[pulseview.git] / pv / data / logicsegment.cpp

/*
 * This file is part of the PulseView project.
 *
 * Copyright (C) 2012 Joel Holdsworth <joel@airwebreathe.org.uk>
 *
 * 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 <extdef.h>

#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <cmath>

#include "logicsegment.hpp"

#include <libsigrokcxx/libsigrokcxx.hpp>

using std::lock_guard;
using std::recursive_mutex;
using std::max;
using std::min;
using std::pair;
using std::shared_ptr;

using sigrok::Logic;

namespace pv {
namespace data {

const int LogicSegment::MipMapScalePower = 4;
const int LogicSegment::MipMapScaleFactor = 1 << MipMapScalePower;
const float LogicSegment::LogMipMapScaleFactor = logf(MipMapScaleFactor);
const uint64_t LogicSegment::MipMapDataUnit = 64*1024;	// bytes

LogicSegment::LogicSegment(shared_ptr<Logic> logic, uint64_t samplerate) :
	Segment(samplerate, logic->unit_size()),
	last_append_sample_(0)
{
	lock_guard<recursive_mutex> lock(mutex_);
	memset(mip_map_, 0, sizeof(mip_map_));
	append_payload(logic);
}

LogicSegment::~LogicSegment()
{
	lock_guard<recursive_mutex> lock(mutex_);
	for (MipMapLevel &l : mip_map_)
		free(l.data);
}

uint64_t LogicSegment::unpack_sample(const uint8_t *ptr) const
{
#ifdef HAVE_UNALIGNED_LITTLE_ENDIAN_ACCESS
	return *(uint64_t*)ptr;
#else
	uint64_t value = 0;
	switch (unit_size_) {
	default:
		value |= ((uint64_t)ptr[7]) << 56;
		/* FALLTHRU */
	case 7:
		value |= ((uint64_t)ptr[6]) << 48;
		/* FALLTHRU */
	case 6:
		value |= ((uint64_t)ptr[5]) << 40;
		/* FALLTHRU */
	case 5:
		value |= ((uint64_t)ptr[4]) << 32;
		/* FALLTHRU */
	case 4:
		value |= ((uint32_t)ptr[3]) << 24;
		/* FALLTHRU */
	case 3:
		value |= ((uint32_t)ptr[2]) << 16;
		/* FALLTHRU */
	case 2:
		value |= ptr[1] << 8;
		/* FALLTHRU */
	case 1:
		value |= ptr[0];
		/* FALLTHRU */
	case 0:
		break;
	}
	return value;
#endif
}

void LogicSegment::pack_sample(uint8_t *ptr, uint64_t value)
{
#ifdef HAVE_UNALIGNED_LITTLE_ENDIAN_ACCESS
	*(uint64_t*)ptr = value;
#else
	switch (unit_size_) {
	default:
		ptr[7] = value >> 56;
		/* FALLTHRU */
	case 7:
		ptr[6] = value >> 48;
		/* FALLTHRU */
	case 6:
		ptr[5] = value >> 40;
		/* FALLTHRU */
	case 5:
		ptr[4] = value >> 32;
		/* FALLTHRU */
	case 4:
		ptr[3] = value >> 24;
		/* FALLTHRU */
	case 3:
		ptr[2] = value >> 16;
		/* FALLTHRU */
	case 2:
		ptr[1] = value >> 8;
		/* FALLTHRU */
	case 1:
		ptr[0] = value;
		/* FALLTHRU */
	case 0:
		break;
	}
#endif
}

void LogicSegment::append_payload(shared_ptr<Logic> logic)
{
	assert(unit_size_ == logic->unit_size());
	assert((logic->data_length() % unit_size_) == 0);

	lock_guard<recursive_mutex> lock(mutex_);

	append_samples(logic->data_pointer(),
		logic->data_length() / unit_size_);

