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author jpayne
date Tue, 18 Mar 2025 17:55:14 -0400
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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 * (http://userguide.icu-project.org/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__ */