stringprep.h: GNU Libidn API Reference Manual

## stringprep.h stringprep.h — Stringprep-related functions |

## Functions

#define | stringprep_nameprep()
#define | stringprep_nameprep_no_unassigned()
#define | stringprep_plain()
#define | stringprep_kerberos5()
#define | stringprep_xmpp_nodeprep()
#define | stringprep_xmpp_resourceprep()
#define | stringprep_iscsi()
int | stringprep_4i ()
int | stringprep_4zi ()
int | stringprep ()
int | stringprep_profile ()
const char * | stringprep_strerror ()
const char * | stringprep_check_version ()
int | stringprep_unichar_to_utf8 ()
uint32_t | stringprep_utf8_to_unichar ()
uint32_t * | stringprep_utf8_to_ucs4 ()
char * | stringprep_ucs4_to_utf8 ()
char * | stringprep_utf8_nfkc_normalize ()
uint32_t * | stringprep_ucs4_nfkc_normalize ()
const char * | stringprep_locale_charset ()
char * | stringprep_convert ()
char * | stringprep_locale_to_utf8 ()
char * | stringprep_utf8_to_locale ()

## Types and Values

#define | IDNAPI
#define | STRINGPREP_VERSION
enum | Stringprep_rc
enum | Stringprep_profile_flags
enum | Stringprep_profile_steps
#define | STRINGPREP_MAX_MAP_CHARS
struct | Stringprep_table_element
struct | Stringprep_table
typedef | Stringprep_profile
struct | Stringprep_profiles

## Description

Stringprep-related functions.

## Functions

### stringprep_nameprep()

    #define             stringprep_nameprep(in, maxlen)

Prepare the input UTF-8 string according to the nameprep profile. The AllowUnassigned flag is true, use `stringprep_nameprep_no_unassigned()` if you want a false AllowUnassigned. Returns 0 iff successful, or an error code.

#### Parameters

in | input/output array with string to prepare. |
maxlen | maximum length of input/output array. |

### stringprep_nameprep_no_unassigned()

    #define             stringprep_nameprep_no_unassigned(in, maxlen)

Prepare the input UTF-8 string according to the nameprep profile. The AllowUnassigned flag is false, use `stringprep_nameprep()` for true AllowUnassigned. Returns 0 iff successful, or an error code.

#### Parameters

in | input/output array with string to prepare. |
maxlen | maximum length of input/output array. |

### stringprep_plain()

    #define             stringprep_plain(in, maxlen)

Prepare the input UTF-8 string according to the draft SASL ANONYMOUS profile. Returns 0 iff successful, or an error code.

#### Parameters

in | input/output array with string to prepare. |
maxlen | maximum length of input/output array. |

### stringprep_kerberos5()

    #define             stringprep_kerberos5(in, maxlen)

Prepare the input UTF-8 string according to the draft Kerberos 5 node identifier profile. Returns 0 iff successful, or an error code.

#### Parameters

in | input/output array with string to prepare. |
maxlen | maximum length of input/output array. |

### stringprep_xmpp_nodeprep()

    #define             stringprep_xmpp_nodeprep(in, maxlen)

Prepare the input UTF-8 string according to the draft XMPP node identifier profile. Returns 0 iff successful, or an error code.

#### Parameters

in | input/output array with string to prepare. |
maxlen | maximum length of input/output array. |

### stringprep_xmpp_resourceprep()

    #define             stringprep_xmpp_resourceprep(in, maxlen)

Prepare the input UTF-8 string according to the draft XMPP resource identifier profile. Returns 0 iff successful, or an error code.

#### Parameters

in | input/output array with string to prepare. |
maxlen | maximum length of input/output array. |

### stringprep_iscsi()

    #define             stringprep_iscsi(in, maxlen)

Prepare the input UTF-8 string according to the draft iSCSI stringprep profile. Returns 0 iff successful, or an error code.

#### Parameters

in | input/output array with string to prepare. |
maxlen | maximum length of input/output array. |

### stringprep_4i ()

    int
    stringprep_4i (uint32_t *ucs4,
                   size_t *len,
                   size_t maxucs4len,
                   Stringprep_profile_flags flags,
                   const Stringprep_profile *profile);

Prepare the input UCS-4 string according to the stringprep profile, and write back the result to the input string.

