ustring.h File Reference

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

`#include "unicode/utypes.h"`
`#include "unicode/putil.h"`
`#include "unicode/uiter.h"`

Go to the source code of this file.

## Macros

#define | UBRK_TYPEDEF_UBREAK_ITERATOR
#define | U_STRING_DECL(var, cs, length) static const UChar var[(length)+1]=L ## cs
| Unicode String literals in C. More...
#define | U_STRING_INIT(var, cs, length)

## Typedefs

typedef struct UBreakIterator | UBreakIterator
| Simple declaration for u_strToTitle() to avoid including unicode/ubrk.h. More...
typedef UChar(* | UNESCAPE_CHAR_AT) (int32_t offset, void *context)
| Callback function for u_unescapeAt() that returns a character of the source text given an offset and a context pointer. More...

## Functions

U_CAPI int32_t | u_strlen (const UChar *s)
| Determine the length of an array of UChar. More...
U_CAPI int32_t | u_countChar32 (const UChar *s, int32_t length)
| Count Unicode code points in the length UChar code units of the string. More...
U_CAPI UBool | u_strHasMoreChar32Than (const UChar *s, int32_t length, int32_t number)
| Check if the string contains more Unicode code points than a certain number. More...
U_CAPI UChar * | u_strcat (UChar *dst, const UChar *src)
| Concatenate two ustrings. More...
U_CAPI UChar * | u_strncat (UChar *dst, const UChar *src, int32_t n)
| Concatenate two ustrings. More...
U_CAPI UChar * | u_strstr (const UChar *s, const UChar *substring)
| Find the first occurrence of a substring in a string. More...
U_CAPI UChar * | u_strFindFirst (const UChar *s, int32_t length, const UChar *substring, int32_t subLength)
| Find the first occurrence of a substring in a string. More...
U_CAPI UChar * | u_strchr (const UChar *s, UChar c)
| Find the first occurrence of a BMP code point in a string. More...
U_CAPI UChar * | u_strchr32 (const UChar *s, UChar32 c)
| Find the first occurrence of a code point in a string. More...
U_CAPI UChar * | u_strrstr (const UChar *s, const UChar *substring)
| Find the last occurrence of a substring in a string. More...
U_CAPI UChar * | u_strFindLast (const UChar *s, int32_t length, const UChar *substring, int32_t subLength)
| Find the last occurrence of a substring in a string. More...
U_CAPI UChar * | u_strrchr (const UChar *s, UChar c)
| Find the last occurrence of a BMP code point in a string. More...
U_CAPI UChar * | u_strrchr32 (const UChar *s, UChar32 c)
| Find the last occurrence of a code point in a string. More...
U_CAPI UChar * | u_strpbrk (const UChar *string, const UChar *matchSet)
| Locates the first occurrence in the string `string` of any of the characters in the string `matchSet`. More...
U_CAPI int32_t | u_strcspn (const UChar *string, const UChar *matchSet)
| Returns the number of consecutive characters in `string`, beginning with the first, that do not occur somewhere in `matchSet`. More...
U_CAPI int32_t | u_strspn (const UChar *string, const UChar *matchSet)
| Returns the number of consecutive characters in `string`, beginning with the first, that occur somewhere in `matchSet`. More...
U_CAPI UChar * | u_strtok_r (UChar *src, const UChar *delim, UChar **saveState)
| The string tokenizer API allows an application to break a string into tokens. More...
U_CAPI int32_t | u_strcmp (const UChar *s1, const UChar *s2)
| Compare two Unicode strings for bitwise equality (code unit order). More...
U_CAPI int32_t | u_strcmpCodePointOrder (const UChar *s1, const UChar *s2)
| Compare two Unicode strings in code point order. More...
U_CAPI int32_t | u_strCompare (const UChar *s1, int32_t length1, const UChar *s2, int32_t length2, UBool codePointOrder)
