[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 <cassert>
#include <cstring>
#include <cstdlib>
#include <cmath>

#include "logic.hpp"
#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 std::vector;

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(pv::data::Logic& owner, shared_ptr<sigrok::Logic> data,
	uint64_t samplerate) :
	Segment(samplerate, data->unit_size()),
	owner_(owner),
	last_append_sample_(0)
{
	lock_guard<recursive_mutex> lock(mutex_);
	memset(mip_map_, 0, sizeof(mip_map_));
	append_payload(data);
}

LogicSegment::LogicSegment(pv::data::Logic& owner, unsigned int unit_size,
	uint64_t samplerate) :
	Segment(samplerate, unit_size),
	owner_(owner),
	last_append_sample_(0)
{
	memset(mip_map_, 0, sizeof(mip_map_));
}

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<sigrok::Logic> logic)
{
	assert(unit_size_ == logic->unit_size());
	assert((logic->data_length() % unit_size_) == 0);

	append_payload(logic->data_pointer(), logic->data_length());
}

void LogicSegment::append_payload(void *data, uint64_t data_size)
{
	assert((data_size % unit_size_) == 0);

	lock_guard<recursive_mutex> lock(mutex_);

	uint64_t prev_sample_count = sample_count_;
	uint64_t sample_count = data_size / unit_size_;

	append_samples(data, sample_count);

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

	if (sample_count > 1)
		owner_.notify_samples_added(this, prev_sample_count + 1,
			prev_sample_count + 1 + sample_count);
	else
		owner_.notify_samples_added(this, prev_sample_count + 1,
			prev_sample_count + 1);
}

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)
{
	return (SegmentLogicDataIterator*)begin_raw_sample_iteration(start);
}

