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ICU 77.1: common/unicode/ustring.h File Reference

C API: Unicode string handling functions. More...

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C API: Unicode string handling functions.

These C API functions provide general Unicode string handling.

Some functions are equivalent in name, signature, and behavior to the ANSI C <string.h> functions. (For example, they do not check for bad arguments like NULL string pointers.) In some cases, only the thread-safe variant of such a function is implemented here (see u_strtok_r()).

Other functions provide more Unicode-specific functionality like locale-specific upper/lower-casing and string comparison in code point order.

ICU uses 16-bit Unicode (UTF-16) in the form of arrays of UChar code units. UTF-16 encodes each Unicode code point with either one or two UChar code units. (This is the default form of Unicode, and a forward-compatible extension of the original, fixed-width form that was known as UCS-2. UTF-16 superseded UCS-2 with Unicode 2.0 in 1996.)

Some APIs accept a 32-bit UChar32 value for a single code point.

ICU also handles 16-bit Unicode text with unpaired surrogates. Such text is not well-formed UTF-16. Code-point-related functions treat unpaired surrogates as surrogate code points, i.e., as separate units.

Although UTF-16 is a variable-width encoding form (like some legacy multi-byte encodings), it is much more efficient even for random access because the code unit values for single-unit characters vs. lead units vs. trail units are completely disjoint. This means that it is easy to determine character (code point) boundaries from random offsets in the string.

Unicode (UTF-16) string processing is optimized for the single-unit case. Although it is important to support supplementary characters (which use pairs of lead/trail code units called "surrogates"), their occurrence is rare. Almost all characters in modern use require only a single UChar code unit (i.e., their code point values are <=0xffff).

For more details see the User Guide Strings chapter (https://unicode-org.github.io/icu/userguide/strings/). For a discussion of the handling of unpaired surrogates see also Jitterbug 2145 and its icu mailing list proposal on 2002-sep-18.

Definition in file ustring.h.

Unicode String literals in C.

We need one macro to declare a variable for the string and to statically preinitialize it if possible, and a second macro to dynamically initialize such a string variable if necessary.

The macros are defined for maximum performance. They work only for strings that contain "invariant characters", i.e., only latin letters, digits, and some punctuation. See utypes.h for details.

A pair of macros for a single string must be used with the same parameters. The string parameter must be a C string literal. The length of the string, not including the terminating NUL, must be specified as a constant. The U_STRING_DECL macro should be invoked exactly once for one such string variable before it is used.

Usage:

U_STRING_DECL(ustringVar1, "Quick-Fox 2", 11);
U_STRING_DECL(ustringVar2, "jumps 5%", 8);
static UBool didInit=false;

int32_t function() {
    if(!didInit) {
        U_STRING_INIT(ustringVar1, "Quick-Fox 2", 11);
        U_STRING_INIT(ustringVar2, "jumps 5%", 8);
        didInit=true;
    }
    return u_strcmp(ustringVar1, ustringVar2);
}

Note that the macros will NOT consistently work if their argument is another #define. The following will not work on all platforms, don't use it.

#define GLUCK "Mr. Gluck"
U_STRING_DECL(var, GLUCK, 9)
U_STRING_INIT(var, GLUCK, 9)

Instead, use the string literal "Mr. Gluck" as the argument to both macro calls.

Stable:

ICU 2.0

Definition at line 935 of file ustring.h.

Callback function for u_unescapeAt() that returns a character of the source text given an offset and a context pointer.

The context pointer will be whatever is passed into u_unescapeAt().

Parameters

Returns

the character represented by the escape sequence at offset

See also

u_unescapeAt

Stable:

ICU 2.0

Definition at line 1008 of file ustring.h.

Copy ustring to a byte string encoded in the default codepage.

Adds a null terminator. Performs a UChar to host byte conversion

Parameters

dst The destination string. src The source string.

Returns

A pointer to dst.

Stable:

ICU 2.0

Copy ustring to a byte string encoded in the default codepage.

Copies at most n characters. The result will be null terminated if the length of src is less than n. Performs a UChar to host byte conversion

Parameters

dst The destination string. src The source string. n The maximum number of characters to copy.

Returns

A pointer to dst.

Stable:

ICU 2.0

Count Unicode code points in the length UChar code units of the string.

A code point may occupy either one or two UChar code units. Counting code points involves reading all code units.

This functions is basically the inverse of the U16_FWD_N() macro (see utf.h).

Parameters

s The input string. length The number of UChar code units to be checked, or -1 to count all code points before the first NUL (U+0000).

Returns

The number of code points in the specified code units.

Stable:

ICU 2.0

Compare two strings case-insensitively using full case folding.

This is equivalent to u_strcmp(u_strFoldCase(s1, n, options), u_strFoldCase(s2, n, options)).

