gfx/harfbuzz/src/hb-bit-page.hh

   1 /*
   2  * Copyright © 2012,2017  Google, Inc.
   3  * Copyright © 2021 Behdad Esfahbod
   4  *
   5  *  This is part of HarfBuzz, a text shaping library.
   6  *
   7  * Permission is hereby granted, without written agreement and without
   8  * license or royalty fees, to use, copy, modify, and distribute this
   9  * software and its documentation for any purpose, provided that the
  10  * above copyright notice and the following two paragraphs appear in
  11  * all copies of this software.
  12  *
  13  * IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE TO ANY PARTY FOR
  14  * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
  15  * ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN
  16  * IF THE COPYRIGHT HOLDER HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
  17  * DAMAGE.
  18  *
  19  * THE COPYRIGHT HOLDER SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING,
  20  * BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
  21  * FITNESS FOR A PARTICULAR PURPOSE.  THE SOFTWARE PROVIDED HEREUNDER IS
  22  * ON AN "AS IS" BASIS, AND THE COPYRIGHT HOLDER HAS NO OBLIGATION TO
  23  * PROVIDE MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS.
  24  *
  25  * Google Author(s): Behdad Esfahbod
  26  */
  27
  28 #ifndef HB_BIT_PAGE_HH
  29 #define HB_BIT_PAGE_HH
  30
  31 #include "hb.hh"
  32
  33
  34 /* Compiler-assisted vectorization. */
  35
  36 /* Type behaving similar to vectorized vars defined using __attribute__((vector_size(...))),
  37  * basically a fixed-size bitset. We can't use the compiler type because hb_vector_t cannot
  38  * guarantee alignment requirements. */
  39 template <typename elt_t, unsigned int byte_size>
  40 struct hb_vector_size_t
  41 {
  42   elt_t& operator [] (unsigned int i) { return v[i]; }
  43   const elt_t& operator [] (unsigned int i) const { return v[i]; }
  44
  45   void init0 ()
  46   {
  47     for (unsigned int i = 0; i < ARRAY_LENGTH (v); i++)
  48       v[i] = 0;
  49   }
  50   void init1 ()
  51   {
  52     for (unsigned int i = 0; i < ARRAY_LENGTH (v); i++)
  53       v[i] = (elt_t) -1;
  54   }
  55
  56   template <typename Op>
  57   hb_vector_size_t process (const Op& op) const
  58   {
  59     hb_vector_size_t r;
  60     for (unsigned int i = 0; i < ARRAY_LENGTH (v); i++)
  61       r.v[i] = op (v[i]);
  62     return r;
  63   }
  64   template <typename Op>
  65   hb_vector_size_t process (const Op& op, const hb_vector_size_t &o) const
  66   {
  67     hb_vector_size_t r;
  68     for (unsigned int i = 0; i < ARRAY_LENGTH (v); i++)
  69       r.v[i] = op (v[i], o.v[i]);
  70     return r;
  71   }
  72   hb_vector_size_t operator | (const hb_vector_size_t &o) const
  73   { return process (hb_bitwise_or, o); }
  74   hb_vector_size_t operator & (const hb_vector_size_t &o) const
  75   { return process (hb_bitwise_and, o); }
  76   hb_vector_size_t operator ^ (const hb_vector_size_t &o) const
  77   { return process (hb_bitwise_xor, o); }
  78   hb_vector_size_t operator ~ () const
  79   { return process (hb_bitwise_neg); }
  80
  81   hb_array_t<const elt_t> iter () const
  82   { return hb_array (v); }
  83
  84   private:
  85   static_assert (0 == byte_size % sizeof (elt_t), "");
  86   elt_t v[byte_size / sizeof (elt_t)];
  87 };
  88
  89
  90 struct hb_bit_page_t
  91 {
  92   void init0 () { v.init0 (); population = 0; }
  93   void init1 () { v.init1 (); population = PAGE_BITS; }
  94
  95   void dirty () { population = UINT_MAX; }
  96
  97   static inline constexpr unsigned len ()
  98   { return ARRAY_LENGTH_CONST (v); }
  99
 100   operator bool () const { return !is_empty (); }
 101   bool is_empty () const
 102   {
 103     if (has_population ()) return !population;
 104     return
 105     + hb_iter (v)