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

void LogicSegment::end_sample_iteration(SegmentLogicDataIterator* it)
{
	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(
	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.emplace_back(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 (true) {
				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 (true) {
				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.emplace_back(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.emplace_back(end, end_sample);
	edges.emplace_back(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 <cassert>
	23	#include <cstring>
	24	#include <cstdlib>
	25	#include <cmath>
	26
	27	#include "logic.hpp"
	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	using std::vector;
	39
	40	using sigrok::Logic;
	41
	42	namespace pv {
	43	namespace data {
	44
	45	const int LogicSegment::MipMapScalePower = 4;
	46	const int LogicSegment::MipMapScaleFactor = 1 << MipMapScalePower;
	47	const float LogicSegment::LogMipMapScaleFactor = logf(MipMapScaleFactor);
	48	const uint64_t LogicSegment::MipMapDataUnit = 64*1024; // bytes
	49
	50	LogicSegment::LogicSegment(pv::data::Logic& owner, shared_ptr<sigrok::Logic> data,
	51	uint64_t samplerate) :
	52	Segment(samplerate, data->unit_size()),
	53	owner_(owner),
	54	last_append_sample_(0)
	55	{
	56	lock_guard<recursive_mutex> lock(mutex_);
	57	memset(mip_map_, 0, sizeof(mip_map_));
	58	append_payload(data);
	59	}
	60
	61	LogicSegment::LogicSegment(pv::data::Logic& owner, unsigned int unit_size,
	62	uint64_t samplerate) :
	63	Segment(samplerate, unit_size),
	64	owner_(owner),
	65	last_append_sample_(0)
	66	{
	67	memset(mip_map_, 0, sizeof(mip_map_));
	68	}
	69
	70	LogicSegment::~LogicSegment()
	71	{
	72	lock_guard<recursive_mutex> lock(mutex_);
	73	for (MipMapLevel &l : mip_map_)
	74	free(l.data);
	75	}
	76
	77	uint64_t LogicSegment::unpack_sample(const uint8_t *ptr) const
	78	{
	79	#ifdef HAVE_UNALIGNED_LITTLE_ENDIAN_ACCESS
	80	return (uint64_t)ptr;
	81	#else
	82	uint64_t value = 0;
	83	switch (unit_size_) {
	84	default:
	85	value \|= ((uint64_t)ptr[7]) << 56;
	86	/* FALLTHRU */
	87	case 7:
	88	value \|= ((uint64_t)ptr[6]) << 48;
	89	/* FALLTHRU */
	90	case 6:
	91	value \|= ((uint64_t)ptr[5]) << 40;
	92	/* FALLTHRU */
	93	case 5:
	94	value \|= ((uint64_t)ptr[4]) << 32;
	95	/* FALLTHRU */
	96	case 4:
	97	value \|= ((uint32_t)ptr[3]) << 24;
	98	/* FALLTHRU */
	99	case 3:
	100	value \|= ((uint32_t)ptr[2]) << 16;
	101	/* FALLTHRU */
	102	case 2:
	103	value \|= ptr[1] << 8;
	104	/* FALLTHRU */
	105	case 1:
	106	value \|= ptr[0];
	107	/* FALLTHRU */
	108	case 0:
	109	break;
	110	}
	111	return value;
	112	#endif
	113	}
	114
	115	void LogicSegment::pack_sample(uint8_t *ptr, uint64_t value)
	116	{
	117	#ifdef HAVE_UNALIGNED_LITTLE_ENDIAN_ACCESS
	118	(uint64_t)ptr = value;
	119	#else
	120	switch (unit_size_) {
	121	default:
	122	ptr[7] = value >> 56;
	123	/* FALLTHRU */
	124	case 7:
	125	ptr[6] = value >> 48;
	126	/* FALLTHRU */
	127	case 6:
	128	ptr[5] = value >> 40;
	129	/* FALLTHRU */
	130	case 5:
	131	ptr[4] = value >> 32;
	132	/* FALLTHRU */
	133	case 4:
	134	ptr[3] = value >> 24;
	135	/* FALLTHRU */
	136	case 3:
	137	ptr[2] = value >> 16;
	138	/* FALLTHRU */
	139	case 2:
	140	ptr[1] = value >> 8;
	141	/* FALLTHRU */
	142	case 1:
	143	ptr[0] = value;
	144	/* FALLTHRU */
	145	case 0:
	146	break;
	147	}
	148	#endif
	149	}
	150
	151	void LogicSegment::append_payload(shared_ptr<sigrok::Logic> logic)
	152	{
	153	assert(unit_size_ == logic->unit_size());
	154	assert((logic->data_length() % unit_size_) == 0);
	155
	156	append_payload(logic->data_pointer(), logic->data_length());
	157	}
	158
	159	void LogicSegment::append_payload(void *data, uint64_t data_size)
	160	{
	161	assert((data_size % unit_size_) == 0);
	162
	163	lock_guard<recursive_mutex> lock(mutex_);
	164
	165	uint64_t prev_sample_count = sample_count_;
	166	uint64_t sample_count = data_size / unit_size_;
	167
	168	append_samples(data, sample_count);
	169
	170	// Generate the first mip-map from the data
	171	append_payload_to_mipmap();
	172
	173	if (sample_count > 1)
	174	owner_.notify_samples_added(this, prev_sample_count + 1,
	175	prev_sample_count + 1 + sample_count);
	176	else
	177	owner_.notify_samples_added(this, prev_sample_count + 1,
	178	prev_sample_count + 1);
	179	}
	180
	181	const uint8_t* LogicSegment::get_samples(int64_t start_sample,
	182	int64_t end_sample) const
	183	{
	184	assert(start_sample >= 0);
	185	assert(start_sample <= (int64_t)sample_count_);
	186	assert(end_sample >= 0);
	187	assert(end_sample <= (int64_t)sample_count_);
	188	assert(start_sample <= end_sample);
	189
	190	lock_guard<recursive_mutex> lock(mutex_);