Parameters

s1 A string to compare. s2 A string to compare. length The number of characters in each string to case-fold and then compare. options A bit set of options:

• U_FOLD_CASE_DEFAULT or 0 is used for default options: Comparison in code unit order with default case folding.
• U_COMPARE_CODE_POINT_ORDER Set to choose code point order instead of code unit order (see u_strCompare for details).
• U_FOLD_CASE_EXCLUDE_SPECIAL_I

Returns

A negative, zero, or positive integer indicating the comparison result.

Stable:

ICU 2.0

Find the first occurrence of a BMP code point in a string.

A surrogate code point is found only if its match in the text is not part of a surrogate pair. A NUL character is found at the string terminator.

Parameters

s The string to search (contains count UChars). c The BMP code point to find. count The length of the string.

Returns

A pointer to the first occurrence of c in s or NULL if c is not in s.

Stable:

ICU 2.0

See also

u_strchr

u_memchr32

u_strFindFirst

Find the first occurrence of a code point in a string.

A surrogate code point is found only if its match in the text is not part of a surrogate pair. A NUL character is found at the string terminator.

Parameters

s The string to search (contains count UChars). c The code point to find. count The length of the string.

Returns

A pointer to the first occurrence of c in s or NULL if c is not in s.

Stable:

ICU 2.0

See also

u_strchr32

u_memchr

u_strFindFirst

Compare the first count UChars of each buffer.

Parameters

buf1 The first string to compare. buf2 The second string to compare. count The maximum number of UChars to compare.

Returns

When buf1 < buf2, a negative number is returned. When buf1 == buf2, 0 is returned. When buf1 > buf2, a positive number is returned.

Stable:

ICU 2.0

Compare two Unicode strings in code point order.

This is different in UTF-16 from u_memcmp() if supplementary characters are present. For details, see u_strCompare().

Parameters

s1 A string to compare. s2 A string to compare. count The maximum number of characters to compare.

Returns

a negative/zero/positive integer corresponding to whether the first string is less than/equal to/greater than the second one in code point order

Stable:

ICU 2.0

Synonym for memcpy(), but with UChars only.

Parameters

dest The destination string src The source string (can be NULL/invalid if count<=0) count The number of characters to copy; no-op if <=0

Returns

A pointer to dest

Stable:

ICU 2.0

Synonym for memmove(), but with UChars only.

Parameters

dest The destination string src The source string (can be NULL/invalid if count<=0) count The number of characters to move; no-op if <=0

Returns

A pointer to dest

Stable:

ICU 2.0

Find the last occurrence of a BMP code point in a string.

A surrogate code point is found only if its match in the text is not part of a surrogate pair. A NUL character is found at the string terminator.

Parameters

s The string to search (contains count UChars). c The BMP code point to find. count The length of the string.

Returns

A pointer to the last occurrence of c in s or NULL if c is not in s.

Stable:

ICU 2.4

See also

u_strrchr

u_memrchr32

u_strFindLast

Find the last occurrence of a code point in a string.

A surrogate code point is found only if its match in the text is not part of a surrogate pair. A NUL character is found at the string terminator.

Parameters

s The string to search (contains count UChars). c The code point to find. count The length of the string.

Returns

A pointer to the last occurrence of c in s or NULL if c is not in s.

Stable:

ICU 2.4

See also

u_strrchr32

u_memrchr

u_strFindLast

Initialize count characters of dest to c.

Parameters

dest The destination string. c The character to initialize the string. count The maximum number of characters to set.

Returns

A pointer to dest.

Stable:

ICU 2.0

Compare two strings case-insensitively using full case folding.

This is equivalent to u_strcmp(u_strFoldCase(s1, options), u_strFoldCase(s2, options)).

Parameters

s1 A string to compare. s2 A string to compare. options A bit set of options:

• U_FOLD_CASE_DEFAULT or 0 is used for default options: Comparison in code unit order with default case folding.
• U_COMPARE_CODE_POINT_ORDER Set to choose code point order instead of code unit order (see u_strCompare for details).
• U_FOLD_CASE_EXCLUDE_SPECIAL_I

Returns

A negative, zero, or positive integer indicating the comparison result.

Stable:

ICU 2.0

Compare two strings case-insensitively using full case folding.

This is equivalent to u_strCompare(u_strFoldCase(s1, options), u_strFoldCase(s2, options), (options&U_COMPARE_CODE_POINT_ORDER)!=0).

The comparison can be done in UTF-16 code unit order or in code point order. They differ only when comparing supplementary code points (U+10000..U+10ffff) to BMP code points near the end of the BMP (i.e., U+e000..U+ffff). In code unit order, high BMP code points sort after supplementary code points because they are stored as pairs of surrogates which are at U+d800..U+dfff.

This functions works with strings of different explicitly specified lengths unlike the ANSI C-like u_strcmp() and u_memcmp() etc. NUL-terminated strings are possible with length arguments of -1.

