[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, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
 */

#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,
				const uint64_t expected_num_samples) :
	Segment(samplerate, logic->unit_size()),
	last_append_sample_(0)
{
	set_capacity(expected_num_samples);

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

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

void LogicSegment::get_samples(uint8_t *const data,
	int64_t start_sample, int64_t end_sample) const
{
	assert(data);
	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_);

	const size_t size = (end_sample - start_sample) * unit_size_;
	memcpy(data, (const uint8_t*)data_.data() + start_sample * unit_size_, size);
}

void LogicSegment::reallocate_mipmap_level(MipMapLevel &m)
{
	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;
	const uint8_t *src_ptr;
	uint8_t *dest_ptr;
	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
	const uint8_t *const end_src_ptr = (uint8_t*)data_.data() +
		m0.length * unit_size_ * MipMapScaleFactor;
	for (src_ptr = (uint8_t*)data_.data() +
			prev_length * unit_size_ * MipMapScaleFactor;
			src_ptr < end_src_ptr;) {
		// Accumulate transitions which have occurred in this sample
		accumulator = 0;
		diff_counter = MipMapScaleFactor;
		while (diff_counter-- > 0) {
			const uint64_t sample = unpack_sample(src_ptr);
			accumulator |= last_append_sample_ ^ sample;
			last_append_sample_ = sample;
			src_ptr += unit_size_;
		}

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

	// 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 computed
		if (m.length == prev_length)
			break;

		reallocate_mipmap_level(m);

		// Subsample the level lower level
		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_sample(uint64_t index) const
{
	assert(index < sample_count_);

