Method patchWithLibKtx

tools/ktx/command_patch.cpp:238–293

This is an alternate way to perform patching bu using libktx to create a ktxTexture. Kept for reference. This was has the following advantage: 1. it can be used for operations that will change the length of the file; and the following disadvantages: 1. it will only work on valid (per libktx's checks) KTX files; 2. KTXwriter will be updated to show either the current version of libktx or "__defa

// 2. KTXwriter will be updated to show either the current version of libktx or "__default__".
//    The latter happens if the current or newly provided app id contains "__default__".
void CommandPatch::patchWithLibKtx(std::FILE* input) {
    ktxTexture2* texture;
    auto ret = ktxTexture2_CreateFromStdioStream(input, KTX_TEXTURE_CREATE_NO_FLAGS, &texture);
    if (ret != KTX_SUCCESS)
        fatal(rc::INVALID_FILE, "Failed to create KTX2 texture: {}", ktxErrorString(ret));
    // Creating the texture2 object fixes the bytesPlane fields.
    switch (texture->supercompressionScheme) {
      case KTX_SS_BASIS_LZ:
      {
        uint32_t* pBdb = texture->pDfd + 1;
        if (KHR_DFDVAL(pBdb, MODEL) != KHR_DF_MODEL_ETC1S) {
            std::fclose(input);
            fatal(rc::DFD_FAILURE, "Input file \"{}\" has invalid color model for supercompression scheme",
                  options.inputFilepath);
        }
      }
        [[fallthrough]];
      case KTX_SS_ZLIB:
      case KTX_SS_ZSTD:
        // Loading the data causes any unsized DFDs to be reconstructed into sized.
        ret = ktxTexture2_LoadDeflatedImageData(texture, nullptr, 0);
        if (ret != KTX_SUCCESS)
            fatal(rc::INVALID_FILE, "Failed to load data for KTX2 texture: {}", ktxErrorString(ret));
        break;
      case KTX_SS_NONE:
        if (options.verbose)
            warning("Input file \"{}\" is not supercompressed.",
                    options.inputFilepath);
        [[fallthrough]];
      default:
        std::fclose(input);
        return;
    }

    if (options.operation == Operation::makeUnsized_e) {
      KHR_DFDSETVAL(texture->pDfd+1, BYTESPLANE0, 0);
      KHR_DFDSETVAL(texture->pDfd+1, BYTESPLANE1, 0);
    }

    const auto updateMetadataValue = [&](const char* const key,
                                 const std::string& value) {
        ktxHashList_DeleteKVPair(&texture->kvDataHead, key);
        ktxHashList_AddKVPair(&texture->kvDataHead, key,
                static_cast<uint32_t>(value.size() + 1), // +1 to include \0
                value.c_str());
    };

    if (options.changeWriter) {
        // Create or modify KTXwriter metadata.
        const auto writer = fmt::format("{} {}", commandName, version(options.testrun));
        updateMetadataValue(KTX_WRITER_KEY, writer);
    }

    std::fseek(input, 0, SEEK_SET); // Seek to start.
    ktxTexture_WriteToStdioStream(ktxTexture(texture), input);
}
#endif