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GLib Reference Manual | |
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| Top | Description | ||||
Character Set ConversionCharacter Set Conversion — Convert strings between different character sets |
#include <glib.h> 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 * 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); GIConv; gchar * g_convert_with_iconv (const gchar *str,gssize len,GIConv converter,gsize *bytes_read,gsize *bytes_written,GError **error); #define G_CONVERT_ERROR GIConv g_iconv_open (const gchar *to_codeset,const gchar *from_codeset); gsize g_iconv (GIConv converter,gchar **inbuf,gsize *inbytes_left,gchar **outbuf,gsize *outbytes_left); gint g_iconv_close (GIConv converter); gchar * g_locale_to_utf8 (const gchar *opsysstring,gssize len,gsize *bytes_read,gsize *bytes_written,GError **error); gchar * g_filename_to_utf8 (const gchar *opsysstring,gssize len,gsize *bytes_read,gsize *bytes_written,GError **error); gchar * g_filename_from_utf8 (const gchar *utf8string,gssize len,gsize *bytes_read,gsize *bytes_written,GError **error); gboolean g_get_filename_charsets (G_CONST_RETURN gchar ***charsets); gchar * g_filename_display_name (const gchar *filename); gchar * g_filename_display_basename (const gchar *filename); gchar * g_locale_from_utf8 (const gchar *utf8string,gssize len,gsize *bytes_read,gsize *bytes_written,GError **error); enum GConvertError; gboolean g_get_charset (G_CONST_RETURN char **charset);
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.
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
"Presentación.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 ó 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 ó 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(3) 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 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 open(2) or fopen(3).
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
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.
Figure 2, “Conversion between File Name Encodings” illustrates how
these functions are used to convert between UTF-8 and the
encoding for file names in the file system.
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.
If you get a file name from the file system from a function
such as readdir(3) or gtk_file_chooser_get_filename(),
you do not need to do any conversion to pass that
file name to functions like open(2), rename(2), or
fopen(3) — those are "raw" file names which the file
system understands.
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.
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(3). 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.
gchar * g_convert (const gchar *str,gssize len,const gchar *to_codeset,const gchar *from_codeset,gsize *bytes_read,gsize *bytes_written,GError **error);
Converts a string from one character set to another.
Note that you should use g_iconv() for streaming
conversions[2].
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the string to convert |
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the length of the string, or -1 if the string is nul-terminated[1]. |
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name of character set into which to convert str
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character set of str. |
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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 the byte offset after the last valid
input sequence. |
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the number of bytes stored in the output buffer (not including the terminating nul). |
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location to store the error occuring, or NULL to ignore
errors. Any of the errors in GConvertError may occur. |
Returns : |
If the conversion was successful, a newly allocated
nul-terminated 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);
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[2].
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the string to convert |
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the length of the string, or -1 if the string is nul-terminated[1]. |
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name of character set into which to convert str
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character set of str. |
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UTF-8 string to use in place of character 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. |
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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. |
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the number of bytes stored in the output buffer (not including the terminating nul). |
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location to store the error occuring, or NULL to ignore
errors. Any of the errors in GConvertError may occur. |
Returns : |
If the conversion was successful, a newly allocated
nul-terminated 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);
Converts a string from one character set to another.
Note that you should use g_iconv() for streaming
conversions[2].
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the string to convert |
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the length of the string, or -1 if the string is nul-terminated[1]. |
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conversion descriptor from g_iconv_open()
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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 the byte offset after the last valid
input sequence. |
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the number of bytes stored in the output buffer (not including the terminating nul). |
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location to store the error occuring, or NULL to ignore
errors. Any of the errors in GConvertError may occur. |
Returns : |
If the conversion was successful, a newly allocated
nul-terminated string, which must be freed with
g_free(). Otherwise NULL and error will be set. |
#define G_CONVERT_ERROR g_convert_error_quark()
Error domain for character set conversions. Errors in this domain will be from the GConvertError enumeration. See GError for information on error domains.
GIConv g_iconv_open (const gchar *to_codeset,const gchar *from_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.
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destination codeset |
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source codeset |
Returns : |
a "conversion descriptor", or (GIConv)-1 if opening the converter failed. |
gsize g_iconv (GIConv converter,gchar **inbuf,gsize *inbytes_left,gchar **outbuf,gsize *outbytes_left);
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.
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conversion descriptor from g_iconv_open()
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bytes to convert |
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inout parameter, bytes remaining to convert in inbuf
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converted output bytes |
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inout parameter, bytes available to fill in outbuf
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Returns : |
count of non-reversible conversions, or -1 on error |
gint g_iconv_close (GIConv converter);
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.