	// Generate the first mip-map from the data
	append_payload_to_mipmap();
}

const uint8_t* LogicSegment::get_samples(int64_t start_sample,
	int64_t end_sample) const
{
	assert(start_sample >= 0);
	assert(start_sample <= (int64_t)sample_count_);
	assert(end_sample >= 0);
	assert(end_sample <= (int64_t)sample_count_);
	assert(start_sample <= end_sample);

	lock_guard<recursive_mutex> lock(mutex_);

	return get_raw_samples(start_sample, (end_sample-start_sample));
}

SegmentLogicDataIterator* LogicSegment::begin_sample_iteration(uint64_t start) const
{
	return (SegmentLogicDataIterator*)begin_raw_sample_iteration(start);
}

void LogicSegment::continue_sample_iteration(SegmentLogicDataIterator* it, uint64_t increase) const
{
	Segment::continue_raw_sample_iteration((SegmentRawDataIterator*)it, increase);
}

void LogicSegment::end_sample_iteration(SegmentLogicDataIterator* it) const
{
	Segment::end_raw_sample_iteration((SegmentRawDataIterator*)it);
}

void LogicSegment::reallocate_mipmap_level(MipMapLevel &m)
{
	lock_guard<recursive_mutex> lock(mutex_);

	const uint64_t new_data_length = ((m.length + MipMapDataUnit - 1) /
		MipMapDataUnit) * MipMapDataUnit;

	if (new_data_length > m.data_length) {
		m.data_length = new_data_length;

		// Padding is added to allow for the uint64_t write word
		m.data = realloc(m.data, new_data_length * unit_size_ +
			sizeof(uint64_t));
	}
}

void LogicSegment::append_payload_to_mipmap()
{
	MipMapLevel &m0 = mip_map_[0];
	uint64_t prev_length;
	uint8_t *dest_ptr;
	SegmentRawDataIterator* it;
	uint64_t accumulator;
	unsigned int diff_counter;

	// Expand the data buffer to fit the new samples
	prev_length = m0.length;
	m0.length = sample_count_ / MipMapScaleFactor;

	// Break off if there are no new samples to compute
	if (m0.length == prev_length)
		return;

	reallocate_mipmap_level(m0);

	dest_ptr = (uint8_t*)m0.data + prev_length * unit_size_;

	// Iterate through the samples to populate the first level mipmap
	uint64_t start_sample = prev_length * MipMapScaleFactor;
	uint64_t end_sample = m0.length * MipMapScaleFactor;

	it = begin_raw_sample_iteration(start_sample);
	for (uint64_t i = start_sample; i < end_sample;) {
		// Accumulate transitions which have occurred in this sample
		accumulator = 0;
		diff_counter = MipMapScaleFactor;
		while (diff_counter-- > 0) {
			const uint64_t sample = unpack_sample(it->value);
			accumulator |= last_append_sample_ ^ sample;
			last_append_sample_ = sample;
			continue_raw_sample_iteration(it, 1);
			i++;
		}

		pack_sample(dest_ptr, accumulator);
		dest_ptr += unit_size_;
	}
	end_raw_sample_iteration(it);

	// Compute higher level mipmaps
	for (unsigned int level = 1; level < ScaleStepCount; level++) {
		MipMapLevel &m = mip_map_[level];
		const MipMapLevel &ml = mip_map_[level-1];

		// Expand the data buffer to fit the new samples
		prev_length = m.length;
		m.length = ml.length / MipMapScaleFactor;

		// Break off if there are no more samples to be computed
		if (m.length == prev_length)
			break;

		reallocate_mipmap_level(m);

		// Subsample the lower level
		const uint8_t* src_ptr = (uint8_t*)ml.data +
			unit_size_ * prev_length * MipMapScaleFactor;
		const uint8_t *const end_dest_ptr =
			(uint8_t*)m.data + unit_size_ * m.length;

		for (dest_ptr = (uint8_t*)m.data +
				unit_size_ * prev_length;
				dest_ptr < end_dest_ptr;
				dest_ptr += unit_size_) {
			accumulator = 0;
			diff_counter = MipMapScaleFactor;
			while (diff_counter-- > 0) {
				accumulator |= unpack_sample(src_ptr);
				src_ptr += unit_size_;
			}

			pack_sample(dest_ptr, accumulator);
		}
	}
}

uint64_t LogicSegment::get_unpacked_sample(uint64_t index) const
{
	assert(index < sample_count_);

	const uint8_t* data = get_raw_samples(index, 1);
	uint64_t sample = unpack_sample(data);
	delete[] data;

	return sample;
}

void LogicSegment::get_subsampled_edges(
	std::vector<EdgePair> &edges,
	uint64_t start, uint64_t end,
	float min_length, int sig_index)
{
	uint64_t index = start;
	unsigned int level;
	bool last_sample;
	bool fast_forward;

	assert(end <= get_sample_count());
	assert(start <= end);
	assert(min_length > 0);
	assert(sig_index >= 0);
	assert(sig_index < 64);

	lock_guard<recursive_mutex> lock(mutex_);

	const uint64_t block_length = (uint64_t)max(min_length, 1.0f);
	const unsigned int min_level = max((int)floorf(logf(min_length) /
		LogMipMapScaleFactor) - 1, 0);
	const uint64_t sig_mask = 1ULL << sig_index;

