Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1685 insertions, 0 deletions

diff --git a/intl/icu/source/common/unicode/ustring.h b/intl/icu/source/common/unicode/ustring.h
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+++ b/intl/icu/source/common/unicode/ustring.h
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+// © 2016 and later: Unicode, Inc. and others.
+// License & terms of use: http://www.unicode.org/copyright.html
+/*
+**********************************************************************
+*   Copyright (C) 1998-2014, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+**********************************************************************
+*
+* File ustring.h
+*
+* Modification History:
+*
+*   Date        Name        Description
+*   12/07/98    bertrand    Creation.
+******************************************************************************
+*/
+
+#ifndef USTRING_H
+#define USTRING_H
+
+#include "unicode/utypes.h"
+#include "unicode/putil.h"
+#include "unicode/uiter.h"
+
+/**
+ * \def UBRK_TYPEDEF_UBREAK_ITERATOR
+ * @internal 
+ */
+
+#ifndef UBRK_TYPEDEF_UBREAK_ITERATOR
+#   define UBRK_TYPEDEF_UBREAK_ITERATOR
+/** Simple declaration for u_strToTitle() to avoid including unicode/ubrk.h. @stable ICU 2.1*/
+    typedef struct UBreakIterator UBreakIterator;
+#endif
+
+/**
+ * \file
+ * \brief 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 UTF-16 superseded UCS-2 with Unicode 2.0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.
+ */
+
+/**
+ * \defgroup ustring_ustrlen String Length
+ * \ingroup ustring_strlen
+ */
+/*@{*/
+/**
+ * Determine the length of an array of UChar.
+ *
+ * @param s The array of UChars, NULL (U+0000) terminated.
+ * @return The number of UChars in <code>chars</code>, minus the terminator.
+ * @stable ICU 2.0
+ */
+U_CAPI int32_t U_EXPORT2
+u_strlen(const UChar *s);
+/*@}*/
+
+/**
+ * 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).
+ *
+ * @param s The input string.
+ * @param length The number of UChar code units to be checked, or -1 to count all
+ *               code points before the first NUL (U+0000).
+ * @return The number of code points in the specified code units.
+ * @stable ICU 2.0
+ */
+U_CAPI int32_t U_EXPORT2
+u_countChar32(const UChar *s, int32_t length);
+
+/**
+ * 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.
+ *
+ * @param s The input string.
+ * @param length The length of the string, or -1 if it is NUL-terminated.
+ * @param number The number of code points in the string is compared against
+ *               the 'number' parameter.
+ * @return 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_CAPI UBool U_EXPORT2
+u_strHasMoreChar32Than(const UChar *s, int32_t length, int32_t number);
+
+/**
+ * Concatenate two ustrings.  Appends a copy of <code>src</code>,
+ * including the null terminator, to <code>dst</code>. The initial copied
+ * character from <code>src</code> overwrites the null terminator in <code>dst</code>.
+ *
+ * @param dst The destination string.
+ * @param src The source string.
+ * @return A pointer to <code>dst</code>.
+ * @stable ICU 2.0
+ */
+U_CAPI UChar* U_EXPORT2
+u_strcat(UChar     *dst, 
+    const UChar     *src);
+
+/**
+ * Concatenate two ustrings.  
+ * Appends at most <code>n</code> characters from <code>src</code> to <code>dst</code>.
+ * Adds a terminating NUL.
+ * If src is too long, then only <code>n-1</code> characters will be copied
+ * before the terminating NUL.
+ * If <code>n&lt;=0</code> then dst is not modified.
+ *
+ * @param dst The destination string.
+ * @param src The source string (can be NULL/invalid if n<=0).
+ * @param n The maximum number of characters to append; no-op if <=0.
+ * @return A pointer to <code>dst</code>.
+ * @stable ICU 2.0
+ */
+U_CAPI UChar* U_EXPORT2
+u_strncat(UChar     *dst, 
+     const UChar     *src, 
+     int32_t     n);
+
+/**
+ * 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.
+ *
+ * @param s The string to search (NUL-terminated).
+ * @param substring The substring to find (NUL-terminated).
+ * @return A pointer to the first occurrence of <code>substring</code> in <code>s</code>,
+ *         or <code>s</code> itself if the <code>substring</code> is empty,
+ *         or <code>NULL</code> if <code>substring</code> is not in <code>s</code>.
+ * @stable ICU 2.0
+ *
+ * @see u_strrstr
+ * @see u_strFindFirst
+ * @see u_strFindLast
+ */
+U_CAPI UChar * U_EXPORT2
+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.
