ewah/ewah_rlw.c

   1 /**
   2  * Copyright 2013, GitHub, Inc
   3  * Copyright 2009-2013, Daniel Lemire, Cliff Moon,
   4  *      David McIntosh, Robert Becho, Google Inc. and Veronika Zenz
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version 2
   9  * of the License, or (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19 #include "git-compat-util.h"
  20 #include "ewok.h"
  21 #include "ewok_rlw.h"
  22
  23 static inline int next_word(struct rlw_iterator *it)
  24 {
  25         if (it->pointer >= it->size)
  26                 return 0;
  27
  28         it->rlw.word = &it->buffer[it->pointer];
  29         it->pointer += rlw_get_literal_words(it->rlw.word) + 1;
  30
  31         it->rlw.literal_words = rlw_get_literal_words(it->rlw.word);
  32         it->rlw.running_len = rlw_get_running_len(it->rlw.word);
  33         it->rlw.running_bit = rlw_get_run_bit(it->rlw.word);
  34         it->rlw.literal_word_offset = 0;
  35
  36         return 1;
  37 }
  38
  39 void rlwit_init(struct rlw_iterator *it, struct ewah_bitmap *from_ewah)
  40 {
  41         it->buffer = from_ewah->buffer;
  42         it->size = from_ewah->buffer_size;
  43         it->pointer = 0;
  44
  45         next_word(it);
  46
  47         it->literal_word_start = rlwit_literal_words(it) +
  48                 it->rlw.literal_word_offset;
  49 }
  50
  51 void rlwit_discard_first_words(struct rlw_iterator *it, size_t x)
  52 {
  53         while (x > 0) {
  54                 size_t discard;
  55
  56                 if (it->rlw.running_len > x) {
  57                         it->rlw.running_len -= x;
  58                         return;
  59                 }
  60
  61                 x -= it->rlw.running_len;
  62                 it->rlw.running_len = 0;
  63
  64                 discard = (x > it->rlw.literal_words) ? it->rlw.literal_words : x;
  65
  66                 it->literal_word_start += discard;
  67                 it->rlw.literal_words -= discard;
  68                 x -= discard;
  69
  70                 if (x > 0 || rlwit_word_size(it) == 0) {
  71                         if (!next_word(it))
  72                                 break;
  73
  74                         it->literal_word_start =
  75                                 rlwit_literal_words(it) + it->rlw.literal_word_offset;
  76                 }
  77         }
  78 }
  79
  80 size_t rlwit_discharge(
  81         struct rlw_iterator *it, struct ewah_bitmap *out, size_t max, int negate)
  82 {
  83         size_t index = 0;
  84
  85         while (index < max && rlwit_word_size(it) > 0) {
  86                 size_t pd, pl = it->rlw.running_len;
  87
  88                 if (index + pl > max)
  89                         pl = max - index;
  90
  91                 ewah_add_empty_words(out, it->rlw.running_bit ^ negate, pl);
  92                 index += pl;
  93
  94                 pd = it->rlw.literal_words;
  95                 if (pd + index > max)
  96                         pd = max - index;
  97
  98                 ewah_add_dirty_words(out,
  99                         it->buffer + it->literal_word_start, pd, negate);
 100
 101                 rlwit_discard_first_words(it, pd + pl);
 102                 index += pd;
 103         }
 104
 105         return index;
 106 }