	// Store the initial state
	last_sample = (get_unpacked_sample(start) & sig_mask) != 0;
	edges.push_back(pair<int64_t, bool>(index++, last_sample));

	while (index + block_length <= end) {
		//----- Continue to search -----//
		level = min_level;

		// We cannot fast-forward if there is no mip-map data at
		// at the minimum level.
		fast_forward = (mip_map_[level].data != nullptr);

		if (min_length < MipMapScaleFactor) {
			// Search individual samples up to the beginning of
			// the next first level mip map block
			const uint64_t final_index = min(end,
				pow2_ceil(index, MipMapScalePower));

			for (; index < final_index &&
					(index & ~((uint64_t)(~0) << MipMapScalePower)) != 0;
					index++) {
				const bool sample =
					(get_unpacked_sample(index) & sig_mask) != 0;

				// If there was a change we cannot fast forward
				if (sample != last_sample) {
					fast_forward = false;
					break;
				}
			}
		} else {
			// If resolution is less than a mip map block,
			// round up to the beginning of the mip-map block
			// for this level of detail
			const int min_level_scale_power =
				(level + 1) * MipMapScalePower;
			index = pow2_ceil(index, min_level_scale_power);
			if (index >= end)
				break;

			// We can fast forward only if there was no change
			const bool sample =
				(get_unpacked_sample(index) & sig_mask) != 0;
			if (last_sample != sample)
				fast_forward = false;
		}

		if (fast_forward) {

			// Fast forward: This involves zooming out to higher
			// levels of the mip map searching for changes, then
			// zooming in on them to find the point where the edge
			// begins.

			// Slide right and zoom out at the beginnings of mip-map
			// blocks until we encounter a change
			while (1) {
				const int level_scale_power =
					(level + 1) * MipMapScalePower;
				const uint64_t offset =
					index >> level_scale_power;

				// Check if we reached the last block at this
				// level, or if there was a change in this block
				if (offset >= mip_map_[level].length ||
					(get_subsample(level, offset) &
						sig_mask))
					break;

				if ((offset & ~((uint64_t)(~0) << MipMapScalePower)) == 0) {
					// If we are now at the beginning of a
					// higher level mip-map block ascend one
					// level
					if (level + 1 >= ScaleStepCount ||
						!mip_map_[level + 1].data)
						break;

					level++;
				} else {
					// Slide right to the beginning of the
					// next mip map block
					index = pow2_ceil(index + 1,
						level_scale_power);
				}
			}

			// Zoom in, and slide right until we encounter a change,
			// and repeat until we reach min_level
			while (1) {
				assert(mip_map_[level].data);

				const int level_scale_power =
					(level + 1) * MipMapScalePower;
				const uint64_t offset =
					index >> level_scale_power;

				// Check if we reached the last block at this
				// level, or if there was a change in this block
				if (offset >= mip_map_[level].length ||
						(get_subsample(level, offset) &
						sig_mask)) {
					// Zoom in unless we reached the minimum
					// zoom
					if (level == min_level)
						break;

					level--;
				} else {
					// Slide right to the beginning of the
					// next mip map block
					index = pow2_ceil(index + 1,
						level_scale_power);
				}
			}

			// If individual samples within the limit of resolution,
			// do a linear search for the next transition within the
			// block
			if (min_length < MipMapScaleFactor) {
				for (; index < end; index++) {
					const bool sample = (get_unpacked_sample(index) &
						sig_mask) != 0;
					if (sample != last_sample)
						break;
				}
			}
		}

		//----- Store the edge -----//

		// Take the last sample of the quanization block
		const int64_t final_index = index + block_length;
		if (index + block_length > end)
			break;

