third_party/harfbuzz-ng/src/hb-utf-private.hh

   1 /*
   2  * Copyright © 2011,2012,2014  Google, Inc.
   3  *
   4  *  This is part of HarfBuzz, a text shaping library.
   5  *
   6  * Permission is hereby granted, without written agreement and without
   7  * license or royalty fees, to use, copy, modify, and distribute this
   8  * software and its documentation for any purpose, provided that the
   9  * above copyright notice and the following two paragraphs appear in
  10  * all copies of this software.
  11  *
  12  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
  13  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
  14  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
  15  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
  16  * DAMAGE.
  17  *
  18  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
  19  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  20  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
  21  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
  22  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  23  *
  24  * Google Author(s): Behdad Esfahbod
  25  */
  26
  27 #ifndef HB_UTF_PRIVATE_HH
  28 #define HB_UTF_PRIVATE_HH
  29
  30 #include "hb-private.hh"
  31
  32 template <typename T, bool validate=true> struct hb_utf_t;
  33
  34
  35 /* UTF-8 */
  36
  37 template <>
  38 struct hb_utf_t<uint8_t, true>
  39 {
  40   static inline const uint8_t *
  41   next (const uint8_t *text,
  42         const uint8_t *end,
  43         hb_codepoint_t *unicode,
  44         hb_codepoint_t replacement)
  45   {
  46     /* Written to only accept well-formed sequences.
  47      * Based on ideas from ICU's U8_NEXT.
  48      * Generates one "replacement" for each ill-formed byte. */
  49
  50     hb_codepoint_t c = *text++;
  51
  52     if (c > 0x7Fu)
  53     {
  54       if (hb_in_range (c, 0xC2u, 0xDFu)) /* Two-byte */
  55       {
  56         unsigned int t1;
  57         if (likely (text < end &&
  58                     (t1 = text[0] - 0x80u) <= 0x3Fu))
  59         {
  60           c = ((c&0x1Fu)<<6) | t1;
  61           text++;
  62         }
  63         else
  64           goto error;
  65       }
  66       else if (hb_in_range (c, 0xE0u, 0xEFu)) /* Three-byte */
  67       {
  68         unsigned int t1, t2;
  69         if (likely (1 < end - text &&
  70                     (t1 = text[0] - 0x80u) <= 0x3Fu &&
  71                     (t2 = text[1] - 0x80u) <= 0x3Fu))
  72         {
  73           c = ((c&0xFu)<<12) | (t1<<6) | t2;
  74           if (unlikely (c < 0x0800u || hb_in_range (c, 0xD800u, 0xDFFFu)))
  75             goto error;
  76           text += 2;
  77         }
  78         else
  79           goto error;
  80       }
  81       else if (hb_in_range (c, 0xF0u, 0xF4u)) /* Four-byte */
  82       {
  83         unsigned int t1, t2, t3;
  84         if (likely (2 < end - text &&
  85                     (t1 = text[0] - 0x80u) <= 0x3Fu &&
  86                     (t2 = text[1] - 0x80u) <= 0x3Fu &&
  87                     (t3 = text[2] - 0x80u) <= 0x3Fu))
  88         {
  89           c = ((c&0x7u)<<18) | (t1<<12) | (t2<<6) | t3;
  90           if (unlikely (!hb_in_range (c, 0x10000u, 0x10FFFFu)))
  91             goto error;
  92           text += 3;
  93         }
  94         else
  95           goto error;
  96       }
  97       else
  98         goto error;
  99     }
 100
 101     *unicode = c;
 102     return text;
 103
 104   error:
 105     *unicode = replacement;
 106     return text;
 107   }
 108
 109   static inline const uint8_t *
