## idna.h

idna.h — IDNA-related functions

## Functions

const char * | idna_strerror ()
int | idna_to_ascii_4i ()
int | idna_to_unicode_44i ()
int | idna_to_ascii_4z ()
int | idna_to_ascii_8z ()
int | idna_to_ascii_lz ()
int | idna_to_unicode_4z4z ()
int | idna_to_unicode_8z4z ()
int | idna_to_unicode_8z8z ()
int | idna_to_unicode_8zlz ()
int | idna_to_unicode_lzlz ()

## Types and Values

#define | IDNAPI
enum | Idna_rc
enum | Idna_flags
#define | IDNA_ACE_PREFIX

## Description

IDNA-related functions.

## Functions

### idna_strerror ()

    const char *
    idna_strerror (Idna_rc rc);

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

IDNA_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. IDNA_STRINGPREP_ERROR: Error during string preparation. IDNA_PUNYCODE_ERROR: Error during punycode operation. IDNA_CONTAINS_NON_LDH: For IDNA_USE_STD3_ASCII_RULES, indicate that the string contains non-LDH ASCII characters. IDNA_CONTAINS_MINUS: For IDNA_USE_STD3_ASCII_RULES, indicate that the string contains a leading or trailing hyphen-minus (U+002D). IDNA_INVALID_LENGTH: The final output string is not within the (inclusive) range 1 to 63 characters. IDNA_NO_ACE_PREFIX: The string does not contain the ACE prefix (for ToUnicode). IDNA_ROUNDTRIP_VERIFY_ERROR: The ToASCII operation on output string does not equal the input. IDNA_CONTAINS_ACE_PREFIX: The input contains the ACE prefix (for ToASCII). IDNA_ICONV_ERROR: Character encoding conversion error. IDNA_MALLOC_ERROR: Could not allocate buffer (this is typically a fatal error). IDNA_DLOPEN_ERROR: Could not dlopen the libcidn DSO (only used internally in libc).

#### Parameters

rc | an Idna_rc return code. |

#### Returns

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

### idna_to_ascii_4i ()

    int
    idna_to_ascii_4i (const uint32_t *in,
                      size_t inlen,
                      char *out,
                      int flags);

The ToASCII operation takes a sequence of Unicode code points that make up one domain label and transforms it into a sequence of code points in the ASCII range (0..7F). If ToASCII succeeds, the original sequence and the resulting sequence are equivalent labels.

It is important to note that the ToASCII operation can fail. ToASCII fails if any step of it fails. If any step of the ToASCII operation fails on any label in a domain name, that domain name MUST NOT be used as an internationalized domain name. The method for deadling with this failure is application-specific.

The inputs to ToASCII are a sequence of code points, the AllowUnassigned flag, and the UseSTD3ASCIIRules flag. The output of ToASCII is either a sequence of ASCII code points or a failure condition.

ToASCII never alters a sequence of code points that are all in the ASCII range to begin with (although it could fail). Applying the ToASCII operation multiple times has exactly the same effect as applying it just once.

#### Parameters

in | input array with unicode code points. |
inlen | length of input array with unicode code points. |
out | output zero terminated string that must have room for at least 63 characters plus the terminating zero. |
flags | an Idna_flags value, e.g., `IDNA_ALLOW_UNASSIGNED` or `IDNA_USE_STD3_ASCII_RULES`. |

#### Returns

Returns 0 on success, or an Idna_rc error code.

### idna_to_unicode_44i ()

    int
    idna_to_unicode_44i (const uint32_t *in,
                         size_t inlen,
                         uint32_t *out,
                         size_t *outlen,
                         int flags);

The ToUnicode operation takes a sequence of Unicode code points that make up one domain label and returns a sequence of Unicode code points. If the input sequence is a label in ACE form, then the result is an equivalent internationalized label that is not in ACE form, otherwise the original sequence is returned unaltered.

ToUnicode never fails. If any step fails, then the original input sequence is returned immediately in that step.