		// Store the final state
		const bool final_sample =
			(get_unpacked_sample(final_index - 1) & sig_mask) != 0;
		edges.push_back(pair<int64_t, bool>(index, final_sample));

		index = final_index;
		last_sample = final_sample;
	}

	// Add the final state
	const bool end_sample = get_unpacked_sample(end) & sig_mask;
	if (last_sample != end_sample)
		edges.push_back(pair<int64_t, bool>(end, end_sample));
	edges.push_back(pair<int64_t, bool>(end + 1, end_sample));
}

uint64_t LogicSegment::get_subsample(int level, uint64_t offset) const
{
	assert(level >= 0);
	assert(mip_map_[level].data);
	return unpack_sample((uint8_t*)mip_map_[level].data +
		unit_size_ * offset);
}

uint64_t LogicSegment::pow2_ceil(uint64_t x, unsigned int power)
{
	const uint64_t p = 1 << power;
	return (x + p - 1) / p * p;
}

} // namespace data
} // namespace pv
Commit	Line	Data
	1	/*
	2	* This file is part of the PulseView project.
	3	*
	4	* Copyright (C) 2012 Joel Holdsworth <joel@airwebreathe.org.uk>
	5	*
	6	* This program is free software; you can redistribute it and/or modify
	7	* it under the terms of the GNU General Public License as published by
	8	* the Free Software Foundation; either version 2 of the License, or
	9	* (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
	20	#include <extdef.h>
	21
	22	#include <assert.h>
	23	#include <string.h>
	24	#include <stdlib.h>
	25	#include <cmath>
	26
	27	#include "logicsegment.hpp"
	28
	29	#include <libsigrokcxx/libsigrokcxx.hpp>
	30
	31	using std::lock_guard;
	32	using std::recursive_mutex;
	33	using std::max;
	34	using std::min;
	35	using std::pair;
	36	using std::shared_ptr;
	37
	38	using sigrok::Logic;
	39
	40	namespace pv {
	41	namespace data {
	42
	43	const int LogicSegment::MipMapScalePower = 4;
	44	const int LogicSegment::MipMapScaleFactor = 1 << MipMapScalePower;
	45	const float LogicSegment::LogMipMapScaleFactor = logf(MipMapScaleFactor);
	46	const uint64_t LogicSegment::MipMapDataUnit = 64*1024; // bytes
	47
	48	LogicSegment::LogicSegment(shared_ptr<Logic> logic, uint64_t samplerate) :
	49	Segment(samplerate, logic->unit_size()),
	50	last_append_sample_(0)
	51	{
	52	lock_guard<recursive_mutex> lock(mutex_);
	53	memset(mip_map_, 0, sizeof(mip_map_));
	54	append_payload(logic);
	55	}
	56
	57	LogicSegment::~LogicSegment()
	58	{
	59	lock_guard<recursive_mutex> lock(mutex_);
	60	for (MipMapLevel &l : mip_map_)
	61	free(l.data);
	62	}
	63
	64	uint64_t LogicSegment::unpack_sample(const uint8_t *ptr) const
	65	{
	66	#ifdef HAVE_UNALIGNED_LITTLE_ENDIAN_ACCESS
	67	return (uint64_t)ptr;
	68	#else
	69	uint64_t value = 0;
	70	switch (unit_size_) {
	71	default:
	72	value \|= ((uint64_t)ptr[7]) << 56;
	73	/* FALLTHRU */
	74	case 7:
	75	value \|= ((uint64_t)ptr[6]) << 48;
	76	/* FALLTHRU */
	77	case 6:
	78	value \|= ((uint64_t)ptr[5]) << 40;
	79	/* FALLTHRU */
	80	case 5:
	81	value \|= ((uint64_t)ptr[4]) << 32;
	82	/* FALLTHRU */
	83	case 4:
	84	value \|= ((uint32_t)ptr[3]) << 24;
	85	/* FALLTHRU */
	86	case 3:
	87	value \|= ((uint32_t)ptr[2]) << 16;
	88	/* FALLTHRU */
	89	case 2:
	90	value \|= ptr[1] << 8;
	91	/* FALLTHRU */
	92	case 1:
	93	value \|= ptr[0];
	94	/* FALLTHRU */
	95	case 0:
	96	break;
	97	}
	98	return value;
	99	#endif
	100	}
	101
	102	void LogicSegment::pack_sample(uint8_t *ptr, uint64_t value)
	103	{
	104	#ifdef HAVE_UNALIGNED_LITTLE_ENDIAN_ACCESS
	105	(uint64_t)ptr = value;
	106	#else
	107	switch (unit_size_) {
	108	default:
	109	ptr[7] = value >> 56;
	110	/* FALLTHRU */
	111	case 7:
	112	ptr[6] = value >> 48;
	113	/* FALLTHRU */
	114	case 6:
	115	ptr[5] = value >> 40;
