/**

 * 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/>.

 */

#include "git-compat-util.h"

#include "ewok.h"

#include "ewok_rlw.h"

static inline int next_word(struct rlw_iterator *it)

{

  if (it->pointer >= it->size)

    return 0;

  it->rlw.word = &it->buffer[it->pointer];

  it->pointer += rlw_get_literal_words(it->rlw.word) + 1;

  it->rlw.literal_words = rlw_get_literal_words(it->rlw.word);

  it->rlw.running_len = rlw_get_running_len(it->rlw.word);

  it->rlw.running_bit = rlw_get_run_bit(it->rlw.word);

  it->rlw.literal_word_offset = 0;

  return 1;

}

void rlwit_init(struct rlw_iterator *it, struct ewah_bitmap *from_ewah)

{

  it->buffer = from_ewah->buffer;

  it->size = from_ewah->buffer_size;

  it->pointer = 0;

  next_word(it);

  it->literal_word_start = rlwit_literal_words(it) +

    it->rlw.literal_word_offset;

}

void rlwit_discard_first_words(struct rlw_iterator *it, size_t x)

{

  while (x > 0) {

    size_t discard;

    if (it->rlw.running_len > x) {

      it->rlw.running_len -= x;

      return;

    }

    x -= it->rlw.running_len;

    it->rlw.running_len = 0;

    discard = (x > it->rlw.literal_words) ? it->rlw.literal_words : x;

    it->literal_word_start += discard;

    it->rlw.literal_words -= discard;

    x -= discard;

    if (x > 0 || rlwit_word_size(it) == 0) {

      if (!next_word(it))

        break;

      it->literal_word_start =

        rlwit_literal_words(it) + it->rlw.literal_word_offset;

    }

  }

}

size_t rlwit_discharge(

  struct rlw_iterator *it, struct ewah_bitmap *out, size_t max, int negate)

{

  size_t index = 0;

  while (index < max && rlwit_word_size(it) > 0) {

    size_t pd, pl = it->rlw.running_len;

    if (index + pl > max)

      pl = max - index;

    ewah_add_empty_words(out, it->rlw.running_bit ^ negate, pl);

    index += pl;

    pd = it->rlw.literal_words;

    if (pd + index > max)

      pd = max - index;

    ewah_add_dirty_words(out,

      it->buffer + it->literal_word_start, pd, negate);

    rlwit_discard_first_words(it, pd + pl);

    index += pd;

  }

  return index;

}