The Punycode decoder can never output more code points than it inputs, but Nameprep can, and therefore ToUnicode can. Note that the number of octets needed to represent a sequence of code points depends on the particular character encoding used.

The inputs to ToUnicode are a sequence of code points, the AllowUnassigned flag, and the UseSTD3ASCIIRules flag. The output of ToUnicode is always a sequence of Unicode code points.

#### Parameters

in | input array with unicode code points. |
inlen | length of input array with unicode code points. |
out | output array with unicode code points. |
outlen | on input, maximum size of output array with unicode code points, on exit, actual size of output array with unicode code points. |
flags | an Idna_flags value, e.g., `IDNA_ALLOW_UNASSIGNED` or `IDNA_USE_STD3_ASCII_RULES`. |

#### Returns

Returns Idna_rc error condition, but it must only be used for debugging purposes. The output buffer is always guaranteed to contain the correct data according to the specification (sans malloc induced errors). NB! This means that you normally ignore the return code from this function, as checking it means breaking the standard.

### idna_to_ascii_4z ()

    int
    idna_to_ascii_4z (const uint32_t *input,
                      char **output,
                      int flags);

Convert UCS-4 domain name to ASCII string. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.

#### Parameters

input | zero terminated input Unicode string. |
output | pointer to newly allocated output string. |
flags | an Idna_flags value, e.g., `IDNA_ALLOW_UNASSIGNED` or `IDNA_USE_STD3_ASCII_RULES`. |

#### Returns

Returns `IDNA_SUCCESS` on success, or error code.

### idna_to_ascii_8z ()

    int
    idna_to_ascii_8z (const char *input,
                      char **output,
                      int flags);

Convert UTF-8 domain name to ASCII string. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.

#### Parameters

input | zero terminated input UTF-8 string. |
output | pointer to newly allocated output string. |
flags | an Idna_flags value, e.g., `IDNA_ALLOW_UNASSIGNED` or `IDNA_USE_STD3_ASCII_RULES`. |

#### Returns

Returns `IDNA_SUCCESS` on success, or error code.

### idna_to_ascii_lz ()

    int
    idna_to_ascii_lz (const char *input,
                      char **output,
                      int flags);

Convert domain name in the locale's encoding to ASCII string. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.

#### Parameters

input | zero terminated input string encoded in the current locale's character set. |
output | pointer to newly allocated output string. |
flags | an Idna_flags value, e.g., `IDNA_ALLOW_UNASSIGNED` or `IDNA_USE_STD3_ASCII_RULES`. |

#### Returns

Returns `IDNA_SUCCESS` on success, or error code.

### idna_to_unicode_4z4z ()

    int
    idna_to_unicode_4z4z (const uint32_t *input,
                          uint32_t **output,
                          int flags);

Convert possibly ACE encoded domain name in UCS-4 format into a UCS-4 string. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.

#### Parameters

input | zero-terminated Unicode string. |
output | pointer to newly allocated output Unicode string. |
flags | an Idna_flags value, e.g., `IDNA_ALLOW_UNASSIGNED` or `IDNA_USE_STD3_ASCII_RULES`. |

#### Returns

Returns `IDNA_SUCCESS` on success, or error code.

### idna_to_unicode_8z4z ()

    int
    idna_to_unicode_8z4z (const char *input,
                          uint32_t **output,
                          int flags);

Convert possibly ACE encoded domain name in UTF-8 format into a UCS-4 string. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.

#### Parameters

input | zero-terminated UTF-8 string. |
output | pointer to newly allocated output Unicode string. |
flags | an Idna_flags value, e.g., `IDNA_ALLOW_UNASSIGNED` or `IDNA_USE_STD3_ASCII_RULES`. |

#### Returns

Returns `IDNA_SUCCESS` on success, or error code.

### idna_to_unicode_8z8z ()

    int
    idna_to_unicode_8z8z (const char *input,
                          char **output,
                          int flags);

Convert possibly ACE encoded domain name in UTF-8 format into a UTF-8 string. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.