The input is not required to be zero terminated (`ucs4` [`len` ] = 0). The output will not be zero terminated unless `ucs4` [`len` ] = 0. Instead, see `stringprep_4zi()` if your input is zero terminated or if you want the output to be.

Since the stringprep operation can expand the string, `maxucs4len` indicate how large the buffer holding the string is. This function will not read or write to code points outside that size.

The `flags` are one of Stringprep_profile_flags values, or 0.

The `profile` contain the Stringprep_profile instructions to perform. Your application can define new profiles, possibly re-using the generic stringprep tables that always will be part of the library, or use one of the currently supported profiles.

#### Parameters

ucs4 | input/output array with string to prepare. |
len | on input, length of input array with Unicode code points, on exit, length of output array with Unicode code points. |
maxucs4len | maximum length of input/output array. |
flags | a Stringprep_profile_flags value, or 0. |
profile | pointer to Stringprep_profile to use. |

#### Returns

Returns `STRINGPREP_OK` iff successful, or an Stringprep_rc error code.

### stringprep_4zi ()

    int
    stringprep_4zi (uint32_t *ucs4,
                    size_t maxucs4len,
                    Stringprep_profile_flags flags,
                    const Stringprep_profile *profile);

Prepare the input zero terminated UCS-4 string according to the stringprep profile, and write back the result to the input string.

Since the stringprep operation can expand the string, `maxucs4len` indicate how large the buffer holding the string is. This function will not read or write to code points outside that size.

The `flags` are one of Stringprep_profile_flags values, or 0.

The `profile` contain the Stringprep_profile instructions to perform. Your application can define new profiles, possibly re-using the generic stringprep tables that always will be part of the library, or use one of the currently supported profiles.

#### Parameters

ucs4 | input/output array with zero terminated string to prepare. |
maxucs4len | maximum length of input/output array. |
flags | a Stringprep_profile_flags value, or 0. |
profile | pointer to Stringprep_profile to use. |

#### Returns

Returns `STRINGPREP_OK` iff successful, or an Stringprep_rc error code.

### stringprep ()

    int
    stringprep (char *in,
                size_t maxlen,
                Stringprep_profile_flags flags,
                const Stringprep_profile *profile);

Prepare the input zero terminated UTF-8 string according to the stringprep profile, and write back the result to the input string.

Note that you must convert strings entered in the systems locale into UTF-8 before using this function, see `stringprep_locale_to_utf8()`.

Since the stringprep operation can expand the string, `maxlen` indicate how large the buffer holding the string is. This function will not read or write to characters outside that size.

The `flags` are one of Stringprep_profile_flags values, or 0.

The `profile` contain the Stringprep_profile instructions to perform. Your application can define new profiles, possibly re-using the generic stringprep tables that always will be part of the library, or use one of the currently supported profiles.

#### Parameters

in | input/output array with string to prepare. |
maxlen | maximum length of input/output array. |
flags | a Stringprep_profile_flags value, or 0. |
profile | pointer to Stringprep_profile to use. |

#### Returns

Returns `STRINGPREP_OK` iff successful, or an error code.

### stringprep_profile ()

    int
    stringprep_profile (const char *in,
                        char **out,
                        const char *profile,
                        Stringprep_profile_flags flags);

Prepare the input zero terminated UTF-8 string according to the stringprep profile, and return the result in a newly allocated variable.

Note that you must convert strings entered in the systems locale into UTF-8 before using this function, see `stringprep_locale_to_utf8()`.

The output `out` variable must be deallocated by the caller.

The `flags` are one of Stringprep_profile_flags values, or 0.

The `profile` specifies the name of the stringprep profile to use. It must be one of the internally supported stringprep profiles.

#### Parameters

in | input array with UTF-8 string to prepare. |
out | output variable with pointer to newly allocate string. |
profile | name of stringprep profile to use. |
flags | a Stringprep_profile_flags value, or 0. |

#### Returns

Returns `STRINGPREP_OK` iff successful, or an error code.