	return unpack_sample((uint8_t*)data_.data() + index * unit_size_);
}

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_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_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_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_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_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_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, write to the Free Software
	18	* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	19	*/
	20
	21	#include <extdef.h>
	22
	23	#include <assert.h>
	24	#include <string.h>
	25	#include <stdlib.h>
	26	#include <cmath>
	27
	28	#include "logicsegment.hpp"
	29
	30	#include <libsigrokcxx/libsigrokcxx.hpp>
	31
	32	using std::lock_guard;
	33	using std::recursive_mutex;
	34	using std::max;
	35	using std::min;
	36	using std::pair;
	37	using std::shared_ptr;
	38
	39	using sigrok::Logic;
	40
	41	namespace pv {
	42	namespace data {
	43
	44	const int LogicSegment::MipMapScalePower = 4;
	45	const int LogicSegment::MipMapScaleFactor = 1 << MipMapScalePower;
	46	const float LogicSegment::LogMipMapScaleFactor = logf(MipMapScaleFactor);
	47	const uint64_t LogicSegment::MipMapDataUnit = 64*1024; // bytes
	48
	49	LogicSegment::LogicSegment(shared_ptr<Logic> logic, uint64_t samplerate,
	50	const uint64_t expected_num_samples) :
	51	Segment(samplerate, logic->unit_size()),
	52	last_append_sample_(0)
	53	{
	54	set_capacity(expected_num_samples);
	55
	56	lock_guard<recursive_mutex> lock(mutex_);
	57	memset(mip_map_, 0, sizeof(mip_map_));
	58	append_payload(logic);
	59	}
	60
	61	LogicSegment::~LogicSegment()
	62	{
	63	lock_guard<recursive_mutex> lock(mutex_);
	64	for (MipMapLevel &l : mip_map_)
	65	free(l.data);
	66	}
	67
	68	uint64_t LogicSegment::unpack_sample(const uint8_t *ptr) const
	69	{
	70	#ifdef HAVE_UNALIGNED_LITTLE_ENDIAN_ACCESS
	71	return (uint64_t)ptr;
	72	#else
	73	uint64_t value = 0;
	74	switch (unit_size_) {
	75	default:
	76	value \|= ((uint64_t)ptr[7]) << 56;
	77	/* FALLTHRU */
	78	case 7:
	79	value \|= ((uint64_t)ptr[6]) << 48;
	80	/* FALLTHRU */
	81	case 6:
	82	value \|= ((uint64_t)ptr[5]) << 40;
	83	/* FALLTHRU */
	84	case 5:
	85	value \|= ((uint64_t)ptr[4]) << 32;
	86	/* FALLTHRU */
	87	case 4:
	88	value \|= ((uint32_t)ptr[3]) << 24;
	89	/* FALLTHRU */
	90	case 3:
	91	value \|= ((uint32_t)ptr[2]) << 16;
	92	/* FALLTHRU */
	93	case 2:
	94	value \|= ptr[1] << 8;
	95	/* FALLTHRU */
	96	case 1:
	97	value \|= ptr[0];
	98	/* FALLTHRU */
	99	case 0:
	100	break;
	101	}
	102	return value;
	103	#endif
	104	}
	105
	106	void LogicSegment::pack_sample(uint8_t *ptr, uint64_t value)
	107	{
	108	#ifdef HAVE_UNALIGNED_LITTLE_ENDIAN_ACCESS
	109	(uint64_t)ptr = value;
	110	#else
	111	switch (unit_size_) {
	112	default:
	113	ptr[7] = value >> 56;
	114	/* FALLTHRU */
	115	case 7:
	116	ptr[6] = value >> 48;
	117	/* FALLTHRU */
	118	case 6:
	119	ptr[5] = value >> 40;
	120	/* FALLTHRU */
	121	case 5:
	122	ptr[4] = value >> 32;
	123	/* FALLTHRU */
	124	case 4:
	125	ptr[3] = value >> 24;
	126	/* FALLTHRU */
	127	case 3:
	128	ptr[2] = value >> 16;
	129	/* FALLTHRU */
	130	case 2:
	131	ptr[1] = value >> 8;
	132	/* FALLTHRU */
	133	case 1:
	134	ptr[0] = value;
	135	/* FALLTHRU */
	136	case 0:
	137	break;
	138	}
	139	#endif
	140	}
	141
	142	void LogicSegment::append_payload(shared_ptr<Logic> logic)
	143	{
	144	assert(unit_size_ == logic->unit_size());
	145	assert((logic->data_length() % unit_size_) == 0);
	146
	147	lock_guard<recursive_mutex> lock(mutex_);
	148
	149	append_data(logic->data_pointer(),
	150	logic->data_length() / unit_size_);
	151
	152	// Generate the first mip-map from the data
	153	append_payload_to_mipmap();
	154	}
	155
	156	void LogicSegment::get_samples(uint8_t *const data,
	157	int64_t start_sample, int64_t end_sample) const
	158	{
	159	assert(data);
	160	assert(start_sample >= 0);
	161	assert(start_sample <= (int64_t)sample_count_);
	162	assert(end_sample >= 0);
	163	assert(end_sample <= (int64_t)sample_count_);
	164	assert(start_sample <= end_sample);
	165
	166	lock_guard<recursive_mutex> lock(mutex_);
	167
	168	const size_t size = (end_sample - start_sample) * unit_size_;
	169	memcpy(data, (const uint8_t)data_.data() + start_sample unit_size_, size);
	170	}
	171
	172	void LogicSegment::reallocate_mipmap_level(MipMapLevel &m)