+ *
+ * @param s The string to search.
+ * @param length The length of s (number of UChars), or -1 if it is NUL-terminated.
+ * @param substring The substring to find (NUL-terminated).
+ * @param subLength The length of substring (number of UChars), or -1 if it is NUL-terminated.
+ * @return A pointer to the first occurrence of <code>substring</code> in <code>s</code>,
+ *         or <code>s</code> itself if the <code>substring</code> is empty,
+ *         or <code>NULL</code> if <code>substring</code> is not in <code>s</code>.
+ * @stable ICU 2.4
+ *
+ * @see u_strstr
+ * @see u_strFindLast
+ */
+U_CAPI UChar * U_EXPORT2
+u_strFindFirst(const UChar *s, int32_t length, const UChar *substring, int32_t subLength);
+
+/**
+ * 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.
+ *
+ * @param s The string to search (NUL-terminated).
+ * @param c The BMP code point to find.
+ * @return A pointer to the first occurrence of <code>c</code> in <code>s</code>
+ *         or <code>NULL</code> if <code>c</code> is not in <code>s</code>.
+ * @stable ICU 2.0
+ *
+ * @see u_strchr32
+ * @see u_memchr
+ * @see u_strstr
+ * @see u_strFindFirst
+ */
+U_CAPI UChar * U_EXPORT2
+u_strchr(const UChar *s, UChar 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.
+ *
+ * @param s The string to search (NUL-terminated).
+ * @param c The code point to find.
+ * @return A pointer to the first occurrence of <code>c</code> in <code>s</code>
+ *         or <code>NULL</code> if <code>c</code> is not in <code>s</code>.
+ * @stable ICU 2.0
+ *
+ * @see u_strchr
+ * @see u_memchr32
+ * @see u_strstr
+ * @see u_strFindFirst
+ */
+U_CAPI UChar * U_EXPORT2
+u_strchr32(const UChar *s, UChar32 c);
+
+/**
+ * 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.
+ *
+ * @param s The string to search (NUL-terminated).
+ * @param substring The substring to find (NUL-terminated).
+ * @return A pointer to the last occurrence of <code>substring</code> in <code>s</code>,
+ *         or <code>s</code> itself if the <code>substring</code> is empty,
+ *         or <code>NULL</code> if <code>substring</code> is not in <code>s</code>.
+ * @stable ICU 2.4
+ *
+ * @see u_strstr
+ * @see u_strFindFirst
+ * @see u_strFindLast
+ */
+U_CAPI UChar * U_EXPORT2
+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.
+ *
+ * @param s The string to search.
+ * @param length The length of s (number of UChars), or -1 if it is NUL-terminated.
+ * @param substring The substring to find (NUL-terminated).
+ * @param subLength The length of substring (number of UChars), or -1 if it is NUL-terminated.
+ * @return A pointer to the last occurrence of <code>substring</code> in <code>s</code>,
+ *         or <code>s</code> itself if the <code>substring</code> is empty,
+ *         or <code>NULL</code> if <code>substring</code> is not in <code>s</code>.
+ * @stable ICU 2.4
+ *
+ * @see u_strstr
+ * @see u_strFindLast
+ */
+U_CAPI UChar * U_EXPORT2
+u_strFindLast(const UChar *s, int32_t length, const UChar *substring, int32_t subLength);
+
+/**
+ * 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.
+ *
+ * @param s The string to search (NUL-terminated).
+ * @param c The BMP code point to find.
+ * @return A pointer to the last occurrence of <code>c</code> in <code>s</code>
+ *         or <code>NULL</code> if <code>c</code> is not in <code>s</code>.
+ * @stable ICU 2.4
+ *
+ * @see u_strrchr32
+ * @see u_memrchr
+ * @see u_strrstr
+ * @see u_strFindLast
+ */
+U_CAPI UChar * U_EXPORT2
+u_strrchr(const UChar *s, UChar 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.
+ *
+ * @param s The string to search (NUL-terminated).
+ * @param c The code point to find.
+ * @return A pointer to the last occurrence of <code>c</code> in <code>s</code>
+ *         or <code>NULL</code> if <code>c</code> is not in <code>s</code>.
+ * @stable ICU 2.4
+ *
+ * @see u_strrchr
+ * @see u_memchr32
+ * @see u_strrstr
+ * @see u_strFindLast
+ */
+U_CAPI UChar * U_EXPORT2
+u_strrchr32(const UChar *s, UChar32 c);
+
+/**
+ * Locates the first occurrence in the string <code>string</code> of any of the characters
+ * in the string <code>matchSet</code>.