Parameters

s1 First source string. length1 Length of first source string, or -1 if NUL-terminated. s2 Second source string. length2 Length of second source string, or -1 if NUL-terminated. options A bit set of options:

• U_FOLD_CASE_DEFAULT or 0 is used for default options: Comparison in code unit order with default case folding.
• U_COMPARE_CODE_POINT_ORDER Set to choose code point order instead of code unit order (see u_strCompare for details).
• U_FOLD_CASE_EXCLUDE_SPECIAL_I

pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.

Returns

<0 or 0 or >0 as usual for string comparisons

Stable:

ICU 2.2

Concatenate two ustrings.

Appends a copy of src, including the null terminator, to dst. The initial copied character from src overwrites the null terminator in dst.

Parameters

dst The destination string. src The source string.

Returns

A pointer to dst.

Stable:

ICU 2.0

Find the first occurrence of a BMP code point in a string.

A surrogate code point is found only if its match in the text is not part of a surrogate pair. A NUL character is found at the string terminator.

Parameters

s The string to search (NUL-terminated). c The BMP code point to find.

Returns

A pointer to the first occurrence of c in s or NULL if c is not in s.

Stable:

ICU 2.0

See also

u_strchr32

u_memchr

u_strstr

u_strFindFirst

Find the first occurrence of a code point in a string.

A surrogate code point is found only if its match in the text is not part of a surrogate pair. A NUL character is found at the string terminator.

Parameters

s The string to search (NUL-terminated). c The code point to find.

Returns

A pointer to the first occurrence of c in s or NULL if c is not in s.

Stable:

ICU 2.0

See also

u_strchr

u_memchr32

u_strstr

u_strFindFirst

Compare two Unicode strings for bitwise equality (code unit order).

Parameters

s1 A string to compare. s2 A string to compare.

Returns

0 if s1 and s2 are bitwise equal; a negative value if s1 is bitwise less than s2,; a positive value if s1 is bitwise greater than s2.

Stable:

ICU 2.0

Compare two Unicode strings in code point order.

See u_strCompare for details.

Parameters

s1 A string to compare. s2 A string to compare.

Returns

a negative/zero/positive integer corresponding to whether the first string is less than/equal to/greater than the second one in code point order

Stable:

ICU 2.0

Compare two Unicode strings (binary order).

The comparison can be done in code unit order or in code point order. They differ only in UTF-16 when comparing supplementary code points (U+10000..U+10ffff) to BMP code points near the end of the BMP (i.e., U+e000..U+ffff). In code unit order, high BMP code points sort after supplementary code points because they are stored as pairs of surrogates which are at U+d800..U+dfff.

This functions works with strings of different explicitly specified lengths unlike the ANSI C-like u_strcmp() and u_memcmp() etc. NUL-terminated strings are possible with length arguments of -1.

Parameters

s1 First source string. length1 Length of first source string, or -1 if NUL-terminated. s2 Second source string. length2 Length of second source string, or -1 if NUL-terminated. codePointOrder Choose between code unit order (false) and code point order (true).

Returns

<0 or 0 or >0 as usual for string comparisons

Stable:

ICU 2.2

Compare two Unicode strings (binary order) as presented by UCharIterator objects.

Works otherwise just like u_strCompare().

Both iterators are reset to their start positions. When the function returns, it is undefined where the iterators have stopped.

Parameters

iter1 First source string iterator. iter2 Second source string iterator. codePointOrder Choose between code unit order (false) and code point order (true).

Returns

<0 or 0 or >0 as usual for string comparisons

See also

u_strCompare

Stable:

ICU 2.6

Copy a ustring.

Adds a null terminator.

Parameters

dst The destination string. src The source string.

Returns

A pointer to dst.

Stable:

ICU 2.0

Returns the number of consecutive characters in string, beginning with the first, that do not occur somewhere in matchSet.

Works just like C's strcspn but with Unicode.

Parameters

string The string in which to search, NUL-terminated. matchSet A NUL-terminated string defining a set of code points for which to search in the text string.

Returns

The number of initial characters in string that do not occur in matchSet.

See also

u_strspn

Stable:

ICU 2.0

Find the first occurrence of a substring in a string.

The substring is found at code point boundaries. That means that if the substring begins with a trail surrogate or ends with a lead surrogate, then it is found only if these surrogates stand alone in the text. Otherwise, the substring edge units would be matched against halves of surrogate pairs.

Parameters

s The string to search. length The length of s (number of UChars), or -1 if it is NUL-terminated. substring The substring to find (NUL-terminated). subLength The length of substring (number of UChars), or -1 if it is NUL-terminated.

Returns

A pointer to the first occurrence of substring in s, or s itself if the substring is empty, or NULL if substring is not in s.

Stable:

ICU 2.4

See also

u_strstr

u_strFindLast

Find the last occurrence of a substring in a string.

