Check in the pristine copy of ICU 4.6...

icu46/source/common/unicode/utf.h

Index: icu46/source/common/unicode/utf.h
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+/*
+*******************************************************************************
+*
+*   Copyright (C) 1999-2010, International Business Machines
+*   Corporation and others.  All Rights Reserved.
+*
+*******************************************************************************
+*   file name:  utf.h
+*   encoding:   US-ASCII
+*   tab size:   8 (not used)
+*   indentation:4
+*
+*   created on: 1999sep09
+*   created by: Markus W. Scherer
+*/
+
+/**
+ * \file
+ * \brief C API: Code point macros
+ *
+ * This file defines macros for checking whether a code point is
+ * a surrogate or a non-character etc.
+ *
+ * The UChar and UChar32 data types for Unicode code units and code points
+ * are defined in umachines.h because they can be machine-dependent.
+ *
+ * utf.h is included by utypes.h and itself includes utf8.h and utf16.h after some
+ * common definitions. Those files define macros for efficiently getting code points
+ * in and out of UTF-8/16 strings.
+ * utf16.h macros have "U16_" prefixes.
+ * utf8.h defines similar macros with "U8_" prefixes for UTF-8 string handling.
+ *
+ * ICU processes 16-bit Unicode strings.
+ * Most of the time, such strings are well-formed UTF-16.
+ * Single, unpaired surrogates must be handled as well, and are treated in ICU
+ * like regular code points where possible.
+ * (Pairs of surrogate code points are indistinguishable from supplementary
+ * code points encoded as pairs of supplementary code units.)
+ *
+ * In fact, almost all Unicode code points in normal text (>99%)
+ * are on the BMP (<=U+ffff) and even <=U+d7ff.
+ * ICU functions handle supplementary code points (U+10000..U+10ffff)
+ * but are optimized for the much more frequently occurring BMP code points.
+ *
+ * utf.h defines UChar to be an unsigned 16-bit integer. If this matches wchar_t, then
+ * UChar is defined to be exactly wchar_t, otherwise uint16_t.
+ *
+ * UChar32 is defined to be a signed 32-bit integer (int32_t), large enough for a 21-bit
+ * Unicode code point (Unicode scalar value, 0..0x10ffff).
+ * Before ICU 2.4, the definition of UChar32 was similarly platform-dependent as
+ * the definition of UChar. For details see the documentation for UChar32 itself.
+ *
+ * utf.h also defines a small number of C macros for single Unicode code points.
+ * These are simple checks for surrogates and non-characters.
+ * For actual Unicode character properties see uchar.h.
+ *
+ * By default, string operations must be done with error checking in case
+ * a string is not well-formed UTF-16.
+ * The macros will detect if a surrogate code unit is unpaired
+ * (lead unit without trail unit or vice versa) and just return the unit itself
+ * as the code point.
+ * (It is an accidental property of Unicode and UTF-16 that all
+ * malformed sequences can be expressed unambiguously with a distinct subrange
+ * of Unicode code points.)
+ *
+ * The regular "safe" macros require that the initial, passed-in string index
+ * is within bounds. They only check the index when they read more than one
+ * code unit. This is usually done with code similar to the following loop:
+ * <pre>while(i<length) {
+ *   U16_NEXT(s, i, length, c);
+ *   // use c
+ * }</pre>
+ *
+ * When it is safe to assume that text is well-formed UTF-16
+ * (does not contain single, unpaired surrogates), then one can use
+ * U16_..._UNSAFE macros.
+ * These do not check for proper code unit sequences or truncated text and may
+ * yield wrong results or even cause a crash if they are used with "malformed"
+ * text.
+ * In practice, U16_..._UNSAFE macros will produce slightly less code but
+ * should not be faster because the processing is only different when a
+ * surrogate code unit is detected, which will be rare.
+ *
+ * Similarly for UTF-8, there are "safe" macros without a suffix,
+ * and U8_..._UNSAFE versions.
+ * The performance differences are much larger here because UTF-8 provides so
+ * many opportunities for malformed sequences.
+ * The unsafe UTF-8 macros are entirely implemented inside the macro definitions
+ * and are fast, while the safe UTF-8 macros call functions for all but the
+ * trivial (ASCII) cases.
+ * (ICU 3.6 optimizes U8_NEXT() and U8_APPEND() to handle most other common
+ * characters inline as well.)
+ *
+ * Unlike with UTF-16, malformed sequences cannot be expressed with distinct
+ * code point values (0..U+10ffff). They are indicated with negative values instead.
+ *
+ * For more information see the ICU User Guide Strings chapter
+ * (http://icu-project.org/userguide/strings.html).
+ *
+ * <em>Usage:</em>
+ * ICU coding guidelines for if() statements should be followed when using these macros.
+ * Compound statements (curly braces {}) must be used  for if-else-while... 
+ * bodies and all macro statements should be terminated with semicolon.
