LZMA.cpp

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#include <sourcepp/compression/LZMA.h>
 
#include <BufferStream.h>
#include <lzma.h>
 
using namespace sourcepp;
 
std::optional<std::vector<std::byte>> compression::compressValveLZMA(std::span<const std::byte> data, uint8_t compressLevel) {
    // Shift over 4 bytes for Valve LZMA header signature
    std::vector<std::byte> compressedData(sizeof(uint32_t) + data.size() * 2);
 
    lzma_options_lzma options{};
    if (lzma_lzma_preset(&options, std::clamp<uint8_t>(compressLevel, 0, 9))) {
        return std::nullopt;
    }
 
    lzma_stream stream = LZMA_STREAM_INIT;
 
    if (lzma_alone_encoder(&stream, &options) != LZMA_OK) {
        lzma_end(&stream);
        return std::nullopt;
    }
 
    stream.next_in = reinterpret_cast<const uint8_t*>(data.data());
    stream.avail_in = data.size();
    stream.next_out = reinterpret_cast<uint8_t*>(compressedData.data() + sizeof(uint32_t));
    stream.avail_out = compressedData.size() - sizeof(uint32_t);
 
    lzma_ret ret = lzma_code(&stream, LZMA_FINISH);
    lzma_end(&stream);
    if (ret != LZMA_STREAM_END) {
        return std::nullopt;
    }
 
    // Switch out normal header with Valve one
    BufferStream compressedStream{compressedData};
    compressedStream.seek(0).write(VALVE_LZMA_SIGNATURE);
    const auto properties = compressedStream.read<uint8_t>();
    const auto dictionarySize = compressedStream.read<uint32_t>();
    compressedStream
        .seek_u(sizeof(uint32_t))
        .write<uint32_t>(data.size())
        .write(compressedData.size() - (sizeof(uint32_t) * 3) + (sizeof(uint8_t) * 5))
        .write(properties)
        .write(dictionarySize);
 
    compressedData.resize(stream.total_out + sizeof(uint32_t));
    return compressedData;
}
 
std::optional<std::vector<std::byte>> compression::decompressValveLZMA(std::span<const std::byte> data) {
    if (data.size() < 18) {
        // Valve LZMA header length + 1 null byte
        return std::nullopt;
    }
 
    std::vector<std::byte> compressedData{data.begin() + sizeof(uint32_t), data.end()};
    std::vector<std::byte> uncompressedData;
    {
        // Switch out Valve header with normal one
        BufferStreamReadOnly in{data};
        if (in.read<uint32_t>() != VALVE_LZMA_SIGNATURE) {
            return std::nullopt;
        }
        const uint64_t uncompressedLength = in.read<uint32_t>();
        in.skip<uint32_t>(); // compressed length is easily inferred
        const auto properties = in.read<uint8_t>();
        const auto dictionarySize = in.read<uint32_t>();
        BufferStream out{compressedData.data(), compressedData.size()};
        out
            .write(properties)
            .write(dictionarySize)
            .write(uncompressedLength);
 
        uncompressedData.resize(uncompressedLength);
    }
 
    lzma_stream stream = LZMA_STREAM_INIT;
    stream.next_in = reinterpret_cast<const uint8_t*>(compressedData.data());
    stream.avail_in = compressedData.size();
    stream.next_out = reinterpret_cast<uint8_t*>(uncompressedData.data());
    stream.avail_out = uncompressedData.size();
 
    if (lzma_alone_decoder(&stream, UINT64_MAX) != LZMA_OK) {
        lzma_end(&stream);
        return std::nullopt;
    }
    while (true) {
        const auto ret = lzma_code(&stream, LZMA_RUN);
        if (ret == LZMA_STREAM_END || stream.avail_out == 0) {
            break;
        }
        if (ret != LZMA_OK) {
            lzma_end(&stream);
            return std::nullopt;
        }
    }
    if (const auto ret = lzma_code(&stream, LZMA_FINISH); ret != LZMA_OK && ret != LZMA_STREAM_END) {
        lzma_end(&stream);
        return std::nullopt;
    }
    lzma_end(&stream);
 
    return uncompressedData;
}