Function writePackAppendFast

src/packFileSerializer.ts:1686–1886

(
  packFiles: NewPackedFile[],
  path: string,
  existingPackToAppend?: Pack,
  replaceDuplicates?: boolean,
  dependencyPacks: string[] = [],
)

};
// Fast append-only implementation for existing packs - much faster than sorted insertion
export const writePackAppendFast = async (
  packFiles: NewPackedFile[],
  path: string,
  existingPackToAppend?: Pack,
  replaceDuplicates?: boolean,
  dependencyPacks: string[] = [],
) => {
  let outFile: BinaryFile | undefined;
  let sourceFile: BinaryFile | undefined;
  const timestamp = format(new Date(), "ddMMyy_HHmmss");
  const outPath = existingPackToAppend ? `${path}_${timestamp}` : path;
  try {
    if (packFiles.length < 1) return;
    ensurePackFilesReadyForWrite(packFiles);
    if (existingPackToAppend) {
      // FAST PATH: Clone existing pack and append new files
      console.log("Fast append mode: cloning existing pack and appending new files");
      // Open source file for reading
      sourceFile = new BinaryFile(existingPackToAppend.path, "r", true);
      console.log("trying to open source file:", existingPackToAppend.path);
      await sourceFile.open();
      console.log("source file opened");
      // Open output file for writing
      outFile = new BinaryFile(outPath, "w", true);
      await outFile.open();
      // Handle duplicate replacement logic
      const newFileNames = new Set(packFiles.map((pf) => pf.name));
      const filesToKeep = replaceDuplicates
        ? existingPackToAppend.packedFiles.filter((pf) => !newFileNames.has(pf.name))
        : existingPackToAppend.packedFiles;
      // Calculate new counts and sizes
      const originalFileCount = existingPackToAppend.packedFiles.length;
      const keptFileCount = filesToKeep.length;
      const replacedFileCount = originalFileCount - keptFileCount;
      const newFileCount = keptFileCount + packFiles.length;
      // Use existing dependency packs if not provided
      const finalDependencyPacks =
        dependencyPacks.length > 0 ? dependencyPacks : existingPackToAppend.dependencyPacks || [];
      // Calculate pack_file_index_size based on dependency packs
      const pack_file_index_size = finalDependencyPacks.reduce(
        (acc, dep) => acc + Buffer.byteLength(dep, "utf8") + 1,
        0,
      );
      // Calculate additional index size needed for new files
      const newIndexSize = packFiles.reduce((acc, pack) => acc + new Blob([pack.name]).size + 1 + 5, 0);
      // For pack files, the packed_file_index_size in header refers to the file index section
      // We need to calculate the total size of existing + new file index entries
      const keptIndexSize = filesToKeep.reduce((acc, pf) => acc + new Blob([pf.name]).size + 1 + 5, 0);
      const totalIndexSize = keptIndexSize + newIndexSize;
      // Write updated header with new counts
      const headerAccumulator = new BufferAccumulator(outFile);
      headerAccumulator.addString(gameToPackHeader[appData.currentGame]);
      headerAccumulator.addInt32(existingPackToAppend.packHeader.byteMask);
      headerAccumulator.addInt32(existingPackToAppend.packHeader.refFileCount);
      headerAccumulator.addInt32(pack_file_index_size);
      headerAccumulator.addInt32(newFileCount); // Updated file count
      headerAccumulator.addInt32(totalIndexSize); // Updated index size
      headerAccumulator.addInt32(0x7fffffff); // header_buffer