text: /*
  ******************************************************************************
  *
  *   Copyright (C) 1999-2006, International Business Machines
  *   Corporation and others.  All Rights Reserved.
  *
  ******************************************************************************
  *   file name:  utf_impl.c
  *   encoding:   US-ASCII
  *   tab size:   8 (not used)
  *   indentation:4
  *
  *   created on: 1999sep13
  *   created by: Markus W. Scherer
  *
  *   This file provides implementation functions for macros in the utfXX.h
  *   that would otherwise be too long as macros.
  */
  
  #include "base/third_party/icu/icu_utf.h"
  
  namespace base_icu {
  
  /**
   * UTF8_ERROR_VALUE_1 and UTF8_ERROR_VALUE_2 are special error values for UTF-8,
   * which need 1 or 2 bytes in UTF-8:
   * \code
   * U+0015 = NAK = Negative Acknowledge, C0 control character
   * U+009f = highest C1 control character
   * \endcode
   *
   * These are used by UTF8_..._SAFE macros so that they can return an error value
   * that needs the same number of code units (bytes) as were seen by
   * a macro. They should be tested with UTF_IS_ERROR() or UTF_IS_VALID().
   *
   * @deprecated ICU 2.4. Obsolete, see utf_old.h.
   */
  #define CBUTF8_ERROR_VALUE_1 0x15
  
  /**
   * See documentation on UTF8_ERROR_VALUE_1 for details.
   *
   * @deprecated ICU 2.4. Obsolete, see utf_old.h.
   */
  #define CBUTF8_ERROR_VALUE_2 0x9f
  
  
  /**
   * Error value for all UTFs. This code point value will be set by macros with e>
   * checking if an error is detected.
   *
   * @deprecated ICU 2.4. Obsolete, see utf_old.h.
   */
  #define CBUTF_ERROR_VALUE 0xffff
  
  /*
   * This table could be replaced on many machines by
   * a few lines of assembler code using an
   * "index of first 0-bit from msb" instruction and
   * one or two more integer instructions.
   *
   * For example, on an i386, do something like
   * - MOV AL, leadByte
   * - NOT AL         (8-bit, leave b15..b8==0..0, reverse only b7..b0)
   * - MOV AH, 0
   * - BSR BX, AX     (16-bit)
   * - MOV AX, 6      (result)
   * - JZ finish      (ZF==1 if leadByte==0xff)
   * - SUB AX, BX (result)
   * -finish:
   * (BSR: Bit Scan Reverse, scans for a 1-bit, starting from the MSB)
   *
   * In Unicode, all UTF-8 byte sequences with more than 4 bytes are illegal;
   * lead bytes above 0xf4 are illegal.
   * We keep them in this table for skipping long ISO 10646-UTF-8 sequences.
   */
  const uint8_t
  utf8_countTrailBytes[256]={
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
  
      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
      1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
  
      2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
      3, 3, 3, 3, 3,
      3, 3, 3,    /* illegal in Unicode */
      4, 4, 4, 4, /* illegal in Unicode */
      5, 5,       /* illegal in Unicode */
      0, 0        /* illegal bytes 0xfe and 0xff */
  };
  
  static const UChar32
  utf8_minLegal[4]={ 0, 0x80, 0x800, 0x10000 };
  
  static const UChar32
  utf8_errorValue[6]={
      CBUTF8_ERROR_VALUE_1, CBUTF8_ERROR_VALUE_2, CBUTF_ERROR_VALUE, 0x10ffff,
      0x3ffffff, 0x7fffffff
  };
  
