Dec 5, 2000 Dave Steck Novell, Inc. UTF-8 Conversion Functions 1. Strings in the LDAP C SDK should be encoded in UTF-8 format. However, most platforms do not provide APIs for converting to this format. If they do, they are platform-specific. As a result, most applications (knowingly or not) use local strings with LDAP functions. This works fine for 7-bit ASCII characters, but will fail with 8-bit European characters, Asian characters, etc. We propose adding the following platform-independent conversion functions to the OpenLDAP SDK. There are 4 functions for converting between UTF-8 and wide characters, and 4 functions for converting between UTF-8 and multibyte characters. For multibyte to UTF-8 conversions, charset translation is necessary. While a full charset translator is not practical or appropriate for the LDAP SDK, we can pass the translator function in as an argument. A NULL for this argument will use the ANSI C functions mbtowc, mbstowcs, wctomb, and wcstombs. 2. UTF-8 <--> Wide Character conversions The following new conversion routines will be added, following the pattern of the ANSI C conversion routines (mbtowc, mbstowcs, etc). These routines use the wchar_t type. wchar_t is 2 bytes on some systems and 4 bytes on others. However the advantage of using wchar_t is that all the standard wide character string functions may be used on these strings: wcslen, wcscpy, etc. int ldap_x_utf8_to_wc - Convert a single UTF-8 encoded character to a wide character. int ldap_x_utf8s_to_wcs - Convert a UTF-8 string to a wide character string. int ldap_x_wc_to_utf8 - Convert a single wide character to a UTF-8 sequence. int ldap_x_wcs_to_utf8s - Convert a wide character string to a UTF-8 string. 2.1 ldap_x_utf8_to_wc - Convert a single UTF-8 encoded character to a wide character. int ldap_x_utf8_to_wc ( wchar_t *wchar, const char *utf8char ) wchar (OUT) Points to a wide character code to receive the converted character. utf8char (IN) Address of the UTF8 sequence of bytes. Return Value: If successful, the function returns the length in bytes of the UTF-8 input character. If utf8char is NULL or points to an empty string, the function returns 1 and a NULL is written to wchar. If utf8char contains an invalid UTF-8 sequence -1 is returned. 2.2 ldap_x_utf8s_to_wcs - Convert a UTF-8 string to a wide character string. int ldap_x_utf8s_to_wcs (wchar_t *wcstr, const char *utf8str, size_t count) wcstr (OUT) Points to a wide char buffer to receive the converted wide char string. The output string will be null terminated if there is space for it in the buffer. utf8str (IN) Address of the null-terminated UTF-8 string to convert. count (IN) The number of UTF-8 characters to convert, or equivalently, the size of the output buffer in wide characters. Return Value: If successful, the function returns the number of wide characters written to wcstr, excluding the null termination character, if any. If wcstr is NULL, the function returns the number of wide characters required to contain the converted string, excluding the null termination character. If an invalid UTF-8 sequence is encountered, the function returns -1. If the return value equals count, there was not enough space to fit the string and the null terminator in the buffer. 2.3 ldap_x_wc_to_utf8 - Convert a single wide character to a UTF-8 sequence. int ldap_x_wc_to_utf8 ( char *utf8char, wchar_t wchar, count ) utf8char (OUT) Points to a byte array to receive the converted UTF-8 string. wchar (IN) The wide character to convert. count (IN) The maximum number of bytes to write to the output buffer. Normally set this to LDAP_MAX_UTF8_LEN, which is defined as 3 or 6 depending on the size of wchar_t. A partial character will not be written. Return Value: If successful, the function returns the length in bytes of the converted UTF-8 output character. If wchar is NULL, the function returns 1 and a NULL is written to utf8char. If wchar cannot be converted to a UTF-8 character, the function returns -1. 2.4 int ldap_x_wcs_to_utf8s - Convert a wide character string to a UTF-8 string. int ldap_x_wcs_to_utf8s (char *utf8str, const wchar_t *wcstr, size_t count) utf8str (OUT) Points to a byte array to receive the converted UTF-8 string. The output string will be null terminated if there is space for it in the buffer. wcstr (IN) Address of the null-terminated wide char string to convert. count (IN) The size of the output buffer in bytes. Return Value: If successful, the function returns the number of bytes written to utf8str, excluding the null termination character, if any. If utf8str is NULL, the function returns the number of bytes required to contain the converted string, excluding the null termination character. The 'count' parameter is ignored. If the function encounters a wide character that cannot be mapped to a UTF-8 sequence, the function returns -1. If the return value equals count, there was not enough space to fit the string and the null terminator in the buffer. 