icuSources/common/unicode/utf.h

   1 /*
   2 *******************************************************************************
   3 *
   4 *   Copyright (C) 1999-2011, International Business Machines
   5 *   Corporation and others.  All Rights Reserved.
   6 *
   7 *******************************************************************************
   8 *   file name:  utf.h
   9 *   encoding:   US-ASCII
  10 *   tab size:   8 (not used)
  11 *   indentation:4
  12 *
  13 *   created on: 1999sep09
  14 *   created by: Markus W. Scherer
  15 */
  16
  17 /**
  18  * \file
  19  * \brief C API: Code point macros
  20  *
  21  * This file defines macros for checking whether a code point is
  22  * a surrogate or a non-character etc.
  23  *
  24  * The UChar and UChar32 data types for Unicode code units and code points
  25  * are defined in umachine.h because they can be machine-dependent.
  26  *
  27  * If U_NO_DEFAULT_INCLUDE_UTF_HEADERS is 0 then utf.h is included by utypes.h
  28  * and itself includes utf8.h and utf16.h after some
  29  * common definitions.
  30  * If U_NO_DEFAULT_INCLUDE_UTF_HEADERS is 1 then each of these headers must be
  31  * included explicitly if their definitions are used.
  32  *
  33  * utf8.h and utf16.h define macros for efficiently getting code points
  34  * in and out of UTF-8/16 strings.
  35  * utf16.h macros have "U16_" prefixes.
  36  * utf8.h defines similar macros with "U8_" prefixes for UTF-8 string handling.
  37  *
  38  * ICU mostly processes 16-bit Unicode strings.
  39  * Most of the time, such strings are well-formed UTF-16.
  40  * Single, unpaired surrogates must be handled as well, and are treated in ICU
  41  * like regular code points where possible.
  42  * (Pairs of surrogate code points are indistinguishable from supplementary
  43  * code points encoded as pairs of supplementary code units.)
  44  *
  45  * In fact, almost all Unicode code points in normal text (>99%)
  46  * are on the BMP (<=U+ffff) and even <=U+d7ff.
  47  * ICU functions handle supplementary code points (U+10000..U+10ffff)
  48  * but are optimized for the much more frequently occurring BMP code points.
  49  *
  50  * umachine.h defines UChar to be an unsigned 16-bit integer.
  51  * Where available, UChar is defined to be a char16_t
  52  * or a wchar_t (if that is an unsigned 16-bit type), otherwise uint16_t.
  53  *
  54  * UChar32 is defined to be a signed 32-bit integer (int32_t), large enough for a 21-bit
  55  * Unicode code point (Unicode scalar value, 0..0x10ffff).
  56  * Before ICU 2.4, the definition of UChar32 was similarly platform-dependent as
  57  * the definition of UChar. For details see the documentation for UChar32 itself.
  58  *
  59  * utf.h defines a small number of C macros for single Unicode code points.
  60  * These are simple checks for surrogates and non-characters.
  61  * For actual Unicode character properties see uchar.h.
  62  *
  63  * By default, string operations must be done with error checking in case
  64  * a string is not well-formed UTF-16.
  65  * The macros will 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 regular "safe" macros require that the initial, passed-in string index
  70  * is within bounds. They only check the index when they read more than one
  71  * code unit. This is usually done with code similar to the following loop:
  72  * <pre>while(i<length) {
  73  *   U16_NEXT(s, i, length, c);
  74  *   // use c
  75  * }</pre>
  76  *
  77  * When it is safe to assume that text is well-formed UTF-16
  78  * (does not contain single, unpaired surrogates), then one can use
  79  * U16_..._UNSAFE macros.
  80  * These do not check for proper code unit sequences or truncated text and may
  81  * yield wrong results or even cause a crash if they are used with "malformed"
  82  * text.
  83  * In practice, U16_..._UNSAFE macros will produce slightly less code but
  84  * should not be faster because the processing is only different when a
  85  * surrogate code unit is detected, which will be rare.
  86  *
  87  * Similarly for UTF-8, there are "safe" macros without a suffix,
  88  * and U8_..._UNSAFE versions.
  89  * The performance differences are much larger here because UTF-8 provides so
  90  * many opportunities for malformed sequences.
  91  * The unsafe UTF-8 macros are entirely implemented inside the macro definitions
  92  * and are fast, while the safe UTF-8 macros call functions for all but the
  93  * trivial (ASCII) cases.
  94  * (ICU 3.6 optimizes U8_NEXT() and U8_APPEND() to handle most other common
  95  * characters inline as well.)
  96  *
  97  * Unlike with UTF-16, malformed sequences cannot be expressed with distinct
  98  * code point values (0..U+10ffff). They are indicated with negative values instead.
  99  *
 100  * For more information see the ICU User Guide Strings chapter
 101  * (http://userguide.icu-project.org/strings).
 102  *
 103  * <em>Usage:</em>
 104  * ICU coding guidelines for if() statements should be followed when using these macros.
