5 UTF-8 Conversion Functions
8 1. Strings in the LDAP C SDK should be encoded in UTF-8 format.
9 However, most platforms do not provide APIs for converting to
10 this format. If they do, they are platform-specific.
12 As a result, most applications (knowingly or not) use local strings
13 with LDAP functions. This works fine for 7-bit ASCII characters,
14 but will fail with 8-bit European characters, Asian characters, etc.
16 We propose adding the following platform-independent conversion functions
17 to the OpenLDAP SDK. There are 4 functions for converting between UTF-8
18 and wide characters, and 4 functions for converting between UTF-8 and
21 For multibyte to UTF-8 conversions, charset translation is necessary.
22 While a full charset translator is not practical or appropriate for the
23 LDAP SDK, we can pass the translator function in as an argument.
24 A NULL for this argument will use the ANSI C functions mbtowc, mbstowcs,
27 2. UTF-8 <--> Wide Character conversions
29 The following new conversion routines will be added, following the pattern of
30 the ANSI C conversion routines (mbtowc, mbstowcs, etc). These routines use
31 the wchar_t type. wchar_t is 2 bytes on some systems and 4 bytes on others.
32 However the advantage of using wchar_t is that all the standard wide character
33 string functions may be used on these strings: wcslen, wcscpy, etc.
35 int ldap_x_utf8_to_wc - Convert a single UTF-8 encoded character to a wide character.
36 int ldap_x_utf8s_to_wcs - Convert a UTF-8 string to a wide character string.
37 int ldap_x_wc_to_utf8 - Convert a single wide character to a UTF-8 sequence.
38 int ldap_x_wcs_to_utf8s - Convert a wide character string to a UTF-8 string.
41 2.1 ldap_x_utf8_to_wc - Convert a single UTF-8 encoded character to a wide character.
43 int ldap_x_utf8_to_wc ( wchar_t *wchar, const char *utf8char )
45 wchar (OUT) Points to a wide character code to receive the
48 utf8char (IN) Address of the UTF8 sequence of bytes.
51 If successful, the function returns the length in
52 bytes of the UTF-8 input character.
54 If utf8char is NULL or points to an empty string, the
55 function returns 1 and a NULL is written to wchar.
57 If utf8char contains an invalid UTF-8 sequence -1 is returned.
60 2.2 ldap_x_utf8s_to_wcs - Convert a UTF-8 string to a wide character string.
62 int ldap_x_utf8s_to_wcs (wchar_t *wcstr, const char *utf8str, size_t count)
64 wcstr (OUT) Points to a wide char buffer to receive the
65 converted wide char string. The output string will be
66 null terminated if there is space for it in the
69 utf8str (IN) Address of the null-terminated UTF-8 string to convert.
71 count (IN) The number of UTF-8 characters to convert, or
72 equivalently, the size of the output buffer in wide
76 If successful, the function returns the number of wide
77 characters written to wcstr, excluding the null termination
80 If wcstr is NULL, the function returns the number of wide
81 characters required to contain the converted string,
82 excluding the null termination character.
84 If an invalid UTF-8 sequence is encountered, the
87 If the return value equals count, there was not enough space to fit the
88 string and the null terminator in the buffer.
91 2.3 ldap_x_wc_to_utf8 - Convert a single wide character to a UTF-8 sequence.
93 int ldap_x_wc_to_utf8 ( char *utf8char, wchar_t wchar, count )
95 utf8char (OUT) Points to a byte array to receive the converted UTF-8
98 wchar (IN) The wide character to convert.
100 count (IN) The maximum number of bytes to write to the output
101 buffer. Normally set this to LDAP_MAX_UTF8_LEN, which
102 is defined as 3 or 6 depending on the size of wchar_t.
103 A partial character will not be written.
106 If successful, the function returns the length in bytes of
107 the converted UTF-8 output character.
109 If wchar is NULL, the function returns 1 and a NULL is
112 If wchar cannot be converted to a UTF-8 character, the
116 2.4 int ldap_x_wcs_to_utf8s - Convert a wide character string to a UTF-8 string.
118 int ldap_x_wcs_to_utf8s (char *utf8str, const wchar_t *wcstr, size_t count)
120 utf8str (OUT) Points to a byte array to receive the converted
121 UTF-8 string. The output string will be null
122 terminated if there is space for it in the
126 wcstr (IN) Address of the null-terminated wide char string to convert.
128 count (IN) The size of the output buffer in bytes.
131 If successful, the function returns the number of bytes
132 written to utf8str, excluding the null termination
135 If utf8str is NULL, the function returns the number of
136 bytes required to contain the converted string, excluding
137 the null termination character. The 'count' parameter is ignored.
139 If the function encounters a wide character that cannot
140 be mapped to a UTF-8 sequence, the function returns -1.
142 If the return value equals count, there was not enough space to fit
143 the string and the null terminator in the buffer.