+ * Works just like C's strpbrk but with Unicode.
+ *
+ * @param string The string in which to search, NUL-terminated.
+ * @param matchSet A NUL-terminated string defining a set of code points
+ *                 for which to search in the text string.
+ * @return A pointer to the  character in <code>string</code> that matches one of the
+ *         characters in <code>matchSet</code>, or NULL if no such character is found.
+ * @stable ICU 2.0
+ */
+U_CAPI UChar * U_EXPORT2
+u_strpbrk(const UChar *string, const UChar *matchSet);
+
+/**
+ * Returns the number of consecutive characters in <code>string</code>,
+ * beginning with the first, that do not occur somewhere in <code>matchSet</code>.
+ * Works just like C's strcspn but with Unicode.
+ *
+ * @param string The string in which to search, NUL-terminated.
+ * @param matchSet A NUL-terminated string defining a set of code points
+ *                 for which to search in the text string.
+ * @return The number of initial characters in <code>string</code> that do not
+ *         occur in <code>matchSet</code>.
+ * @see u_strspn
+ * @stable ICU 2.0
+ */
+U_CAPI int32_t U_EXPORT2
+u_strcspn(const UChar *string, const UChar *matchSet);
+
+/**
+ * Returns the number of consecutive characters in <code>string</code>,
+ * beginning with the first, that occur somewhere in <code>matchSet</code>.
+ * Works just like C's strspn but with Unicode.
+ *
+ * @param string The string in which to search, NUL-terminated.
+ * @param matchSet A NUL-terminated string defining a set of code points
+ *                 for which to search in the text string.
+ * @return The number of initial characters in <code>string</code> that do
+ *         occur in <code>matchSet</code>.
+ * @see u_strcspn
+ * @stable ICU 2.0
+ */
+U_CAPI int32_t U_EXPORT2
+u_strspn(const UChar *string, const UChar *matchSet);
+
+/**
+ * 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.
+ *
+ * @param 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.
+ * @param delim Set of delimiter characters (Unicode code points).
+ * @param 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).
+ * @return A pointer to the next token found in src, or NULL
+ *         when there are no more tokens.
+ * @stable ICU 2.0
+ */
+U_CAPI UChar * U_EXPORT2
+u_strtok_r(UChar    *src, 
+     const UChar    *delim,
+           UChar   **saveState);
+
+/**
+ * Compare two Unicode strings for bitwise equality (code unit order).
+ *
+ * @param s1 A string to compare.
+ * @param s2 A string to compare.
+ * @return 0 if <code>s1</code> and <code>s2</code> are bitwise equal; a negative
+ * value if <code>s1</code> is bitwise less than <code>s2,</code>; a positive
+ * value if <code>s1</code> is bitwise greater than <code>s2</code>.
+ * @stable ICU 2.0
+ */
+U_CAPI int32_t  U_EXPORT2
+u_strcmp(const UChar     *s1, 
+         const UChar     *s2);
+
+/**
+ * Compare two Unicode strings in code point order.
+ * See u_strCompare for details.
+ *
+ * @param s1 A string to compare.
+ * @param s2 A string to compare.
+ * @return 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_CAPI int32_t U_EXPORT2
+u_strcmpCodePointOrder(const UChar *s1, const UChar *s2);
+
+/**
+ * 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.
+ *
+ * @param s1 First source string.
+ * @param length1 Length of first source string, or -1 if NUL-terminated.
+ *
+ * @param s2 Second source string.
+ * @param length2 Length of second source string, or -1 if NUL-terminated.
+ *
+ * @param codePointOrder Choose between code unit order (false)
+ *                       and code point order (true).
+ *
+ * @return <0 or 0 or >0 as usual for string comparisons
+ *
+ * @stable ICU 2.2
+ */
+U_CAPI int32_t U_EXPORT2
+u_strCompare(const UChar *s1, int32_t length1,
+             const UChar *s2, int32_t length2,
+             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.
+ *
+ * @param iter1 First source string iterator.
+ * @param iter2 Second source string iterator.
+ * @param codePointOrder Choose between code unit order (false)
+ *                       and code point order (true).
+ *
+ * @return <0 or 0 or >0 as usual for string comparisons
+ *
+ * @see u_strCompare
+ *
+ * @stable ICU 2.6
+ */
+U_CAPI int32_t U_EXPORT2
+u_strCompareIter(UCharIterator *iter1, UCharIterator *iter2, UBool codePointOrder);
+
+/**
+ * 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.
+ *
+ * @param s1 First source string.
+ * @param length1 Length of first source string, or -1 if NUL-terminated.
