git/ewah/ewah_rlw.c

/**
 * 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;
}