icu/unicode/utf.h

   1 /*
   2 *******************************************************************************
   3 *
   4 *   Copyright (C) 1999-2004, 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 umachines.h because they can be machine-dependent.
  26  *
  27  * utf.h is included by utypes.h and itself includes utf8.h and utf16.h after some
  28  * common definitions. Those files define macros for efficiently getting code points
  29  * in and out of UTF-8/16 strings.
  30  * utf16.h macros have "U16_" prefixes.
  31  * utf8.h defines similar macros with "U8_" prefixes for UTF-8 string handling.
  32  *
  33  * ICU processes 16-bit Unicode strings.
  34  * Most of the time, such strings are well-formed UTF-16.
  35  * Single, unpaired surrogates must be handled as well, and are treated in ICU
  36  * like regular code points where possible.
  37  * (Pairs of surrogate code points are indistinguishable from supplementary
  38  * code points encoded as pairs of supplementary code units.)
  39  *
  40  * In fact, almost all Unicode code points in normal text (>99%)
  41  * are on the BMP (<=U+ffff) and even <=U+d7ff.
  42  * ICU functions handle supplementary code points (U+10000..U+10ffff)
  43  * but are optimized for the much more frequently occurring BMP code points.
  44  *
  45  * utf.h defines UChar to be an unsigned 16-bit integer. If this matches wchar_t, then
  46  * UChar is defined to be exactly wchar_t, otherwise uint16_t.
  47  *
  48  * UChar32 is defined to be a signed 32-bit integer (int32_t), large enough for a 21-bit
  49  * Unicode code point (Unicode scalar value, 0..0x10ffff).
  50  * Before ICU 2.4, the definition of UChar32 was similarly platform-dependent as
  51  * the definition of UChar. For details see the documentation for UChar32 itself.
  52  *
  53  * utf.h also defines a small number of C macros for single Unicode code points.
  54  * These are simple checks for surrogates and non-characters.
  55  * For actual Unicode character properties see uchar.h.
  56  *
  57  * By default, string operations must be done with error checking in case
  58  * a string is not well-formed UTF-16.
  59  * The macros will detect if a surrogate code unit is unpaired
  60  * (lead unit without trail unit or vice versa) and just return the unit itself
  61  * as the code point.
  62  * (It is an accidental property of Unicode and UTF-16 that all
  63  * malformed sequences can be expressed unambiguously with a distinct subrange
  64  * of Unicode code points.)
  65  *
  66  * When it is safe to assume that text is well-formed UTF-16
  67  * (does not contain single, unpaired surrogates), then one can use
  68  * U16_..._UNSAFE macros.
  69  * These do not check for proper code unit sequences or truncated text and may
  70  * yield wrong results or even cause a crash if they are used with "malformed"
  71  * text.
  72  * In practice, U16_..._UNSAFE macros will produce slightly less code but
  73  * should not be faster because the processing is only different when a
  74  * surrogate code unit is detected, which will be rare.
  75  *
  76  * Similarly for UTF-8, there are "safe" macros without a suffix,
  77  * and U8_..._UNSAFE versions.
  78  * The performance differences are much larger here because UTF-8 provides so
  79  * many opportunities for malformed sequences.
  80  * The unsafe UTF-8 macros are entirely implemented inside the macro definitions
  81  * and are fast, while the safe UTF-8 macros call functions for all but the
  82  * trivial (ASCII) cases.
  83  *
  84  * Unlike with UTF-16, malformed sequences cannot be expressed with distinct
  85  * code point values (0..U+10ffff). They are indicated with negative values instead.
  86  *
  87  * For more information see the ICU User Guide Strings chapter
  88  * (http://oss.software.ibm.com/icu/userguide/).
  89  *
  90  * <em>Usage:</em>
  91  * ICU coding guidelines for if() statements should be followed when using these macros.
  92  * Compound statements (curly braces {}) must be used  for if-else-while...
  93  * bodies and all macro statements should be terminated with semicolon.
  94  *
  95  * @stable ICU 2.4
  96  */
  97
  98 #ifndef __UTF_H__
  99 #define __UTF_H__
 100
 101 #include "unicode/utypes.h"
 102 /* include the utfXX.h after the following definitions */
 103
 104 /* single-code point definitions -------------------------------------------- */
 105
 106 /**
 107  * This value is intended for sentinel values for APIs that
 108  * (take or) return single code points (UChar32).
