source/common/unicode/utf8.h - external/github.com/unicode-org/icu - Git at Google

 /*
 *******************************************************************************
 *
 *   Copyright (C) 1999-2001, 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: UTF-8 macros
 *
 *   This file defines macros to deal with UTF-8 code units and code points.
 *   Signatures and semantics are the same as for the similarly named macros
 *   in utf16.h.
 *   utf8.h is included by utf.h after unicode/umachine.h
 *   and some common definitions.</p>
 *   <p><b>Usage:</b>  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.</p>
 */


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

 #ifndef __UTF8_H__
 #define __UTF8_H__

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

 #ifdef U_UTF8_IMPL
 U_CAPI const uint8_t
 utf8_countTrailBytes[256];
 #else
 U_CFUNC const uint8_t /* U_IMPORT2? */ U_IMPORT
 utf8_countTrailBytes[256];
 #endif

 /*
  * Count the trail bytes for a lead byte -
  * this macro should be used so that the assembler code
  * that is mentioned in utf_impl.c could be used here.
  */
 #define UTF8_COUNT_TRAIL_BYTES(leadByte) (utf8_countTrailBytes[(uint8_t)leadByte])

 /* use a macro here, too - there may be a simpler way with some machines */
 #define UTF8_MASK_LEAD_BYTE(leadByte, countTrailBytes) ((leadByte)&=(1<<(6-(countTrailBytes)))-1)

 U_CAPI UChar32 U_EXPORT2
 utf8_nextCharSafeBody(const uint8_t *s, UTextOffset *pi, UTextOffset length, UChar32 c, UBool strict);

 U_CAPI UTextOffset U_EXPORT2
 utf8_appendCharSafeBody(uint8_t *s, UTextOffset i, UTextOffset length, UChar32 c);

 U_CAPI UChar32 U_EXPORT2
 utf8_prevCharSafeBody(const uint8_t *s, UTextOffset start, UTextOffset *pi, UChar32 c, UBool strict);

 U_CAPI UTextOffset U_EXPORT2
 utf8_back1SafeBody(const uint8_t *s, UTextOffset start, UTextOffset i);

 /*
  * For the semantics of all of these macros, see utf16.h.
  * The UTF-8 macros favor sequences more the shorter they are.
  * Sometimes, only the single-byte case is covered by a macro,
  * while longer sequences are handled by a function call.
  */

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

 /* classes of code unit values */
 #define UTF8_IS_SINGLE(uchar) (((uchar)&0x80)==0)
 #define UTF8_IS_LEAD(uchar) ((uint8_t)((uchar)-0xc0)<0x3e)
 #define UTF8_IS_TRAIL(uchar) (((uchar)&0xc0)==0x80)

 /* number of code units per code point */
 #define UTF8_NEED_MULTIPLE_UCHAR(c) ((uint32_t)(c)>0x7f)

 /*
  * ICU does not deal with code points >0x10ffff
  * unless necessary for advancing in the byte stream.
  *
  * These length macros take into account that for values >0x10ffff
  * the "safe" append macros would write the error code point 0xffff
  * with 3 bytes.
  * Code point comparisons need to be in uint32_t because UChar32
  * may be a signed type, and negative values must be recognized.
  */
 #if 1
 #   define UTF8_CHAR_LENGTH(c) \
         ((uint32_t)(c)<=0x7f ? 1 : \
             ((uint32_t)(c)<=0x7ff ? 2 : \
                 ((uint32_t)((c)-0x10000)>0xfffff ? 3 : 4) \
             ) \
         )
 #else
 #   define UTF8_CHAR_LENGTH(c) \
         ((uint32_t)(c)<=0x7f ? 1 : \
             ((uint32_t)(c)<=0x7ff ? 2 : \
                 ((uint32_t)(c)<=0xffff ? 3 : \
                     ((uint32_t)(c)<=0x10ffff ? 4 : \
                         ((uint32_t)(c)<=0x3ffffff ? 5 : \
                             ((uint32_t)(c)<=0x7fffffff ? 6 : 3) \
                         ) \
                     ) \
                 ) \
             ) \
         )
 #endif

 #define UTF8_MAX_CHAR_LENGTH 4

 /* average number of code units compared to UTF-16 */
 #define UTF8_ARRAY_SIZE(size) ((5*(size))/2)

