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The C and C++ Include Header Files

/usr/include/unicode/utf.h


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     1	// © 2016 and later: Unicode, Inc. and others.
     2	// License & terms of use: http://www.unicode.org/copyright.html
     3	/*
     4	*******************************************************************************
     5	*
     6	*   Copyright (C) 1999-2011, International Business Machines
     7	*   Corporation and others.  All Rights Reserved.
     8	*
     9	*******************************************************************************
    10	*   file name:  utf.h
    11	*   encoding:   UTF-8
    12	*   tab size:   8 (not used)
    13	*   indentation:4
    14	*
    15	*   created on: 1999sep09
    16	*   created by: Markus W. Scherer
    17	*/
    18	
    19	/**
    20	 * \file
    21	 * \brief C API: Code point macros
    22	 *
    23	 * This file defines macros for checking whether a code point is
    24	 * a surrogate or a non-character etc.
    25	 *
    26	 * If U_NO_DEFAULT_INCLUDE_UTF_HEADERS is 0 then utf.h is included by utypes.h
    27	 * and itself includes utf8.h and utf16.h after some
    28	 * common definitions.
    29	 * If U_NO_DEFAULT_INCLUDE_UTF_HEADERS is 1 then each of these headers must be
    30	 * included explicitly if their definitions are used.
    31	 *
    32	 * utf8.h and utf16.h define macros for efficiently getting code points
    33	 * in and out of UTF-8/16 strings.
    34	 * utf16.h macros have "U16_" prefixes.
    35	 * utf8.h defines similar macros with "U8_" prefixes for UTF-8 string handling.
    36	 *
    37	 * ICU mostly processes 16-bit Unicode strings.
    38	 * Most of the time, such strings are well-formed UTF-16.
    39	 * Single, unpaired surrogates must be handled as well, and are treated in ICU
    40	 * like regular code points where possible.
    41	 * (Pairs of surrogate code points are indistinguishable from supplementary
    42	 * code points encoded as pairs of supplementary code units.)
    43	 *
    44	 * In fact, almost all Unicode code points in normal text (>99%)
    45	 * are on the BMP (<=U+ffff) and even <=U+d7ff.
    46	 * ICU functions handle supplementary code points (U+10000..U+10ffff)
    47	 * but are optimized for the much more frequently occurring BMP code points.
    48	 *
    49	 * umachine.h defines UChar to be an unsigned 16-bit integer.
    50	 * Since ICU 59, ICU uses char16_t in C++, UChar only in C,
    51	 * and defines UChar=char16_t by default. See the UChar API docs for details.
    52	 *
    53	 * UChar32 is defined to be a signed 32-bit integer (int32_t), large enough for a 21-bit
    54	 * Unicode code point (Unicode scalar value, 0..0x10ffff) and U_SENTINEL (-1).
    55	 * Before ICU 2.4, the definition of UChar32 was similarly platform-dependent as
    56	 * the definition of UChar. For details see the documentation for UChar32 itself.
    57	 *
    58	 * utf.h defines a small number of C macros for single Unicode code points.
    59	 * These are simple checks for surrogates and non-characters.
    60	 * For actual Unicode character properties see uchar.h.
    61	 *
    62	 * By default, string operations must be done with error checking in case
    63	 * a string is not well-formed UTF-16 or UTF-8.
    64	 *
    65	 * The U16_ macros detect if a surrogate code unit is unpaired
    66	 * (lead unit without trail unit or vice versa) and just return the unit itself
    67	 * as the code point.
    68	 *
    69	 * The U8_ macros detect illegal byte sequences and return a negative value.
    70	 * Starting with ICU 60, the observable length of a single illegal byte sequence
    71	 * skipped by one of these macros follows the Unicode 6+ recommendation
    72	 * which is consistent with the W3C Encoding Standard.
    73	 *
    74	 * There are ..._OR_FFFD versions of both U16_ and U8_ macros
    75	 * that return U+FFFD for illegal code unit sequences.
    76	 *
    77	 * The regular "safe" macros require that the initial, passed-in string index
    78	 * is within bounds. They only check the index when they read more than one
    79	 * code unit. This is usually done with code similar to the following loop:
    80	 * <pre>while(i<length) {
    81	 *   U16_NEXT(s, i, length, c);
    82	 *   // use c
    83	 * }</pre>
    84	 *
    85	 * When it is safe to assume that text is well-formed UTF-16
    86	 * (does not contain single, unpaired surrogates), then one can use
    87	 * U16_..._UNSAFE macros.
    88	 * These do not check for proper code unit sequences or truncated text and may
    89	 * yield wrong results or even cause a crash if they are used with "malformed"
    90	 * text.
    91	 * In practice, U16_..._UNSAFE macros will produce slightly less code but
    92	 * should not be faster because the processing is only different when a
    93	 * surrogate code unit is detected, which will be rare.
    94	 *
    95	 * Similarly for UTF-8, there are "safe" macros without a suffix,
    96	 * and U8_..._UNSAFE versions.
    97	 * The performance differences are much larger here because UTF-8 provides so
    98	 * many opportunities for malformed sequences.
    99	 * The unsafe UTF-8 macros are entirely implemented inside the macro definitions
   100	 * and are fast, while the safe UTF-8 macros call functions for some complicated cases.