### stringprep_strerror ()

    const char *
    stringprep_strerror (Stringprep_rc rc);

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

STRINGPREP_OK: 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. STRINGPREP_CONTAINS_UNASSIGNED: String contain unassigned Unicode code points, which is forbidden by the profile. STRINGPREP_CONTAINS_PROHIBITED: String contain code points prohibited by the profile. STRINGPREP_BIDI_BOTH_L_AND_RAL: String contain code points with conflicting bidirection category. STRINGPREP_BIDI_LEADTRAIL_NOT_RAL: Leading and trailing character in string not of proper bidirectional category. STRINGPREP_BIDI_CONTAINS_PROHIBITED: Contains prohibited code points detected by bidirectional code. STRINGPREP_TOO_SMALL_BUFFER: Buffer handed to function was too small. This usually indicate a problem in the calling application. STRINGPREP_PROFILE_ERROR: The stringprep profile was inconsistent. This usually indicate an internal error in the library. STRINGPREP_FLAG_ERROR: The supplied flag conflicted with profile. This usually indicate a problem in the calling application. STRINGPREP_UNKNOWN_PROFILE: The supplied profile name was not known to the library. STRINGPREP_ICONV_ERROR: Character encoding conversion error. STRINGPREP_NFKC_FAILED: The Unicode NFKC operation failed. This usually indicate an internal error in the library. STRINGPREP_MALLOC_ERROR: The `malloc()` was out of memory. This is usually a fatal error.

#### Parameters

rc | a Stringprep_rc return code. |

#### Returns

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

### stringprep_check_version ()

    const char *
    stringprep_check_version (const char *req_version);

Check that the version of the library is at minimum the requested one and return the version string; return NULL if the condition is not satisfied. If a NULL is passed to this function, no check is done, but the version string is simply returned.

See `STRINGPREP_VERSION` for a suitable `req_version` string.

#### Parameters

req_version | Required version number, or NULL. |

#### Returns

Version string of run-time library, or NULL if the run-time library does not meet the required version number.

### stringprep_unichar_to_utf8 ()

    int
    stringprep_unichar_to_utf8 (uint32_t c,
                                char *outbuf);

Converts a single character to UTF-8.

#### Parameters

c | a ISO10646 character code |
outbuf | output buffer, must have at least 6 bytes of space. If `NULL`, the length will be computed and returned and nothing will be written to `outbuf` . |

#### Returns

number of bytes written.

### stringprep_utf8_to_unichar ()

    uint32_t
    stringprep_utf8_to_unichar (const char *p);

Converts a sequence of bytes encoded as UTF-8 to a Unicode character. If `p` does not point to a valid UTF-8 encoded character, results are undefined.

#### Parameters

p | a pointer to Unicode character encoded as UTF-8 |

#### Returns

the resulting character.

### stringprep_utf8_to_ucs4 ()

    uint32_t *
    stringprep_utf8_to_ucs4 (const char *str,
                             ssize_t len,
                             size_t *items_written);

Convert a string from UTF-8 to a 32-bit fixed width representation as UCS-4. The function now performs error checking to verify that the input is valid UTF-8 (before it was documented to not do error checking).

#### Parameters

str | a UTF-8 encoded string |
len | the maximum length of `str` to use. If `len` < 0, then the string is nul-terminated. |
items_written | location to store the number of characters in the result, or `NULL`. |

#### Returns

a pointer to a newly allocated UCS-4 string. This value must be deallocated by the caller.

### stringprep_ucs4_to_utf8 ()

    char *
    stringprep_ucs4_to_utf8 (const uint32_t *str,
                             ssize_t len,
                             size_t *items_read,
                             size_t *items_written);

Convert a string from a 32-bit fixed width representation as UCS-4. to UTF-8. The result will be terminated with a 0 byte.

#### Parameters

str | a UCS-4 encoded string |
len | the maximum length of `str` to use. If `len` < 0, then the string is terminated with a 0 character. |
items_read | location to store number of characters read read, or `NULL`. |
items_written | location to store number of bytes written or `NULL`. The value here stored does not include the trailing 0 byte. |

#### Returns

a pointer to a newly allocated UTF-8 string. This value must be deallocated by the caller. If an error occurs, `NULL` will be returned.

