analogsegment.cpp

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/*
 * 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 <algorithm>

#include "analogsegment.hpp"

using std::lock_guard;
using std::recursive_mutex;
using std::max;
using std::max_element;
using std::min;
using std::min_element;

namespace pv {
namespace data {

const int AnalogSegment::EnvelopeScalePower = 4;
const int AnalogSegment::EnvelopeScaleFactor = 1 << EnvelopeScalePower;
const float AnalogSegment::LogEnvelopeScaleFactor =
    logf(EnvelopeScaleFactor);
const uint64_t AnalogSegment::EnvelopeDataUnit = 64*1024;   // bytes

AnalogSegment::AnalogSegment(
    uint64_t samplerate, const uint64_t expected_num_samples) :
    Segment(samplerate, sizeof(float))
{
    set_capacity(expected_num_samples);

    lock_guard<recursive_mutex> lock(mutex_);
    memset(envelope_levels_, 0, sizeof(envelope_levels_));
}

AnalogSegment::~AnalogSegment()
{
    lock_guard<recursive_mutex> lock(mutex_);
    for (Envelope &e : envelope_levels_)
        free(e.samples);
}

void AnalogSegment::append_interleaved_samples(const float *data,
    size_t sample_count, size_t stride)
{
    assert(unit_size_ == sizeof(float));

    lock_guard<recursive_mutex> lock(mutex_);

    // If we're out of memory, this will throw std::bad_alloc
    data_.resize((sample_count_ + sample_count) * sizeof(float));

    float *dst = (float*)data_.data() + sample_count_;
    const float *dst_end = dst + sample_count;
    while (dst != dst_end) {
        *dst++ = *data;
        data += stride;
    }

    sample_count_ += sample_count;

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

const float* AnalogSegment::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_);

    float *const data = new float[end_sample - start_sample];
    memcpy(data, (float*)data_.data() + start_sample, sizeof(float) *
        (end_sample - start_sample));
    return data;
}

void AnalogSegment::get_envelope_section(EnvelopeSection &s,
    uint64_t start, uint64_t end, float min_length) const
{
    assert(end <= get_sample_count());
    assert(start <= end);
    assert(min_length > 0);

    lock_guard<recursive_mutex> lock(mutex_);

    const unsigned int min_level = max((int)floorf(logf(min_length) /
        LogEnvelopeScaleFactor) - 1, 0);
    const unsigned int scale_power = (min_level + 1) *
        EnvelopeScalePower;
    start >>= scale_power;
    end >>= scale_power;

    s.start = start << scale_power;
    s.scale = 1 << scale_power;
    s.length = end - start;
    s.samples = new EnvelopeSample[s.length];
    memcpy(s.samples, envelope_levels_[min_level].samples + start,
        s.length * sizeof(EnvelopeSample));
}

void AnalogSegment::reallocate_envelope(Envelope &e)
{
    const uint64_t new_data_length = ((e.length + EnvelopeDataUnit - 1) /
        EnvelopeDataUnit) * EnvelopeDataUnit;
    if (new_data_length > e.data_length) {
        e.data_length = new_data_length;
        e.samples = (EnvelopeSample*)realloc(e.samples,
            new_data_length * sizeof(EnvelopeSample));
    }
}

void AnalogSegment::append_payload_to_envelope_levels()
{
    Envelope &e0 = envelope_levels_[0];
    uint64_t prev_length;
    EnvelopeSample *dest_ptr;

    // Expand the data buffer to fit the new samples
    prev_length = e0.length;
    e0.length = sample_count_ / EnvelopeScaleFactor;

    // Break off if there are no new samples to compute
    if (e0.length == prev_length)
        return;

    reallocate_envelope(e0);

    dest_ptr = e0.samples + prev_length;

    // Iterate through the samples to populate the first level mipmap
    const float *const end_src_ptr = (float*)data_.data() +
        e0.length * EnvelopeScaleFactor;
    for (const float *src_ptr = (float*)data_.data() +
            prev_length * EnvelopeScaleFactor;
            src_ptr < end_src_ptr; src_ptr += EnvelopeScaleFactor) {
        const EnvelopeSample sub_sample = {
            *min_element(src_ptr, src_ptr + EnvelopeScaleFactor),
            *max_element(src_ptr, src_ptr + EnvelopeScaleFactor),
        };

        *dest_ptr++ = sub_sample;
    }

    // Compute higher level mipmaps
    for (unsigned int level = 1; level < ScaleStepCount; level++) {
        Envelope &e = envelope_levels_[level];
        const Envelope &el = envelope_levels_[level-1];

        // Expand the data buffer to fit the new samples
        prev_length = e.length;
        e.length = el.length / EnvelopeScaleFactor;

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

        reallocate_envelope(e);

        // Subsample the level lower level
        const EnvelopeSample *src_ptr =
            el.samples + prev_length * EnvelopeScaleFactor;
        const EnvelopeSample *const end_dest_ptr = e.samples + e.length;
        for (dest_ptr = e.samples + prev_length;
                dest_ptr < end_dest_ptr; dest_ptr++) {
            const EnvelopeSample *const end_src_ptr =
                src_ptr + EnvelopeScaleFactor;

            EnvelopeSample sub_sample = *src_ptr++;
            while (src_ptr < end_src_ptr) {
                sub_sample.min = min(sub_sample.min, src_ptr->min);
                sub_sample.max = max(sub_sample.max, src_ptr->max);
                src_ptr++;
            }

            *dest_ptr = sub_sample;
        }
    }
}

} // namespace data
} // namespace pv