text: /**
   * Copyright 2013, GitHub, Inc
   * Copyright 2009-2013, Daniel Lemire, Cliff Moon,
   * David McIntosh, Robert Becho, Google Inc. and Veronika Zenz
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * as published by the Free Software Foundation; either version 2
   * of the License, or (at your option) any later version.
   *
   * This program is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   * GNU General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, see <http://www.gnu.org/licenses/>.
   */
  #ifndef __EWOK_BITMAP_H__
  #define __EWOK_BITMAP_H__
  
  #include <unistd.h>
  #include <stdlib.h>
  #include <stdint.h>
  
  struct strbuf;
  typedef uint64_t eword_t;
  #define BITS_IN_EWORD (sizeof(eword_t) * 8)
  
  /**
   * Do not use __builtin_popcountll. The GCC implementation
   * is notoriously slow on all platforms.
   *
   * See: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=36041
   */
  static inline uint32_t ewah_bit_popcount64(uint64_t x)
  {
     x = (x & 0x5555555555555555ULL) + ((x >>  1) & 0x5555555555555555ULL);
     x = (x & 0x3333333333333333ULL) + ((x >>  2) & 0x3333333333333333ULL);
     x = (x & 0x0F0F0F0F0F0F0F0FULL) + ((x >>  4) & 0x0F0F0F0F0F0F0F0FULL);
     return (x * 0x0101010101010101ULL) >> 56;
  }
  
  /* __builtin_ctzll was not available until 3.4.0 */
  #if defined(__GNUC__) && (__GNUC__ > 3 || (__GNUC__ == 3  && __GNUC_MINOR > 3))
  #define ewah_bit_ctz64(x) __builtin_ctzll(x)
  #else
  static inline int ewah_bit_ctz64(uint64_t x)
  {
     int n = 0;
     if ((x & 0xffffffff) == 0) { x >>= 32; n += 32; }
     if ((x &     0xffff) == 0) { x >>= 16; n += 16; }
     if ((x &       0xff) == 0) { x >>=  8; n +=  8; }
     if ((x &        0xf) == 0) { x >>=  4; n +=  4; }
     if ((x &        0x3) == 0) { x >>=  2; n +=  2; }
     if ((x &        0x1) == 0) { x >>=  1; n +=  1; }
     return n + !x;
  }
  #endif
  
  typedef struct ewah_bitmap {
     eword_t *buffer;
     size_t buffer_size;
     size_t alloc_size;
     size_t bit_size;
     eword_t *rlw;
  } ewah_bitmap;
  
  typedef void (*ewah_callback)(size_t pos, void *);
  
  struct ewah_bitmap *ewah_pool_new(void);
  void ewah_pool_free(struct ewah_bitmap *self);
  
  /**
   * Allocate a new EWAH Compressed bitmap
   */
  struct ewah_bitmap *ewah_new(void);
  
  /**
   * Free all the memory of the bitmap
   */
  void ewah_free(struct ewah_bitmap *self);
  
  int ewah_serialize_to(struct ewah_bitmap *self,
              int (*write_fun)(void *out, const void *buf, size_t len),
              void *out);
  int ewah_serialize_strbuf(struct ewah_bitmap *self, struct strbuf *);
  
  ssize_t ewah_read_mmap(struct ewah_bitmap *self, const void *map, size_t len);
  
  uint32_t ewah_checksum(struct ewah_bitmap *self);
  
  /**
   * Call the given callback with the position of every single bit
   * that has been set on the bitmap.
   *
   * This is an efficient operation that does not fully decompress
   * the bitmap.
   */
  void ewah_each_bit(struct ewah_bitmap *self, ewah_callback callback, void *payload);
  
  /**
   * Set a given bit on the bitmap.
   *
   * The bit at position `pos` will be set to true. Because of the
   * way that the bitmap is compressed, a set bit cannot be unset
   * later on.
   *
   * Furthermore, since the bitmap uses streaming compression, bits
   * can only set incrementally.
   *
   * E.g.
   *    ewah_set(bitmap, 1); // ok
   *    ewah_set(bitmap, 76); // ok
   *    ewah_set(bitmap, 77); // ok
   *    ewah_set(bitmap, 8712800127); // ok
   *    ewah_set(bitmap, 25); // failed, assert raised
   */
  void ewah_set(struct ewah_bitmap *self, size_t i);
  
  typedef struct ewah_iterator {
     const eword_t *buffer;
     size_t buffer_size;
  
     size_t pointer;
     eword_t compressed, literals;
     eword_t rl, lw;
     int b;
  } ewah_iterator;
  
  /**
   * Initialize a new iterator to run through the bitmap in uncompressed form.
   *
   * The iterator can be stack allocated. The underlying bitmap must not be freed
   * before the iteration is over.
   *
   * E.g.
   *
   *    struct ewah_bitmap *bitmap = ewah_new();
   *    struct ewah_iterator it;
   *
   *    ewah_iterator_init(&it, bitmap);
   */
  void ewah_iterator_init(struct ewah_iterator *it, struct ewah_bitmap *parent);
  
  /**
   * Yield every single word in the bitmap in uncompressed form. This is:
   * yield single words (32-64 bits) where each bit represents an actual
   * bit from the bitmap.
   *
   * Return: true if a word was yield, false if there are no words left
   */
  int ewah_iterator_next(eword_t *next, struct ewah_iterator *it);
  
  void ewah_xor(
     struct ewah_bitmap *ewah_i,
     struct ewah_bitmap *ewah_j,
     struct ewah_bitmap *out);
  
  /**
   * Direct word access
   */
  size_t ewah_add_empty_words(struct ewah_bitmap *self, int v, size_t number);
  void ewah_add_dirty_words(
     struct ewah_bitmap *self, const eword_t *buffer, size_t number, int negate);
  size_t ewah_add(struct ewah_bitmap *self, eword_t word);
  
  
  /**
   * Uncompressed, old-school bitmap that can be efficiently compressed
   * into an `ewah_bitmap`.
   */
  typedef struct bitmap {
     eword_t *words;
     size_t word_alloc;
  } bitmap;
  
  struct bitmap *bitmap_new(void);
  struct bitmap *bitmap_word_alloc(size_t word_alloc);
  void bitmap_set(struct bitmap *self, size_t pos);
  void bitmap_unset(struct bitmap *self, size_t pos);
  int bitmap_get(struct bitmap *self, size_t pos);
  void bitmap_reset(struct bitmap *self);
  void bitmap_free(struct bitmap *self);
  int bitmap_equals(struct bitmap *self, struct bitmap *other);
  int bitmap_is_subset(struct bitmap *self, struct bitmap *super);
  
  struct ewah_bitmap * bitmap_to_ewah(struct bitmap *bitmap);
  struct bitmap *ewah_to_bitmap(struct ewah_bitmap *ewah);
  
  void bitmap_and_not(struct bitmap *self, struct bitmap *other);
  void bitmap_or_ewah(struct bitmap *self, struct ewah_bitmap *other);
  void bitmap_or(struct bitmap *self, const struct bitmap *other);
  
  size_t bitmap_popcount(struct bitmap *self);
  
  #endif
  
  