 #define UTF8_GET_CHAR_UNSAFE(s, i, c) { \
     UTextOffset __I=(UTextOffset)(i); \
     UTF8_SET_CHAR_START_UNSAFE(s, __I); \
     UTF8_NEXT_CHAR_UNSAFE(s, __I, c); \
 }

 #define UTF8_GET_CHAR_SAFE(s, start, i, length, c, strict) { \
     UTextOffset __I=(UTextOffset)(i); \
     UTF8_SET_CHAR_START_SAFE(s, start, __I); \
     UTF8_NEXT_CHAR_SAFE(s, __I, length, c, strict); \
 }

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

 /*
  * Read a Unicode scalar value from an array of UTF-8 bytes.
  * Only values <=0x10ffff are accepted, and if an error occurs,
  * then c will be set such that UTF_IS_ERROR(c).
  * The _UNSAFE macro is fast and does not check for errors.
  * The _SAFE macro checks for errors and optionally for
  * irregular sequences, too, i.e., for sequences that
  * are longer than necessary, such as <c0 80> instead of <0>.
  * The strict checks also check for non-characters.
  */
 #define UTF8_NEXT_CHAR_UNSAFE(s, i, c) { \
     (c)=(s)[(i)++]; \
     if((uint8_t)((c)-0xc0)<0x35) { \
         uint8_t __count=UTF8_COUNT_TRAIL_BYTES(c); \
         UTF8_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; \
         } \
     } \
 }

 #define UTF8_APPEND_CHAR_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); \
     } \
 }

 #define UTF8_FWD_1_UNSAFE(s, i) { \
     (i)+=1+UTF8_COUNT_TRAIL_BYTES((s)[i]); \
 }

 #define UTF8_FWD_N_UNSAFE(s, i, n) { \
     UTextOffset __N=(n); \
     while(__N>0) { \
         UTF8_FWD_1_UNSAFE(s, i); \
         --__N; \
     } \
 }

 #define UTF8_SET_CHAR_START_UNSAFE(s, i) { \
     while(UTF8_IS_TRAIL((s)[i])) { --(i); } \
 }

 #define UTF8_NEXT_CHAR_SAFE(s, i, length, c, strict) { \
     (c)=(s)[(i)++]; \
     if((c)>=0x80) { \
         if(UTF8_IS_LEAD(c)) { \
             (c)=utf8_nextCharSafeBody(s, &(i), (UTextOffset)(length), c, strict); \
         } else { \
             (c)=UTF8_ERROR_VALUE_1; \
         } \
     } \
 }

 #define UTF8_APPEND_CHAR_SAFE(s, i, length, c) { \
     if((uint32_t)(c)<=0x7f) { \
         (s)[(i)++]=(uint8_t)(c); \
     } else { \
         (i)=utf8_appendCharSafeBody(s, (UTextOffset)(i), (UTextOffset)(length), c); \
     } \
 }

 #define UTF8_FWD_1_SAFE(s, i, length) { \
     uint8_t __b=(s)[(i)++]; \
     if(UTF8_IS_LEAD(__b)) { \
         uint8_t __count=UTF8_COUNT_TRAIL_BYTES(__b); \
         if((i)+__count>(length)) { \
             __count=(uint8_t)((length)-(i)); \
         } \
         while(__count>0 && UTF8_IS_TRAIL((s)[i])) { \
             ++(i); \
             --__count; \
         } \
     } \
 }

 #define UTF8_FWD_N_SAFE(s, i, length, n) { \
     UTextOffset __N=(n); \
     while(__N>0 && (i)<(length)) { \
         UTF8_FWD_1_SAFE(s, i, length); \
         --__N; \
     } \
 }

 #define UTF8_SET_CHAR_START_SAFE(s, start, i) { \
     if(UTF8_IS_TRAIL((s)[(i)])) { \
         (i)=utf8_back1SafeBody(s, start, (UTextOffset)(i)); \
     } \
 }

 /* definitions with backward iteration -------------------------------------- */

 #define UTF8_PREV_CHAR_UNSAFE(s, i, c) { \
     (c)=(s)[--(i)]; \
     if(UTF8_IS_TRAIL(c)) { \
         uint8_t __b, __count=1, __shift=6; \
 \
         /* c is a trail byte */ \
         (c)&=0x3f; \
         for(;;) { \
             __b=(s)[--(i)]; \
             if(__b>=0xc0) { \
                 UTF8_MASK_LEAD_BYTE(__b, __count); \
                 (c)|=(UChar32)__b<<__shift; \
                 break; \
             } else { \
                 (c)|=(UChar32)(__b&0x3f)<<__shift; \
                 ++__count; \
                 __shift+=6; \
             } \
         } \
     } \
 }

