Function DecodePAAFileMip

engine/Poseidon/Graphics/Textures/PAADecoder.cpp:553–684

}

DecodedImage DecodePAAFileMip(const std::string& path, int mipLevel)
{
    DecodedImage img;
    std::ifstream file(path, std::ios::binary | std::ios::ate);
    if (!file.good())
        return img;

    auto fileSize = file.tellg();
    file.seekg(0, std::ios::beg);
    std::vector<char> fileData(fileSize);
    file.read(fileData.data(), fileSize);
    file.close();

    if (mipLevel == 0)
        return DecodePAABuffer(fileData.data(), static_cast<size_t>(fileSize), detectIsPaa(path));

    // For mip > 0, parse the PAA structure and skip to the requested mip
    bool isPaa = detectIsPaa(path);
    QIStream in(fileData.data(), static_cast<int>(fileSize));

    int desc = fgetiw(in);
    bool alpha = false;
    PacFormat format = PacFormatFromDesc(desc, alpha);
    if (format == PacFormatN)
    {
        in.seekg(-2, QIOS::cur);
        format = isPaa ? PacARGB4444 : PacP8;
    }

    PacPalette pal;
    int offsets[16];
    for (int i = 0; i < 16; i++)
        offsets[i] = -1;
    if (pal.Load(in, offsets, 16))
        return img;

    // Iterate through mip levels to reach the requested one
    PacLevelMem mip;
    for (int m = 0; m <= mipLevel; m++)
    {
        mip = PacLevelMem(); // fresh for each level
        if (m < 16 && offsets[m] >= 0)
            mip.SetStart(offsets[m]);
        // For mips > 0 with known offsets, set expected dimensions
        if (m > 0 && offsets[m] >= 0)
        {
            // will be read by Init anyway
        }
        if (mip.Init(in, format) != 0)
            return img;
    }

    img.width = mip._w;
    img.height = mip._h;
    // Reject absurd dimensions (mip header is attacker-controlled) before
    // width*height*4 overflows int into a tiny rgba alloc the decoders overrun.
    if (img.width <= 0 || img.height <= 0 || img.width > 8192 || img.height > 8192)
        return img;