+ *
+ * @param s2 Second source string.
+ * @param length2 Length of second source string, or -1 if NUL-terminated.
+ *
+ * @param 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
+ *
+ * @param pErrorCode Must be a valid pointer to an error code value,
+ *                  which must not indicate a failure before the function call.
+ *
+ * @return <0 or 0 or >0 as usual for string comparisons
+ *
+ * @stable ICU 2.2
+ */
+U_CAPI int32_t U_EXPORT2
+u_strCaseCompare(const UChar *s1, int32_t length1,
+                 const UChar *s2, int32_t length2,
+                 uint32_t options,
+                 UErrorCode *pErrorCode);
+
+/**
+ * Compare two ustrings for bitwise equality. 
+ * Compares at most <code>n</code> characters.
+ *
+ * @param ucs1 A string to compare (can be NULL/invalid if n<=0).
+ * @param ucs2 A string to compare (can be NULL/invalid if n<=0).
+ * @param n The maximum number of characters to compare; always returns 0 if n<=0.
+ * @return 0 if <code>s1</code> and <code>s2</code> are bitwise equal; a negative
+ * value if <code>s1</code> is bitwise less than <code>s2</code>; a positive
+ * value if <code>s1</code> is bitwise greater than <code>s2</code>.
+ * @stable ICU 2.0
+ */
+U_CAPI int32_t U_EXPORT2
+u_strncmp(const UChar     *ucs1, 
+     const UChar     *ucs2, 
+     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().
+ *
+ * @param s1 A string to compare.
+ * @param s2 A string to compare.
+ * @param n The maximum number of characters to compare.
+ * @return 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_CAPI int32_t U_EXPORT2
+u_strncmpCodePointOrder(const UChar *s1, const UChar *s2, int32_t n);
+
+/**
+ * Compare two strings case-insensitively using full case folding.
+ * This is equivalent to u_strcmp(u_strFoldCase(s1, options), u_strFoldCase(s2, options)).
+ *
+ * @param s1 A string to compare.
+ * @param s2 A string to compare.
+ * @param 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
+ *
+ * @return A negative, zero, or positive integer indicating the comparison result.
+ * @stable ICU 2.0
+ */
+U_CAPI int32_t U_EXPORT2
+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, at most n, options),
+ * u_strFoldCase(s2, at most n, options)).
+ *
+ * @param s1 A string to compare.
+ * @param s2 A string to compare.
+ * @param n The maximum number of characters each string to case-fold and then compare.
+ * @param 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
+ *
+ * @return A negative, zero, or positive integer indicating the comparison result.
+ * @stable ICU 2.0
+ */
+U_CAPI int32_t U_EXPORT2
+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, n, options),
+ * u_strFoldCase(s2, n, options)).
+ *
+ * @param s1 A string to compare.
+ * @param s2 A string to compare.
+ * @param length The number of characters in each string to case-fold and then compare.
+ * @param 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
+ *
+ * @return A negative, zero, or positive integer indicating the comparison result.
+ * @stable ICU 2.0
+ */
+U_CAPI int32_t U_EXPORT2
+u_memcasecmp(const UChar *s1, const UChar *s2, int32_t length, uint32_t options);
+
+/**
+ * Copy a ustring. Adds a null terminator.
+ *
+ * @param dst The destination string.
+ * @param src The source string.
+ * @return A pointer to <code>dst</code>.
+ * @stable ICU 2.0
+ */
+U_CAPI UChar* U_EXPORT2
+u_strcpy(UChar     *dst, 
+    const UChar     *src);
+
+/**
+ * Copy a ustring.
+ * Copies at most <code>n</code> characters.  The result will be null terminated
+ * if the length of <code>src</code> is less than <code>n</code>.
+ *
+ * @param dst The destination string.
+ * @param src The source string (can be NULL/invalid if n<=0).
+ * @param n The maximum number of characters to copy; no-op if <=0.
+ * @return A pointer to <code>dst</code>.
+ * @stable ICU 2.0
+ */
+U_CAPI UChar* U_EXPORT2
+u_strncpy(UChar     *dst, 
+     const UChar     *src, 
+     int32_t     n);
+
+#if !UCONFIG_NO_CONVERSION
+
+/**
+ * Copy a byte string encoded in the default codepage to a ustring.
+ * Adds a null terminator.
+ * Performs a host byte to UChar conversion
+ *
+ * @param dst The destination string.
+ * @param src The source string.
+ * @return A pointer to <code>dst</code>.