	116	/* FALLTHRU */
	117	case 5:
	118	ptr[4] = value >> 32;
	119	/* FALLTHRU */
	120	case 4:
	121	ptr[3] = value >> 24;
	122	/* FALLTHRU */
	123	case 3:
	124	ptr[2] = value >> 16;
	125	/* FALLTHRU */
	126	case 2:
	127	ptr[1] = value >> 8;
	128	/* FALLTHRU */
	129	case 1:
	130	ptr[0] = value;
	131	/* FALLTHRU */
	132	case 0:
	133	break;
	134	}
	135	#endif
	136	}
	137
	138	void LogicSegment::append_payload(shared_ptr<Logic> logic)
	139	{
	140	assert(unit_size_ == logic->unit_size());
	141	assert((logic->data_length() % unit_size_) == 0);
	142
	143	lock_guard<recursive_mutex> lock(mutex_);
	144
	145	append_samples(logic->data_pointer(),
	146	logic->data_length() / unit_size_);
	147
	148	// Generate the first mip-map from the data
	149	append_payload_to_mipmap();
	150	}
	151
	152	const uint8_t* LogicSegment::get_samples(int64_t start_sample,
	153	int64_t end_sample) const
	154	{
	155	assert(start_sample >= 0);
	156	assert(start_sample <= (int64_t)sample_count_);
	157	assert(end_sample >= 0);
	158	assert(end_sample <= (int64_t)sample_count_);
	159	assert(start_sample <= end_sample);
	160
	161	lock_guard<recursive_mutex> lock(mutex_);
	162
	163	return get_raw_samples(start_sample, (end_sample-start_sample));
	164	}
	165
	166	SegmentLogicDataIterator* LogicSegment::begin_sample_iteration(uint64_t start) const
	167	{
	168	return (SegmentLogicDataIterator*)begin_raw_sample_iteration(start);
	169	}
	170
	171	void LogicSegment::continue_sample_iteration(SegmentLogicDataIterator* it, uint64_t increase) const
	172	{
	173	Segment::continue_raw_sample_iteration((SegmentRawDataIterator*)it, increase);
	174	}
	175
	176	void LogicSegment::end_sample_iteration(SegmentLogicDataIterator* it) const
	177	{
	178	Segment::end_raw_sample_iteration((SegmentRawDataIterator*)it);
	179	}
	180
	181	void LogicSegment::reallocate_mipmap_level(MipMapLevel &m)
	182	{
	183	lock_guard<recursive_mutex> lock(mutex_);
	184
	185	const uint64_t new_data_length = ((m.length + MipMapDataUnit - 1) /
	186	MipMapDataUnit) * MipMapDataUnit;
	187
	188	if (new_data_length > m.data_length) {
	189	m.data_length = new_data_length;
	190
	191	// Padding is added to allow for the uint64_t write word
	192	m.data = realloc(m.data, new_data_length * unit_size_ +
	193	sizeof(uint64_t));
	194	}
	195	}
	196
	197	void LogicSegment::append_payload_to_mipmap()
	198	{
	199	MipMapLevel &m0 = mip_map_[0];
	200	uint64_t prev_length;
	201	uint8_t *dest_ptr;
	202	SegmentRawDataIterator* it;
	203	uint64_t accumulator;
	204	unsigned int diff_counter;
	205
	206	// Expand the data buffer to fit the new samples
	207	prev_length = m0.length;
	208	m0.length = sample_count_ / MipMapScaleFactor;
	209
	210	// Break off if there are no new samples to compute
	211	if (m0.length == prev_length)
	212	return;
	213
	214	reallocate_mipmap_level(m0);
	215
	216	dest_ptr = (uint8_t)m0.data + prev_length unit_size_;
	217
	218	// Iterate through the samples to populate the first level mipmap
	219	uint64_t start_sample = prev_length * MipMapScaleFactor;
	220	uint64_t end_sample = m0.length * MipMapScaleFactor;
	221
	222	it = begin_raw_sample_iteration(start_sample);
	223	for (uint64_t i = start_sample; i < end_sample;) {
	224	// Accumulate transitions which have occurred in this sample
	225	accumulator = 0;
	226	diff_counter = MipMapScaleFactor;
	227	while (diff_counter-- > 0) {
	228	const uint64_t sample = unpack_sample(it->value);
	229	accumulator \|= last_append_sample_ ^ sample;
	230	last_append_sample_ = sample;
	231	continue_raw_sample_iteration(it, 1);
	232	i++;
	233	}
	234
	235	pack_sample(dest_ptr, accumulator);