The substring is found at code point boundaries. That means that if the substring begins with a trail surrogate or ends with a lead surrogate, then it is found only if these surrogates stand alone in the text. Otherwise, the substring edge units would be matched against halves of surrogate pairs.

Parameters

s The string to search. length The length of s (number of UChars), or -1 if it is NUL-terminated. substring The substring to find (NUL-terminated). subLength The length of substring (number of UChars), or -1 if it is NUL-terminated.

Returns

A pointer to the last occurrence of substring in s, or s itself if the substring is empty, or NULL if substring is not in s.

Stable:

ICU 2.4

See also

u_strstr

u_strFindLast

Case-folds the characters in a string.

Case-folding is locale-independent and not context-sensitive, but there is an option for whether to include or exclude mappings for dotted I and dotless i that are marked with 'T' in CaseFolding.txt.

The result may be longer or shorter than the original. The source string and the destination buffer are allowed to overlap.

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string. src The original string srcLength The length of the original string. If -1, then src must be zero-terminated. options Either U_FOLD_CASE_DEFAULT or U_FOLD_CASE_EXCLUDE_SPECIAL_I pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.

Returns

The length of the result string. It may be greater than destCapacity. In that case, only some of the result was written to the destination buffer.

Stable:

ICU 2.0

Convert a Java Modified UTF-8 string to a 16-bit Unicode string.

If the input string is not well-formed and no substitution char is specified, then the U_INVALID_CHAR_FOUND error code is set.

This function behaves according to the documentation for Java DataInput.readUTF() except that it takes a length parameter rather than interpreting the first two input bytes as the length. See http://java.sun.com/javase/6/docs/api/java/io/DataInput.html#readUTF()

The output string may not be well-formed UTF-16.

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. subchar The substitution character to use in place of an illegal input sequence, or U_SENTINEL if the function is to return with U_INVALID_CHAR_FOUND instead. A substitution character can be any valid Unicode code point (up to U+10FFFF) except for surrogate code points (U+D800..U+DFFF). The recommended value is U+FFFD "REPLACEMENT CHARACTER". pNumSubstitutions Output parameter receiving the number of substitutions if subchar>=0. Set to 0 if no substitutions occur or subchar<0. pNumSubstitutions can be NULL. pErrorCode Pointer to a standard ICU error code. Its input value must pass the U_SUCCESS() test, or else the function returns immediately. Check for U_FAILURE() on output or use with function chaining. (See User Guide for details.)

Returns

The pointer to destination buffer.

See also

u_strFromUTF8WithSub

u_strFromUTF8Lenient

u_strToJavaModifiedUTF8

Stable:

ICU 4.4

Convert a UTF-32 string to UTF-16.

If the input string is not well-formed, then the U_INVALID_CHAR_FOUND error code is set.

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.

Returns

The pointer to destination buffer.

See also

u_strFromUTF32WithSub

u_strToUTF32

Stable:

ICU 2.0

Convert a UTF-32 string to UTF-16.

Same as u_strFromUTF32() except for the additional subchar which is output for illegal input sequences, instead of stopping with the U_INVALID_CHAR_FOUND error code. With subchar==U_SENTINEL, this function behaves exactly like u_strFromUTF32().

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. subchar The substitution character to use in place of an illegal input sequence, or U_SENTINEL if the function is to return with U_INVALID_CHAR_FOUND instead. A substitution character can be any valid Unicode code point (up to U+10FFFF) except for surrogate code points (U+D800..U+DFFF). The recommended value is U+FFFD "REPLACEMENT CHARACTER". pNumSubstitutions Output parameter receiving the number of substitutions if subchar>=0. Set to 0 if no substitutions occur or subchar<0. pNumSubstitutions can be NULL. pErrorCode Pointer to a standard ICU error code. Its input value must pass the U_SUCCESS() test, or else the function returns immediately. Check for U_FAILURE() on output or use with function chaining. (See User Guide for details.)

Returns

The pointer to destination buffer.

See also

u_strFromUTF32

u_strToUTF32WithSub

Stable:

ICU 4.2

Convert a UTF-8 string to UTF-16.

If the input string is not well-formed, then the U_INVALID_CHAR_FOUND error code is set.

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.

Returns

The pointer to destination buffer.

Stable:

ICU 2.0

See also

u_strFromUTF8WithSub

u_strFromUTF8Lenient

Convert a UTF-8 string to UTF-16.

Same as u_strFromUTF8() except that this function is designed to be very fast, which it achieves by being lenient about malformed UTF-8 sequences. This function is intended for use in environments where UTF-8 text is expected to be well-formed.

Its semantics are:

• Well-formed UTF-8 text is correctly converted to well-formed UTF-16 text.
• The function will not read beyond the input string, nor write beyond the destCapacity.
• Malformed UTF-8 results in "garbage" 16-bit Unicode strings which may not be well-formed UTF-16. The function will resynchronize to valid code point boundaries within a small number of code points after an illegal sequence.
• Non-shortest forms are not detected and will result in "spoofing" output.

