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7 TLD Functions

Organizations that manage some Top Level Domains (TLDs) have published tables with characters they accept within the domain. The reason may be to reduce complexity that come from using the full Unicode range, and to protect themselves from future (backwards incompatible) changes in the IDN or Unicode specifications. Libidn implement an infrastructure for defining and checking strings against such tables. Libidn also ship some tables from TLDs that we have managed to get permission to use them from. Because these tables are even less static than Unicode or StringPrep tables, it is likely that they will be updated from time to time (even in backwards incompatible ways). The Libidn interface provide a “version” field for each TLD table, which can be compared for equality to guarantee the same operation over time.

From a design point of view, you can regard the TLD tables for IDN as the “localization” step that come after the “internationalization” step provided by the IETF standards.

The TLD functionality rely on up-to-date tables. The latest version of Libidn aim to provide these, but tables with unclear copying conditions, or generally experimental tables, are not included. Some such tables can be found at https://github.com/gnuthor/tldchk.

7.1 Header file tld.h

To use the functions explained in this chapter, you need to include the file tld.h using: 

#include <tld.h>

7.2 Core Functions

tld_check_4t

Function: int tld_check_4t (const uint32_t * in, size_t inlen, size_t * errpos, const Tld_table * tld)

in: Array of unicode code points to process. Does not need to be zero terminated.

inlen: Number of unicode code points.

errpos: Position of offending character is returned here.

tld: A Tld_table data structure representing the restrictions for which the input should be tested.

Test each of the code points in in for whether or not they are allowed by the data structure in tld , return the position of the first character for which this is not the case in errpos .

Return value: Returns the Tld_rc value TLD_SUCCESS if all code points are valid or when tld is null, TLD_INVALID if a character is not allowed, or additional error codes on general failure conditions.

tld_check_4tz

Function: int tld_check_4tz (const uint32_t * in, size_t * errpos, const Tld_table * tld)

in: Zero terminated array of unicode code points to process.

errpos: Position of offending character is returned here.

tld: A Tld_table data structure representing the restrictions for which the input should be tested.

Test each of the code points in in for whether or not they are allowed by the data structure in tld , return the position of the first character for which this is not the case in errpos .

Return value: Returns the Tld_rc value TLD_SUCCESS if all code points are valid or when tld is null, TLD_INVALID if a character is not allowed, or additional error codes on general failure conditions.

7.3 Utility Functions

tld_get_4

Function: int tld_get_4 (const uint32_t * in, size_t inlen, char ** out)

in: Array of unicode code points to process. Does not need to be zero terminated.

inlen: Number of unicode code points.

out: Zero terminated ascii result string pointer.

Isolate the top-level domain of in and return it as an ASCII string in out .

Return value: Return TLD_SUCCESS on success, or the corresponding Tld_rc error code otherwise.

tld_get_4z

Function: int tld_get_4z (const uint32_t * in, char ** out)

in: Zero terminated array of unicode code points to process.

out: Zero terminated ascii result string pointer.

Isolate the top-level domain of in and return it as an ASCII string in out .

Return value: Return TLD_SUCCESS on success, or the corresponding Tld_rc error code otherwise.

tld_get_z

Function: int tld_get_z (const char * in, char ** out)

in: Zero terminated character array to process.

out: Zero terminated ascii result string pointer.

Isolate the top-level domain of in and return it as an ASCII string in out . The input string in may be UTF-8, ISO-8859-1 or any ASCII compatible character encoding.

Return value: Return TLD_SUCCESS on success, or the corresponding Tld_rc error code otherwise.

tld_get_table

Function: const Tld_table * tld_get_table (const char * tld, const Tld_table ** tables)

tld: TLD name (e.g. "com") as zero terminated ASCII byte string.

tables: Zero terminated array of Tld_table info-structures for TLDs.

Get the TLD table for a named TLD by searching through the given TLD table array.

Return value: Return structure corresponding to TLD tld by going thru tables , or return NULL if no such structure is found. Get the TLD table for a named TLD by searching through the given TLD table array.

Return value: Return structure corresponding to TLD tld by going thru tables , or return NULL if no such structure is found.

tld_default_table

Function: const Tld_table * tld_default_table (const char * tld, const Tld_table ** overrides)

tld: TLD name (e.g. "com") as zero terminated ASCII byte string.

overrides: Additional zero terminated array of Tld_table info-structures for TLDs, or NULL to only use library default tables.