 #define UTF8_BACK_1_UNSAFE(s, i) { \
     while(UTF8_IS_TRAIL((s)[--(i)])) {} \
 }

 #define UTF8_BACK_N_UNSAFE(s, i, n) { \
     UTextOffset __N=(n); \
     while(__N>0) { \
         UTF8_BACK_1_UNSAFE(s, i); \
         --__N; \
     } \
 }

 #define UTF8_SET_CHAR_LIMIT_UNSAFE(s, i) { \
     UTF8_BACK_1_UNSAFE(s, i); \
     UTF8_FWD_1_UNSAFE(s, i); \
 }

 #define UTF8_PREV_CHAR_SAFE(s, start, i, c, strict) { \
     (c)=(s)[--(i)]; \
     if((c)>=0x80) { \
         if((c)<=0xbf) { \
             (c)=utf8_prevCharSafeBody(s, start, &(i), c, strict); \
         } else { \
             (c)=UTF8_ERROR_VALUE_1; \
         } \
     } \
 }

 #define UTF8_BACK_1_SAFE(s, start, i) { \
     if(UTF8_IS_TRAIL((s)[--(i)])) { \
         (i)=utf8_back1SafeBody(s, start, (UTextOffset)(i)); \
     } \
 }

 #define UTF8_BACK_N_SAFE(s, start, i, n) { \
     UTextOffset __N=(n); \
     while(__N>0 && (i)>(start)) { \
         UTF8_BACK_1_SAFE(s, start, i); \
         --__N; \
     } \
 }

 /*
  * Need to use UTF8_FWD_1_SAFE() because UTF8_BACK_1_SAFE()
  * may have started from the middle of the sequence and not checked
  * all trail bytes.
  */
 #define UTF8_SET_CHAR_LIMIT_SAFE(s, start, i, length) { \
     if((start)<(i) && (i)<(length)) { \
         UTF8_BACK_1_SAFE(s, start, i); \
         UTF8_FWD_1_SAFE(s, i, length); \
     } \
 }

 #endif
	/*
	*******************************************************************************
	*
	* Copyright (C) 1999-2001, 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: UTF-8 macros
	*
	* This file defines macros to deal with UTF-8 code units and code points.
	* Signatures and semantics are the same as for the similarly named macros
	* in utf16.h.
	* utf8.h is included by utf.h after unicode/umachine.h
	* and some common definitions.</p>
	* <p><b>Usage:</b> 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.</p>
	*/


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

	#ifndef __UTF8_H__
	#define __UTF8_H__

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

	#ifdef U_UTF8_IMPL
	U_CAPI const uint8_t
	utf8_countTrailBytes[256];
	#else
	U_CFUNC const uint8_t /* U_IMPORT2? */ U_IMPORT
	utf8_countTrailBytes[256];
	#endif

	/*
	* Count the trail bytes for a lead byte -
	* this macro should be used so that the assembler code
	* that is mentioned in utf_impl.c could be used here.
	*/
	#define UTF8_COUNT_TRAIL_BYTES(leadByte) (utf8_countTrailBytes[(uint8_t)leadByte])

	/* use a macro here, too - there may be a simpler way with some machines */
	#define UTF8_MASK_LEAD_BYTE(leadByte, countTrailBytes) ((leadByte)&=(1<<(6-(countTrailBytes)))-1)

	U_CAPI UChar32 U_EXPORT2
	utf8_nextCharSafeBody(const uint8_t s, UTextOffset pi, UTextOffset length, UChar32 c, UBool strict);

	U_CAPI UTextOffset U_EXPORT2
	utf8_appendCharSafeBody(uint8_t *s, UTextOffset i, UTextOffset length, UChar32 c);

	U_CAPI UChar32 U_EXPORT2
	utf8_prevCharSafeBody(const uint8_t s, UTextOffset start, UTextOffset pi, UChar32 c, UBool strict);

	U_CAPI UTextOffset U_EXPORT2
	utf8_back1SafeBody(const uint8_t *s, UTextOffset start, UTextOffset i);