   101	 *
   102	 * Unlike with UTF-16, malformed sequences cannot be expressed with distinct
   103	 * code point values (0..U+10ffff). They are indicated with negative values instead.
   104	 *
   105	 * For more information see the ICU User Guide Strings chapter
   106	 * (https://unicode-org.github.io/icu/userguide/strings).
   107	 *
   108	 * <em>Usage:</em>
   109	 * ICU coding guidelines for if() statements should be followed when using these macros.
   110	 * Compound statements (curly braces {}) must be used  for if-else-while... 
   111	 * bodies and all macro statements should be terminated with semicolon.
   112	 *
   113	 * @stable ICU 2.4
   114	 */
   115	
   116	#ifndef __UTF_H__
   117	#define __UTF_H__
   118	
   119	#include "unicode/umachine.h"
   120	/* include the utfXX.h after the following definitions */
   121	
   122	/* single-code point definitions -------------------------------------------- */
   123	
   124	/**
   125	 * Is this code point a Unicode noncharacter?
   126	 * @param c 32-bit code point
   127	 * @return true or false
   128	 * @stable ICU 2.4
   129	 */
   130	#define U_IS_UNICODE_NONCHAR(c) \
   131	    ((c)>=0xfdd0 && \
   132	     ((c)<=0xfdef || ((c)&0xfffe)==0xfffe) && (c)<=0x10ffff)
   133	
   134	/**
   135	 * Is c a Unicode code point value (0..U+10ffff)
   136	 * that can be assigned a character?
   137	 *
   138	 * Code points that are not characters include:
   139	 * - single surrogate code points (U+d800..U+dfff, 2048 code points)
   140	 * - the last two code points on each plane (U+__fffe and U+__ffff, 34 code points)
   141	 * - U+fdd0..U+fdef (new with Unicode 3.1, 32 code points)
   142	 * - the highest Unicode code point value is U+10ffff
   143	 *
   144	 * This means that all code points below U+d800 are character code points,
   145	 * and that boundary is tested first for performance.
   146	 *
   147	 * @param c 32-bit code point
   148	 * @return true or false
   149	 * @stable ICU 2.4
   150	 */
   151	#define U_IS_UNICODE_CHAR(c) \
   152	    ((uint32_t)(c)<0xd800 || \
   153	        (0xdfff<(c) && (c)<=0x10ffff && !U_IS_UNICODE_NONCHAR(c)))
   154	
   155	/**
   156	 * Is this code point a BMP code point (U+0000..U+ffff)?
   157	 * @param c 32-bit code point
   158	 * @return true or false
   159	 * @stable ICU 2.8
   160	 */
   161	#define U_IS_BMP(c) ((uint32_t)(c)<=0xffff)
   162	
   163	/**
   164	 * Is this code point a supplementary code point (U+10000..U+10ffff)?
   165	 * @param c 32-bit code point
   166	 * @return true or false
   167	 * @stable ICU 2.8
   168	 */
   169	#define U_IS_SUPPLEMENTARY(c) ((uint32_t)((c)-0x10000)<=0xfffff)
   170	 
   171	/**
   172	 * Is this code point a lead surrogate (U+d800..U+dbff)?
   173	 * @param c 32-bit code point
   174	 * @return true or false
   175	 * @stable ICU 2.4
   176	 */
   177	#define U_IS_LEAD(c) (((c)&0xfffffc00)==0xd800)
   178	
   179	/**
   180	 * Is this code point a trail surrogate (U+dc00..U+dfff)?
   181	 * @param c 32-bit code point
   182	 * @return true or false
   183	 * @stable ICU 2.4
   184	 */
   185	#define U_IS_TRAIL(c) (((c)&0xfffffc00)==0xdc00)
   186	
   187	/**
   188	 * Is this code point a surrogate (U+d800..U+dfff)?
   189	 * @param c 32-bit code point
   190	 * @return true or false
   191	 * @stable ICU 2.4
   192	 */
   193	#define U_IS_SURROGATE(c) (((c)&0xfffff800)==0xd800)
   194	
   195	/**
   196	 * Assuming c is a surrogate code point (U_IS_SURROGATE(c)),
   197	 * is it a lead surrogate?
   198	 * @param c 32-bit code point
   199	 * @return true or false
   200	 * @stable ICU 2.4
   201	 */
   202	#define U_IS_SURROGATE_LEAD(c) (((c)&0x400)==0)
   203	
   204	/**
   205	 * Assuming c is a surrogate code point (U_IS_SURROGATE(c)),
   206	 * is it a trail surrogate?
   207	 * @param c 32-bit code point
   208	 * @return true or false
   209	 * @stable ICU 4.2
   210	 */
   211	#define U_IS_SURROGATE_TRAIL(c) (((c)&0x400)!=0)
   212	
   213	/* include the utfXX.h ------------------------------------------------------ */
   214	
   215	#if !U_NO_DEFAULT_INCLUDE_UTF_HEADERS
   216	
   217	#include "unicode/utf8.h"
   218	#include "unicode/utf16.h"
   219	
   220	/* utf_old.h contains deprecated, pre-ICU 2.4 definitions */
   221	#include "unicode/utf_old.h"
   222	
   223	#endif  /* !U_NO_DEFAULT_INCLUDE_UTF_HEADERS */
   224	
   225	#endif  /* __UTF_H__ */