Get the TLD table for a named TLD, using the internal defaults, possibly overridden by the (optional) supplied tables.

Return value: Return structure corresponding to TLD tld_str , first looking through overrides then thru built-in list, or NULL if no such structure found.

7.4 High-Level Wrapper Functions

tld_check_4

Function: int tld_check_4 (const uint32_t * in, size_t inlen, size_t * errpos, const Tld_table ** overrides)

in: Array of unicode code points to process. Does not need to be zero terminated.

inlen: Number of unicode code points.

errpos: Position of offending character is returned here.

overrides: A Tld_table array of additional domain restriction structures that complement and supersede the built-in information.

Test each of the code points in in for whether or not they are allowed by the information in overrides or by the built-in TLD restriction data. When data for the same TLD is available both internally and in overrides , the information in overrides takes precedence. If several entries for a specific TLD are found, the first one is used. If overrides is NULL , only the built-in information is used. The position of the first offending character is returned in errpos .

Return value: Returns the Tld_rc value TLD_SUCCESS if all code points are valid or when tld is null, TLD_INVALID if a character is not allowed, or additional error codes on general failure conditions.

tld_check_4z

Function: int tld_check_4z (const uint32_t * in, size_t * errpos, const Tld_table ** overrides)

in: Zero-terminated array of unicode code points to process.

errpos: Position of offending character is returned here.

overrides: A Tld_table array of additional domain restriction structures that complement and supersede the built-in information.

Test each of the code points in in for whether or not they are allowed by the information in overrides or by the built-in TLD restriction data. When data for the same TLD is available both internally and in overrides , the information in overrides takes precedence. If several entries for a specific TLD are found, the first one is used. If overrides is NULL , only the built-in information is used. The position of the first offending character is returned in errpos .

Return value: Returns the Tld_rc value TLD_SUCCESS if all code points are valid or when tld is null, TLD_INVALID if a character is not allowed, or additional error codes on general failure conditions.

tld_check_8z

Function: int tld_check_8z (const char * in, size_t * errpos, const Tld_table ** overrides)

in: Zero-terminated UTF8 string to process.

errpos: Position of offending character is returned here.

overrides: A Tld_table array of additional domain restriction structures that complement and supersede the built-in information.

Test each of the characters in in for whether or not they are allowed by the information in overrides or by the built-in TLD restriction data. When data for the same TLD is available both internally and in overrides , the information in overrides takes precedence. If several entries for a specific TLD are found, the first one is used. If overrides is NULL , only the built-in information is used. The position of the first offending character is returned in errpos . Note that the error position refers to the decoded character offset rather than the byte position in the string.

Return value: Returns the Tld_rc value TLD_SUCCESS if all characters are valid or when tld is null, TLD_INVALID if a character is not allowed, or additional error codes on general failure conditions.

tld_check_lz

Function: int tld_check_lz (const char * in, size_t * errpos, const Tld_table ** overrides)

in: Zero-terminated string in the current locales encoding to process.

errpos: Position of offending character is returned here.

overrides: A Tld_table array of additional domain restriction structures that complement and supersede the built-in information.

Test each of the characters in in for whether or not they are allowed by the information in overrides or by the built-in TLD restriction data. When data for the same TLD is available both internally and in overrides , the information in overrides takes precedence. If several entries for a specific TLD are found, the first one is used. If overrides is NULL , only the built-in information is used. The position of the first offending character is returned in errpos . Note that the error position refers to the decoded character offset rather than the byte position in the string.

Return value: Returns the Tld_rc value TLD_SUCCESS if all characters are valid or when tld is null, TLD_INVALID if a character is not allowed, or additional error codes on general failure conditions.

7.5 Error Handling

tld_strerror

Function: const char * tld_strerror (Tld_rc rc)

rc: tld return code

Convert a return code integer to a text string. This string can be used to output a diagnostic message to the user.

TLD_SUCCESS: Successful operation. This value is guaranteed to always be zero, the remaining ones are only guaranteed to hold non-zero values, for logical comparison purposes.

TLD_INVALID: Invalid character found.

TLD_NODATA: No input data was provided.

TLD_MALLOC_ERROR: Error during memory allocation.

TLD_ICONV_ERROR: Character encoding conversion error.

TLD_NO_TLD: No top-level domain found in domain string.

Return value: Returns a pointer to a statically allocated string containing a description of the error with the return code rc .

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