 110   prev (const uint8_t *text,
 111         const uint8_t *start,
 112         hb_codepoint_t *unicode,
 113         hb_codepoint_t replacement)
 114   {
 115     const uint8_t *end = text--;
 116     while (start < text && (*text & 0xc0) == 0x80 && end - text < 4)
 117       text--;
 118
 119     if (likely (next (text, end, unicode, replacement) == end))
 120       return text;
 121
 122     *unicode = replacement;
 123     return end - 1;
 124   }
 125
 126   static inline unsigned int
 127   strlen (const uint8_t *text)
 128   {
 129     return ::strlen ((const char *) text);
 130   }
 131 };
 132
 133
 134 /* UTF-16 */
 135
 136 template <>
 137 struct hb_utf_t<uint16_t, true>
 138 {
 139   static inline const uint16_t *
 140   next (const uint16_t *text,
 141         const uint16_t *end,
 142         hb_codepoint_t *unicode,
 143         hb_codepoint_t replacement)
 144   {
 145     hb_codepoint_t c = *text++;
 146
 147     if (likely (!hb_in_range (c, 0xD800u, 0xDFFFu)))
 148     {
 149       *unicode = c;
 150       return text;
 151     }
 152
 153     if (likely (hb_in_range (c, 0xD800u, 0xDBFFu)))
 154     {
 155       /* High-surrogate in c */
 156       hb_codepoint_t l;
 157       if (text < end && ((l = *text), likely (hb_in_range (l, 0xDC00u, 0xDFFFu))))
 158       {
 159         /* Low-surrogate in l */
 160         *unicode = (c << 10) + l - ((0xD800u << 10) - 0x10000u + 0xDC00u);
 161          text++;
 162          return text;
 163       }
 164     }
 165
 166     /* Lonely / out-of-order surrogate. */
 167     *unicode = replacement;
 168     return text;
 169   }
 170
 171   static inline const uint16_t *
 172   prev (const uint16_t *text,
 173         const uint16_t *start,
 174         hb_codepoint_t *unicode,
 175         hb_codepoint_t replacement)
 176   {
 177     const uint16_t *end = text--;
 178     hb_codepoint_t c = *text;
 179
 180     if (likely (!hb_in_range (c, 0xD800u, 0xDFFFu)))
 181     {
 182       *unicode = c;
 183       return text;
 184     }
 185
 186     if (likely (start < text && hb_in_range (c, 0xDC00u, 0xDFFFu)))
 187       text--;
 188
 189     if (likely (next (text, end, unicode, replacement) == end))
 190       return text;
 191
 192     *unicode = replacement;
 193     return end - 1;
 194   }
 195
 196
 197   static inline unsigned int
 198   strlen (const uint16_t *text)
 199   {
 200     unsigned int l = 0;
 201     while (*text++) l++;
 202     return l;
 203   }
 204 };
 205
 206
 207 /* UTF-32 */
 208
 209 template <bool validate>
 210 struct hb_utf_t<uint32_t, validate>
 211 {
 212   static inline const uint32_t *
 213   next (const uint32_t *text,
 214         const uint32_t *end HB_UNUSED,
 215         hb_codepoint_t *unicode,
 216         hb_codepoint_t replacement)
 217   {
 218     hb_codepoint_t c = *text++;
 219     if (validate && unlikely (c > 0x10FFFFu || hb_in_range (c, 0xD800u, 0xDFFFu)))
 220       goto error;
 221     *unicode = c;
 222     return text;
 223
 224   error:
 225     *unicode = replacement;
 226     return text;
 227   }
 228
 229   static inline const uint32_t *
 230   prev (const uint32_t *text,
 231         const uint32_t *start HB_UNUSED,
 232         hb_codepoint_t *unicode,
 233         hb_codepoint_t replacement)
 234   {
 235     next (text - 1, text, unicode, replacement);
 236     return text - 1;
 237   }
 238
 239   static inline unsigned int
 240   strlen (const uint32_t *text)
 241   {
 242     unsigned int l = 0;
 243     while (*text++) l++;
 244     return l;
 245   }
 246 };
 247
 248
 249 #endif /* HB_UTF_PRIVATE_HH */