| Compare two Unicode strings (binary order). More...
U_CAPI int32_t | u_strCompareIter (UCharIterator *iter1, UCharIterator *iter2, UBool codePointOrder)
| Compare two Unicode strings (binary order) as presented by UCharIterator objects. More...
U_CAPI int32_t | u_strCaseCompare (const UChar *s1, int32_t length1, const UChar *s2, int32_t length2, uint32_t options, UErrorCode *pErrorCode)
| Compare two strings case-insensitively using full case folding. More...
U_CAPI int32_t | u_strncmp (const UChar *ucs1, const UChar *ucs2, int32_t n)
| Compare two ustrings for bitwise equality. More...
U_CAPI int32_t | u_strncmpCodePointOrder (const UChar *s1, const UChar *s2, int32_t n)
| Compare two Unicode strings in code point order. More...
U_CAPI int32_t | u_strcasecmp (const UChar *s1, const UChar *s2, uint32_t options)
| Compare two strings case-insensitively using full case folding. More...
U_CAPI int32_t | u_strncasecmp (const UChar *s1, const UChar *s2, int32_t n, uint32_t options)
| Compare two strings case-insensitively using full case folding. More...
U_CAPI int32_t | u_memcasecmp (const UChar *s1, const UChar *s2, int32_t length, uint32_t options)
| Compare two strings case-insensitively using full case folding. More...
U_CAPI UChar * | u_strcpy (UChar *dst, const UChar *src)
| Copy a ustring. More...
U_CAPI UChar * | u_strncpy (UChar *dst, const UChar *src, int32_t n)
| Copy a ustring. More...
U_CAPI UChar * | u_uastrcpy (UChar *dst, const char *src)
| Copy a byte string encoded in the default codepage to a ustring. More...
U_CAPI UChar * | u_uastrncpy (UChar *dst, const char *src, int32_t n)
| Copy a byte string encoded in the default codepage to a ustring. More...
U_CAPI char * | u_austrcpy (char *dst, const UChar *src)
| Copy ustring to a byte string encoded in the default codepage. More...
U_CAPI char * | u_austrncpy (char *dst, const UChar *src, int32_t n)
| Copy ustring to a byte string encoded in the default codepage. More...
U_CAPI UChar * | u_memcpy (UChar *dest, const UChar *src, int32_t count)
| Synonym for memcpy(), but with UChars only. More...
U_CAPI UChar * | u_memmove (UChar *dest, const UChar *src, int32_t count)
| Synonym for memmove(), but with UChars only. More...
U_CAPI UChar * | u_memset (UChar *dest, UChar c, int32_t count)
| Initialize `count` characters of `dest` to `c`. More...
U_CAPI int32_t | u_memcmp (const UChar *buf1, const UChar *buf2, int32_t count)
| Compare the first `count` UChars of each buffer. More...
U_CAPI int32_t | u_memcmpCodePointOrder (const UChar *s1, const UChar *s2, int32_t count)
| Compare two Unicode strings in code point order. More...
U_CAPI UChar * | u_memchr (const UChar *s, UChar c, int32_t count)
| Find the first occurrence of a BMP code point in a string. More...
U_CAPI UChar * | u_memchr32 (const UChar *s, UChar32 c, int32_t count)
| Find the first occurrence of a code point in a string. More...
U_CAPI UChar * | u_memrchr (const UChar *s, UChar c, int32_t count)
| Find the last occurrence of a BMP code point in a string. More...
U_CAPI UChar * | u_memrchr32 (const UChar *s, UChar32 c, int32_t count)
| Find the last occurrence of a code point in a string. More...
U_CAPI int32_t | u_unescape (const char *src, UChar *dest, int32_t destCapacity)
| Unescape a string of characters and write the resulting Unicode characters to the destination buffer. More...
U_CAPI UChar32 | u_unescapeAt (UNESCAPE_CHAR_AT charAt, int32_t *offset, int32_t length, void *context)
| Unescape a single sequence. More...