 109  * It is outside of the Unicode code point range 0..0x10ffff.
 110  *
 111  * For example, a "done" or "error" value in a new API
 112  * could be indicated with U_SENTINEL.
 113  *
 114  * ICU APIs designed before ICU 2.4 usually define service-specific "done"
 115  * values, mostly 0xffff.
 116  * Those may need to be distinguished from
 117  * actual U+ffff text contents by calling functions like
 118  * CharacterIterator::hasNext() or UnicodeString::length().
 119  *
 120  * @return -1
 121  * @see UChar32
 122  * @stable ICU 2.4
 123  */
 124 #define U_SENTINEL (-1)
 125
 126 /**
 127  * Is this code point a Unicode noncharacter?
 128  * @param c 32-bit code point
 129  * @return TRUE or FALSE
 130  * @stable ICU 2.4
 131  */
 132 #define U_IS_UNICODE_NONCHAR(c) \
 133     ((c)>=0xfdd0 && \
 134      ((uint32_t)(c)<=0xfdef || ((c)&0xfffe)==0xfffe) && \
 135      (uint32_t)(c)<=0x10ffff)
 136
 137 /**
 138  * Is c a Unicode code point value (0..U+10ffff)
 139  * that can be assigned a character?
 140  *
 141  * Code points that are not characters include:
 142  * - single surrogate code points (U+d800..U+dfff, 2048 code points)
 143  * - the last two code points on each plane (U+__fffe and U+__ffff, 34 code points)
 144  * - U+fdd0..U+fdef (new with Unicode 3.1, 32 code points)
 145  * - the highest Unicode code point value is U+10ffff
 146  *
 147  * This means that all code points below U+d800 are character code points,
 148  * and that boundary is tested first for performance.
 149  *
 150  * @param c 32-bit code point
 151  * @return TRUE or FALSE
 152  * @stable ICU 2.4
 153  */
 154 #define U_IS_UNICODE_CHAR(c) \
 155     ((uint32_t)(c)<0xd800 || \
 156         ((uint32_t)(c)>0xdfff && \
 157          (uint32_t)(c)<=0x10ffff && \
 158          !U_IS_UNICODE_NONCHAR(c)))
 159
 160 #ifndef U_HIDE_DRAFT_API
 161
 162 /**
 163  * Is this code point a BMP code point (U+0000..U+ffff)?
 164  * @param c 32-bit code point
 165  * @return TRUE or FALSE
 166  * @draft ICU 2.8
 167  */
 168 #define U_IS_BMP(c) ((uint32_t)(c)<=0xffff)
 169
 170 /**
 171  * Is this code point a supplementary code point (U+10000..U+10ffff)?
 172  * @param c 32-bit code point
 173  * @return TRUE or FALSE
 174  * @draft ICU 2.8
 175  */
 176 #define U_IS_SUPPLEMENTARY(c) ((uint32_t)((c)-0x10000)<=0xfffff)
 177
 178 #endif /*U_HIDE_DRAFT_API*/
 179
 180 /**
 181  * Is this code point a lead surrogate (U+d800..U+dbff)?
 182  * @param c 32-bit code point
 183  * @return TRUE or FALSE
 184  * @stable ICU 2.4
 185  */
 186 #define U_IS_LEAD(c) (((c)&0xfffffc00)==0xd800)
 187
 188 /**
 189  * Is this code point a trail surrogate (U+dc00..U+dfff)?
 190  * @param c 32-bit code point
 191  * @return TRUE or FALSE
 192  * @stable ICU 2.4
 193  */
 194 #define U_IS_TRAIL(c) (((c)&0xfffffc00)==0xdc00)
 195
 196 /**
 197  * Is this code point a surrogate (U+d800..U+dfff)?
 198  * @param c 32-bit code point
 199  * @return TRUE or FALSE
 200  * @stable ICU 2.4
 201  */
 202 #define U_IS_SURROGATE(c) (((c)&0xfffff800)==0xd800)
 203
 204 /**
 205  * Assuming c is a surrogate code point (U_IS_SURROGATE(c)),
 206  * is it a lead surrogate?
 207  * @param c 32-bit code point
 208  * @return TRUE or FALSE
 209  * @stable ICU 2.4
 210  */
 211 #define U_IS_SURROGATE_LEAD(c) (((c)&0x400)==0)
 212
 213 /* include the utfXX.h ------------------------------------------------------ */
 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