release/src/router/php/ext/json/utf8_decode.c

   1 /* utf8_decode.c */
   2
   3 /* 2005-12-25 */
   4
   5 /*
   6 Copyright (c) 2005 JSON.org
   7
   8 Permission is hereby granted, free of charge, to any person obtaining a copy
   9 of this software and associated documentation files (the "Software"), to deal
  10 in the Software without restriction, including without limitation the rights
  11 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  12 copies of the Software, and to permit persons to whom the Software is
  13 furnished to do so, subject to the following conditions:
  14
  15 The above copyright notice and this permission notice shall be included in all
  16 copies or substantial portions of the Software.
  17
  18 The Software shall be used for Good, not Evil.
  19
  20 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  21 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  22 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  23 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  24 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  25 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  26 SOFTWARE.
  27 */
  28
  29 #include "utf8_decode.h"
  30
  31 /*
  32     Very Strict UTF-8 Decoder
  33
  34     UTF-8 is a multibyte character encoding of Unicode. A character can be
  35     represented by 1-4 bytes. The bit pattern of the first byte indicates the
  36     number of continuation bytes.
  37
  38     Most UTF-8 decoders tend to be lenient, attempting to recover as much
  39     information as possible, even from badly encoded input. This UTF-8
  40     decoder is not lenient. It will reject input which does not include
  41     proper continuation bytes. It will reject aliases (or suboptimal
  42     codings). It will reject surrogates. (Surrogate encoding should only be
  43     used with UTF-16.)
  44
  45     Code     Contination Minimum Maximum
  46     0xxxxxxx           0       0     127
  47     10xxxxxx       error
  48     110xxxxx           1     128    2047
  49     1110xxxx           2    2048   65535 excluding 55296 - 57343
  50     11110xxx           3   65536 1114111
  51     11111xxx       error
  52 */
  53
  54
  55 /*
  56     Get the next byte. It returns UTF8_END if there are no more bytes.
  57 */
  58 static int
  59 get(json_utf8_decode *utf8)
  60 {
  61     int c;
  62     if (utf8->the_index >= utf8->the_length) {
  63         return UTF8_END;
  64     }
  65     c = utf8->the_input[utf8->the_index] & 0xFF;
  66     utf8->the_index += 1;
  67     return c;
  68 }
  69
  70
  71 /*
  72     Get the 6-bit payload of the next continuation byte.
  73     Return UTF8_ERROR if it is not a contination byte.
  74 */
  75 static int
  76 cont(json_utf8_decode *utf8)
  77 {
  78     int c = get(utf8);
  79     return ((c & 0xC0) == 0x80) ? (c & 0x3F) : UTF8_ERROR;
  80 }
  81
  82
  83 /*
  84     Initialize the UTF-8 decoder. The decoder is not reentrant,
  85 */
  86 void
  87 utf8_decode_init(json_utf8_decode *utf8, char p[], int length)
  88 {
  89     utf8->the_index = 0;
  90     utf8->the_input = p;
  91     utf8->the_length = length;
  92     utf8->the_char = 0;
  93     utf8->the_byte = 0;
  94 }
  95
  96
  97 /*
  98     Get the current byte offset. This is generally used in error reporting.
  99 */
 100 int
 101 utf8_decode_at_byte(json_utf8_decode *utf8)
 102 {
 103     return utf8->the_byte;
 104 }
 105
 106
 107 /*
 108     Get the current character offset. This is generally used in error reporting.
 109     The character offset matches the byte offset if the text is strictly ASCII.
 110 */
 111 int
 112 utf8_decode_at_character(json_utf8_decode *utf8)
 113 {
 114     return utf8->the_char > 0 ? utf8->the_char - 1 : 0;
 115 }
 116
 117
 118 /*
 119     Extract the next character.
 120     Returns: the character (between 0 and 1114111)
 121          or  UTF8_END   (the end)
 122          or  UTF8_ERROR (error)
 123 */
 124 int
 125 utf8_decode_next(json_utf8_decode *utf8)
 126 {
 127     int c;  /* the first byte of the character */
 128     int r;  /* the result */
 129
 130     if (utf8->the_index >= utf8->the_length) {
 131         return utf8->the_index == utf8->the_length ? UTF8_END : UTF8_ERROR;
 132     }
 133     utf8->the_byte = utf8->the_index;
 134     utf8->the_char += 1;
 135     c = get(utf8);
 136 /*
 137     Zero continuation (0 to 127)
 138 */
 139     if ((c & 0x80) == 0) {
 140         return c;
 141     }
 142 /*
 143     One contination (128 to 2047)
 144 */
 145     if ((c & 0xE0) == 0xC0) {
 146         int c1 = cont(utf8);
 147         if (c1 < 0) {
 148             return UTF8_ERROR;
 149         }
 150         r = ((c & 0x1F) << 6) | c1;
 151         return r >= 128 ? r : UTF8_ERROR;
 152     }
 153 /*
 154     Two continuation (2048 to 55295 and 57344 to 65535)
 155 */
 156     if ((c & 0xF0) == 0xE0) {
 157         int c1 = cont(utf8);
 158         int c2 = cont(utf8);
 159         if (c1 < 0 || c2 < 0) {
 160             return UTF8_ERROR;
 161         }
 162         r = ((c & 0x0F) << 12) | (c1 << 6) | c2;
 163         return r >= 2048 && (r < 55296 || r > 57343) ? r : UTF8_ERROR;
 164     }
 165 /*
 166     Three continuation (65536 to 1114111)
 167 */
 168     if ((c & 0xF8) == 0xF0) {
 169         int c1 = cont(utf8);
 170         int c2 = cont(utf8);
 171         int c3 = cont(utf8);
 172         if (c1 < 0 || c2 < 0 || c3 < 0) {
 173             return UTF8_ERROR;
 174         }
 175         r = ((c & 0x0F) << 18) | (c1 << 12) | (c2 << 6) | c3;
 176         return r >= 65536 && r <= 1114111 ? r : UTF8_ERROR;
 177     }
 178     return UTF8_ERROR;
 179 }