Provided by: libunac1-dev_1.8.0-10_amd64 
NAME
unac - remove accents from string or character
SYNOPSIS
#include <unac.h>
const char* unac_version();
int unac_string(const char* charset,
const char* in, int in_length,
char** out, int* out_length);
int unac_string_utf16(const char* in, int in_length,
char** out, int* out_length);
/* MACRO: side effect on unaccented and length arguments */
unac_char_utf16(unsigned short c,
unsigned short* unaccented,
int length);
const char* unac_version()
/*
* The level argument can be one of:
* UNAC_DEBUG_NONE UNAC_DEBUG_LOW UNAC_DEBUG_HIGH
*/
void unac_debug(int level)
typedef void (*unac_debug_print_t)(const char* message, void* data);
void unac_debug_callback(int level, unac_debug_print_t function, void* data)
DESCRIPTION
unac is a C library that removes accents from characters, regardless of the character set
(ISO-8859-15, ISO-CELTIC, KOI8-RU...) as long as iconv(3) is able to convert it into
UTF-16 (Unicode).
The unac_string function is given a charset (ISO-8859-15 for instance) and a string. It
converts the string into UTF-16 and calls the unac_string_utf16 function to remove all
accents from the UTF-16 version. The unaccented string is then converted into the original
charset (ISO-8859-15 for instance) and returned to the caller of unac_string.
unac does a little more than removing accents: every character that is made of two
character such as æ (ISO-8859-15 octal code 346) will be expanded in two characters a and
e. Should a character be made of three characters, it would be decomposed in the same
way.
The conversion from and to UTF-16 is done with iconv(3). The iconv -l command will list
all available charsets. Using UTF-16 as a pivot implies an overhead but ensures that
accents can be removed from all character for which there is an equivalent character in
Unicode.
unac_char_utf16 is a CPP macro that returns a pointer to the unaccented equivalent of a
given UTF-16 character. It is the basic building block of unac.
unac_string_utf16 repeatidly applies the unac_char_utf16 macro to each character of an
UTF-16 string.
FUNCTIONS
int unac_string(const char* charset, const char* in, size_t in_length, char** out, size_t*
out_length)
Returns the unaccented equivalent of the string 'in' of length 'in_length' bytes.
The returned string is stored in the pointer pointed by the 'out' argument and the
length of the 'out' string, in bytes, is stored in the integer pointed by the
'out_length ' argument. If the '*out' pointer is not null, it must point to an
area allocated by malloc(3) and the length of the array must be specified in the
'*out_length' argument. Both arguments '*out' and '*out_length' will be replaced
with the return values when the function returns on success. The '*out' pointer may
point to a memory location that has been reallocated (using realloc(3)) by the
unac_string function. There is no guarantee that '*out' is identical to the value
given by the caller. The pointer provided as '*out' by the caller may not be
useable when the function returns (either error or success). If the '*out' pointer
is null, the unac_string function allocates a new memory block using malloc(3). It
is the responsibility of the caller to deallocate the area returned in the '*out'
pointer.
The return value of unac_string is 0 on success and -1 on error, in which case the
errno variable is set to the corresponding error code. See the ERROR section below
for more information. The iconv(3) manual page may also help.
int unac_string_utf16(const char* in, int in_length, char** out, int* out_length)
Has the same effect as unac_string("UTF-16", in, in_length, out, out_length).
Since the unac_string_utf16 is the backend function of the unac_string function it
is more efficient because no charset conversion of the input string (from and to
UTF-16) is necessary.
unac_char_utf16(const unsigned short c, unsigned short* p, int l)
Warning: this is a macro, each argument may be evaluated more than once. Returns
the unaccented equivalent of the UTF-16 character 'c' in the pointer 'p'. The
length of the unsigned short array pointed by 'p' is returned in the 'l' argument.
const char* unac_version()
Return the version number of unac.
void unac_debug(int level)
Set the debug level of the unac library to 'level'. Possible values are:
UNAC_DEBUG_NONE for no debug at all, UNAC_DEBUG_LOW for terse human readable
information, UNAC_DEBUG_HIGH for very detailed information only usable when
translating a few strings.
unac_debug_callback with anything but UNAC_DEBUG_NONE is not thread safe.
void unac_debug_callback(int level, unac_debug_print_t function, void* data)
Set the debug level and define a printing function callback. The 'level' is the
same as in unac_debug. The 'function' is in charge of dealing with the debug
messages, presumably to print them to the user. The 'data' is an opaque pointer
that is passed along to function, should it need to manage a persistent context.
The prototype of 'function' accepts two arguments. The first is the debug message
(const char*), the second is the opaque pointer given as 'data' argument to
unac_debug_callback.
If 'function' is NULL, messages are printed on the standard error output using
fprintf(stderr...).
unac_debug_callback with anything but UNAC_DEBUG_NONE is not thread safe.
ERRORS
EINVAL
the requested conversion pair is not available. For instance, when specifying the
ISO-0000 charset (imaginary), it means it is not possible to convert from ISO-0000
to UTF-16.
EXAMPLES
Convert the été string into ete.