+ *
+ * @stable ICU 2.4
+ */
+
+#ifndef __UTF_H__
+#define __UTF_H__
+
+#include "unicode/utypes.h"
+/* include the utfXX.h after the following definitions */
+
+/* single-code point definitions -------------------------------------------- */
+
+/**
+ * This value is intended for sentinel values for APIs that
+ * (take or) return single code points (UChar32).
+ * It is outside of the Unicode code point range 0..0x10ffff.
+ * 
+ * For example, a "done" or "error" value in a new API
+ * could be indicated with U_SENTINEL.
+ *
+ * ICU APIs designed before ICU 2.4 usually define service-specific "done"
+ * values, mostly 0xffff.
+ * Those may need to be distinguished from
+ * actual U+ffff text contents by calling functions like
+ * CharacterIterator::hasNext() or UnicodeString::length().
+ *
+ * @return -1
+ * @see UChar32
+ * @stable ICU 2.4
+ */
+#define U_SENTINEL (-1)
+
+/**
+ * Is this code point a Unicode noncharacter?
+ * @param c 32-bit code point
+ * @return TRUE or FALSE
+ * @stable ICU 2.4
+ */
+#define U_IS_UNICODE_NONCHAR(c) \
+    ((c)>=0xfdd0 && \
+     ((uint32_t)(c)<=0xfdef || ((c)&0xfffe)==0xfffe) && \
+     (uint32_t)(c)<=0x10ffff)
+
+/**
+ * Is c a Unicode code point value (0..U+10ffff)
+ * that can be assigned a character?
+ *
+ * Code points that are not characters include:
+ * - single surrogate code points (U+d800..U+dfff, 2048 code points)
+ * - the last two code points on each plane (U+__fffe and U+__ffff, 34 code points)
+ * - U+fdd0..U+fdef (new with Unicode 3.1, 32 code points)
+ * - the highest Unicode code point value is U+10ffff
+ *
+ * This means that all code points below U+d800 are character code points,
+ * and that boundary is tested first for performance.
+ *
+ * @param c 32-bit code point
+ * @return TRUE or FALSE
+ * @stable ICU 2.4
+ */
+#define U_IS_UNICODE_CHAR(c) \
+    ((uint32_t)(c)<0xd800 || \
+        ((uint32_t)(c)>0xdfff && \
+         (uint32_t)(c)<=0x10ffff && \
+         !U_IS_UNICODE_NONCHAR(c)))
+
+/**
+ * Is this code point a BMP code point (U+0000..U+ffff)?
+ * @param c 32-bit code point
+ * @return TRUE or FALSE
+ * @stable ICU 2.8
+ */
+#define U_IS_BMP(c) ((uint32_t)(c)<=0xffff)
+
+/**
+ * Is this code point a supplementary code point (U+10000..U+10ffff)?
+ * @param c 32-bit code point
+ * @return TRUE or FALSE
+ * @stable ICU 2.8
+ */
+#define U_IS_SUPPLEMENTARY(c) ((uint32_t)((c)-0x10000)<=0xfffff)
+ 
+/**
+ * Is this code point a lead surrogate (U+d800..U+dbff)?
+ * @param c 32-bit code point
+ * @return TRUE or FALSE
+ * @stable ICU 2.4
+ */
+#define U_IS_LEAD(c) (((c)&0xfffffc00)==0xd800)
+
+/**
+ * Is this code point a trail surrogate (U+dc00..U+dfff)?
+ * @param c 32-bit code point
+ * @return TRUE or FALSE
+ * @stable ICU 2.4
+ */
+#define U_IS_TRAIL(c) (((c)&0xfffffc00)==0xdc00)
+
+/**
+ * Is this code point a surrogate (U+d800..U+dfff)?
+ * @param c 32-bit code point
+ * @return TRUE or FALSE
+ * @stable ICU 2.4
+ */
+#define U_IS_SURROGATE(c) (((c)&0xfffff800)==0xd800)
+
+/**
+ * Assuming c is a surrogate code point (U_IS_SURROGATE(c)),
+ * is it a lead surrogate?
+ * @param c 32-bit code point
+ * @return TRUE or FALSE
+ * @stable ICU 2.4
+ */
+#define U_IS_SURROGATE_LEAD(c) (((c)&0x400)==0)
+
+/**
+ * Assuming c is a surrogate code point (U_IS_SURROGATE(c)),
+ * is it a trail surrogate?
+ * @param c 32-bit code point
+ * @return TRUE or FALSE
+ * @stable ICU 4.2
+ */
+#define U_IS_SURROGATE_TRAIL(c) (((c)&0x400)!=0)
+
+/* include the utfXX.h ------------------------------------------------------ */
+
+#include "unicode/utf8.h"
+#include "unicode/utf16.h"
+
+/* utf_old.h contains deprecated, pre-ICU 2.4 definitions */
+#include "unicode/utf_old.h"
+
+#endif
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