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a conversion descriptor from g_iconv_open()
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Returns : |
-1 on error, 0 on success |
gchar * g_locale_to_utf8 (const gchar *opsysstring,gssize len,gsize *bytes_read,gsize *bytes_written,GError **error);
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 into a UTF-8 string.
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a string in the encoding of the current locale. On Windows this means the system codepage. |
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the length of the string, or -1 if the string is nul-terminated[1]. |
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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 the byte offset after the last valid
input sequence. |
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the number of bytes stored in the output buffer (not including the terminating nul). |
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location to store the error occuring, or NULL to ignore
errors. Any of the errors in GConvertError may occur. |
Returns : |
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);
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.
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a string in the encoding for filenames |
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the length of the string, or -1 if the string is nul-terminated[1]. |
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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 the byte offset after the last valid
input sequence. |
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the number of bytes stored in the output buffer (not including the terminating nul). |
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location to store the error occuring, or NULL to ignore
errors. Any of the errors in GConvertError may occur. |
Returns : |
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);
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.
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a UTF-8 encoded string. |
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the length of the string, or -1 if the string is nul-terminated. |
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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 the byte offset after the last valid
input sequence. |
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the number of bytes stored in the output buffer (not including the terminating nul). |
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location to store the error occuring, or NULL to ignore
errors. Any of the errors in GConvertError may occur. |
Returns : |
The converted string, or NULL on an error. |
gboolean g_get_filename_charsets (G_CONST_RETURN gchar ***charsets);
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. 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.
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return location for the NULL-terminated list of encoding names |
Returns : |
TRUE if the filename encoding is UTF-8. |
Since 2.6
gchar * g_filename_display_name (const gchar *filename);
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 can not 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.
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a pathname hopefully in the GLib file name encoding |
Returns : |
a newly allocated string containing a rendition of the filename in valid UTF-8 |
Since 2.6
gchar * g_filename_display_basename (const gchar *filename);
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 can not 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.
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an absolute pathname in the GLib file name encoding |
Returns : |
a newly allocated string containing a rendition of the basename of the filename in valid UTF-8 |
Since 2.6
gchar * g_locale_from_utf8 (const gchar *utf8string,gssize len,gsize *bytes_read,gsize *bytes_written,GError **error);
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. On Windows this means the system codepage.
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a UTF-8 encoded string |
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the length of the string, or -1 if the string is nul-terminated[1]. |
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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 the byte offset after the last valid
input sequence. |
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the number of bytes stored in the output buffer (not including the terminating nul). |
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location to store the error occuring, or NULL to ignore
errors. Any of the errors in GConvertError may occur. |
Returns : |
The converted string, or NULL on an error. |
typedef enum
{
G_CONVERT_ERROR_NO_CONVERSION,
G_CONVERT_ERROR_ILLEGAL_SEQUENCE,
G_CONVERT_ERROR_FAILED,
G_CONVERT_ERROR_PARTIAL_INPUT,
G_CONVERT_ERROR_BAD_URI,
G_CONVERT_ERROR_NOT_ABSOLUTE_PATH
} GConvertError;
Error codes returned by character set conversion routines.
| Conversion between the requested character sets is not supported. | |
| Invalid byte sequence in conversion input. | |
| Conversion failed for some reason. | |
| Partial character sequence at end of input. | |
| URI is invalid. | |
| Pathname is not an absolute path. |
gboolean g_get_charset (G_CONST_RETURN char **charset);
Obtains the character set for the current
locale; you might use this character set as an argument to
g_convert(), to convert from the current locale's encoding to some
other encoding. (Frequently g_locale_to_utf8() and g_locale_from_utf8()
are nice shortcuts, though.)
On Windows the character set returned by this function is the so-called system default ANSI code-page. That is the character set used by the "narrow" versions of C library and Win32 functions that handle file names. It might be different from the character set used by the C library's current locale.
The return value is TRUE if the locale's encoding is UTF-8, in that
case you can perhaps avoid calling g_convert().
The string returned in charset is not allocated, and should not be
freed.
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return location for character set name |
Returns : |
TRUE if the returned charset is UTF-8 |
[1]
Note that some encodings may allow nul bytes to
occur inside strings. In that case, using -1 for
the len parameter is unsafe.
[2]
Despite the fact that byes_read can return information about partial
characters, the g_convert_... functions
are not generally suitable for streaming. If the underlying converter
being used 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.)