	/*
	* For the semantics of all of these macros, see utf16.h.
	* The UTF-8 macros favor sequences more the shorter they are.
	* Sometimes, only the single-byte case is covered by a macro,
	* while longer sequences are handled by a function call.
	*/

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

	/* classes of code unit values */
	#define UTF8_IS_SINGLE(uchar) (((uchar)&0x80)==0)
	#define UTF8_IS_LEAD(uchar) ((uint8_t)((uchar)-0xc0)<0x3e)
	#define UTF8_IS_TRAIL(uchar) (((uchar)&0xc0)==0x80)

	/* number of code units per code point */
	#define UTF8_NEED_MULTIPLE_UCHAR(c) ((uint32_t)(c)>0x7f)

	/*
	* ICU does not deal with code points >0x10ffff
	* unless necessary for advancing in the byte stream.
	*
	* These length macros take into account that for values >0x10ffff
	* the "safe" append macros would write the error code point 0xffff
	* with 3 bytes.
	* Code point comparisons need to be in uint32_t because UChar32
	* may be a signed type, and negative values must be recognized.
	*/
	#if 1
	# define UTF8_CHAR_LENGTH(c) \
	((uint32_t)(c)<=0x7f ? 1 : \
	((uint32_t)(c)<=0x7ff ? 2 : \
	((uint32_t)((c)-0x10000)>0xfffff ? 3 : 4) \
	) \
	)
	#else
	# define UTF8_CHAR_LENGTH(c) \
	((uint32_t)(c)<=0x7f ? 1 : \
	((uint32_t)(c)<=0x7ff ? 2 : \
	((uint32_t)(c)<=0xffff ? 3 : \
	((uint32_t)(c)<=0x10ffff ? 4 : \
	((uint32_t)(c)<=0x3ffffff ? 5 : \
	((uint32_t)(c)<=0x7fffffff ? 6 : 3) \
	) \
	) \
	) \
	) \
	)
	#endif

	#define UTF8_MAX_CHAR_LENGTH 4

	/* average number of code units compared to UTF-16 */
	#define UTF8_ARRAY_SIZE(size) ((5*(size))/2)

	#define UTF8_GET_CHAR_UNSAFE(s, i, c) { \
	UTextOffset __I=(UTextOffset)(i); \
	UTF8_SET_CHAR_START_UNSAFE(s, __I); \
	UTF8_NEXT_CHAR_UNSAFE(s, __I, c); \
	}

	#define UTF8_GET_CHAR_SAFE(s, start, i, length, c, strict) { \
	UTextOffset __I=(UTextOffset)(i); \
	UTF8_SET_CHAR_START_SAFE(s, start, __I); \
	UTF8_NEXT_CHAR_SAFE(s, __I, length, c, strict); \
	}

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

	/*
	* Read a Unicode scalar value from an array of UTF-8 bytes.
	* Only values <=0x10ffff are accepted, and if an error occurs,
	* then c will be set such that UTF_IS_ERROR(c).
	* The _UNSAFE macro is fast and does not check for errors.
	* The _SAFE macro checks for errors and optionally for
	* irregular sequences, too, i.e., for sequences that
	* are longer than necessary, such as <c0 80> instead of <0>.
	* The strict checks also check for non-characters.
	*/
	#define UTF8_NEXT_CHAR_UNSAFE(s, i, c) { \
	(c)=(s)[(i)++]; \
	if((uint8_t)((c)-0xc0)<0x35) { \
	uint8_t __count=UTF8_COUNT_TRAIL_BYTES(c); \
	UTF8_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; \
	} \
	} \
	}

	#define UTF8_APPEND_CHAR_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); \
	} \
	}

	#define UTF8_FWD_1_UNSAFE(s, i) { \
	(i)+=1+UTF8_COUNT_TRAIL_BYTES((s)[i]); \
	}

	#define UTF8_FWD_N_UNSAFE(s, i, n) { \
	UTextOffset __N=(n); \
	while(__N>0) { \
	UTF8_FWD_1_UNSAFE(s, i); \
	--__N; \
	} \
	}

	#define UTF8_SET_CHAR_START_UNSAFE(s, i) { \
	while(UTF8_IS_TRAIL((s)[i])) { --(i); } \
	}

	#define UTF8_NEXT_CHAR_SAFE(s, i, length, c, strict) { \
	(c)=(s)[(i)++]; \
	if((c)>=0x80) { \
	if(UTF8_IS_LEAD(c)) { \
	(c)=utf8_nextCharSafeBody(s, &(i), (UTextOffset)(length), c, strict); \
	} else { \
	(c)=UTF8_ERROR_VALUE_1; \
	} \
	} \
	}