U_CAPI int32_t | u_strToUpper (UChar *dest, int32_t destCapacity, const UChar *src, int32_t srcLength, const char *locale, UErrorCode *pErrorCode)
| Uppercase the characters in a string. More...
U_CAPI int32_t | u_strToLower (UChar *dest, int32_t destCapacity, const UChar *src, int32_t srcLength, const char *locale, UErrorCode *pErrorCode)
| Lowercase the characters in a string. More...
U_CAPI int32_t | u_strToTitle (UChar *dest, int32_t destCapacity, const UChar *src, int32_t srcLength, UBreakIterator *titleIter, const char *locale, UErrorCode *pErrorCode)
| Titlecase a string. More...
U_CAPI int32_t | u_strFoldCase (UChar *dest, int32_t destCapacity, const UChar *src, int32_t srcLength, uint32_t options, UErrorCode *pErrorCode)
| Case-folds the characters in a string. More...
U_CAPI wchar_t * | u_strToWCS (wchar_t *dest, int32_t destCapacity, int32_t *pDestLength, const UChar *src, int32_t srcLength, UErrorCode *pErrorCode)
| Convert a UTF-16 string to a wchar_t string. More...
U_CAPI UChar * | u_strFromWCS (UChar *dest, int32_t destCapacity, int32_t *pDestLength, const wchar_t *src, int32_t srcLength, UErrorCode *pErrorCode)
| Convert a wchar_t string to UTF-16. More...
U_CAPI char * | u_strToUTF8 (char *dest, int32_t destCapacity, int32_t *pDestLength, const UChar *src, int32_t srcLength, UErrorCode *pErrorCode)
| Convert a UTF-16 string to UTF-8. More...
U_CAPI UChar * | u_strFromUTF8 (UChar *dest, int32_t destCapacity, int32_t *pDestLength, const char *src, int32_t srcLength, UErrorCode *pErrorCode)
| Convert a UTF-8 string to UTF-16. More...
U_CAPI char * | u_strToUTF8WithSub (char *dest, int32_t destCapacity, int32_t *pDestLength, const UChar *src, int32_t srcLength, UChar32 subchar, int32_t *pNumSubstitutions, UErrorCode *pErrorCode)
| Convert a UTF-16 string to UTF-8. More...
U_CAPI UChar * | u_strFromUTF8WithSub (UChar *dest, int32_t destCapacity, int32_t *pDestLength, const char *src, int32_t srcLength, UChar32 subchar, int32_t *pNumSubstitutions, UErrorCode *pErrorCode)
| Convert a UTF-8 string to UTF-16. More...
U_CAPI UChar * | u_strFromUTF8Lenient (UChar *dest, int32_t destCapacity, int32_t *pDestLength, const char *src, int32_t srcLength, UErrorCode *pErrorCode)
| Convert a UTF-8 string to UTF-16. More...
U_CAPI UChar32 * | u_strToUTF32 (UChar32 *dest, int32_t destCapacity, int32_t *pDestLength, const UChar *src, int32_t srcLength, UErrorCode *pErrorCode)
| Convert a UTF-16 string to UTF-32. More...
U_CAPI UChar * | u_strFromUTF32 (UChar *dest, int32_t destCapacity, int32_t *pDestLength, const UChar32 *src, int32_t srcLength, UErrorCode *pErrorCode)
| Convert a UTF-32 string to UTF-16. More...
U_CAPI UChar32 * | u_strToUTF32WithSub (UChar32 *dest, int32_t destCapacity, int32_t *pDestLength, const UChar *src, int32_t srcLength, UChar32 subchar, int32_t *pNumSubstitutions, UErrorCode *pErrorCode)
| Convert a UTF-16 string to UTF-32. More...
U_CAPI UChar * | u_strFromUTF32WithSub (UChar *dest, int32_t destCapacity, int32_t *pDestLength, const UChar32 *src, int32_t srcLength, UChar32 subchar, int32_t *pNumSubstitutions, UErrorCode *pErrorCode)
| Convert a UTF-32 string to UTF-16. More...
U_CAPI char * | u_strToJavaModifiedUTF8 (char *dest, int32_t destCapacity, int32_t *pDestLength, const UChar *src, int32_t srcLength, UErrorCode *pErrorCode)
| Convert a 16-bit Unicode string to Java Modified UTF-8. More...
U_CAPI UChar * | u_strFromJavaModifiedUTF8WithSub (UChar *dest, int32_t destCapacity, int32_t *pDestLength, const char *src, int32_t srcLength, UChar32 subchar, int32_t *pNumSubstitutions, UErrorCode *pErrorCode)
| Convert a Java Modified UTF-8 string to a 16-bit Unicode string. More...

