utf8.h

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/*
*******************************************************************************
*
*   Copyright (C) 1999-2004, International Business Machines
*   Corporation and others.  All Rights Reserved.
*
*******************************************************************************
*   file name:  utf8.h
*   encoding:   US-ASCII
*   tab size:   8 (not used)
*   indentation:4
*
*   created on: 1999sep13
*   created by: Markus W. Scherer
*/

/**
 * \file
 * \brief C API: 8-bit Unicode handling macros
 * 
 * This file defines macros to deal with 8-bit Unicode (UTF-8) code units (bytes) and strings.
 * utf8.h is included by utf.h after unicode/umachine.h
 * and some common definitions.
 *
 * For more information see utf.h and the ICU User Guide Strings chapter
 * (http://oss.software.ibm.com/icu/userguide/).
 *
 * <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.
 */

#ifndef __UTF8_H__
#define __UTF8_H__

/* utf.h must be included first. */
#ifndef __UTF_H__
#   include "unicode/utf.h"
#endif

/* internal definitions ----------------------------------------------------- */

/**
 * \var utf8_countTrailBytes
 * Internal array with numbers of trail bytes for any given byte used in
 * lead byte position.
 * @internal
 */
#ifdef U_UTF8_IMPL
U_INTERNAL const uint8_t 
#elif defined(U_STATIC_IMPLEMENTATION)
U_CFUNC const uint8_t
#else
U_CFUNC U_IMPORT const uint8_t /* U_IMPORT2? */ /*U_IMPORT*/ 
#endif
utf8_countTrailBytes[256];

/**
 * Count the trail bytes for a UTF-8 lead byte.
 * @internal
 */
#define U8_COUNT_TRAIL_BYTES(leadByte) (utf8_countTrailBytes[(uint8_t)leadByte])

/**
 * Mask a UTF-8 lead byte, leave only the lower bits that form part of the code point value.
 * @internal
 */
#define U8_MASK_LEAD_BYTE(leadByte, countTrailBytes) ((leadByte)&=(1<<(6-(countTrailBytes)))-1)

/**
 * Function for handling "next code point" with error-checking.
 * @internal
 */
U_INTERNAL UChar32 U_EXPORT2
utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict);

/**
 * Function for handling "append code point" with error-checking.
 * @internal
 */
U_INTERNAL int32_t U_EXPORT2
utf8_appendCharSafeBody(uint8_t *s, int32_t i, int32_t length, UChar32 c, UBool *pIsError);

/**
 * Function for handling "previous code point" with error-checking.
 * @internal
 */
U_INTERNAL UChar32 U_EXPORT2
utf8_prevCharSafeBody(const uint8_t *s, int32_t start, int32_t *pi, UChar32 c, UBool strict);

/**
 * Function for handling "skip backward one code point" with error-checking.
 * @internal
 */
U_INTERNAL int32_t U_EXPORT2
utf8_back1SafeBody(const uint8_t *s, int32_t start, int32_t i);

/* single-code point definitions -------------------------------------------- */

/**
 * Does this code unit (byte) encode a code point by itself (US-ASCII 0..0x7f)?
 * @param c 8-bit code unit (byte)
 * @return TRUE or FALSE
 * @stable ICU 2.4
 */
#define U8_IS_SINGLE(c) (((c)&0x80)==0)

/**
 * Is this code unit (byte) a UTF-8 lead byte?
 * @param c 8-bit code unit (byte)
 * @return TRUE or FALSE
 * @stable ICU 2.4
 */
#define U8_IS_LEAD(c) ((uint8_t)((c)-0xc0)<0x3e)

/**
 * Is this code unit (byte) a UTF-8 trail byte?
 * @param c 8-bit code unit (byte)
 * @return TRUE or FALSE
 * @stable ICU 2.4
 */
#define U8_IS_TRAIL(c) (((c)&0xc0)==0x80)

/**
 * How many code units (bytes) are used for the UTF-8 encoding
 * of this Unicode code point?
 * @param c 32-bit code point
 * @return 1..4, or 0 if c is a surrogate or not a Unicode code point
 * @stable ICU 2.4
 */
#define U8_LENGTH(c) \
    ((uint32_t)(c)<=0x7f ? 1 : \
        ((uint32_t)(c)<=0x7ff ? 2 : \
            ((uint32_t)(c)<=0xd7ff ? 3 : \
                ((uint32_t)(c)<=0xdfff || (uint32_t)(c)>0x10ffff ? 0 : \
                    ((uint32_t)(c)<=0xffff ? 3 : 4)\
                ) \
            ) \
        ) \
    )

/**
 * The maximum number of UTF-8 code units (bytes) per Unicode code point (U+0000..U+10ffff).
 * @return 4
 * @stable ICU 2.4
 */
#define U8_MAX_LENGTH 4

/**
 * Get a code point from a string at a random-access offset,
 * without changing the offset.
 * The offset may point to either the lead byte or one of the trail bytes
 * for a code point, in which case the macro will read all of the bytes
 * for the code point.
 * The result is undefined if the offset points to an illegal UTF-8
 * byte sequence.
 * Iteration through a string is more efficient with U8_NEXT_UNSAFE or U8_NEXT.
 *
 * @param s const uint8_t * string
 * @param i string offset
 * @param c output UChar32 variable
 * @see U8_GET
 * @stable ICU 2.4
 */
#define U8_GET_UNSAFE(s, i, c) { \
    int32_t _u8_get_unsafe_index=(int32_t)(i); \
    U8_SET_CP_START_UNSAFE(s, _u8_get_unsafe_index); \
    U8_NEXT_UNSAFE(s, _u8_get_unsafe_index, c); \
}

