237 lines
8.1 KiB
C
237 lines
8.1 KiB
C
/*
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*******************************************************************************
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*
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* Copyright (C) 1999-2010, International Business Machines
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* Corporation and others. All Rights Reserved.
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*
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*******************************************************************************
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* file name: utf.h
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* encoding: US-ASCII
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* tab size: 8 (not used)
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* indentation:4
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*
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* created on: 1999sep09
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* created by: Markus W. Scherer
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*/
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/**
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* \file
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* \brief C API: Code point macros
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*
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* This file defines macros for checking whether a code point is
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* a surrogate or a non-character etc.
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*
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* The UChar and UChar32 data types for Unicode code units and code points
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* are defined in umachines.h because they can be machine-dependent.
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*
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* utf.h is included by utypes.h and itself includes utf8.h and utf16.h after some
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* common definitions. Those files define macros for efficiently getting code points
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* in and out of UTF-8/16 strings.
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* utf16.h macros have "U16_" prefixes.
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* utf8.h defines similar macros with "U8_" prefixes for UTF-8 string handling.
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*
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* ICU processes 16-bit Unicode strings.
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* Most of the time, such strings are well-formed UTF-16.
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* Single, unpaired surrogates must be handled as well, and are treated in ICU
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* like regular code points where possible.
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* (Pairs of surrogate code points are indistinguishable from supplementary
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* code points encoded as pairs of supplementary code units.)
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*
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* In fact, almost all Unicode code points in normal text (>99%)
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* are on the BMP (<=U+ffff) and even <=U+d7ff.
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* ICU functions handle supplementary code points (U+10000..U+10ffff)
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* but are optimized for the much more frequently occurring BMP code points.
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*
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* utf.h defines UChar to be an unsigned 16-bit integer. If this matches wchar_t, then
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* UChar is defined to be exactly wchar_t, otherwise uint16_t.
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*
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* UChar32 is defined to be a signed 32-bit integer (int32_t), large enough for a 21-bit
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* Unicode code point (Unicode scalar value, 0..0x10ffff).
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* Before ICU 2.4, the definition of UChar32 was similarly platform-dependent as
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* the definition of UChar. For details see the documentation for UChar32 itself.
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*
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* utf.h also defines a small number of C macros for single Unicode code points.
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* These are simple checks for surrogates and non-characters.
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* For actual Unicode character properties see uchar.h.
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*
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* By default, string operations must be done with error checking in case
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* a string is not well-formed UTF-16.
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* The macros will detect if a surrogate code unit is unpaired
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* (lead unit without trail unit or vice versa) and just return the unit itself
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* as the code point.
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* (It is an accidental property of Unicode and UTF-16 that all
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* malformed sequences can be expressed unambiguously with a distinct subrange
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* of Unicode code points.)
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*
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* The regular "safe" macros require that the initial, passed-in string index
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* is within bounds. They only check the index when they read more than one
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* code unit. This is usually done with code similar to the following loop:
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* <pre>while(i<length) {
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* U16_NEXT(s, i, length, c);
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* // use c
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* }</pre>
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*
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* When it is safe to assume that text is well-formed UTF-16
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* (does not contain single, unpaired surrogates), then one can use
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* U16_..._UNSAFE macros.
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* These do not check for proper code unit sequences or truncated text and may
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* yield wrong results or even cause a crash if they are used with "malformed"
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* text.
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* In practice, U16_..._UNSAFE macros will produce slightly less code but
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* should not be faster because the processing is only different when a
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* surrogate code unit is detected, which will be rare.
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*
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* Similarly for UTF-8, there are "safe" macros without a suffix,
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* and U8_..._UNSAFE versions.
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* The performance differences are much larger here because UTF-8 provides so
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* many opportunities for malformed sequences.
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* The unsafe UTF-8 macros are entirely implemented inside the macro definitions
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* and are fast, while the safe UTF-8 macros call functions for all but the
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* trivial (ASCII) cases.
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* (ICU 3.6 optimizes U8_NEXT() and U8_APPEND() to handle most other common
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* characters inline as well.)
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*
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* Unlike with UTF-16, malformed sequences cannot be expressed with distinct
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* code point values (0..U+10ffff). They are indicated with negative values instead.
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*
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* For more information see the ICU User Guide Strings chapter
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* (http://icu-project.org/userguide/strings.html).
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*
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* <em>Usage:</em>
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* ICU coding guidelines for if() statements should be followed when using these macros.
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* Compound statements (curly braces {}) must be used for if-else-while...
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* bodies and all macro statements should be terminated with semicolon.