  /*
   * Handle the non-inline part of the U8_NEXT() macro and its obsolete sibling
   * UTF8_NEXT_CHAR_SAFE().
   *
   * The "strict" parameter controls the error behavior:
   * <0  "Safe" behavior of U8_NEXT(): All illegal byte sequences yield a negative
   *     code point result.
   *  0  Obsolete "safe" behavior of UTF8_NEXT_CHAR_SAFE(..., FALSE):
   *     All illegal byte sequences yield a positive code point such that this
   *     result code point would be encoded with the same number of bytes as
   *     the illegal sequence.
   * >0  Obsolete "strict" behavior of UTF8_NEXT_CHAR_SAFE(..., TRUE):
   *     Same as the obsolete "safe" behavior, but non-characters are also treated
   *     like illegal sequences.
   *
   * The special negative (<0) value -2 is used for lenient treatment of surrogate
   * code points as legal. Some implementations use this for roundtripping of
   * Unicode 16-bit strings that are not well-formed UTF-16, that is, they
   * contain unpaired surrogates.
   *
   * Note that a UBool is the same as an int8_t.
   */
  UChar32
  utf8_nextCharSafeBody(const uint8_t *s, int32_t *pi, int32_t length, UChar32 c, UBool strict) {
      int32_t i=*pi;
      uint8_t count=CBU8_COUNT_TRAIL_BYTES(c);
      if((i)+count<=(length)) {
          uint8_t trail, illegal=0;
  
          CBU8_MASK_LEAD_BYTE((c), count);
          /* count==0 for illegally leading trail bytes and the illegal bytes 0xfe and 0xff */
          switch(count) {
          /* each branch falls through to the next one */
          case 5:
          case 4:
              /* count>=4 is always illegal: no more than 3 trail bytes in Unicode's UTF-8 */
              illegal=1;
              break;
          case 3:
              trail=s[(i)++];
              (c)=((c)<<6)|(trail&0x3f);
              if(c<0x110) {
                  illegal|=(trail&0xc0)^0x80;
              } else {
                  /* code point>0x10ffff, outside Unicode */
                  illegal=1;
                  break;
              }
          case 2:
              trail=s[(i)++];
              (c)=((c)<<6)|(trail&0x3f);
              illegal|=(trail&0xc0)^0x80;
          case 1:
              trail=s[(i)++];
              (c)=((c)<<6)|(trail&0x3f);
              illegal|=(trail&0xc0)^0x80;
              break;
          case 0:
              if(strict>=0) {
                  return CBUTF8_ERROR_VALUE_1;
              } else {
                  return CBU_SENTINEL;
              }
          /* no default branch to optimize switch()  - all values are covered */
          }
  
          /*
           * All the error handling should return a value
           * that needs count bytes so that UTF8_GET_CHAR_SAFE() works right.
           *
           * Starting with Unicode 3.0.1, non-shortest forms are illegal.
           * Starting with Unicode 3.2, surrogate code points must not be
           * encoded in UTF-8, and there are no irregular sequences any more.
           *
           * U8_ macros (new in ICU 2.4) return negative values for error conditions.
           */
  
          /* correct sequence - all trail bytes have (b7..b6)==(10)? */
          /* illegal is also set if count>=4 */
          if(illegal || (c)<utf8_minLegal[count] || (CBU_IS_SURROGATE(c) && strict!=-2)) {
              /* error handling */
              uint8_t errorCount=count;
              /* don't go beyond this sequence */
              i=*pi;
              while(count>0 && CBU8_IS_TRAIL(s[i])) {
                  ++(i);
                  --count;
              }
              if(strict>=0) {
                  c=utf8_errorValue[errorCount-count];
              } else {
                  c=CBU_SENTINEL;
              }
          } else if((strict)>0 && CBU_IS_UNICODE_NONCHAR(c)) {
              /* strict: forbid non-characters like U+fffe */
              c=utf8_errorValue[count];
          }
      } else /* too few bytes left */ {
          /* error handling */
          int32_t i0=i;
          /* don't just set (i)=(length) in case there is an illegal sequence */
          while((i)<(length) && CBU8_IS_TRAIL(s[i])) {
              ++(i);
          }
          if(strict>=0) {
              c=utf8_errorValue[i-i0];
          } else {
              c=CBU_SENTINEL;
          }
      }
      *pi=i;
      return c;
  }
  
  }  // namespace base_icu
  