 106     | hb_none
 107     ;
 108   }
 109   uint32_t hash () const
 110   {
 111     return hb_bytes_t ((const char *) &v, sizeof (v)).hash ();
 112   }
 113
 114   void add (hb_codepoint_t g) { elt (g) |= mask (g); dirty (); }
 115   void del (hb_codepoint_t g) { elt (g) &= ~mask (g); dirty (); }
 116   void set (hb_codepoint_t g, bool value) { if (value) add (g); else del (g); }
 117   bool get (hb_codepoint_t g) const { return elt (g) & mask (g); }
 118
 119   void add_range (hb_codepoint_t a, hb_codepoint_t b)
 120   {
 121     elt_t *la = &elt (a);
 122     elt_t *lb = &elt (b);
 123     if (la == lb)
 124       *la |= (mask (b) << 1) - mask(a);
 125     else
 126     {
 127       *la |= ~(mask (a) - 1llu);
 128       la++;
 129
 130       hb_memset (la, 0xff, (char *) lb - (char *) la);
 131
 132       *lb |= ((mask (b) << 1) - 1llu);
 133     }
 134     dirty ();
 135   }
 136   void del_range (hb_codepoint_t a, hb_codepoint_t b)
 137   {
 138     elt_t *la = &elt (a);
 139     elt_t *lb = &elt (b);
 140     if (la == lb)
 141       *la &= ~((mask (b) << 1llu) - mask(a));
 142     else
 143     {
 144       *la &= mask (a) - 1;
 145       la++;
 146
 147       hb_memset (la, 0, (char *) lb - (char *) la);
 148
 149       *lb &= ~((mask (b) << 1) - 1llu);
 150     }
 151     dirty ();
 152   }
 153   void set_range (hb_codepoint_t a, hb_codepoint_t b, bool v)
 154   { if (v) add_range (a, b); else del_range (a, b); }
 155
 156
 157   // Writes out page values to the array p. Returns the number of values
 158   // written. At most size codepoints will be written.
 159   unsigned int write (uint32_t        base,
 160                       unsigned int    start_value,
 161                       hb_codepoint_t *p,
 162                       unsigned int    size) const
 163   {
 164     unsigned int start_v = start_value / ELT_BITS;
 165     unsigned int start_bit = start_value & ELT_MASK;
 166     unsigned int count = 0;
 167     for (unsigned i = start_v; i < len () && count < size; i++)
 168     {
 169       elt_t bits = v[i];
 170       uint32_t v_base = base | (i * ELT_BITS);
 171       for (unsigned int j = start_bit; j < ELT_BITS && count < size; j++)
 172       {
 173         if ((elt_t(1) << j) & bits) {
 174           *p++ = v_base | j;
 175           count++;
 176         }
 177       }
 178       start_bit = 0;
 179     }
 180     return count;
 181   }
 182
 183   // Writes out the values NOT in this page to the array p. Returns the
 184   // number of values written. At most size codepoints will be written.
 185   // Returns the number of codepoints written. next_value holds the next value
 186   // that should be written (if not present in this page). This is used to fill
 187   // any missing value gaps between this page and the previous page, if any.
 188   // next_value is updated to one more than the last value present in this page.
 189   unsigned int write_inverted (uint32_t        base,
 190                                unsigned int    start_value,
 191                                hb_codepoint_t *p,
 192                                unsigned int    size,
 193                                hb_codepoint_t *next_value) const
 194   {
 195     unsigned int start_v = start_value / ELT_BITS;
 196     unsigned int start_bit = start_value & ELT_MASK;
 197     unsigned int count = 0;
 198     for (unsigned i = start_v; i < len () && count < size; i++)
 199     {
 200       elt_t bits = v[i];
 201       uint32_t v_offset = i * ELT_BITS;
 202       for (unsigned int j = start_bit; j < ELT_BITS && count < size; j++)
 203       {
 204         if ((elt_t(1) << j) & bits)
 205         {
 206           hb_codepoint_t value = base | v_offset | j;
 207           // Emit all the missing values from next_value up to value - 1.