## Detailed Description

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.

## Macro Definition Documentation

## U_STRING_DECL

#define U_STRING_DECL | ( |  | var,
|  |  | cs,
|  |  | length
| ) |  | static const UChar var[(length)+1]=L ## cs

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.

## U_STRING_INIT

#define U_STRING_INIT | ( |  | var,
|  |  | cs,
|  |  | length
| ) |  |

Stable:
  ICU 2.0

Definition at line 937 of file ustring.h.

## UBRK_TYPEDEF_UBREAK_ITERATOR

#define UBRK_TYPEDEF_UBREAK_ITERATOR

Internal:
  Do not use.

This API is for internal use only.

Definition at line 31 of file ustring.h.

## Typedef Documentation

## UBreakIterator

typedef struct UBreakIterator UBreakIterator

Simple declaration for u_strToTitle() to avoid including unicode/ubrk.h.

Stable:
  ICU 2.1

Definition at line 1 of file ustring.h.

## UNESCAPE_CHAR_AT

typedef UChar( * UNESCAPE_CHAR_AT) (int32_t offset, void *context)

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

  offset | pointer to the offset that will be passed to u_unescapeAt().
  context | an opaque pointer passed directly into u_unescapeAt()

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.

## Function Documentation

## u_austrcpy()

U_CAPI char* u_austrcpy | ( | char * | dst,
|  | const UChar * | src
| ) |  |

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

## u_austrncpy()

U_CAPI char* u_austrncpy | ( | char * | dst,
|  | const UChar * | src,
|  | int32_t | n
| ) |  |

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

## u_countChar32()

U_CAPI int32_t u_countChar32 | ( | const UChar * | s,
|  | int32_t | length
| ) |  |

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

## u_memcasecmp()

U_CAPI int32_t u_memcasecmp | ( | const UChar * | s1,
|  | const UChar * | s2,
|  | int32_t | length,
|  | uint32_t | options
| ) |  |

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

## u_memchr()

U_CAPI UChar* u_memchr | ( | const UChar * | s,
|  | UChar | c,
|  | int32_t | count
| ) |  |

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

## u_memchr32()

U_CAPI UChar* u_memchr32 | ( | const UChar * | s,
|  | UChar32 | c,
|  | int32_t | count
| ) |  |

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

## u_memcmp()

U_CAPI int32_t u_memcmp | ( | const UChar * | buf1,
|  | const UChar * | buf2,
|  | int32_t | count
| ) |  |

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

## u_memcmpCodePointOrder()

U_CAPI int32_t u_memcmpCodePointOrder | ( | const UChar * | s1,
|  | const UChar * | s2,
|  | int32_t | count
| ) |  |

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

## u_memcpy()

U_CAPI UChar* u_memcpy | ( | UChar * | dest,
|  | const UChar * | src,
|  | int32_t | count
| ) |  |

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

## u_memmove()

U_CAPI UChar* u_memmove | ( | UChar * | dest,
|  | const UChar * | src,
|  | int32_t | count
| ) |  |

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

## u_memrchr()

U_CAPI UChar* u_memrchr | ( | const UChar * | s,
|  | UChar | c,
|  | int32_t | count
| ) |  |

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

## u_memrchr32()

U_CAPI UChar* u_memrchr32 | ( | const UChar * | s,
|  | UChar32 | c,
|  | int32_t | count
| ) |  |

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

## u_memset()

U_CAPI UChar* u_memset | ( | UChar * | dest,
|  | UChar | c,
|  | int32_t | count
| ) |  |

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

## u_strcasecmp()

U_CAPI int32_t u_strcasecmp | ( | const UChar * | s1,
|  | const UChar * | s2,
|  | uint32_t | options
| ) |  |

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

## u_strCaseCompare()

U_CAPI int32_t u_strCaseCompare | ( | const UChar * | s1,
|  | int32_t | length1,
|  | const UChar * | s2,
|  | int32_t | length2,
|  | uint32_t | options,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strcat()

U_CAPI UChar* u_strcat | ( | UChar * | dst,
|  | const UChar * | src
| ) |  |

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

## u_strchr()

U_CAPI UChar* u_strchr | ( | const UChar * | s,
|  | UChar | c
| ) |  |

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

## u_strchr32()

U_CAPI UChar* u_strchr32 | ( | const UChar * | s,
|  | UChar32 | c
| ) |  |

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

## u_strcmp()

U_CAPI int32_t u_strcmp | ( | const UChar * | s1,
|  | const UChar * | s2
| ) |  |

