ComfyUI_frontend/src/scripts/metadata/flac.ts

export function getFromFlacBuffer(buffer: ArrayBuffer): Record<string, string> {
  const dataView = new DataView(buffer);

  // Verify the FLAC signature
  const signature = String.fromCharCode(...new Uint8Array(buffer, 0, 4));
  if (signature !== "fLaC") {
    console.error("Not a valid FLAC file");
    return;
  }

  // Parse metadata blocks
  let offset = 4;
  let vorbisComment = null;
  while (offset < dataView.byteLength) {
    const isLastBlock = dataView.getUint8(offset) & 0x80;
    const blockType = dataView.getUint8(offset) & 0x7f;
    const blockSize = dataView.getUint32(offset, false) & 0xffffff;
    offset += 4;

    if (blockType === 4) {
      // Vorbis Comment block type
      vorbisComment = parseVorbisComment(
        new DataView(buffer, offset, blockSize)
      );
    }

    offset += blockSize;
    if (isLastBlock) break;
  }

  return vorbisComment;
}

export function getFromFlacFile(file: File): Promise<Record<string, string>> {
  return new Promise((r) => {
    const reader = new FileReader();
    reader.onload = function (event) {
      const arrayBuffer = event.target.result as ArrayBuffer;
      r(getFromFlacBuffer(arrayBuffer));
    };
    reader.readAsArrayBuffer(file);
  });
}

// Function to parse the Vorbis Comment block
function parseVorbisComment(dataView: DataView): Record<string, string> {
  let offset = 0;
  const vendorLength = dataView.getUint32(offset, true);
  offset += 4;
  const vendorString = getString(dataView, offset, vendorLength);
  offset += vendorLength;

  const userCommentListLength = dataView.getUint32(offset, true);
  offset += 4;
  const comments = {};
  for (let i = 0; i < userCommentListLength; i++) {
    const commentLength = dataView.getUint32(offset, true);
    offset += 4;
    const comment = getString(dataView, offset, commentLength);
    offset += commentLength;

    const [key, value] = comment.split("=");

    comments[key] = value;
  }

  return comments;
}

function getString(dataView: DataView, offset: number, length: number): string {
  let string = "";
  for (let i = 0; i < length; i++) {
    string += String.fromCharCode(dataView.getUint8(offset + i));
  }
  return string;
}