#include <unac.h>
char* out = 0;
int out_length = 0;
if(unac_string("ISO-8859-1", "été", strlen("été"), &out, &out_length)) {
perror("unac_string");
} else {
printf("%.*s0, out_length, out);
free(out);
}
IMPLEMENTATION NOTES
The endianness of the UTF-16 strings manipulated by unac must always be big endian. When
using iconv(3) to translate strings, UTF-16BE should be used instead of UTF-16 to make
sure it is big endian (BE). On some systems where UTF-16BE is not available, unac will
rely on UTF-16 and hope it is properly big endian encoded. For more information check
RFC2781 (http://www.faqs.org/rfcs/rfc2781.html: UTF-16, an encoding of ISO 10646).
The unac library uses the Unicode database to map accented letters to their unaccented
equivalent. Mapping tables are generated from the UnicodeData-4.0.0.txt file (as found at
http://www.unicode.org/Public/4.0-Update/) by the builder perl script. The builder script
inserts these tables in the unac.h and unac.c files, replacing the existing ones. Looking
for the 'Generated by builder' string in the unac.[ch] files allows it to spot the various
parts handled by the builder script.
Some desirable decompositions may not be included in the UnicodeData file, such as AE. To
complement the standard decompositions for the purpose of the unac library, the unaccent-
local-map.perl script is used. It maps character names (such as LATIN SMALL LETTER AE) to
an array of character names into which it will be decomposed. This script is used by the
builder script and has precedence over decomposition rules defined in the Unicode data
file.
The library data occupies 30KB where a simple minded table would occupy around 512Kbytes.
The idea used to compress the tables is that many Unicode characters do not have
unaccented equivalent. Instead of relying on a table mapping each Unicode character to
the corresponding unaccented character, an intermediate array of pointers is created. In
the drawing below, the range of UTF-16 character is not accurate but illustrates the
method. The unac_data_table points to a set of unac_dataXX arrays. Each pointer covers a
range of UTF-16 characters (4 in the example below). When a range of character does not
contain any accented character, unac_data_table always points to the same array :
unac_data0. Since there are many characters without accents, this is enough to achieve a
good compression.
unac_data15 unac_data16
[ NULL, NULL, NULL, e ] <---- /------> [ a, NULL, NULL, NULL ]
| |
| |
^ ^
|-----| |-----| |-----| |-----| |-----| |-----|
[ ... a b c d e f g h i j k é à 0 1 2 3 4 5 6 7 8 9 A... ] unac_data_table
|-----| |-----| |-----| |-----| |-----| |-----|
v v v v
| | | |
| | | |
--------------------------------------/
|
V
[ NULL, NULL, NULL, NULL ]
unac_data0
Beside this simple optimization, a table (unac_positions) listing the actual position of
the unaccented replacement within a block (unac_dataXX) is necessary because they are not
of fixed length. Some characters such as æ will be replaced by two characters a and e
therefore unac_dataXX has a variable size.
The unaccented equivalent of an UTF-16 character is calculated by applying a compatibility
decomposition and then stripping all characters that belong to the mark category. For a
precise definition see the Unicode-4.0 normalization forms at
http://www.unicode.org/unicode/reports/tr15/.
All original Unicode data files were taken from http://www.unicode.org/Public and are
subject to the UCD Terms of Use.
http://www.unicode.org/Public/4.0-Update/UCD-4.0.0.html#UCD_Terms
Disclaimer
The Unicode Character Database is provided as is by Unicode, Inc. No claims are made as to
fitness for any particular purpose. No warranties of any kind are expressed or implied.
The recipient agrees to determine applicability of information provided. If this file has
been purchased on magnetic or optical media from Unicode, Inc., the sole remedy for any
claim will be exchange of defective media within 90 days of receipt.
This disclaimer is applicable for all other data files accompanying the Unicode Character
Database, some of which have been compiled by the Unicode Consortium, and some of which
have been supplied by other sources.
Limitations on Rights to Redistribute This Data
Recipient is granted the right to make copies in any form for internal distribution and to
freely use the information supplied in the creation of products supporting the UnicodeTM
Standard. The files in the Unicode Character Database can be redistributed to third
parties or other organizations (whether for profit or not) as long as this notice and the
disclaimer notice are retained. Information can be extracted from these files and used in
documentation or programs, as long as there is an accompanying notice indicating the
source.
The file Unihan.txt contains older and inconsistent Terms of Use. That language is
overridden by these terms.
BUGS
The input string must not contain partially formed characters, there is no support for
this case.
UTF-16 surrogates are not handled.
Unicode may contain bugs in the decomposition of characters. When you suspect such a bug
on a given string, add a test case with the faulty string in the t_unac.in test script
(you will find it in the source distribution) and run make check. It will describe, in a
very verbose way, how the string was unaccented. You may then fix the
UnicodeData-4.0.0.txt file and run make check again to make sure the problem is solved.
Please send such fixes to the author and to the Unicode consortium.
SEE ALSO
unaccent(1), iconv(3)
http://www.unicode.org/
http://oss.software.ibm.com/icu/
http://www.gnu.org/manual/glibc-2.2.5/libc.html
AUTHOR
Loic Dachary loic@senga.org
http://www.senga.org/unac/
local unac(3)