147 3. Multi-byte <--> UTF-8 Conversions
149 These functions convert the string in a two-step process, from multibyte
150 to Wide, then from Wide to UTF8, or vice versa. This conversion requires a
151 charset translation routine, which is passed in as an argument.
153 ldap_x_mb_to_utf8 - Convert a multi-byte character to a UTF-8 character.
154 ldap_x_mbs_to_utf8s - Convert a multi-byte string to a UTF-8 string.
155 ldap_x_utf8_to_mb - Convert a UTF-8 character to a multi-byte character.
156 ldap_x_utf8s_to_mbs - Convert a UTF-8 string to a multi-byte string.
158 3.1 ldap_x_mb_to_utf8 - Convert a multi-byte character to a UTF-8 character.
160 int ldap_x_mb_to_utf8 ( char *utf8char, const char *mbchar, size_t mbsize, int (*f_mbtowc)(wchar_t *wchar, const char *mbchar, size_t count) )
162 utf8char (OUT) Points to a byte buffer to receive the converted
163 UTF-8 character. May be NULL. The output is not
166 mbchar (IN) Address of a sequence of bytes forming a multibyte character.
168 mbsize (IN) The maximum number of bytes of the mbchar argument to
169 check. This should normally be MB_CUR_MAX.
171 f_mbtowc (IN) The function to use for converting a multibyte
172 character to a wide character. If NULL, the local
173 ANSI C routine mbtowc is used.
176 If successful, the function returns the length in bytes of
177 the UTF-8 output character.
179 If utf8char is NULL, count is ignored and the funtion
180 returns the number of bytes that would be written to the
183 If count is zero, 0 is returned and nothing is written to
186 If mbchar is NULL or points to an empty string, the
187 function returns 1 and a null byte is written to utf8char.
189 If mbchar contains an invalid multi-byte character, -1 is returned.
192 3.2 ldap_x_mbs_to_utf8s - Convert a multi-byte string to a UTF-8 string.
194 int ldap_x_mbs_to_utf8s (char *utf8str, const char *mbstr, size_t count,
195 size_t (*f_mbstowcs)(wchar_t *wcstr, const char *mbstr, size_t count))
197 utf8str (OUT) Points to a buffer to receive the converted UTF-8 string.
200 mbchar (IN) Address of the null-terminated multi-byte input string.
202 count (IN) The size of the output buffer in bytes.
204 f_mbstowcs (IN) The function to use for converting a multibyte string
205 to a wide character string. If NULL, the local ANSI
206 C routine mbstowcs is used.
209 If successful, the function returns the length in
210 bytes of the UTF-8 output string, excluding the null
211 terminator, if present.
213 If utf8str is NULL, count is ignored and the function
214 returns the number of bytes required for the output string,
217 If count is zero, 0 is returned and nothing is written to utf8str.
219 If mbstr is NULL or points to an empty string, the
220 function returns 1 and a null byte is written to utf8str.
222 If mbstr contains an invalid multi-byte character, -1 is returned.
224 If the returned value is equal to count, the entire null-terminated
225 string would not fit in the output buffer.
228 3.3 ldap_x_utf8_to_mb - Convert a UTF-8 character to a multi-byte character.
230 int ldap_x_utf8_to_mb ( char *mbchar, const char *utf8char,
231 int (*f_wctomb)(char *mbchar, wchar_t wchar) )
233 mbchar (OUT) Points to a byte buffer to receive the converted multi-byte
234 character. May be NULL.
236 utf8char (IN) Address of the UTF-8 character sequence.
238 f_wctomb (IN) The function to use for converting a wide character
239 to a multibyte character. If NULL, the local
240 ANSI C routine wctomb is used.
244 If successful, the function returns the length in
245 bytes of the multi-byte output character.
247 If utf8char is NULL or points to an empty string, the
248 function returns 1 and a null byte is written to mbchar.
250 If utf8char contains an invalid UTF-8 sequence, -1 is returned.
253 3.4 int ldap_x_utf8s_to_mbs - Convert a UTF-8 string to a multi-byte string.
256 int ldap_x_utf8s_to_mbs ( char *mbstr, const char *utf8str, size_t count,
257 size_t (*f_wcstombs)(char *mbstr, const wchar_t *wcstr, size_t count) )
259 mbstr (OUT) Points to a byte buffer to receive the converted
260 multi-byte string. May be NULL.
262 utf8str (IN) Address of the null-terminated UTF-8 string to convert.
264 count (IN) The size of the output buffer in bytes.
266 f_wcstombs (IN) The function to use for converting a wide character
267 string to a multibyte string. If NULL, the local
268 ANSI C routine wcstombs is used.
271 If successful, the function returns the number of bytes
272 written to mbstr, excluding the null termination
275 If mbstr is NULL, count is ignored and the funtion
276 returns the number of bytes required for the output string,
279 If count is zero, 0 is returned and nothing is written to
282 If utf8str is NULL or points to an empty string, the
283 function returns 1 and a null byte is written to mbstr.
285 If an invalid UTF-8 character is encountered, the
288 The output string will be null terminated if there is space for it in