	173	{
	174	const uint64_t new_data_length = ((m.length + MipMapDataUnit - 1) /
	175	MipMapDataUnit) * MipMapDataUnit;
	176	if (new_data_length > m.data_length) {
	177	m.data_length = new_data_length;
	178
	179	// Padding is added to allow for the uint64_t write word
	180	m.data = realloc(m.data, new_data_length * unit_size_ +
	181	sizeof(uint64_t));
	182	}
	183	}
	184
	185	void LogicSegment::append_payload_to_mipmap()
	186	{
	187	MipMapLevel &m0 = mip_map_[0];
	188	uint64_t prev_length;
	189	const uint8_t *src_ptr;
	190	uint8_t *dest_ptr;
	191	uint64_t accumulator;
	192	unsigned int diff_counter;
	193
	194	// Expand the data buffer to fit the new samples
	195	prev_length = m0.length;
	196	m0.length = sample_count_ / MipMapScaleFactor;
	197
	198	// Break off if there are no new samples to compute
	199	if (m0.length == prev_length)
	200	return;
	201
	202	reallocate_mipmap_level(m0);
	203
	204	dest_ptr = (uint8_t)m0.data + prev_length unit_size_;
	205
	206	// Iterate through the samples to populate the first level mipmap
	207	const uint8_t const end_src_ptr = (uint8_t)data_.data() +
	208	m0.length * unit_size_ * MipMapScaleFactor;
	209	for (src_ptr = (uint8_t*)data_.data() +
	210	prev_length * unit_size_ * MipMapScaleFactor;
	211	src_ptr < end_src_ptr;) {
	212	// Accumulate transitions which have occurred in this sample
	213	accumulator = 0;
	214	diff_counter = MipMapScaleFactor;
	215	while (diff_counter-- > 0) {
	216	const uint64_t sample = unpack_sample(src_ptr);
	217	accumulator \|= last_append_sample_ ^ sample;
	218	last_append_sample_ = sample;
	219	src_ptr += unit_size_;
	220	}
	221
	222	pack_sample(dest_ptr, accumulator);
	223	dest_ptr += unit_size_;
	224	}
	225
	226	// Compute higher level mipmaps
	227	for (unsigned int level = 1; level < ScaleStepCount; level++) {
	228	MipMapLevel &m = mip_map_[level];
	229	const MipMapLevel &ml = mip_map_[level-1];
	230
	231	// Expand the data buffer to fit the new samples
	232	prev_length = m.length;
	233	m.length = ml.length / MipMapScaleFactor;
	234
	235	// Break off if there are no more samples to computed
	236	if (m.length == prev_length)
	237	break;
	238
	239	reallocate_mipmap_level(m);
	240
	241	// Subsample the level lower level
	242	src_ptr = (uint8_t*)ml.data +
	243	unit_size_ * prev_length * MipMapScaleFactor;
	244	const uint8_t *const end_dest_ptr =
	245	(uint8_t)m.data + unit_size_ m.length;
	246	for (dest_ptr = (uint8_t*)m.data +
	247	unit_size_ * prev_length;
	248	dest_ptr < end_dest_ptr;
	249	dest_ptr += unit_size_) {
	250	accumulator = 0;
	251	diff_counter = MipMapScaleFactor;
	252	while (diff_counter-- > 0) {
	253	accumulator \|= unpack_sample(src_ptr);
	254	src_ptr += unit_size_;
	255	}
	256
	257	pack_sample(dest_ptr, accumulator);
	258	}
	259	}
	260	}
	261
	262	uint64_t LogicSegment::get_sample(uint64_t index) const
	263	{
	264	assert(index < sample_count_);
	265
	266	return unpack_sample((uint8_t)data_.data() + index unit_size_);
	267	}
	268
	269	void LogicSegment::get_subsampled_edges(
	270	std::vector<EdgePair> &edges,
	271	uint64_t start, uint64_t end,
	272	float min_length, int sig_index)
	273	{
	274	uint64_t index = start;
	275	unsigned int level;
	276	bool last_sample;
	277	bool fast_forward;
	278
	279	assert(end <= get_sample_count());
	280	assert(start <= end);
	281	assert(min_length > 0);
	282	assert(sig_index >= 0);
	283	assert(sig_index < 64);
	284
	285	lock_guard<recursive_mutex> lock(mutex_);
	286
	287	const uint64_t block_length = (uint64_t)max(min_length, 1.0f);
	288	const unsigned int min_level = max((int)floorf(logf(min_length) /
	289	LogMipMapScaleFactor) - 1, 0);
	290	const uint64_t sig_mask = 1ULL << sig_index;
	291
	292	// Store the initial state
	293	last_sample = (get_sample(start) & sig_mask) != 0;
	294	edges.push_back(pair<int64_t, bool>(index++, last_sample));
	295
	296	while (index + block_length <= end) {
	297	//----- Continue to search -----//
	298	level = min_level;
	299
	300	// We cannot fast-forward if there is no mip-map data at
	301	// at the minimum level.
	302	fast_forward = (mip_map_[level].data != nullptr);
	303
	304	if (min_length < MipMapScaleFactor) {
	305	// Search individual samples up to the beginning of
	306	// the next first level mip map block
	307	const uint64_t final_index = min(end,
	308	pow2_ceil(index, MipMapScalePower));