	236	dest_ptr += unit_size_;
	237	}
	238	end_raw_sample_iteration(it);
	239
	240	// Compute higher level mipmaps
	241	for (unsigned int level = 1; level < ScaleStepCount; level++) {
	242	MipMapLevel &m = mip_map_[level];
	243	const MipMapLevel &ml = mip_map_[level-1];
	244
	245	// Expand the data buffer to fit the new samples
	246	prev_length = m.length;
	247	m.length = ml.length / MipMapScaleFactor;
	248
	249	// Break off if there are no more samples to be computed
	250	if (m.length == prev_length)
	251	break;
	252
	253	reallocate_mipmap_level(m);
	254
	255	// Subsample the lower level
	256	const uint8_t* src_ptr = (uint8_t*)ml.data +
	257	unit_size_ * prev_length * MipMapScaleFactor;
	258	const uint8_t *const end_dest_ptr =
	259	(uint8_t)m.data + unit_size_ m.length;
	260
	261	for (dest_ptr = (uint8_t*)m.data +
	262	unit_size_ * prev_length;
	263	dest_ptr < end_dest_ptr;
	264	dest_ptr += unit_size_) {
	265	accumulator = 0;
	266	diff_counter = MipMapScaleFactor;
	267	while (diff_counter-- > 0) {
	268	accumulator \|= unpack_sample(src_ptr);
	269	src_ptr += unit_size_;
	270	}
	271
	272	pack_sample(dest_ptr, accumulator);
	273	}
	274	}
	275	}
	276
	277	uint64_t LogicSegment::get_unpacked_sample(uint64_t index) const
	278	{
	279	assert(index < sample_count_);
	280
	281	const uint8_t* data = get_raw_samples(index, 1);
	282	uint64_t sample = unpack_sample(data);
	283	delete[] data;
	284
	285	return sample;
	286	}
	287
	288	void LogicSegment::get_subsampled_edges(
	289	std::vector<EdgePair> &edges,
	290	uint64_t start, uint64_t end,
	291	float min_length, int sig_index)
	292	{
	293	uint64_t index = start;
	294	unsigned int level;
	295	bool last_sample;
	296	bool fast_forward;
	297
	298	assert(end <= get_sample_count());
	299	assert(start <= end);
	300	assert(min_length > 0);
	301	assert(sig_index >= 0);
	302	assert(sig_index < 64);
	303
	304	lock_guard<recursive_mutex> lock(mutex_);
	305
	306	const uint64_t block_length = (uint64_t)max(min_length, 1.0f);
	307	const unsigned int min_level = max((int)floorf(logf(min_length) /
	308	LogMipMapScaleFactor) - 1, 0);
	309	const uint64_t sig_mask = 1ULL << sig_index;
	310
	311	// Store the initial state
	312	last_sample = (get_unpacked_sample(start) & sig_mask) != 0;
	313	edges.push_back(pair<int64_t, bool>(index++, last_sample));
	314
	315	while (index + block_length <= end) {
	316	//----- Continue to search -----//
	317	level = min_level;
	318
	319	// We cannot fast-forward if there is no mip-map data at
	320	// at the minimum level.
	321	fast_forward = (mip_map_[level].data != nullptr);
	322
	323	if (min_length < MipMapScaleFactor) {
	324	// Search individual samples up to the beginning of
	325	// the next first level mip map block
	326	const uint64_t final_index = min(end,
	327	pow2_ceil(index, MipMapScalePower));
	328
	329	for (; index < final_index &&
	330	(index & ~((uint64_t)(~0) << MipMapScalePower)) != 0;
	331	index++) {
	332	const bool sample =
	333	(get_unpacked_sample(index) & sig_mask) != 0;
	334
	335	// If there was a change we cannot fast forward
	336	if (sample != last_sample) {
	337	fast_forward = false;
	338	break;
	339	}
	340	}
	341	} else {
	342	// If resolution is less than a mip map block,
	343	// round up to the beginning of the mip-map block
	344	// for this level of detail
	345	const int min_level_scale_power =
	346	(level + 1) * MipMapScalePower;
	347	index = pow2_ceil(index, min_level_scale_power);
	348	if (index >= end)
	349	break;
	350
	351	// We can fast forward only if there was no change
	352	const bool sample =