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

## u_strcmpCodePointOrder()

U_CAPI int32_t u_strcmpCodePointOrder | ( | const UChar * | s1,
|  | const UChar * | s2
| ) |  |

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

## u_strCompare()

U_CAPI int32_t u_strCompare | ( | const UChar * | s1,
|  | int32_t | length1,
|  | const UChar * | s2,
|  | int32_t | length2,
|  | UBool | codePointOrder
| ) |  |

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

## u_strCompareIter()

U_CAPI int32_t u_strCompareIter | ( | UCharIterator * | iter1,
|  | UCharIterator * | iter2,
|  | UBool | codePointOrder
| ) |  |

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

## u_strcpy()

U_CAPI UChar* u_strcpy | ( | UChar * | dst,
|  | const UChar * | src
| ) |  |

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

## u_strcspn()

U_CAPI int32_t u_strcspn | ( | const UChar * | string,
|  | const UChar * | matchSet
| ) |  |

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

## u_strFindFirst()

U_CAPI UChar* u_strFindFirst | ( | const UChar * | s,
|  | int32_t | length,
|  | const UChar * | substring,
|  | int32_t | subLength
| ) |  |

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

## u_strFindLast()

U_CAPI UChar* u_strFindLast | ( | const UChar * | s,
|  | int32_t | length,
|  | const UChar * | substring,
|  | int32_t | subLength
| ) |  |

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

## u_strFoldCase()

U_CAPI int32_t u_strFoldCase | ( | UChar * | dest,
|  | int32_t | destCapacity,
|  | const UChar * | src,
|  | int32_t | srcLength,
|  | uint32_t | options,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strFromJavaModifiedUTF8WithSub()

U_CAPI UChar* u_strFromJavaModifiedUTF8WithSub | ( | UChar * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const char * | src,
|  | int32_t | srcLength,
|  | UChar32 | subchar,
|  | int32_t * | pNumSubstitutions,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strFromUTF32()

U_CAPI UChar* u_strFromUTF32 | ( | UChar * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const UChar32 * | src,
|  | int32_t | srcLength,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strFromUTF32WithSub()

U_CAPI UChar* u_strFromUTF32WithSub | ( | UChar * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const UChar32 * | src,
|  | int32_t | srcLength,
|  | UChar32 | subchar,
|  | int32_t * | pNumSubstitutions,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strFromUTF8()

U_CAPI UChar* u_strFromUTF8 | ( | UChar * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const char * | src,
|  | int32_t | srcLength,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strFromUTF8Lenient()

U_CAPI UChar* u_strFromUTF8Lenient | ( | UChar * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const char * | src,
|  | int32_t | srcLength,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strFromUTF8WithSub()

U_CAPI UChar* u_strFromUTF8WithSub | ( | UChar * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const char * | src,
|  | int32_t | srcLength,
|  | UChar32 | subchar,
|  | int32_t * | pNumSubstitutions,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strFromWCS()

U_CAPI UChar* u_strFromWCS | ( | UChar * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const wchar_t * | src,
|  | int32_t | srcLength,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strHasMoreChar32Than()

U_CAPI UBool u_strHasMoreChar32Than | ( | const UChar * | s,
|  | int32_t | length,
|  | int32_t | number
| ) |  |

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

## u_strlen()

U_CAPI int32_t u_strlen | ( | const UChar * | s | ) |

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

## u_strncasecmp()

U_CAPI int32_t u_strncasecmp | ( | const UChar * | s1,
|  | const UChar * | s2,
|  | int32_t | n,
|  | uint32_t | options
| ) |  |

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

## u_strncat()

U_CAPI UChar* u_strncat | ( | UChar * | dst,
|  | const UChar * | src,
|  | int32_t | n
| ) |  |

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

## u_strncmp()

U_CAPI int32_t u_strncmp | ( | const UChar * | ucs1,
|  | const UChar * | ucs2,
|  | int32_t | n
| ) |  |

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

## u_strncmpCodePointOrder()

U_CAPI int32_t u_strncmpCodePointOrder | ( | const UChar * | s1,
|  | const UChar * | s2,
|  | int32_t | n
| ) |  |