	309
	310	for (; index < final_index &&
	311	(index & ~((uint64_t)(~0) << MipMapScalePower)) != 0;
	312	index++) {
	313	const bool sample =
	314	(get_sample(index) & sig_mask) != 0;
	315
	316	// If there was a change we cannot fast forward
	317	if (sample != last_sample) {
	318	fast_forward = false;
	319	break;
	320	}
	321	}
	322	} else {
	323	// If resolution is less than a mip map block,
	324	// round up to the beginning of the mip-map block
	325	// for this level of detail
	326	const int min_level_scale_power =
	327	(level + 1) * MipMapScalePower;
	328	index = pow2_ceil(index, min_level_scale_power);
	329	if (index >= end)
	330	break;
	331
	332	// We can fast forward only if there was no change
	333	const bool sample =
	334	(get_sample(index) & sig_mask) != 0;
	335	if (last_sample != sample)
	336	fast_forward = false;
	337	}
	338
	339	if (fast_forward) {
	340
	341	// Fast forward: This involves zooming out to higher
	342	// levels of the mip map searching for changes, then
	343	// zooming in on them to find the point where the edge
	344	// begins.
	345
	346	// Slide right and zoom out at the beginnings of mip-map
	347	// blocks until we encounter a change
	348	while (1) {
	349	const int level_scale_power =
	350	(level + 1) * MipMapScalePower;
	351	const uint64_t offset =
	352	index >> level_scale_power;
	353
	354	// Check if we reached the last block at this
	355	// level, or if there was a change in this block
	356	if (offset >= mip_map_[level].length \|\|
	357	(get_subsample(level, offset) &
	358	sig_mask))
	359	break;
	360
	361	if ((offset & ~((uint64_t)(~0) << MipMapScalePower)) == 0) {
	362	// If we are now at the beginning of a
	363	// higher level mip-map block ascend one
	364	// level
	365	if (level + 1 >= ScaleStepCount \|\|
	366	!mip_map_[level + 1].data)
	367	break;
	368
	369	level++;
	370	} else {
	371	// Slide right to the beginning of the
	372	// next mip map block
	373	index = pow2_ceil(index + 1,
	374	level_scale_power);
	375	}
	376	}
	377
	378	// Zoom in, and slide right until we encounter a change,
	379	// and repeat until we reach min_level
	380	while (1) {
	381	assert(mip_map_[level].data);
	382
	383	const int level_scale_power =
	384	(level + 1) * MipMapScalePower;
	385	const uint64_t offset =
	386	index >> level_scale_power;
	387
	388	// Check if we reached the last block at this
	389	// level, or if there was a change in this block
	390	if (offset >= mip_map_[level].length \|\|
	391	(get_subsample(level, offset) &
	392	sig_mask)) {
	393	// Zoom in unless we reached the minimum
	394	// zoom
	395	if (level == min_level)
	396	break;
	397
	398	level--;
	399	} else {
	400	// Slide right to the beginning of the
	401	// next mip map block
	402	index = pow2_ceil(index + 1,
	403	level_scale_power);
	404	}
	405	}
	406
	407	// If individual samples within the limit of resolution,
	408	// do a linear search for the next transition within the
	409	// block
	410	if (min_length < MipMapScaleFactor) {
	411	for (; index < end; index++) {
	412	const bool sample = (get_sample(index) &
	413	sig_mask) != 0;
	414	if (sample != last_sample)
	415	break;
	416	}
	417	}
	418	}
	419
	420	//----- Store the edge -----//
	421
	422	// Take the last sample of the quanization block
	423	const int64_t final_index = index + block_length;
	424	if (index + block_length > end)
	425	break;
	426
	427	// Store the final state
	428	const bool final_sample =
	429	(get_sample(final_index - 1) & sig_mask) != 0;
	430	edges.push_back(pair<int64_t, bool>(index, final_sample));
	431
	432	index = final_index;
	433	last_sample = final_sample;
	434	}
	435
	436	// Add the final state
	437	const bool end_sample = get_sample(end) & sig_mask;
	438	if (last_sample != end_sample)
	439	edges.push_back(pair<int64_t, bool>(end, end_sample));
	440	edges.push_back(pair<int64_t, bool>(end + 1, end_sample));
	441	}
	442
	443	uint64_t LogicSegment::get_subsample(int level, uint64_t offset) const
	444	{
	445	assert(level >= 0);
	446	assert(mip_map_[level].data);
	447	return unpack_sample((uint8_t*)mip_map_[level].data +
	448	unit_size_ * offset);
	449	}
	450
	451	uint64_t LogicSegment::pow2_ceil(uint64_t x, unsigned int power)
	452	{
	453	const uint64_t p = 1 << power;
	454	return (x + p - 1) / p * p;
	455	}
	456
	457	} // namespace data
	458	} // namespace pv