For further performance improvement, if srcLength is given (>=0), then it must be destCapacity>=srcLength.

There is no inverse u_strToUTF8Lenient() function because there is practically no performance gain from not checking that a UTF-16 string is well-formed.

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). Unlike for other ICU functions, if srcLength>=0 then it must be destCapacity>=srcLength. pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. Unlike for other ICU functions, if srcLength>=0 but destCapacity<srcLength, then *pDestLength will be set to srcLength (and U_BUFFER_OVERFLOW_ERROR will be set) regardless of the actual result length. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. pErrorCode Pointer to a standard ICU error code. Its input value must pass the U_SUCCESS() test, or else the function returns immediately. Check for U_FAILURE() on output or use with function chaining. (See User Guide for details.)

Returns

The pointer to destination buffer.

See also

u_strFromUTF8

u_strFromUTF8WithSub

u_strToUTF8WithSub

Stable:

ICU 3.6

Convert a UTF-8 string to UTF-16.

Same as u_strFromUTF8() except for the additional subchar which is output for illegal input sequences, instead of stopping with the U_INVALID_CHAR_FOUND error code. With subchar==U_SENTINEL, this function behaves exactly like u_strFromUTF8().

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. subchar The substitution character to use in place of an illegal input sequence, or U_SENTINEL if the function is to return with U_INVALID_CHAR_FOUND instead. A substitution character can be any valid Unicode code point (up to U+10FFFF) except for surrogate code points (U+D800..U+DFFF). The recommended value is U+FFFD "REPLACEMENT CHARACTER". pNumSubstitutions Output parameter receiving the number of substitutions if subchar>=0. Set to 0 if no substitutions occur or subchar<0. pNumSubstitutions can be NULL. pErrorCode Pointer to a standard ICU error code. Its input value must pass the U_SUCCESS() test, or else the function returns immediately. Check for U_FAILURE() on output or use with function chaining. (See User Guide for details.)

Returns

The pointer to destination buffer.

See also

u_strFromUTF8

u_strFromUTF8Lenient

u_strToUTF8WithSub

Stable:

ICU 3.6

Convert a wchar_t string to UTF-16.

If it is known at compile time that wchar_t strings are in UTF-16 or UTF-32, then this function simply calls the fast, dedicated function for that. Otherwise, two conversions wchar_t* -> default charset -> UTF-16 are performed.

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.

Returns

The pointer to destination buffer.

Stable:

ICU 2.0

Check if the string contains more Unicode code points than a certain number.

This is more efficient than counting all code points in the entire string and comparing that number with a threshold. This function may not need to scan the string at all if the length is known (not -1 for NUL-termination) and falls within a certain range, and never needs to count more than 'number+1' code points. Logically equivalent to (u_countChar32(s, length)>number). A Unicode code point may occupy either one or two UChar code units.

Parameters

s The input string. length The length of the string, or -1 if it is NUL-terminated. number The number of code points in the string is compared against the 'number' parameter.

Returns

Boolean value for whether the string contains more Unicode code points than 'number'. Same as (u_countChar32(s, length)>number).

Stable:

ICU 2.4

Determine the length of an array of UChar.

Parameters

s The array of UChars, NULL (U+0000) terminated.

Returns

The number of UChars in chars, minus the terminator.

Stable:

ICU 2.0

Compare two strings case-insensitively using full case folding.

This is equivalent to u_strcmp(u_strFoldCase(s1, at most n, options), u_strFoldCase(s2, at most n, options)).

Parameters

s1 A string to compare. s2 A string to compare. n The maximum number of characters each string to case-fold and then compare. options A bit set of options:

• U_FOLD_CASE_DEFAULT or 0 is used for default options: Comparison in code unit order with default case folding.
• U_COMPARE_CODE_POINT_ORDER Set to choose code point order instead of code unit order (see u_strCompare for details).
• U_FOLD_CASE_EXCLUDE_SPECIAL_I

Returns

A negative, zero, or positive integer indicating the comparison result.

Stable:

ICU 2.0

Concatenate two ustrings.

Appends at most n characters from src to dst. Adds a terminating NUL. If src is too long, then only n-1 characters will be copied before the terminating NUL. If n<=0 then dst is not modified.

Parameters

dst The destination string. src The source string (can be NULL/invalid if n<=0). n The maximum number of characters to append; no-op if <=0.

Returns

A pointer to dst.

Stable:

ICU 2.0

Compare two ustrings for bitwise equality.

Compares at most n characters.

Parameters

ucs1 A string to compare (can be NULL/invalid if n<=0). ucs2 A string to compare (can be NULL/invalid if n<=0). n The maximum number of characters to compare; always returns 0 if n<=0.

