The Tor Browser / file revision

 /*

 ******************************************************************************

 *

 *   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

 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 *s, int32 *pi, int32 length, UChar32 c, UBool strict) {

     int32 i=*pi;

     uint8 count=CBU8_COUNT_TRAIL_BYTES(c);

     if((i)+count<=(length)) {

         uint8 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 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 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