+ * @stable ICU 2.0
+ */
+U_CAPI UChar* U_EXPORT2 u_uastrcpy(UChar *dst,
+               const char *src );
+
+/**
+ * Copy a byte string encoded in the default codepage to a ustring.
+ * Copies at most <code>n</code> characters.  The result will be null terminated
+ * if the length of <code>src</code> is less than <code>n</code>.
+ * Performs a host byte to UChar conversion
+ *
+ * @param dst The destination string.
+ * @param src The source string.
+ * @param n The maximum number of characters to copy.
+ * @return A pointer to <code>dst</code>.
+ * @stable ICU 2.0
+ */
+U_CAPI UChar* U_EXPORT2 u_uastrncpy(UChar *dst,
+            const char *src,
+            int32_t n);
+
+/**
+ * Copy ustring to a byte string encoded in the default codepage.
+ * Adds a null terminator.
+ * Performs a UChar to host byte conversion
+ *
+ * @param dst The destination string.
+ * @param src The source string.
+ * @return A pointer to <code>dst</code>.
+ * @stable ICU 2.0
+ */
+U_CAPI char* U_EXPORT2 u_austrcpy(char *dst,
+            const UChar *src );
+
+/**
+ * Copy ustring to a byte string encoded in the default codepage.
+ * Copies at most <code>n</code> characters.  The result will be null terminated
+ * if the length of <code>src</code> is less than <code>n</code>.
+ * Performs a UChar to host byte conversion
+ *
+ * @param dst The destination string.
+ * @param src The source string.
+ * @param n The maximum number of characters to copy.
+ * @return A pointer to <code>dst</code>.
+ * @stable ICU 2.0
+ */
+U_CAPI char* U_EXPORT2 u_austrncpy(char *dst,
+            const UChar *src,
+            int32_t n );
+
+#endif
+
+/**
+ * Synonym for memcpy(), but with UChars only.
+ * @param dest The destination string
+ * @param src The source string (can be NULL/invalid if count<=0)
+ * @param count The number of characters to copy; no-op if <=0
+ * @return A pointer to <code>dest</code>
+ * @stable ICU 2.0
+ */
+U_CAPI UChar* U_EXPORT2
+u_memcpy(UChar *dest, const UChar *src, int32_t count);
+
+/**
+ * Synonym for memmove(), but with UChars only.
+ * @param dest The destination string
+ * @param src The source string (can be NULL/invalid if count<=0)
+ * @param count The number of characters to move; no-op if <=0
+ * @return A pointer to <code>dest</code>
+ * @stable ICU 2.0
+ */
+U_CAPI UChar* U_EXPORT2
+u_memmove(UChar *dest, const UChar *src, int32_t count);
+
+/**
+ * Initialize <code>count</code> characters of <code>dest</code> to <code>c</code>.
+ *
+ * @param dest The destination string.
+ * @param c The character to initialize the string.
+ * @param count The maximum number of characters to set.
+ * @return A pointer to <code>dest</code>.
+ * @stable ICU 2.0
+ */
+U_CAPI UChar* U_EXPORT2
+u_memset(UChar *dest, UChar c, int32_t count);
+
+/**
+ * Compare the first <code>count</code> UChars of each buffer.
+ *
+ * @param buf1 The first string to compare.
+ * @param buf2 The second string to compare.
+ * @param count The maximum number of UChars to compare.
+ * @return 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_CAPI int32_t U_EXPORT2
+u_memcmp(const UChar *buf1, const UChar *buf2, 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().
+ *
+ * @param s1 A string to compare.
+ * @param s2 A string to compare.
+ * @param count The maximum number of characters to compare.
+ * @return 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_CAPI int32_t U_EXPORT2
+u_memcmpCodePointOrder(const UChar *s1, const UChar *s2, 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.
+ *
+ * @param s The string to search (contains <code>count</code> UChars).
+ * @param c The BMP code point to find.
+ * @param count The length of the string.
+ * @return A pointer to the first occurrence of <code>c</code> in <code>s</code>
+ *         or <code>NULL</code> if <code>c</code> is not in <code>s</code>.
+ * @stable ICU 2.0
+ *
+ * @see u_strchr
+ * @see u_memchr32
+ * @see u_strFindFirst
+ */
+U_CAPI UChar* U_EXPORT2
+u_memchr(const UChar *s, UChar 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.
+ *
+ * @param s The string to search (contains <code>count</code> UChars).
+ * @param c The code point to find.
+ * @param count The length of the string.
+ * @return A pointer to the first occurrence of <code>c</code> in <code>s</code>
+ *         or <code>NULL</code> if <code>c</code> is not in <code>s</code>.