Returns

0 if s1 and s2 are bitwise equal; a negative value if s1 is bitwise less than s2; a positive value if s1 is bitwise greater than s2.

Stable:

ICU 2.0

Compare two Unicode strings in code point order.

This is different in UTF-16 from u_strncmp() if supplementary characters are present. For details, see u_strCompare().

Parameters

s1 A string to compare. s2 A string to compare. n The maximum number of characters to compare.

Returns

a negative/zero/positive integer corresponding to whether the first string is less than/equal to/greater than the second one in code point order

Stable:

ICU 2.0

Copy a ustring.

Copies at most n characters. The result will be null terminated if the length of src is less than n.

Parameters

dst The destination string. src The source string (can be NULL/invalid if n<=0). n The maximum number of characters to copy; no-op if <=0.

Returns

A pointer to dst.

Stable:

ICU 2.0

Locates the first occurrence in the string string of any of the characters in the string matchSet.

Works just like C's strpbrk but with Unicode.

Parameters

string The string in which to search, NUL-terminated. matchSet A NUL-terminated string defining a set of code points for which to search in the text string.

Returns

A pointer to the character in string that matches one of the characters in matchSet, or NULL if no such character is found.

Stable:

ICU 2.0

Find the last occurrence of a BMP code point in a string.

A surrogate code point is found only if its match in the text is not part of a surrogate pair. A NUL character is found at the string terminator.

Parameters

s The string to search (NUL-terminated). c The BMP code point to find.

Returns

A pointer to the last occurrence of c in s or NULL if c is not in s.

Stable:

ICU 2.4

See also

u_strrchr32

u_memrchr

u_strrstr

u_strFindLast

Find the last occurrence of a code point in a string.

A surrogate code point is found only if its match in the text is not part of a surrogate pair. A NUL character is found at the string terminator.

Parameters

s The string to search (NUL-terminated). c The code point to find.

Returns

A pointer to the last occurrence of c in s or NULL if c is not in s.

Stable:

ICU 2.4

See also

u_strrchr

u_memchr32

u_strrstr

u_strFindLast

Find the last occurrence of a substring in a string.

The substring is found at code point boundaries. That means that if the substring begins with a trail surrogate or ends with a lead surrogate, then it is found only if these surrogates stand alone in the text. Otherwise, the substring edge units would be matched against halves of surrogate pairs.

Parameters

s The string to search (NUL-terminated). substring The substring to find (NUL-terminated).

Returns

A pointer to the last occurrence of substring in s, or s itself if the substring is empty, or NULL if substring is not in s.

Stable:

ICU 2.4

See also

u_strstr

u_strFindFirst

u_strFindLast

Returns the number of consecutive characters in string, beginning with the first, that occur somewhere in matchSet.

Works just like C's strspn but with Unicode.

Parameters

string The string in which to search, NUL-terminated. matchSet A NUL-terminated string defining a set of code points for which to search in the text string.

Returns

The number of initial characters in string that do occur in matchSet.

See also

u_strcspn

Stable:

ICU 2.0

Find the first occurrence of a substring in a string.

The substring is found at code point boundaries. That means that if the substring begins with a trail surrogate or ends with a lead surrogate, then it is found only if these surrogates stand alone in the text. Otherwise, the substring edge units would be matched against halves of surrogate pairs.

Parameters

s The string to search (NUL-terminated). substring The substring to find (NUL-terminated).

Returns

A pointer to the first occurrence of substring in s, or s itself if the substring is empty, or NULL if substring is not in s.

Stable:

ICU 2.0

See also

u_strrstr

u_strFindFirst

u_strFindLast

Convert a 16-bit Unicode string to Java Modified UTF-8.

See http://java.sun.com/javase/6/docs/api/java/io/DataInput.html#modified-utf-8

This function behaves according to the documentation for Java DataOutput.writeUTF() except that it does not encode the output length in the destination buffer and does not have an output length restriction. See http://java.sun.com/javase/6/docs/api/java/io/DataOutput.html#writeUTF(java.lang.String)

The input string need not be well-formed UTF-16. (Therefore there is no subchar parameter.)

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of chars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. pErrorCode Pointer to a standard ICU error code. Its input value must pass the U_SUCCESS() test, or else the function returns immediately. Check for U_FAILURE() on output or use with function chaining. (See User Guide for details.)

Returns

The pointer to destination buffer.

Stable:

ICU 4.4

See also

u_strToUTF8WithSub

u_strFromJavaModifiedUTF8WithSub

The string tokenizer API allows an application to break a string into tokens.

Unlike strtok(), the saveState (the current pointer within the original string) is maintained in saveState. In the first call, the argument src is a pointer to the string. In subsequent calls to return successive tokens of that string, src must be specified as NULL. The value saveState is set by this function to maintain the function's position within the string, and on each subsequent call you must give this argument the same variable. This function does handle surrogate pairs. This function is similar to the strtok_r() the POSIX Threads Extension (1003.1c-1995) version.