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*
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* @stable ICU 2.4
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*/
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#ifndef __UTF_H__
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#define __UTF_H__
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#include "unicode/utypes.h"
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/* include the utfXX.h after the following definitions */
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/* single-code point definitions -------------------------------------------- */
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/**
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* This value is intended for sentinel values for APIs that
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* (take or) return single code points (UChar32).
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* It is outside of the Unicode code point range 0..0x10ffff.
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*
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* For example, a "done" or "error" value in a new API
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* could be indicated with U_SENTINEL.
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*
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* ICU APIs designed before ICU 2.4 usually define service-specific "done"
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* values, mostly 0xffff.
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* Those may need to be distinguished from
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* actual U+ffff text contents by calling functions like
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* CharacterIterator::hasNext() or UnicodeString::length().
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*
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* @return -1
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* @see UChar32
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* @stable ICU 2.4
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*/
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#define U_SENTINEL (-1)
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/**
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* Is this code point a Unicode noncharacter?
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* @param c 32-bit code point
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* @return TRUE or FALSE
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* @stable ICU 2.4
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*/
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#define U_IS_UNICODE_NONCHAR(c) \
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((c)>=0xfdd0 && \
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((uint32_t)(c)<=0xfdef || ((c)&0xfffe)==0xfffe) && \
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(uint32_t)(c)<=0x10ffff)
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/**
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* Is c a Unicode code point value (0..U+10ffff)
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* that can be assigned a character?
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*
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* Code points that are not characters include:
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* - single surrogate code points (U+d800..U+dfff, 2048 code points)
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* - the last two code points on each plane (U+__fffe and U+__ffff, 34 code points)
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* - U+fdd0..U+fdef (new with Unicode 3.1, 32 code points)
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* - the highest Unicode code point value is U+10ffff
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*
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* This means that all code points below U+d800 are character code points,
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* and that boundary is tested first for performance.
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*
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* @param c 32-bit code point
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* @return TRUE or FALSE
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* @stable ICU 2.4
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*/
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#define U_IS_UNICODE_CHAR(c) \
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((uint32_t)(c)<0xd800 || \
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((uint32_t)(c)>0xdfff && \
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(uint32_t)(c)<=0x10ffff && \
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!U_IS_UNICODE_NONCHAR(c)))
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/**
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* Is this code point a BMP code point (U+0000..U+ffff)?
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* @param c 32-bit code point
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* @return TRUE or FALSE
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* @stable ICU 2.8
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*/
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#define U_IS_BMP(c) ((uint32_t)(c)<=0xffff)
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/**
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* Is this code point a supplementary code point (U+10000..U+10ffff)?
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* @param c 32-bit code point
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* @return TRUE or FALSE
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* @stable ICU 2.8
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*/
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#define U_IS_SUPPLEMENTARY(c) ((uint32_t)((c)-0x10000)<=0xfffff)
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/**
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* Is this code point a lead surrogate (U+d800..U+dbff)?
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* @param c 32-bit code point
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* @return TRUE or FALSE
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* @stable ICU 2.4
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*/
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#define U_IS_LEAD(c) (((c)&0xfffffc00)==0xd800)
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/**
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* Is this code point a trail surrogate (U+dc00..U+dfff)?
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* @param c 32-bit code point
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* @return TRUE or FALSE
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* @stable ICU 2.4
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*/
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#define U_IS_TRAIL(c) (((c)&0xfffffc00)==0xdc00)
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/**
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* Is this code point a surrogate (U+d800..U+dfff)?
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* @param c 32-bit code point
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* @return TRUE or FALSE
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* @stable ICU 2.4
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*/
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#define U_IS_SURROGATE(c) (((c)&0xfffff800)==0xd800)
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/**
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* Assuming c is a surrogate code point (U_IS_SURROGATE(c)),
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* is it a lead surrogate?
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* @param c 32-bit code point
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* @return TRUE or FALSE
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* @stable ICU 2.4
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*/
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#define U_IS_SURROGATE_LEAD(c) (((c)&0x400)==0)
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/**
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* Assuming c is a surrogate code point (U_IS_SURROGATE(c)),
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* is it a trail surrogate?
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* @param c 32-bit code point
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* @return TRUE or FALSE
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* @stable ICU 4.2
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*/
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#define U_IS_SURROGATE_TRAIL(c) (((c)&0x400)!=0)
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/* include the utfXX.h ------------------------------------------------------ */
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#include "unicode/utf8.h"
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#include "unicode/utf16.h"
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/* utf_old.h contains deprecated, pre-ICU 2.4 definitions */
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#include "unicode/utf_old.h"
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#endif
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