+ * @stable ICU 2.0
+ *
+ * @see u_strchr32
+ * @see u_memchr
+ * @see u_strFindFirst
+ */
+U_CAPI UChar* U_EXPORT2
+u_memchr32(const UChar *s, UChar32 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.
+ *
+ * @param s The string to search (contains <code>count</code> UChars).
+ * @param c The BMP code point to find.
+ * @param count The length of the string.
+ * @return A pointer to the last occurrence of <code>c</code> in <code>s</code>
+ *         or <code>NULL</code> if <code>c</code> is not in <code>s</code>.
+ * @stable ICU 2.4
+ *
+ * @see u_strrchr
+ * @see u_memrchr32
+ * @see u_strFindLast
+ */
+U_CAPI UChar* U_EXPORT2
+u_memrchr(const UChar *s, UChar 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.
+ *
+ * @param s The string to search (contains <code>count</code> UChars).
+ * @param c The code point to find.
+ * @param count The length of the string.
+ * @return A pointer to the last occurrence of <code>c</code> in <code>s</code>
+ *         or <code>NULL</code> if <code>c</code> is not in <code>s</code>.
+ * @stable ICU 2.4
+ *
+ * @see u_strrchr32
+ * @see u_memrchr
+ * @see u_strFindLast
+ */
+U_CAPI UChar* U_EXPORT2
+u_memrchr32(const UChar *s, UChar32 c, int32_t count);
+
+/**
+ * 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
+ */
+#if defined(U_DECLARE_UTF16)
+#   define U_STRING_DECL(var, cs, length) static const UChar *var=(const UChar *)U_DECLARE_UTF16(cs)
+    /**@stable ICU 2.0 */
+#   define U_STRING_INIT(var, cs, length)
+#elif U_SIZEOF_WCHAR_T==U_SIZEOF_UCHAR && (U_CHARSET_FAMILY==U_ASCII_FAMILY || defined(U_WCHAR_IS_UTF16))
+#   define U_STRING_DECL(var, cs, length) static const UChar var[(length)+1]=L ## cs
+    /**@stable ICU 2.0 */
+#   define U_STRING_INIT(var, cs, length)
+#else
+#   define U_STRING_DECL(var, cs, length) static UChar var[(length)+1]
+    /**@stable ICU 2.0 */
+#   define U_STRING_INIT(var, cs, length) u_charsToUChars(cs, var, length+1)
+#endif
+
+/**
+ * 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,
+ * \\&quot; => 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.
+ *
+ * @param src a zero-terminated string of invariant characters
+ * @param 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).
+ * @param destCapacity the number of UChars that may be written at
+ * dest.  Ignored if dest == NULL.
+ * @return the length of unescaped string.
+ * @see u_unescapeAt
+ * @see UnicodeString#unescape()
+ * @see UnicodeString#unescapeAt()
+ * @stable ICU 2.0
+ */
+U_CAPI int32_t U_EXPORT2
+u_unescape(const char *src,
+           UChar *dest, int32_t destCapacity);
+
+U_CDECL_BEGIN
+/**
+ * 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().
+ *
+ * @param offset pointer to the offset that will be passed to u_unescapeAt().
+ * @param context an opaque pointer passed directly into u_unescapeAt()
+ * @return the character represented by the escape sequence at
+ * offset
+ * @see u_unescapeAt
+ * @stable ICU 2.0
+ */
+typedef UChar (U_CALLCONV *UNESCAPE_CHAR_AT)(int32_t offset, void *context);
+U_CDECL_END
+
+/**
+ * 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.
+ *
+ * @param charAt callback function that returns a UChar of the source
+ * text given an offset and a context pointer.
+ * @param 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.
+ * @param length the number of characters in the source text.  The
+ * last character of the source text is considered to be at offset
+ * length-1.
+ * @param context an opaque pointer passed directly into charAt.
+ * @return the character represented by the escape sequence at
+ * offset, or (UChar32)0xFFFFFFFF on error.
+ * @see u_unescape()
+ * @see UnicodeString#unescape()
+ * @see UnicodeString#unescapeAt()
+ * @stable ICU 2.0
+ */
+U_CAPI UChar32 U_EXPORT2
+u_unescapeAt(UNESCAPE_CHAR_AT charAt,
+             int32_t *offset,
+             int32_t length,
+             void *context);
+
+/**
+ * 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.
+ *
+ * @param dest      A buffer for the result string. The result will be zero-terminated if
+ *                  the buffer is large enough.
+ * @param 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.
+ * @param src       The original string
+ * @param srcLength The length of the original string. If -1, then src must be zero-terminated.