 208           for (hb_codepoint_t k = *next_value; k < value && count < size; k++)
 209           {
 210             *p++ = k;
 211             count++;
 212           }
 213           // Skip over this value;
 214           *next_value = value + 1;
 215         }
 216       }
 217       start_bit = 0;
 218     }
 219     return count;
 220   }
 221
 222   bool operator == (const hb_bit_page_t &other) const { return is_equal (other); }
 223   bool is_equal (const hb_bit_page_t &other) const
 224   {
 225     for (unsigned i = 0; i < len (); i++)
 226       if (v[i] != other.v[i])
 227         return false;
 228     return true;
 229   }
 230   bool operator <= (const hb_bit_page_t &larger_page) const { return is_subset (larger_page); }
 231   bool is_subset (const hb_bit_page_t &larger_page) const
 232   {
 233     if (has_population () && larger_page.has_population () &&
 234         population > larger_page.population)
 235       return false;
 236
 237     for (unsigned i = 0; i < len (); i++)
 238       if (~larger_page.v[i] & v[i])
 239         return false;
 240     return true;
 241   }
 242
 243   bool has_population () const { return population != UINT_MAX; }
 244   unsigned int get_population () const
 245   {
 246     if (has_population ()) return population;
 247     population =
 248     + hb_iter (v)
 249     | hb_reduce ([] (unsigned pop, const elt_t &_) { return pop + hb_popcount (_); }, 0u)
 250     ;
 251     return population;
 252   }
 253
 254   bool next (hb_codepoint_t *codepoint) const
 255   {
 256     unsigned int m = (*codepoint + 1) & MASK;
 257     if (!m)
 258     {
 259       *codepoint = INVALID;
 260       return false;
 261     }
 262     unsigned int i = m / ELT_BITS;
 263     unsigned int j = m & ELT_MASK;
 264
 265     const elt_t vv = v[i] & ~((elt_t (1) << j) - 1);
 266     for (const elt_t *p = &vv; i < len (); p = &v[++i])
 267       if (*p)
 268       {
 269         *codepoint = i * ELT_BITS + elt_get_min (*p);
 270         return true;
 271       }
 272
 273     *codepoint = INVALID;
 274     return false;
 275   }
 276   bool previous (hb_codepoint_t *codepoint) const
 277   {
 278     unsigned int m = (*codepoint - 1) & MASK;
 279     if (m == MASK)
 280     {
 281       *codepoint = INVALID;
 282       return false;
 283     }
 284     unsigned int i = m / ELT_BITS;
 285     unsigned int j = m & ELT_MASK;
 286
 287     /* Fancy mask to avoid shifting by elt_t bitsize, which is undefined. */
 288     const elt_t mask = j < 8 * sizeof (elt_t) - 1 ?
 289                        ((elt_t (1) << (j + 1)) - 1) :
 290                        (elt_t) -1;
 291     const elt_t vv = v[i] & mask;
 292     const elt_t *p = &vv;
 293     while (true)
 294     {
 295       if (*p)
 296       {
 297         *codepoint = i * ELT_BITS + elt_get_max (*p);
 298         return true;
 299       }
 300       if ((int) i <= 0) break;
 301       p = &v[--i];
 302     }
 303
 304     *codepoint = INVALID;
 305     return false;
 306   }
 307   hb_codepoint_t get_min () const
 308   {
 309     for (unsigned int i = 0; i < len (); i++)
 310       if (v[i])
 311         return i * ELT_BITS + elt_get_min (v[i]);
 312     return INVALID;
 313   }
 314   hb_codepoint_t get_max () const
 315   {
 316     for (int i = len () - 1; i >= 0; i--)
 317       if (v[i])
 318         return i * ELT_BITS + elt_get_max (v[i]);
 319     return 0;
 320   }
 321
 322   static constexpr hb_codepoint_t INVALID = HB_SET_VALUE_INVALID;
 323
 324   typedef unsigned long long elt_t;
 325   static constexpr unsigned PAGE_BITS_LOG_2 = 9; // 512 bits
 326   static constexpr unsigned PAGE_BITS = 1 << PAGE_BITS_LOG_2;
 327   static_assert (1 << PAGE_BITS_LOG_2 == PAGE_BITS, "");
 328   static_assert ((PAGE_BITS & ((PAGE_BITS) - 1)) == 0, "");
 329   static constexpr unsigned PAGE_BITMASK = PAGE_BITS - 1;
 330
 331   static unsigned int elt_get_min (const elt_t &elt) { return hb_ctz (elt); }
 332   static unsigned int elt_get_max (const elt_t &elt) { return hb_bit_storage (elt) - 1; }
 333
 334   typedef hb_vector_size_t<elt_t, PAGE_BITS / 8> vector_t;
 335
 336   static constexpr unsigned ELT_BITS = sizeof (elt_t) * 8;
 337   static constexpr unsigned ELT_MASK = ELT_BITS - 1;
 338
 339   static constexpr unsigned BITS = sizeof (vector_t) * 8;
 340   static constexpr unsigned MASK = BITS - 1;
 341   static_assert ((unsigned) PAGE_BITS == (unsigned) BITS, "");
 342
 343   elt_t &elt (hb_codepoint_t g) { return v[(g & MASK) / ELT_BITS]; }
 344   const elt_t& elt (hb_codepoint_t g) const { return v[(g & MASK) / ELT_BITS]; }
 345   static constexpr elt_t mask (hb_codepoint_t g) { return elt_t (1) << (g & ELT_MASK); }
 346
 347   mutable unsigned population;
 348   vector_t v;
 349 };
 350
 351
 352 #endif /* HB_BIT_PAGE_HH */