squeezelite-esp32/components/spotify/cspot/src/AudioChunk.cpp

#include "AudioChunk.h"

std::vector<uint8_t> audioAESIV({0x72, 0xe0, 0x67, 0xfb, 0xdd, 0xcb, 0xcf, 0x77, 0xeb, 0xe8, 0xbc, 0x64, 0x3f, 0x63, 0x0d, 0x93});

AudioChunk::AudioChunk(uint16_t seqId, std::vector<uint8_t> &audioKey, uint32_t startPosition, uint32_t predictedEndPosition)
{
    this->crypto = std::make_unique<Crypto>();
    this->seqId = seqId;
    this->audioKey = audioKey;
    this->startPosition = startPosition;
    this->endPosition = predictedEndPosition;
    this->decryptedData = std::vector<uint8_t>();
    this->isHeaderFileSizeLoadedSemaphore = std::make_unique<WrappedSemaphore>(2);
    this->isLoadedSemaphore = std::make_unique<WrappedSemaphore>(2);
}

AudioChunk::~AudioChunk()
{
}

void AudioChunk::appendData(std::vector<uint8_t> &data)
{
    this->decryptedData.insert(this->decryptedData.end(), data.begin(), data.end());
}

void AudioChunk::decrypt()
{
    // calculate the IV for right position
    auto calculatedIV = this->getIVSum(startPosition / 16);

    crypto->aesCTRXcrypt(this->audioKey, calculatedIV, decryptedData);

    this->startPosition = this->endPosition - this->decryptedData.size();
    this->isLoaded = true;
}

// Basically just big num addition
std::vector<uint8_t> AudioChunk::getIVSum(uint32_t n)
{
    return bigNumAdd(audioAESIV, n);
}