+ * @param locale    The locale to consider, or "" for the root locale or NULL for the default locale.
+ * @param pErrorCode Must be a valid pointer to an error code value,
+ *                  which must not indicate a failure before the function call.
+ * @return 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_CAPI int32_t U_EXPORT2
+u_strToUpper(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.
+ *
+ * @param dest      A buffer for the result string. The result will be zero-terminated if
+ *                  the buffer is large enough.
+ * @param 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.
+ * @param src       The original string
+ * @param srcLength The length of the original string. If -1, then src must be zero-terminated.
+ * @param locale    The locale to consider, or "" for the root locale or NULL for the default locale.
+ * @param pErrorCode Must be a valid pointer to an error code value,
+ *                  which must not indicate a failure before the function call.
+ * @return 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_CAPI int32_t U_EXPORT2
+u_strToLower(UChar *dest, int32_t destCapacity,
+             const UChar *src, int32_t srcLength,
+             const char *locale,
+             UErrorCode *pErrorCode);
+
+#if !UCONFIG_NO_BREAK_ITERATION
+
+/**
+ * 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.
+ *
+ * @param dest      A buffer for the result string. The result will be zero-terminated if
+ *                  the buffer is large enough.
+ * @param 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.
+ * @param src       The original string
+ * @param srcLength The length of the original string. If -1, then src must be zero-terminated.
+ * @param 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.
+ * @param locale    The locale to consider, or "" for the root locale or NULL for the default locale.
+ * @param pErrorCode Must be a valid pointer to an error code value,
+ *                  which must not indicate a failure before the function call.
+ * @return 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_CAPI int32_t U_EXPORT2
+u_strToTitle(UChar *dest, int32_t destCapacity,
+             const UChar *src, int32_t srcLength,
+             UBreakIterator *titleIter,
+             const char *locale,
+             UErrorCode *pErrorCode);
+
+#endif
+
+/**
+ * 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.
+ *
+ * @param dest      A buffer for the result string. The result will be zero-terminated if
+ *                  the buffer is large enough.
+ * @param 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.
+ * @param src       The original string
+ * @param srcLength The length of the original string. If -1, then src must be zero-terminated.
+ * @param options   Either U_FOLD_CASE_DEFAULT or U_FOLD_CASE_EXCLUDE_SPECIAL_I
+ * @param pErrorCode Must be a valid pointer to an error code value,
+ *                  which must not indicate a failure before the function call.
+ * @return 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_CAPI int32_t U_EXPORT2
+u_strFoldCase(UChar *dest, int32_t destCapacity,
+              const UChar *src, int32_t srcLength,
+              uint32_t options,
+              UErrorCode *pErrorCode);
+
+#if defined(U_WCHAR_IS_UTF16) || defined(U_WCHAR_IS_UTF32) || !UCONFIG_NO_CONVERSION
+/**
+ * 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.
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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).
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param pErrorCode    Must be a valid pointer to an error code value,
+ *                      which must not indicate a failure before the function call.
+ * @return The pointer to destination buffer.
+ * @stable ICU 2.0
+ */
+U_CAPI wchar_t* U_EXPORT2
+u_strToWCS(wchar_t *dest, 
+           int32_t destCapacity,
+           int32_t *pDestLength,
+           const UChar *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.
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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).
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param pErrorCode    Must be a valid pointer to an error code value,
+ *                      which must not indicate a failure before the function call.
+ * @return The pointer to destination buffer.
+ * @stable ICU 2.0
+ */
+U_CAPI UChar* U_EXPORT2
+u_strFromWCS(UChar   *dest,
+             int32_t destCapacity, 
+             int32_t *pDestLength,
+             const wchar_t *src,
+             int32_t srcLength,
+             UErrorCode *pErrorCode);
+#endif /* defined(U_WCHAR_IS_UTF16) || defined(U_WCHAR_IS_UTF32) || !UCONFIG_NO_CONVERSION */
+
+/**
+ * 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.
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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).
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param pErrorCode    Must be a valid pointer to an error code value,
+ *                      which must not indicate a failure before the function call.
+ * @return The pointer to destination buffer.
+ * @stable ICU 2.0
+ * @see u_strToUTF8WithSub
+ * @see u_strFromUTF8
+ */
+U_CAPI char* U_EXPORT2 
+u_strToUTF8(char *dest,           
+            int32_t destCapacity,
+            int32_t *pDestLength,
+            const UChar *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.
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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).
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param pErrorCode    Must be a valid pointer to an error code value,
+ *                      which must not indicate a failure before the function call.
+ * @return The pointer to destination buffer.