	191
	192	return get_raw_samples(start_sample, (end_sample-start_sample));
	193	}
	194
	195	SegmentLogicDataIterator* LogicSegment::begin_sample_iteration(uint64_t start)
	196	{
	197	return (SegmentLogicDataIterator*)begin_raw_sample_iteration(start);
	198	}
	199
	200	void LogicSegment::continue_sample_iteration(SegmentLogicDataIterator* it, uint64_t increase)
	201	{
	202	Segment::continue_raw_sample_iteration((SegmentRawDataIterator*)it, increase);
	203	}
	204
	205	void LogicSegment::end_sample_iteration(SegmentLogicDataIterator* it)
	206	{
	207	Segment::end_raw_sample_iteration((SegmentRawDataIterator*)it);
	208	}
	209
	210	void LogicSegment::reallocate_mipmap_level(MipMapLevel &m)
	211	{
	212	lock_guard<recursive_mutex> lock(mutex_);
	213
	214	const uint64_t new_data_length = ((m.length + MipMapDataUnit - 1) /
	215	MipMapDataUnit) * MipMapDataUnit;
	216
	217	if (new_data_length > m.data_length) {
	218	m.data_length = new_data_length;
	219
	220	// Padding is added to allow for the uint64_t write word
	221	m.data = realloc(m.data, new_data_length * unit_size_ +
	222	sizeof(uint64_t));
	223	}
	224	}
	225
	226	void LogicSegment::append_payload_to_mipmap()
	227	{
	228	MipMapLevel &m0 = mip_map_[0];
	229	uint64_t prev_length;
	230	uint8_t *dest_ptr;
	231	SegmentRawDataIterator* it;
	232	uint64_t accumulator;
	233	unsigned int diff_counter;
	234
	235	// Expand the data buffer to fit the new samples
	236	prev_length = m0.length;
	237	m0.length = sample_count_ / MipMapScaleFactor;
	238
	239	// Break off if there are no new samples to compute
	240	if (m0.length == prev_length)
	241	return;
	242
	243	reallocate_mipmap_level(m0);
	244
	245	dest_ptr = (uint8_t)m0.data + prev_length unit_size_;
	246
	247	// Iterate through the samples to populate the first level mipmap
	248	uint64_t start_sample = prev_length * MipMapScaleFactor;
	249	uint64_t end_sample = m0.length * MipMapScaleFactor;
	250
	251	it = begin_raw_sample_iteration(start_sample);
	252	for (uint64_t i = start_sample; i < end_sample;) {
	253	// Accumulate transitions which have occurred in this sample
	254	accumulator = 0;
	255	diff_counter = MipMapScaleFactor;
	256	while (diff_counter-- > 0) {
	257	const uint64_t sample = unpack_sample(it->value);
	258	accumulator \|= last_append_sample_ ^ sample;
	259	last_append_sample_ = sample;
	260	continue_raw_sample_iteration(it, 1);
	261	i++;
	262	}
	263
	264	pack_sample(dest_ptr, accumulator);
	265	dest_ptr += unit_size_;
	266	}
	267	end_raw_sample_iteration(it);
	268
	269	// Compute higher level mipmaps
	270	for (unsigned int level = 1; level < ScaleStepCount; level++) {
	271	MipMapLevel &m = mip_map_[level];
	272	const MipMapLevel &ml = mip_map_[level-1];
	273
	274	// Expand the data buffer to fit the new samples
	275	prev_length = m.length;
	276	m.length = ml.length / MipMapScaleFactor;
	277
	278	// Break off if there are no more samples to be computed
	279	if (m.length == prev_length)
	280	break;
	281
	282	reallocate_mipmap_level(m);
	283
	284	// Subsample the lower level
	285	const uint8_t* src_ptr = (uint8_t*)ml.data +
	286	unit_size_ * prev_length * MipMapScaleFactor;
	287	const uint8_t *const end_dest_ptr =
	288	(uint8_t)m.data + unit_size_ m.length;
	289
	290	for (dest_ptr = (uint8_t*)m.data +
	291	unit_size_ * prev_length;
	292	dest_ptr < end_dest_ptr;
	293	dest_ptr += unit_size_) {
	294	accumulator = 0;
	295	diff_counter = MipMapScaleFactor;
	296	while (diff_counter-- > 0) {
	297	accumulator \|= unpack_sample(src_ptr);
	298	src_ptr += unit_size_;
	299	}
	300
	301	pack_sample(dest_ptr, accumulator);
	302	}
	303	}
	304	}
	305
	306	uint64_t LogicSegment::get_unpacked_sample(uint64_t index) const
	307	{
	308	assert(index < sample_count_);
	309
	310	const uint8_t* data = get_raw_samples(index, 1);
	311	uint64_t sample = unpack_sample(data);
	312	delete[] data;
	313
	314	return sample;
	315	}
	316
	317	void LogicSegment::get_subsampled_edges(
	318	vector<EdgePair> &edges,
	319	uint64_t start, uint64_t end,
	320	float min_length, int sig_index)
	321	{
	322	uint64_t index = start;
	323	unsigned int level;
	324	bool last_sample;
	325	bool fast_forward;
	326
	327	assert(end <= get_sample_count());
	328	assert(start <= end);
	329	assert(min_length > 0);
	330	assert(sig_index >= 0);
	331	assert(sig_index < 64);
	332
	333	lock_guard<recursive_mutex> lock(mutex_);
	334
	335	const uint64_t block_length = (uint64_t)max(min_length, 1.0f);
	336	const unsigned int min_level = max((int)floorf(logf(min_length) /
	337	LogMipMapScaleFactor) - 1, 0);
	338	const uint64_t sig_mask = 1ULL << sig_index;
	339
	340	// Store the initial state
	341	last_sample = (get_unpacked_sample(start) & sig_mask) != 0;