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

## u_strncpy()

U_CAPI UChar* u_strncpy | ( | UChar * | dst,
|  | const UChar * | src,
|  | int32_t | n
| ) |  |

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

## u_strpbrk()

U_CAPI UChar* u_strpbrk | ( | const UChar * | string,
|  | const UChar * | matchSet
| ) |  |

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

## u_strrchr()

U_CAPI UChar* u_strrchr | ( | const UChar * | s,
|  | UChar | c
| ) |  |

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

## u_strrchr32()

U_CAPI UChar* u_strrchr32 | ( | const UChar * | s,
|  | UChar32 | c
| ) |  |

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

## u_strrstr()

U_CAPI UChar* u_strrstr | ( | const UChar * | s,
|  | const UChar * | substring
| ) |  |

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

## u_strspn()

U_CAPI int32_t u_strspn | ( | const UChar * | string,
|  | const UChar * | matchSet
| ) |  |

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

## u_strstr()

U_CAPI UChar* u_strstr | ( | const UChar * | s,
|  | const UChar * | substring
| ) |  |

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

## u_strToJavaModifiedUTF8()

U_CAPI char* u_strToJavaModifiedUTF8 | ( | char * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const UChar * | src,
|  | int32_t | srcLength,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strtok_r()

U_CAPI UChar* u_strtok_r | ( | UChar * | src,
|  | const UChar * | delim,
|  | UChar ** | saveState
| ) |  |

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

## u_strToLower()

U_CAPI int32_t u_strToLower | ( | UChar * | dest,
|  | int32_t | destCapacity,
|  | const UChar * | src,
|  | int32_t | srcLength,
|  | const char * | locale,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strToTitle()

U_CAPI int32_t u_strToTitle | ( | UChar * | dest,
|  | int32_t | destCapacity,
|  | const UChar * | src,
|  | int32_t | srcLength,
|  | UBreakIterator * | titleIter,
|  | const char * | locale,
|  | UErrorCode * | pErrorCode
| ) |  |

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. The standard titlecase iterator for the root locale implements the algorithm of Unicode TR 21.

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

## u_strToUpper()

U_CAPI int32_t u_strToUpper | ( | UChar * | dest,
|  | int32_t | destCapacity,
|  | const UChar * | src,
|  | int32_t | srcLength,
|  | const char * | locale,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strToUTF32()

U_CAPI UChar32* u_strToUTF32 | ( | UChar32 * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const UChar * | src,
|  | int32_t | srcLength,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strToUTF32WithSub()

U_CAPI UChar32* u_strToUTF32WithSub | ( | UChar32 * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const UChar * | src,
|  | int32_t | srcLength,
|  | UChar32 | subchar,
|  | int32_t * | pNumSubstitutions,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strToUTF8()

U_CAPI char* u_strToUTF8 | ( | char * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const UChar * | src,
|  | int32_t | srcLength,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strToUTF8WithSub()

U_CAPI char* u_strToUTF8WithSub | ( | char * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const UChar * | src,
|  | int32_t | srcLength,
|  | UChar32 | subchar,
|  | int32_t * | pNumSubstitutions,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_strToWCS()

U_CAPI wchar_t* u_strToWCS | ( | wchar_t * | dest,
|  | int32_t | destCapacity,
|  | int32_t * | pDestLength,
|  | const UChar * | src,
|  | int32_t | srcLength,
|  | UErrorCode * | pErrorCode
| ) |  |

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

## u_uastrcpy()

U_CAPI UChar* u_uastrcpy | ( | UChar * | dst,
|  | const char * | src
| ) |  |

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

## u_uastrncpy()

U_CAPI UChar* u_uastrncpy | ( | UChar * | dst,
|  | const char * | src,
|  | int32_t | n
| ) |  |

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

## u_unescape()

U_CAPI int32_t u_unescape | ( | const char * | src,
|  | UChar * | dest,
|  | int32_t | destCapacity
| ) |  |

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

## u_unescapeAt()

U_CAPI UChar32 u_unescapeAt | ( | UNESCAPE_CHAR_AT | charAt,
|  | int32_t * | offset,
|  | int32_t | length,
|  | void * | context
| ) |  |

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