Parameters

src String containing token(s). This string will be modified. After the first call to u_strtok_r(), this argument must be NULL to get to the next token. delim Set of delimiter characters (Unicode code points). saveState The current pointer within the original string, which is set by this function. The saveState parameter should the address of a local variable of type UChar *. (i.e. defined "UChar *myLocalSaveState" and use &myLocalSaveState for this parameter).

Returns

A pointer to the next token found in src, or NULL when there are no more tokens.

Stable:

ICU 2.0

Lowercase the characters in a string.

Casing is locale-dependent and context-sensitive. The result may be longer or shorter than the original. The source string and the destination buffer are allowed to overlap.

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string. src The original string srcLength The length of the original string. If -1, then src must be zero-terminated. locale The locale to consider, or "" for the root locale or NULL for the default locale. pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.

Returns

The length of the result string. It may be greater than destCapacity. In that case, only some of the result was written to the destination buffer.

Stable:

ICU 2.0

Titlecase a string.

Casing is locale-dependent and context-sensitive. Titlecasing uses a break iterator to find the first characters of words that are to be titlecased. It titlecases those characters and lowercases all others.

The titlecase break iterator can be provided to customize for arbitrary styles, using rules and dictionaries beyond the standard iterators. It may be more efficient to always provide an iterator to avoid opening and closing one for each string. If the break iterator passed in is null, the default Unicode algorithm will be used to determine the titlecase positions.

This function uses only the setText(), first() and next() methods of the provided break iterator.

The result may be longer or shorter than the original. The source string and the destination buffer are allowed to overlap.

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string. src The original string srcLength The length of the original string. If -1, then src must be zero-terminated. titleIter A break iterator to find the first characters of words that are to be titlecased. If none is provided (NULL), then a standard titlecase break iterator is opened. locale The locale to consider, or "" for the root locale or NULL for the default locale. pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.

Returns

The length of the result string. It may be greater than destCapacity. In that case, only some of the result was written to the destination buffer.

Stable:

ICU 2.1

Uppercase the characters in a string.

Casing is locale-dependent and context-sensitive. The result may be longer or shorter than the original. The source string and the destination buffer are allowed to overlap.

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string. src The original string srcLength The length of the original string. If -1, then src must be zero-terminated. locale The locale to consider, or "" for the root locale or NULL for the default locale. pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.

Returns

The length of the result string. It may be greater than destCapacity. In that case, only some of the result was written to the destination buffer.

Stable:

ICU 2.0

Convert a UTF-16 string to UTF-32.

If the input string is not well-formed, then the U_INVALID_CHAR_FOUND error code is set.

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChar32s). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.

Returns

The pointer to destination buffer.

See also

u_strToUTF32WithSub

u_strFromUTF32

Stable:

ICU 2.0

Convert a UTF-16 string to UTF-32.

Same as u_strToUTF32() except for the additional subchar which is output for illegal input sequences, instead of stopping with the U_INVALID_CHAR_FOUND error code. With subchar==U_SENTINEL, this function behaves exactly like u_strToUTF32().

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of UChar32s). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. subchar The substitution character to use in place of an illegal input sequence, or U_SENTINEL if the function is to return with U_INVALID_CHAR_FOUND instead. A substitution character can be any valid Unicode code point (up to U+10FFFF) except for surrogate code points (U+D800..U+DFFF). The recommended value is U+FFFD "REPLACEMENT CHARACTER". pNumSubstitutions Output parameter receiving the number of substitutions if subchar>=0. Set to 0 if no substitutions occur or subchar<0. pNumSubstitutions can be NULL. pErrorCode Pointer to a standard ICU error code. Its input value must pass the U_SUCCESS() test, or else the function returns immediately. Check for U_FAILURE() on output or use with function chaining. (See User Guide for details.)

Returns

The pointer to destination buffer.

See also

u_strToUTF32

u_strFromUTF32WithSub

Stable:

ICU 4.2

Convert a UTF-16 string to UTF-8.

If the input string is not well-formed, then the U_INVALID_CHAR_FOUND error code is set.

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of chars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.

Returns

The pointer to destination buffer.

Stable:

ICU 2.0

See also

u_strToUTF8WithSub

u_strFromUTF8

Convert a UTF-16 string to UTF-8.

Same as u_strToUTF8() except for the additional subchar which is output for illegal input sequences, instead of stopping with the U_INVALID_CHAR_FOUND error code. With subchar==U_SENTINEL, this function behaves exactly like u_strToUTF8().