/**
 * Get a code point from a string at a random-access offset,
 * without changing the offset.
 * The offset may point to either the lead byte or one of the trail bytes
 * for a code point, in which case the macro will read all of the bytes
 * for the code point.
 * If the offset points to an illegal UTF-8 byte sequence, then
 * c is set to a negative value.
 * Iteration through a string is more efficient with U8_NEXT_UNSAFE or U8_NEXT.
 *
 * @param s const uint8_t * string
 * @param start starting string offset
 * @param i string offset, start<=i<length
 * @param length string length
 * @param c output UChar32 variable, set to <0 in case of an error
 * @see U8_GET_UNSAFE
 * @stable ICU 2.4
 */
#define U8_GET(s, start, i, length, c) { \
    int32_t _u8_get_index=(int32_t)(i); \
    U8_SET_CP_START(s, start, _u8_get_index); \
    U8_NEXT(s, _u8_get_index, length, c); \
}

/* definitions with forward iteration --------------------------------------- */

/**
 * Get a code point from a string at a code point boundary offset,
 * and advance the offset to the next code point boundary.
 * (Post-incrementing forward iteration.)
 * "Unsafe" macro, assumes well-formed UTF-8.
 *
 * The offset may point to the lead byte of a multi-byte sequence,
 * in which case the macro will read the whole sequence.
 * The result is undefined if the offset points to a trail byte
 * or an illegal UTF-8 sequence.
 *
 * @param s const uint8_t * string
 * @param i string offset
 * @param c output UChar32 variable
 * @see U8_NEXT
 * @stable ICU 2.4
 */
#define U8_NEXT_UNSAFE(s, i, c) { \
    (c)=(s)[(i)++]; \
    if((uint8_t)((c)-0xc0)<0x35) { \
        uint8_t __count=U8_COUNT_TRAIL_BYTES(c); \
        U8_MASK_LEAD_BYTE(c, __count); \
        switch(__count) { \
        /* each following branch falls through to the next one */ \
        case 3: \
            (c)=((c)<<6)|((s)[(i)++]&0x3f); \
        case 2: \
            (c)=((c)<<6)|((s)[(i)++]&0x3f); \
        case 1: \
            (c)=((c)<<6)|((s)[(i)++]&0x3f); \
        /* no other branches to optimize switch() */ \
            break; \
        } \
    } \
}

/**
 * Get a code point from a string at a code point boundary offset,
 * and advance the offset to the next code point boundary.
 * (Post-incrementing forward iteration.)
 * "Safe" macro, checks for illegal sequences and for string boundaries.
 *
 * The offset may point to the lead byte of a multi-byte sequence,
 * in which case the macro will read the whole sequence.
 * If the offset points to a trail byte or an illegal UTF-8 sequence, then
 * c is set to a negative value.
 *
 * @param s const uint8_t * string
 * @param i string offset, i<length
 * @param length string length
 * @param c output UChar32 variable, set to <0 in case of an error
 * @see U8_NEXT_UNSAFE
 * @stable ICU 2.4
 */
#define U8_NEXT(s, i, length, c) { \
    (c)=(s)[(i)++]; \
    if(((uint8_t)(c))>=0x80) { \
        if(U8_IS_LEAD(c)) { \
            (c)=utf8_nextCharSafeBody((const uint8_t *)s, &(i), (int32_t)(length), c, -1); \
        } else { \
            (c)=U_SENTINEL; \
        } \
    } \
}

/**
 * Append a code point to a string, overwriting 1 to 4 bytes.
 * The offset points to the current end of the string contents
 * and is advanced (post-increment).
 * "Unsafe" macro, assumes a valid code point and sufficient space in the string.
 * Otherwise, the result is undefined.
 *
 * @param s const uint8_t * string buffer
 * @param i string offset
 * @param c code point to append
 * @see U8_APPEND
 * @stable ICU 2.4
 */
#define U8_APPEND_UNSAFE(s, i, c) { \
    if((uint32_t)(c)<=0x7f) { \
        (s)[(i)++]=(uint8_t)(c); \
    } else { \
        if((uint32_t)(c)<=0x7ff) { \
            (s)[(i)++]=(uint8_t)(((c)>>6)|0xc0); \
        } else { \
            if((uint32_t)(c)<=0xffff) { \
                (s)[(i)++]=(uint8_t)(((c)>>12)|0xe0); \
            } else { \
                (s)[(i)++]=(uint8_t)(((c)>>18)|0xf0); \
                (s)[(i)++]=(uint8_t)((((c)>>12)&0x3f)|0x80); \
            } \
            (s)[(i)++]=(uint8_t)((((c)>>6)&0x3f)|0x80); \
        } \
        (s)[(i)++]=(uint8_t)(((c)&0x3f)|0x80); \
    } \
}

/**
 * Append a code point to a string, overwriting 1 or 2 code units.
 * The offset points to the current end of the string contents
 * and is advanced (post-increment).
 * "Safe" macro, checks for a valid code point.
 * If a non-ASCII code point is written, checks for sufficient space in the string.
 * If the code point is not valid or trail bytes do not fit,
 * then isError is set to TRUE.
 *
 * @param s const uint8_t * string buffer
 * @param i string offset, i<length
 * @param length size of the string buffer
 * @param c code point to append
 * @param isError output UBool set to TRUE if an error occurs, otherwise not modified
 * @see U8_APPEND_UNSAFE
 * @stable ICU 2.4
 */
#define U8_APPEND(s, i, length, c, isError) { \
    if((uint32_t)(c)<=0x7f) { \
        (s)[(i)++]=(uint8_t)(c); \