 105  * Compound statements (curly braces {}) must be used  for if-else-while...
 106  * bodies and all macro statements should be terminated with semicolon.
 107  *
 108  * @stable ICU 2.4
 109  */
 110
 111 #ifndef __UTF_H__
 112 #define __UTF_H__
 113
 114 #include "unicode/umachine.h"
 115 /* include the utfXX.h after the following definitions */
 116
 117 /* single-code point definitions -------------------------------------------- */
 118
 119 /**
 120  * Is this code point a Unicode noncharacter?
 121  * @param c 32-bit code point
 122  * @return TRUE or FALSE
 123  * @stable ICU 2.4
 124  */
 125 #define U_IS_UNICODE_NONCHAR(c) \
 126     ((c)>=0xfdd0 && \
 127      ((uint32_t)(c)<=0xfdef || ((c)&0xfffe)==0xfffe) && \
 128      (uint32_t)(c)<=0x10ffff)
 129
 130 /**
 131  * Is c a Unicode code point value (0..U+10ffff)
 132  * that can be assigned a character?
 133  *
 134  * Code points that are not characters include:
 135  * - single surrogate code points (U+d800..U+dfff, 2048 code points)
 136  * - the last two code points on each plane (U+__fffe and U+__ffff, 34 code points)
 137  * - U+fdd0..U+fdef (new with Unicode 3.1, 32 code points)
 138  * - the highest Unicode code point value is U+10ffff
 139  *
 140  * This means that all code points below U+d800 are character code points,
 141  * and that boundary is tested first for performance.
 142  *
 143  * @param c 32-bit code point
 144  * @return TRUE or FALSE
 145  * @stable ICU 2.4
 146  */
 147 #define U_IS_UNICODE_CHAR(c) \
 148     ((uint32_t)(c)<0xd800 || \
 149         ((uint32_t)(c)>0xdfff && \
 150          (uint32_t)(c)<=0x10ffff && \
 151          !U_IS_UNICODE_NONCHAR(c)))
 152
 153 /**
 154  * Is this code point a BMP code point (U+0000..U+ffff)?
 155  * @param c 32-bit code point
 156  * @return TRUE or FALSE
 157  * @stable ICU 2.8
 158  */
 159 #define U_IS_BMP(c) ((uint32_t)(c)<=0xffff)
 160
 161 /**
 162  * Is this code point a supplementary code point (U+10000..U+10ffff)?
 163  * @param c 32-bit code point
 164  * @return TRUE or FALSE
 165  * @stable ICU 2.8
 166  */
 167 #define U_IS_SUPPLEMENTARY(c) ((uint32_t)((c)-0x10000)<=0xfffff)
 168
 169 /**
 170  * Is this code point a lead surrogate (U+d800..U+dbff)?
 171  * @param c 32-bit code point
 172  * @return TRUE or FALSE
 173  * @stable ICU 2.4
 174  */
 175 #define U_IS_LEAD(c) (((c)&0xfffffc00)==0xd800)
 176
 177 /**
 178  * Is this code point a trail surrogate (U+dc00..U+dfff)?
 179  * @param c 32-bit code point
 180  * @return TRUE or FALSE
 181  * @stable ICU 2.4
 182  */
 183 #define U_IS_TRAIL(c) (((c)&0xfffffc00)==0xdc00)
 184
 185 /**
 186  * Is this code point a surrogate (U+d800..U+dfff)?
 187  * @param c 32-bit code point
 188  * @return TRUE or FALSE
 189  * @stable ICU 2.4
 190  */
 191 #define U_IS_SURROGATE(c) (((c)&0xfffff800)==0xd800)
 192
 193 /**
 194  * Assuming c is a surrogate code point (U_IS_SURROGATE(c)),
 195  * is it a lead surrogate?
 196  * @param c 32-bit code point
 197  * @return TRUE or FALSE
 198  * @stable ICU 2.4
 199  */
 200 #define U_IS_SURROGATE_LEAD(c) (((c)&0x400)==0)
 201
 202 /**
 203  * Assuming c is a surrogate code point (U_IS_SURROGATE(c)),
 204  * is it a trail surrogate?
 205  * @param c 32-bit code point
 206  * @return TRUE or FALSE
 207  * @stable ICU 4.2
 208  */
 209 #define U_IS_SURROGATE_TRAIL(c) (((c)&0x400)!=0)
 210
 211 /* include the utfXX.h ------------------------------------------------------ */
 212
 213 #if !U_NO_DEFAULT_INCLUDE_UTF_HEADERS
 214
 215 #include "unicode/utf8.h"
 216 #include "unicode/utf16.h"
 217
 218 /* utf_old.h contains deprecated, pre-ICU 2.4 definitions */
 219 #include "unicode/utf_old.h"
 220
 221 #endif  /* !U_NO_DEFAULT_INCLUDE_UTF_HEADERS */
 222
 223 #endif  /* __UTF_H__ */