3. Multi-byte <--> UTF-8 Conversions These functions convert the string in a two-step process, from multibyte to Wide, then from Wide to UTF8, or vice versa. This conversion requires a charset translation routine, which is passed in as an argument. ldap_x_mb_to_utf8 - Convert a multi-byte character to a UTF-8 character. ldap_x_mbs_to_utf8s - Convert a multi-byte string to a UTF-8 string. ldap_x_utf8_to_mb - Convert a UTF-8 character to a multi-byte character. ldap_x_utf8s_to_mbs - Convert a UTF-8 string to a multi-byte string. 3.1 ldap_x_mb_to_utf8 - Convert a multi-byte character to a UTF-8 character. 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) ) utf8char (OUT) Points to a byte buffer to receive the converted UTF-8 character. May be NULL. The output is not null-terminated. mbchar (IN) Address of a sequence of bytes forming a multibyte character. mbsize (IN) The maximum number of bytes of the mbchar argument to check. This should normally be MB_CUR_MAX. f_mbtowc (IN) The function to use for converting a multibyte character to a wide character. If NULL, the local ANSI C routine mbtowc is used. Return Value: If successful, the function returns the length in bytes of the UTF-8 output character. If utf8char is NULL, count is ignored and the funtion returns the number of bytes that would be written to the output char. If count is zero, 0 is returned and nothing is written to utf8char. If mbchar is NULL or points to an empty string, the function returns 1 and a null byte is written to utf8char. If mbchar contains an invalid multi-byte character, -1 is returned. 3.2 ldap_x_mbs_to_utf8s - Convert a multi-byte string to a UTF-8 string. int ldap_x_mbs_to_utf8s (char *utf8str, const char *mbstr, size_t count, size_t (*f_mbstowcs)(wchar_t *wcstr, const char *mbstr, size_t count)) utf8str (OUT) Points to a buffer to receive the converted UTF-8 string. May be NULL. mbchar (IN) Address of the null-terminated multi-byte input string. count (IN) The size of the output buffer in bytes. f_mbstowcs (IN) The function to use for converting a multibyte string to a wide character string. If NULL, the local ANSI C routine mbstowcs is used. Return Value: If successful, the function returns the length in bytes of the UTF-8 output string, excluding the null terminator, if present. If utf8str is NULL, count is ignored and the function returns the number of bytes required for the output string, excluding the NULL. If count is zero, 0 is returned and nothing is written to utf8str. If mbstr is NULL or points to an empty string, the function returns 1 and a null byte is written to utf8str. If mbstr contains an invalid multi-byte character, -1 is returned. If the returned value is equal to count, the entire null-terminated string would not fit in the output buffer. 3.3 ldap_x_utf8_to_mb - Convert a UTF-8 character to a multi-byte character. int ldap_x_utf8_to_mb ( char *mbchar, const char *utf8char, int (*f_wctomb)(char *mbchar, wchar_t wchar) ) mbchar (OUT) Points to a byte buffer to receive the converted multi-byte character. May be NULL. utf8char (IN) Address of the UTF-8 character sequence. f_wctomb (IN) The function to use for converting a wide character to a multibyte character. If NULL, the local ANSI C routine wctomb is used. Return Value: If successful, the function returns the length in bytes of the multi-byte output character. If utf8char is NULL or points to an empty string, the function returns 1 and a null byte is written to mbchar. If utf8char contains an invalid UTF-8 sequence, -1 is returned. 3.4 int ldap_x_utf8s_to_mbs - Convert a UTF-8 string to a multi-byte string. int ldap_x_utf8s_to_mbs ( char *mbstr, const char *utf8str, size_t count, size_t (*f_wcstombs)(char *mbstr, const wchar_t *wcstr, size_t count) ) mbstr (OUT) Points to a byte buffer to receive the converted multi-byte string. May be NULL. utf8str (IN) Address of the null-terminated UTF-8 string to convert. count (IN) The size of the output buffer in bytes. f_wcstombs (IN) The function to use for converting a wide character string to a multibyte string. If NULL, the local ANSI C routine wcstombs is used. Return Value: If successful, the function returns the number of bytes written to mbstr, excluding the null termination character, if any. If mbstr is NULL, count is ignored and the funtion returns the number of bytes required for the output string, excluding the NULL. If count is zero, 0 is returned and nothing is written to mbstr. If utf8str is NULL or points to an empty string, the function returns 1 and a null byte is written to mbstr. If an invalid UTF-8 character is encountered, the function returns -1. The output string will be null terminated if there is space for it in the output buffer.