### stringprep_utf8_nfkc_normalize ()

    char *
    stringprep_utf8_nfkc_normalize (const char *str,
                                    ssize_t len);

Converts a string into canonical form, standardizing such issues as whether a character with an accent is represented as a base character and combining accent or as a single precomposed character.

The normalization mode is NFKC (ALL COMPOSE). It standardizes differences that do not affect the text content, such as the above-mentioned accent representation. It standardizes the "compatibility" characters in Unicode, such as SUPERSCRIPT THREE to the standard forms (in this case DIGIT THREE). Formatting information may be lost but for most text operations such characters should be considered the same. It returns a result with composed forms rather than a maximally decomposed form.

#### Parameters

str | a UTF-8 encoded string. |
len | length of `str` , in bytes, or -1 if `str` is nul-terminated. |

#### Returns

a newly allocated string, that is the NFKC normalized form of `str` .

### stringprep_ucs4_nfkc_normalize ()

    uint32_t *
    stringprep_ucs4_nfkc_normalize (const uint32_t *str,
                                    ssize_t len);

Converts a UCS4 string into canonical form, see `stringprep_utf8_nfkc_normalize()` for more information.

#### Parameters

str | a Unicode string. |
len | length of `str` array, or -1 if `str` is nul-terminated. |

#### Returns

a newly allocated Unicode string, that is the NFKC normalized form of `str` .

### stringprep_locale_charset ()

    const char *
    stringprep_locale_charset (void);

Find out current locale charset. The function respect the CHARSET environment variable, but typically uses nl_langinfo(CODESET) when it is supported. It fall back on "ASCII" if CHARSET isn't set and nl_langinfo isn't supported or return anything.

Note that this function return the application's locale's preferred charset (or thread's locale's preferred charset, if your system support thread-specific locales). It does not return what the system may be using. Thus, if you receive data from external sources you cannot in general use this function to guess what charset it is encoded in. Use stringprep_convert from the external representation into the charset returned by this function, to have data in the locale encoding.

#### Returns

Return the character set used by the current locale. It will never return NULL, but use "ASCII" as a fallback.

### stringprep_convert ()

    char *
    stringprep_convert (const char *str,
                        const char *to_codeset,
                        const char *from_codeset);

Convert the string from one character set to another using the system's `iconv()` function.

#### Parameters

str | input zero-terminated string. |
to_codeset | name of destination character set. |
from_codeset | name of origin character set, as used by `str` . |

#### Returns

Returns newly allocated zero-terminated string which is `str` transcoded into to_codeset.

### stringprep_locale_to_utf8 ()

    char *
    stringprep_locale_to_utf8 (const char *str);

Convert string encoded in the locale's character set into UTF-8 by using `stringprep_convert()`.

#### Parameters

str | input zero terminated string. |

#### Returns

Returns newly allocated zero-terminated string which is `str` transcoded into UTF-8.

### stringprep_utf8_to_locale ()

    char *
    stringprep_utf8_to_locale (const char *str);

Convert string encoded in UTF-8 into the locale's character set by using `stringprep_convert()`.

#### Parameters

str | input zero terminated string. |

#### Returns

Returns newly allocated zero-terminated string which is `str` transcoded into the locale's character set.

## 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

### STRINGPREP_VERSION

    # define STRINGPREP_VERSION "1.42"

String defined via CPP denoting the header file version number. Used together with `stringprep_check_version()` to verify header file and run-time library consistency.

### enum Stringprep_rc

Enumerated return codes of `stringprep()`, `stringprep_profile()` functions (and macros using those functions). The value 0 is guaranteed to always correspond to success.