#### Parameters

input | zero-terminated UTF-8 string. |
output | pointer to newly allocated output UTF-8 string. |
flags | an Idna_flags value, e.g., `IDNA_ALLOW_UNASSIGNED` or `IDNA_USE_STD3_ASCII_RULES`. |

#### Returns

Returns `IDNA_SUCCESS` on success, or error code.

### idna_to_unicode_8zlz ()

    int
    idna_to_unicode_8zlz (const char *input,
                          char **output,
                          int flags);

Convert possibly ACE encoded domain name in UTF-8 format into a string encoded in the current locale's character set. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.

#### Parameters

input | zero-terminated UTF-8 string. |
output | pointer to newly allocated output string encoded in the current locale's character set. |
flags | an Idna_flags value, e.g., `IDNA_ALLOW_UNASSIGNED` or `IDNA_USE_STD3_ASCII_RULES`. |

#### Returns

Returns `IDNA_SUCCESS` on success, or error code.

### idna_to_unicode_lzlz ()

    int
    idna_to_unicode_lzlz (const char *input,
                          char **output,
                          int flags);

Convert possibly ACE encoded domain name in the locale's character set into a string encoded in the current locale's character set. The domain name may contain several labels, separated by dots. The output buffer must be deallocated by the caller.

#### Parameters

input | zero-terminated string encoded in the current locale's character set. |
output | pointer to newly allocated output string encoded in the current locale's character set. |
flags | an Idna_flags value, e.g., `IDNA_ALLOW_UNASSIGNED` or `IDNA_USE_STD3_ASCII_RULES`. |

#### Returns

Returns `IDNA_SUCCESS` on success, or error code.

## Types and Values

### IDNAPI

    #define             IDNAPI

Symbol holding shared library API visibility decorator.

This is used internally by the library header file and should never be used or modified by the application.

https://www.gnu.org/software/gnulib/manual/html_node/Exported-Symbols-of-Shared-Libraries.html

### enum Idna_rc

Enumerated return codes of `idna_to_ascii_4i()`, `idna_to_unicode_44i()` functions (and functions derived from those functions). The value 0 is guaranteed to always correspond to success.

#### Members

IDNA_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. |
IDNA_STRINGPREP_ERROR | Error during string preparation. |
IDNA_PUNYCODE_ERROR | Error during punycode operation. |
IDNA_CONTAINS_NON_LDH | For IDNA_USE_STD3_ASCII_RULES, indicate that the string contains non-LDH ASCII characters. |
IDNA_CONTAINS_LDH | Same as `IDNA_CONTAINS_NON_LDH` , for compatibility with typo in earlier versions. |
IDNA_CONTAINS_MINUS | For IDNA_USE_STD3_ASCII_RULES, indicate that the string contains a leading or trailing hyphen-minus (U+002D). |
IDNA_INVALID_LENGTH | The final output string is not within the (inclusive) range 1 to 63 characters. |
IDNA_NO_ACE_PREFIX | The string does not contain the ACE prefix (for ToUnicode). |
IDNA_ROUNDTRIP_VERIFY_ERROR | The ToASCII operation on output string does not equal the input. |
IDNA_CONTAINS_ACE_PREFIX | The input contains the ACE prefix (for ToASCII). |
IDNA_ICONV_ERROR | Character encoding conversion error. |
IDNA_MALLOC_ERROR | Could not allocate buffer (this is typically a fatal error). |
IDNA_DLOPEN_ERROR | Could not dlopen the libcidn DSO (only used internally in libc). |

### enum Idna_flags

Flags to pass to `idna_to_ascii_4i()`, `idna_to_unicode_44i()` etc.

#### Members

IDNA_ALLOW_UNASSIGNED | Don't reject strings containing unassigned Unicode code points. |
IDNA_USE_STD3_ASCII_RULES | Validate strings according to STD3 rules (i.e., normal host name rules). |

### IDNA_ACE_PREFIX

    #  define IDNA_ACE_PREFIX "xn--"

The IANA allocated prefix to use for IDNA. "xn--"