	353	(get_unpacked_sample(index) & sig_mask) != 0;
	354	if (last_sample != sample)
	355	fast_forward = false;
	356	}
	357
	358	if (fast_forward) {
	359
	360	// Fast forward: This involves zooming out to higher
	361	// levels of the mip map searching for changes, then
	362	// zooming in on them to find the point where the edge
	363	// begins.
	364
	365	// Slide right and zoom out at the beginnings of mip-map
	366	// blocks until we encounter a change
	367	while (1) {
	368	const int level_scale_power =
	369	(level + 1) * MipMapScalePower;
	370	const uint64_t offset =
	371	index >> level_scale_power;
	372
	373	// Check if we reached the last block at this
	374	// level, or if there was a change in this block
	375	if (offset >= mip_map_[level].length \|\|
	376	(get_subsample(level, offset) &
	377	sig_mask))
	378	break;
	379
	380	if ((offset & ~((uint64_t)(~0) << MipMapScalePower)) == 0) {
	381	// If we are now at the beginning of a
	382	// higher level mip-map block ascend one
	383	// level
	384	if (level + 1 >= ScaleStepCount \|\|
	385	!mip_map_[level + 1].data)
	386	break;
	387
	388	level++;
	389	} else {
	390	// Slide right to the beginning of the
	391	// next mip map block
	392	index = pow2_ceil(index + 1,
	393	level_scale_power);
	394	}
	395	}
	396
	397	// Zoom in, and slide right until we encounter a change,
	398	// and repeat until we reach min_level
	399	while (1) {
	400	assert(mip_map_[level].data);
	401
	402	const int level_scale_power =
	403	(level + 1) * MipMapScalePower;
	404	const uint64_t offset =
	405	index >> level_scale_power;
	406
	407	// Check if we reached the last block at this
	408	// level, or if there was a change in this block
	409	if (offset >= mip_map_[level].length \|\|
	410	(get_subsample(level, offset) &
	411	sig_mask)) {
	412	// Zoom in unless we reached the minimum
	413	// zoom
	414	if (level == min_level)
	415	break;
	416
	417	level--;
	418	} else {
	419	// Slide right to the beginning of the
	420	// next mip map block
	421	index = pow2_ceil(index + 1,
	422	level_scale_power);
	423	}
	424	}
	425
	426	// If individual samples within the limit of resolution,
	427	// do a linear search for the next transition within the
	428	// block
	429	if (min_length < MipMapScaleFactor) {
	430	for (; index < end; index++) {
	431	const bool sample = (get_unpacked_sample(index) &
	432	sig_mask) != 0;
	433	if (sample != last_sample)
	434	break;
	435	}
	436	}
	437	}
	438
	439	//----- Store the edge -----//
	440
	441	// Take the last sample of the quanization block
	442	const int64_t final_index = index + block_length;
	443	if (index + block_length > end)
	444	break;
	445
	446	// Store the final state
	447	const bool final_sample =
	448	(get_unpacked_sample(final_index - 1) & sig_mask) != 0;
	449	edges.push_back(pair<int64_t, bool>(index, final_sample));
	450
	451	index = final_index;
	452	last_sample = final_sample;
	453	}
	454
	455	// Add the final state
	456	const bool end_sample = get_unpacked_sample(end) & sig_mask;
	457	if (last_sample != end_sample)
	458	edges.push_back(pair<int64_t, bool>(end, end_sample));
	459	edges.push_back(pair<int64_t, bool>(end + 1, end_sample));
	460	}
	461
	462	uint64_t LogicSegment::get_subsample(int level, uint64_t offset) const
	463	{
	464	assert(level >= 0);
	465	assert(mip_map_[level].data);
	466	return unpack_sample((uint8_t*)mip_map_[level].data +
	467	unit_size_ * offset);
	468	}
	469
	470	uint64_t LogicSegment::pow2_ceil(uint64_t x, unsigned int power)
	471	{
	472	const uint64_t p = 1 << power;
	473	return (x + p - 1) / p * p;
	474	}
	475
	476	} // namespace data
	477	} // namespace pv