocated %NULL-terminated list
 *   of strings holding the individual URIs. The array should be freed
 *   with g_strfreev().
 *
 * Since: 2.6
 */
gchar **
g_uri_list_extract_uris (const gchar *uri_list)
{
  GSList *uris, *u;
  const gchar *p, *q;
  gchar **result;
  gint n_uris = 0;

  uris = NULL;

  p = uri_list;

  /* We don't actually try to validate the URI according to RFC
   * 2396, or even check for allowed characters - we just ignore
   * comments and trim whitespace off the ends.  We also
   * allow LF delimination as well as the specified CRLF.
   *
   * We do allow comments like specified in RFC 2483.
   */
  while (p)
    {
      if (*p != '#')
    {
      while (g_ascii_isspace (*p))
        p++;

      q = p;
      while (*q && (*q != '\n') && (*q != '\r'))
        q++;

      if (q > p)
        {
          q--;
          while (q > p && g_ascii_isspace (*q))
        q--;

          if (q > p)
        {
          uris = g_slist_prepend (uris, g_strndup (p, q - p + 1));
          n_uris++;
        }
        }
    }
      p = strchr (p, '\n');
      if (p)
    p++;
    }

  result = g_new (gchar *, n_uris + 1);

  result[n_uris--] = NULL;
  for (u = uris; u; u = u->next)
    result[n_uris--] = u->data;

  g_slist_free (uris);

  return result;
}

/**
 * g_filename_display_basename:
 * @filename: (type filename): an absolute pathname in the
 *     GLib file name encoding
 *
 * Returns the display basename for the particular filename, guaranteed
 * to be valid UTF-8. The display name might not be identical to the filename,
 * for instance there might be problems converting it to UTF-8, and some files
 * can be translated in the display.
 *
 * If GLib cannot make sense of the encoding of @filename, as a last resort it
 * replaces unknown characters with U+FFFD, the Unicode replacement character.
 * You can search the result for the UTF-8 encoding of this character (which is
 * "\357\277\275" in octal notation) to find out if @filename was in an invalid
 * encoding.
 *
 * You must pass the whole absolute pathname to this functions so that
 * translation of well known locations can be done.
 *
 * This function is preferred over g_filename_display_name() if you know the
 * whole path, as it allows translation.
 *
 * Returns: a newly allocated string containing
 *   a rendition of the basename of the filename in valid UTF-8
 *
 * Since: 2.6
 **/
gchar *
g_filename_display_basename (const gchar *filename)
{
  char *basename;
  char *display_name;

  g_return_val_if_fail (filename != NULL, NULL);

  basename = g_path_get_basename (filename);
  display_name = g_filename_display_name (basename);
  g_free (basename);
  return display_name;
}

/**
 * g_filename_display_name:
 * @filename: (type filename): a pathname hopefully in the
 *     GLib file name encoding
 *
 * Converts a filename into a valid UTF-8 string. The conversion is
 * not necessarily reversible, so you should keep the original around
 * and use the return value of this function only for display purposes.
 * Unlike g_filename_to_utf8(), the result is guaranteed to be non-%NULL
 * even if the filename actually isn't in the GLib file name encoding.
 *
 * If GLib cannot make sense of the encoding of @filename, as a last resort it
 * replaces unknown characters with U+FFFD, the Unicode replacement character.
 * You can search the result for the UTF-8 encoding of this character (which is
 * "\357\277\275" in octal notation) to find out if @filename was in an invalid
 * encoding.
 *
 * If you know the whole pathname of the file you should use
 * g_filename_display_basename(), since that allows location-based
 * translation of filenames.
 *
 * Returns: a newly allocated string containing
 *   a rendition of the filename in valid UTF-8
 *
 * Since: 2.6
 **/
gchar *
g_filename_display_name (const gchar *filename)
{
  gint i;
  const gchar **charsets;
  gchar *display_name = NULL;
  gboolean is_utf8;

  is_utf8 = g_get_filename_charsets (&charsets);

  if (is_utf8)
    {
      if (g_utf8_validate (filename, -1, NULL))
    display_name = g_strdup (filename);
    }

  if (!display_name)
    {
      /* Try to convert from the filename charsets to UTF-8.
       * Skip the first charset if it is UTF-8.
       */
      for (i = is_utf8 ? 1 : 0; charsets[i]; i++)
    {
      display_name = g_convert (filename, -1, "UTF-8", charsets[i],
                    NULL, NULL, NULL);

      if (display_name)
        break;
    }
    }

  /* if all conversions failed, we replace invalid UTF-8
   * by a question mark
   */
  if (!display_name)
    display_name = g_utf8_make_valid (filename, -1);

  return display_name;
}

#ifdef G_OS_WIN32

/* Binary compatibility versions. Not for newly compiled code. */

_GLIB_EXTERN gchar *g_filename_to_utf8_utf8   (const gchar  *opsysstring,
                                               gssize        len,
                                               gsize        *bytes_read,
                                               gsize        *bytes_written,
                                               GError      **error) G_GNUC_MALLOC;
_GLIB_EXTERN gchar *g_filename_from_utf8_utf8 (const gchar  *utf8string,
                                               gssize        len,
                                               gsize        *bytes_read,
                                               gsize        *bytes_written,
                                               GError      **error) G_GNUC_MALLOC;
_GLIB_EXTERN gchar *g_filename_from_uri_utf8  (const gchar  *uri,
                                               gchar       **hostname,
                                               GError      **error) G_GNUC_MALLOC;
_GLIB_EXTERN gchar *g_filename_to_uri_utf8    (const gchar  *filename,
                                               const gchar  *hostname,
                                               GError      **error) G_GNUC_MALLOC;

gchar *
g_filename_to_utf8_utf8 (const gchar *opsysstring,
                         gssize       len,
                         gsize       *bytes_read,
                         gsize       *bytes_written,
                         GError     **error)
{
  return g_filename_to_utf8 (opsysstring, len, bytes_read, bytes_written, error);
}

gchar *
g_filename_from_utf8_utf8 (const gchar *utf8string,
                           gssize       len,
                           gsize       *bytes_read,
                           gsize       *bytes_written,
                           GError     **error)
{
  return g_filename_from_utf8 (utf8string, len, bytes_read, bytes_written, error);
}

gchar *
g_filename_from_uri_utf8 (const gchar *uri,
                          gchar      **hostname,
                          GError     **error)
{
  return g_filename_from_uri (uri, hostname, error);
}

gchar *
g_filename_to_uri_utf8 (const gchar *filename,
                        const gchar *hostname,
                        GError     **error)
{
  return g_filename_to_uri (filename, hostname, error);
}

#endif