	342	edges.emplace_back(index++, last_sample);
	343
	344	while (index + block_length <= end) {
	345	//----- Continue to search -----//
	346	level = min_level;
	347
	348	// We cannot fast-forward if there is no mip-map data at
	349	// at the minimum level.
	350	fast_forward = (mip_map_[level].data != nullptr);
	351
	352	if (min_length < MipMapScaleFactor) {
	353	// Search individual samples up to the beginning of
	354	// the next first level mip map block
	355	const uint64_t final_index = min(end,
	356	pow2_ceil(index, MipMapScalePower));
	357
	358	for (; index < final_index &&
	359	(index & ~((uint64_t)(~0) << MipMapScalePower)) != 0;
	360	index++) {
	361	const bool sample =
	362	(get_unpacked_sample(index) & sig_mask) != 0;
	363
	364	// If there was a change we cannot fast forward
	365	if (sample != last_sample) {
	366	fast_forward = false;
	367	break;
	368	}
	369	}
	370	} else {
	371	// If resolution is less than a mip map block,
	372	// round up to the beginning of the mip-map block
	373	// for this level of detail
	374	const int min_level_scale_power =
	375	(level + 1) * MipMapScalePower;
	376	index = pow2_ceil(index, min_level_scale_power);
	377	if (index >= end)
	378	break;
	379
	380	// We can fast forward only if there was no change
	381	const bool sample =
	382	(get_unpacked_sample(index) & sig_mask) != 0;
	383	if (last_sample != sample)
	384	fast_forward = false;
	385	}
	386
	387	if (fast_forward) {
	388
	389	// Fast forward: This involves zooming out to higher
	390	// levels of the mip map searching for changes, then
	391	// zooming in on them to find the point where the edge
	392	// begins.
	393
	394	// Slide right and zoom out at the beginnings of mip-map
	395	// blocks until we encounter a change
	396	while (true) {
	397	const int level_scale_power =
	398	(level + 1) * MipMapScalePower;
	399	const uint64_t offset =
	400	index >> level_scale_power;
	401
	402	// Check if we reached the last block at this
	403	// level, or if there was a change in this block
	404	if (offset >= mip_map_[level].length \|\|
	405	(get_subsample(level, offset) &
	406	sig_mask))
	407	break;
	408
	409	if ((offset & ~((uint64_t)(~0) << MipMapScalePower)) == 0) {
	410	// If we are now at the beginning of a
	411	// higher level mip-map block ascend one
	412	// level
	413	if (level + 1 >= ScaleStepCount \|\|
	414	!mip_map_[level + 1].data)
	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	// Zoom in, and slide right until we encounter a change,
	427	// and repeat until we reach min_level
	428	while (true) {
	429	assert(mip_map_[level].data);
	430
	431	const int level_scale_power =
	432	(level + 1) * MipMapScalePower;
	433	const uint64_t offset =
	434	index >> level_scale_power;
	435
	436	// Check if we reached the last block at this
	437	// level, or if there was a change in this block
	438	if (offset >= mip_map_[level].length \|\|
	439	(get_subsample(level, offset) &
	440	sig_mask)) {
	441	// Zoom in unless we reached the minimum
	442	// zoom
	443	if (level == min_level)
	444	break;
	445
	446	level--;
	447	} else {
	448	// Slide right to the beginning of the
	449	// next mip map block
	450	index = pow2_ceil(index + 1,
	451	level_scale_power);
	452	}
	453	}
	454
	455	// If individual samples within the limit of resolution,
	456	// do a linear search for the next transition within the
	457	// block
	458	if (min_length < MipMapScaleFactor) {
	459	for (; index < end; index++) {
	460	const bool sample = (get_unpacked_sample(index) &
	461	sig_mask) != 0;
	462	if (sample != last_sample)
	463	break;
	464	}
	465	}
	466	}
	467
	468	//----- Store the edge -----//
	469
	470	// Take the last sample of the quanization block
	471	const int64_t final_index = index + block_length;
	472	if (index + block_length > end)
	473	break;
	474
	475	// Store the final state
	476	const bool final_sample =
	477	(get_unpacked_sample(final_index - 1) & sig_mask) != 0;
	478	edges.emplace_back(index, final_sample);
	479
	480	index = final_index;
	481	last_sample = final_sample;
	482	}
	483
	484	// Add the final state
	485	const bool end_sample = get_unpacked_sample(end) & sig_mask;
	486	if (last_sample != end_sample)
	487	edges.emplace_back(end, end_sample);
	488	edges.emplace_back(end + 1, end_sample);
	489	}
	490
	491	uint64_t LogicSegment::get_subsample(int level, uint64_t offset) const
	492	{
	493	assert(level >= 0);
	494	assert(mip_map_[level].data);
	495	return unpack_sample((uint8_t*)mip_map_[level].data +
	496	unit_size_ * offset);
	497	}
	498
	499	uint64_t LogicSegment::pow2_ceil(uint64_t x, unsigned int power)
	500	{
	501	const uint64_t p = 1 << power;
	502	return (x + p - 1) / p * p;
	503	}
	504
	505	} // namespace data
	506	} // namespace pv