+ * @stable ICU 2.0
+ * @see u_strFromUTF8WithSub
+ * @see u_strFromUTF8Lenient
+ */
+U_CAPI UChar* U_EXPORT2
+u_strFromUTF8(UChar *dest,             
+              int32_t destCapacity,
+              int32_t *pDestLength,
+              const char *src, 
+              int32_t srcLength,
+              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().
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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).
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param 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".
+ * @param 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.
+ * @param 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.)
+ * @return The pointer to destination buffer.
+ * @see u_strToUTF8
+ * @see u_strFromUTF8WithSub
+ * @stable ICU 3.6
+ */
+U_CAPI char* U_EXPORT2
+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-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().
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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).
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param 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".
+ * @param 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.
+ * @param 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.)
+ * @return The pointer to destination buffer.
+ * @see u_strFromUTF8
+ * @see u_strFromUTF8Lenient
+ * @see u_strToUTF8WithSub
+ * @stable ICU 3.6
+ */
+U_CAPI UChar* U_EXPORT2
+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 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.
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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.
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param 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.)
+ * @return The pointer to destination buffer.
+ * @see u_strFromUTF8
+ * @see u_strFromUTF8WithSub
+ * @see u_strToUTF8WithSub
+ * @stable ICU 3.6
+ */
+U_CAPI UChar * U_EXPORT2
+u_strFromUTF8Lenient(UChar *dest,
+                     int32_t destCapacity,
+                     int32_t *pDestLength,
+                     const char *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.
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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).
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param pErrorCode    Must be a valid pointer to an error code value,
+ *                      which must not indicate a failure before the function call.
+ * @return The pointer to destination buffer.
+ * @see u_strToUTF32WithSub
+ * @see u_strFromUTF32
+ * @stable ICU 2.0
+ */
+U_CAPI UChar32* U_EXPORT2 
+u_strToUTF32(UChar32 *dest, 
+             int32_t  destCapacity,
+             int32_t  *pDestLength,
+             const UChar *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.
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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).
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param pErrorCode    Must be a valid pointer to an error code value,
+ *                      which must not indicate a failure before the function call.
+ * @return The pointer to destination buffer.
+ * @see u_strFromUTF32WithSub
+ * @see u_strToUTF32
+ * @stable ICU 2.0
+ */
+U_CAPI UChar* U_EXPORT2 
+u_strFromUTF32(UChar   *dest,
+               int32_t destCapacity, 
+               int32_t *pDestLength,
+               const UChar32 *src,
+               int32_t srcLength,
+               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().
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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).
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param 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".
+ * @param 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.
+ * @param 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.)
+ * @return The pointer to destination buffer.
+ * @see u_strToUTF32
+ * @see u_strFromUTF32WithSub
+ * @stable ICU 4.2
+ */
+U_CAPI UChar32* U_EXPORT2
+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-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().
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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).
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param 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".
+ * @param 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.
+ * @param 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.)
+ * @return The pointer to destination buffer.
+ * @see u_strFromUTF32
+ * @see u_strToUTF32WithSub
+ * @stable ICU 4.2
+ */
+U_CAPI UChar* U_EXPORT2
+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 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.)
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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).
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param 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.)
+ * @return The pointer to destination buffer.
+ * @stable ICU 4.4
+ * @see u_strToUTF8WithSub
+ * @see u_strFromJavaModifiedUTF8WithSub
+ */
+U_CAPI char* U_EXPORT2 
+u_strToJavaModifiedUTF8(
+        char *dest,
+        int32_t destCapacity,
+        int32_t *pDestLength,
+        const UChar *src, 
+        int32_t srcLength,
+        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.
+ *
+ * @param dest          A buffer for the result string. The result will be zero-terminated if
+ *                      the buffer is large enough.
+ * @param 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).
+ * @param 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.
+ * @param src           The original source string
+ * @param srcLength     The length of the original string. If -1, then src must be zero-terminated.
+ * @param 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".
+ * @param 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.
+ * @param 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.)
+ * @return The pointer to destination buffer.
+ * @see u_strFromUTF8WithSub
+ * @see u_strFromUTF8Lenient
+ * @see u_strToJavaModifiedUTF8
+ * @stable ICU 4.4
+ */
+U_CAPI UChar* U_EXPORT2
+u_strFromJavaModifiedUTF8WithSub(
+        UChar *dest,
+        int32_t destCapacity,
+        int32_t *pDestLength,
+        const char *src,
+        int32_t srcLength,
+        UChar32 subchar, int32_t *pNumSubstitutions,
+        UErrorCode *pErrorCode);
+
+#endif