#### Members

STRINGPREP_OK | 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. |
STRINGPREP_CONTAINS_UNASSIGNED | String contain unassigned Unicode code points, which is forbidden by the profile. |
STRINGPREP_CONTAINS_PROHIBITED | String contain code points prohibited by the profile. |
STRINGPREP_BIDI_BOTH_L_AND_RAL | String contain code points with conflicting bidirection category. |
STRINGPREP_BIDI_LEADTRAIL_NOT_RAL | Leading and trailing character in string not of proper bidirectional category. |
STRINGPREP_BIDI_CONTAINS_PROHIBITED | Contains prohibited code points detected by bidirectional code. |
STRINGPREP_TOO_SMALL_BUFFER | Buffer handed to function was too small. This usually indicate a problem in the calling application. |
STRINGPREP_PROFILE_ERROR | The stringprep profile was inconsistent. This usually indicate an internal error in the library. |
STRINGPREP_FLAG_ERROR | The supplied flag conflicted with profile. This usually indicate a problem in the calling application. |
STRINGPREP_UNKNOWN_PROFILE | The supplied profile name was not known to the library. |
STRINGPREP_ICONV_ERROR | Character encoding conversion error. |
STRINGPREP_NFKC_FAILED | The Unicode NFKC operation failed. This usually indicate an internal error in the library. |
STRINGPREP_MALLOC_ERROR | The `malloc()` was out of memory. This is usually a fatal error. |

### enum Stringprep_profile_flags

Stringprep profile flags.

#### Members

STRINGPREP_NO_NFKC | Disable the NFKC normalization, as well as selecting the non-NFKC case folding tables. Usually the profile specifies BIDI and NFKC settings, and applications should not override it unless in special situations. |
STRINGPREP_NO_BIDI | Disable the BIDI step. Usually the profile specifies BIDI and NFKC settings, and applications should not override it unless in special situations. |
STRINGPREP_NO_UNASSIGNED | Make the library return with an error if string contains unassigned characters according to profile. |

### enum Stringprep_profile_steps

Various steps in the stringprep algorithm. You really want to study the source code to understand this one. Only useful if you want to add another profile.

#### Members

STRINGPREP_NFKC | The NFKC step. |
STRINGPREP_BIDI | The BIDI step. |
STRINGPREP_MAP_TABLE | The MAP step. |
STRINGPREP_UNASSIGNED_TABLE | The Unassigned step. |
STRINGPREP_PROHIBIT_TABLE | The Prohibited step. |
STRINGPREP_BIDI_PROHIBIT_TABLE | The BIDI-Prohibited step. |
STRINGPREP_BIDI_RAL_TABLE | The BIDI-RAL step. |
STRINGPREP_BIDI_L_TABLE | The BIDI-L step. |

### STRINGPREP_MAX_MAP_CHARS

    # define STRINGPREP_MAX_MAP_CHARS 4

Maximum number of code points that can replace a single code point, during stringprep mapping.

### struct Stringprep_table_element

    struct Stringprep_table_element {
        uint32_t start;
        uint32_t end;
        uint32_t map[STRINGPREP_MAX_MAP_CHARS];
    };

Stringprep profile table element.

#### Members

uint32_t `start`; | starting codepoint. |
uint32_t `end`; | ending codepoint, 0 if only one character. |
uint32_t `map`[STRINGPREP_MAX_MAP_CHARS]; | codepoints to map `start` into, NULL if end is not 0. |

### struct Stringprep_table

    struct Stringprep_table {
        Stringprep_profile_steps operation;
        Stringprep_profile_flags flags;
        const Stringprep_table_element *table;
        size_t table_size;
    };

Stringprep profile table.

#### Members

Stringprep_profile_steps `operation`; | a Stringprep_profile_steps value |
Stringprep_profile_flags `flags`; | a Stringprep_profile_flags value |
const Stringprep_table_element *`table`; | zero-terminated array of `Stringprep_table_element` elements. |
size_t `table_size`; | size of `table` , to speed up searching. |

### Stringprep_profile

      typedef struct Stringprep_table Stringprep_profile;

Stringprep profile table.

### struct Stringprep_profiles

    struct Stringprep_profiles {
        const char *name;
        const Stringprep_profile *tables;
    };

Element structure

#### Members

const char *`name`; | name of stringprep profile. |
const Stringprep_profile *`tables`; | zero-terminated array of `Stringprep_profile` elements. |