	#define UTF8_APPEND_CHAR_SAFE(s, i, length, c) { \
	if((uint32_t)(c)<=0x7f) { \
	(s)[(i)++]=(uint8_t)(c); \
	} else { \
	(i)=utf8_appendCharSafeBody(s, (UTextOffset)(i), (UTextOffset)(length), c); \
	} \
	}

	#define UTF8_FWD_1_SAFE(s, i, length) { \
	uint8_t __b=(s)[(i)++]; \
	if(UTF8_IS_LEAD(__b)) { \
	uint8_t __count=UTF8_COUNT_TRAIL_BYTES(__b); \
	if((i)+__count>(length)) { \
	__count=(uint8_t)((length)-(i)); \
	} \
	while(__count>0 && UTF8_IS_TRAIL((s)[i])) { \
	++(i); \
	--__count; \
	} \
	} \
	}

	#define UTF8_FWD_N_SAFE(s, i, length, n) { \
	UTextOffset __N=(n); \
	while(__N>0 && (i)<(length)) { \
	UTF8_FWD_1_SAFE(s, i, length); \
	--__N; \
	} \
	}

	#define UTF8_SET_CHAR_START_SAFE(s, start, i) { \
	if(UTF8_IS_TRAIL((s)[(i)])) { \
	(i)=utf8_back1SafeBody(s, start, (UTextOffset)(i)); \
	} \
	}

	/* definitions with backward iteration -------------------------------------- */

	#define UTF8_PREV_CHAR_UNSAFE(s, i, c) { \
	(c)=(s)[--(i)]; \
	if(UTF8_IS_TRAIL(c)) { \
	uint8_t __b, __count=1, __shift=6; \
	\
	/* c is a trail byte */ \
	(c)&=0x3f; \
	for(;;) { \
	__b=(s)[--(i)]; \
	if(__b>=0xc0) { \
	UTF8_MASK_LEAD_BYTE(__b, __count); \
	(c)\|=(UChar32)__b<<__shift; \
	break; \
	} else { \
	(c)\|=(UChar32)(__b&0x3f)<<__shift; \
	++__count; \
	__shift+=6; \
	} \
	} \
	} \
	}

	#define UTF8_BACK_1_UNSAFE(s, i) { \
	while(UTF8_IS_TRAIL((s)[--(i)])) {} \
	}

	#define UTF8_BACK_N_UNSAFE(s, i, n) { \
	UTextOffset __N=(n); \
	while(__N>0) { \
	UTF8_BACK_1_UNSAFE(s, i); \
	--__N; \
	} \
	}

	#define UTF8_SET_CHAR_LIMIT_UNSAFE(s, i) { \
	UTF8_BACK_1_UNSAFE(s, i); \
	UTF8_FWD_1_UNSAFE(s, i); \
	}

	#define UTF8_PREV_CHAR_SAFE(s, start, i, c, strict) { \
	(c)=(s)[--(i)]; \
	if((c)>=0x80) { \
	if((c)<=0xbf) { \
	(c)=utf8_prevCharSafeBody(s, start, &(i), c, strict); \
	} else { \
	(c)=UTF8_ERROR_VALUE_1; \
	} \
	} \
	}

	#define UTF8_BACK_1_SAFE(s, start, i) { \
	if(UTF8_IS_TRAIL((s)[--(i)])) { \
	(i)=utf8_back1SafeBody(s, start, (UTextOffset)(i)); \
	} \
	}

	#define UTF8_BACK_N_SAFE(s, start, i, n) { \
	UTextOffset __N=(n); \
	while(__N>0 && (i)>(start)) { \
	UTF8_BACK_1_SAFE(s, start, i); \
	--__N; \
	} \
	}

	/*
	* Need to use UTF8_FWD_1_SAFE() because UTF8_BACK_1_SAFE()
	* may have started from the middle of the sequence and not checked
	* all trail bytes.
	*/
	#define UTF8_SET_CHAR_LIMIT_SAFE(s, start, i, length) { \
	if((start)<(i) && (i)<(length)) { \
	UTF8_BACK_1_SAFE(s, start, i); \
	UTF8_FWD_1_SAFE(s, i, length); \
	} \
	}

	#endif