<!-- ##### SECTION Title ##### -->
Character Set Conversion
<!-- ##### SECTION Short_Description ##### -->
convert strings between different character sets using <function>iconv()</function>.
<!-- ##### SECTION Long_Description ##### -->
<para>
</para>
<refsect2 id="file-name-encodings">
<title>File Name Encodings</title>
<para>
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
"<filename>Presentación.sxi</filename>". If the
application which created it uses ISO-8859-1 for its encoding,
then the actual file name on disk would look like this:
</para>
<programlisting id="filename-iso8859-1">
Character: P r e s e n t a c i ó n . s x i
Hex code: 50 72 65 73 65 6e 74 61 63 69 f3 6e 2e 73 78 69
</programlisting>
<para>
However, if the application use UTF-8, the actual file name on
disk would look like this:
</para>
<programlisting id="filename-utf-8">
Character: P r e s e n t a c i ó n . s x i
Hex code: 50 72 65 73 65 6e 74 61 63 69 c3 b3 6e 2e 73 78 69
</programlisting>
<para>
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
<function>readdir(3)</function> or from <link
linkend="g_dir_read_name"><function>g_dir_read_name()</function></link>,
and you wish to display the file name to the user, you
<emphasis>will</emphasis> need to convert it into UTF-8. The
opposite case is when the user types the name of a file he
wishes 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 <function>open(2)</function> or
<function>fopen(3)</function>.
</para>
<para>
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 <link
linkend="G_FILENAME_ENCODING"><envar>G_FILENAME_ENCODING</envar></link>
environment variable. For example, if your installation uses
ISO-8859-1 for file names, you can put this in your
<filename>~/.profile</filename>:
</para>
<programlisting>
export G_FILENAME_ENCODING=ISO-8859-1
</programlisting>
<para>
Glib provides the functions <link
linkend="g_filename_to_utf8"><function>g_filename_to_utf8()</function></link>
and <link
linkend="g_filename_from_utf8"><function>g_filename_from_utf8()</function></link>
to perform the necessary conversions. These functions convert
file names from the encoding specified in
<envar>G_FILENAME_ENCODING</envar> to UTF-8 and vice-versa.
<xref linkend="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.
</para>
<figure id="file-name-encodings-diagram">
<title>Conversion between File Name Encodings</title>
<graphic fileref="file-name-encodings.png" format="PNG"/>
</figure>
<refsect3 id="file-name-encodings-checklist">
<title>Checklist for Application Writers</title>
<para>
This section is a practical summary of the detailed
description above. You can use this as a checklist of
things to do to make sure your applications process file
name encodings correctly.
</para>
<orderedlist>
<listitem>
<para>
If you get a file name from the file system from a
function such as <function>readdir(3)</function> or
<function>gtk_file_chooser_get_filename()</function>,
you do not need to do any conversion to pass that
file name to functions like <function>open(2)</function>,
<function>rename(2)</function>, or
<function>fopen(3)</function> — those are "raw"
file names which the file system understands.
</para>
</listitem>
<listitem>
<para>
If you need to display a file name, convert it to UTF-8
first by using <link
linkend="g_filename_to_utf8"><function>g_filename_to_utf8()</function></link>.
If conversion fails, display a string like
"<literal>Unknown file name</literal>". <emphasis>Do
not</emphasis> 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 <envar>G_FILENAME_ENCODING</envar>
environment variable even though he has files whose
names are not encoded in UTF-8.
</para>
</listitem>
<listitem>
<para>
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 <link
linkend="g_filename_from_utf8"><function>g_filename_from_utf8()</function></link>.
Pass the converted file name to functions like
<function>fopen(3)</function>. If conversion fails, ask
the user to enter a different file name. This can
happen if the user types Japanese characters when
<envar>G_FILENAME_ENCODING</envar> is set to
<literal>ISO-8859-1</literal>, for example.
</para>
</listitem>
</orderedlist>
</refsect3>
</refsect2>
<!-- ##### SECTION See_Also ##### -->
<para>
</para>
<!-- ##### FUNCTION g_convert ##### -->
<para>
</para>
@str:
@len:
@to_codeset:
@from_codeset:
@bytes_read:
@bytes_written:
@error:
@Returns:
<!-- ##### FUNCTION g_convert_with_fallback ##### -->
<para>
</para>
@str:
@len:
@to_codeset:
@from_codeset:
@fallback:
@bytes_read:
@bytes_written:
@error:
@Returns:
<!-- ##### STRUCT GIConv ##### -->
<para>
The <structname>GIConv</structname> struct wraps an
<function>iconv()</function> conversion descriptor. It contains private data
and should only be accessed using the following functions.
</para>
<!-- ##### FUNCTION g_convert_with_iconv ##### -->
<para>
</para>
@str:
@len:
@converter:
@bytes_read:
@bytes_written:
@error:
@Returns:
<!-- ##### MACRO G_CONVERT_ERROR ##### -->
<para>
Error domain for character set conversions. Errors in this domain will
be from the #GConvertError enumeration. See #GError for information on
error domains.
</para>
<!-- ##### FUNCTION g_iconv_open ##### -->
<para>
</para>
@to_codeset:
@from_codeset:
@Returns:
<!-- ##### FUNCTION g_iconv ##### -->
<para>
</para>
@converter:
@inbuf:
@inbytes_left:
@outbuf:
@outbytes_left:
@Returns:
<!-- ##### FUNCTION g_iconv_close ##### -->
<para>
</para>
@converter:
@Returns:
<!-- ##### FUNCTION g_locale_to_utf8 ##### -->
<para>
</para>
@opsysstring:
@len:
@bytes_read:
@bytes_written:
@error:
@Returns:
<!-- ##### FUNCTION g_filename_to_utf8 ##### -->
<para>
</para>
@opsysstring:
@len:
@bytes_read:
@bytes_written:
@error:
@Returns:
<!-- ##### FUNCTION g_filename_from_utf8 ##### -->
<para>
</para>
@utf8string:
@len:
@bytes_read:
@bytes_written:
@error:
@Returns:
<!-- ##### FUNCTION g_filename_from_uri ##### -->
<para>
</para>
@uri:
@hostname:
@error:
@Returns:
<!-- ##### FUNCTION g_filename_to_uri ##### -->
<para>
</para>
@filename:
@hostname:
@error:
@Returns:
<!-- ##### FUNCTION g_locale_from_utf8 ##### -->
<para>
</para>
@utf8string:
@len:
@bytes_read:
@bytes_written:
@error:
@Returns:
<!-- ##### ENUM GConvertError ##### -->
<para>
Error codes returned by character set conversion routines.
</para>
@G_CONVERT_ERROR_NO_CONVERSION: Conversion between the requested character sets
is not supported.
@G_CONVERT_ERROR_ILLEGAL_SEQUENCE: Invalid byte sequence in conversion input.
@G_CONVERT_ERROR_FAILED: Conversion failed for some reason.
@G_CONVERT_ERROR_PARTIAL_INPUT: Partial character sequence at end of input.
@G_CONVERT_ERROR_BAD_URI: URI is invalid.
@G_CONVERT_ERROR_NOT_ABSOLUTE_PATH: Pathname is not an absolute path.
<!-- ##### FUNCTION g_get_charset ##### -->
<para>
</para>
@charset:
@Returns:
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