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of chars). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. subchar The substitution character to use in place of an illegal input sequence, or U_SENTINEL if the function is to return with U_INVALID_CHAR_FOUND instead. A substitution character can be any valid Unicode code point (up to U+10FFFF) except for surrogate code points (U+D800..U+DFFF). The recommended value is U+FFFD "REPLACEMENT CHARACTER". pNumSubstitutions Output parameter receiving the number of substitutions if subchar>=0. Set to 0 if no substitutions occur or subchar<0. pNumSubstitutions can be NULL. pErrorCode Pointer to a standard ICU error code. Its input value must pass the U_SUCCESS() test, or else the function returns immediately. Check for U_FAILURE() on output or use with function chaining. (See User Guide for details.)

Returns

The pointer to destination buffer.

See also

u_strToUTF8

u_strFromUTF8WithSub

Stable:

ICU 3.6

Convert a UTF-16 string to a wchar_t string.

If it is known at compile time that wchar_t strings are in UTF-16 or UTF-32, then this function simply calls the fast, dedicated function for that. Otherwise, two conversions UTF-16 -> default charset -> wchar_t* are performed.

Parameters

dest A buffer for the result string. The result will be zero-terminated if the buffer is large enough. destCapacity The size of the buffer (number of wchar_t's). If it is 0, then dest may be NULL and the function will only return the length of the result without writing any of the result string (pre-flighting). pDestLength A pointer to receive the number of units written to the destination. If pDestLength!=NULL then *pDestLength is always set to the number of output units corresponding to the transformation of all the input units, even in case of a buffer overflow. src The original source string srcLength The length of the original string. If -1, then src must be zero-terminated. pErrorCode Must be a valid pointer to an error code value, which must not indicate a failure before the function call.

Returns

The pointer to destination buffer.

Stable:

ICU 2.0

Copy a byte string encoded in the default codepage to a ustring.

Adds a null terminator. Performs a host byte to UChar conversion

Parameters

dst The destination string. src The source string.

Returns

A pointer to dst.

Stable:

ICU 2.0

Copy a byte string encoded in the default codepage to a ustring.

Copies at most n characters. The result will be null terminated if the length of src is less than n. Performs a host byte to UChar conversion

Parameters

dst The destination string. src The source string. n The maximum number of characters to copy.

Returns

A pointer to dst.

Stable:

ICU 2.0

Unescape a string of characters and write the resulting Unicode characters to the destination buffer.

The following escape sequences are recognized:

\uhhhh 4 hex digits; h in [0-9A-Fa-f] \Uhhhhhhhh 8 hex digits \xhh 1-2 hex digits \x{h...} 1-8 hex digits \ooo 1-3 octal digits; o in [0-7] \cX control-X; X is masked with 0x1F

as well as the standard ANSI C escapes:

\a => U+0007, \b => U+0008, \t => U+0009, \n => U+000A, \v => U+000B, \f => U+000C, \r => U+000D, \e => U+001B, \" => U+0022, \' => U+0027, \? => U+003F, \\ => U+005C

Anything else following a backslash is generically escaped. For example, "[a\\-z]" returns "[a-z]".

If an escape sequence is ill-formed, this method returns an empty string. An example of an ill-formed sequence is "\\u" followed by fewer than 4 hex digits.

The above characters are recognized in the compiler's codepage, that is, they are coded as 'u', '\', etc. Characters that are not parts of escape sequences are converted using u_charsToUChars().

This function is similar to UnicodeString::unescape() but not identical to it. The latter takes a source UnicodeString, so it does escape recognition but no conversion.

Parameters

src a zero-terminated string of invariant characters dest pointer to buffer to receive converted and unescaped text and, if there is room, a zero terminator. May be NULL for preflighting, in which case no UChars will be written, but the return value will still be valid. On error, an empty string is stored here (if possible). destCapacity the number of UChars that may be written at dest. Ignored if dest == NULL.

Returns

the length of unescaped string.

See also

u_unescapeAt

UnicodeString::unescape()

UnicodeString::unescapeAt()

Stable:

ICU 2.0

Unescape a single sequence.

The character at offset-1 is assumed (without checking) to be a backslash. This method takes a callback pointer to a function that returns the UChar at a given offset. By varying this callback, ICU functions are able to unescape char* strings, UnicodeString objects, and UFILE pointers.

If offset is out of range, or if the escape sequence is ill-formed, (UChar32)0xFFFFFFFF is returned. See documentation of u_unescape() for a list of recognized sequences.

Parameters

charAt callback function that returns a UChar of the source text given an offset and a context pointer. offset pointer to the offset that will be passed to charAt. The offset value will be updated upon return to point after the last parsed character of the escape sequence. On error the offset is unchanged. length the number of characters in the source text. The last character of the source text is considered to be at offset length-1. context an opaque pointer passed directly into charAt.

Returns

the character represented by the escape sequence at offset, or (UChar32)0xFFFFFFFF on error.

See also

u_unescape()

UnicodeString::unescape()

UnicodeString::unescapeAt()

Stable:

ICU 2.0

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