Function makeMessagePackDecoder

packages/msgpack/src/decoder.ts:18–286

({
  decoderExtensions = [],
}: DecoderOptions<ExtensionType> = {})

};

export function makeMessagePackDecoder<ExtensionType extends object = object>({
  decoderExtensions = [],
}: DecoderOptions<ExtensionType> = {}): {
  decode: DecodeFn<ExtensionType>,
} {
  let textDecoder = new TextDecoder();

  const decodeArrayItems = (input: Uint8Array, len: number) => {
    let acc = 0;
    let array: Array<Input<ExtensionType>> = Array(len);
    for (let i = 0; i < len; i++) {
      let [item, readBytes] = decode(input.slice(acc), acc);
      array[i] = item;
      acc += readBytes;
    }
    return [array, acc] as const;
  };

  const decodeObjectEntries = (input: Uint8Array, size: number, pos = 0) => {
    let acc = 0;
    let entries: Array<[key: string, value: Input<ExtensionType>]> = Array(size);
    for (let i = 0; i < size; i++) {
      let [key, keySize] = decode(input.slice(acc), pos + acc);
      if (typeof key !== 'string') {
        throw new Error(`expected string at ${pos}, but got ${typeof key}`);
      }
      acc += keySize;

      let [value, valueSize] = decode(input.slice(acc), pos + acc);
      acc += valueSize;

      entries[i] = [key, value];
    }

    return [Object.fromEntries(entries), acc] as const;
  };

  const decode: DecodeProcessFn<ExtensionType> = (input: Uint8Array, pos = 0) => {
    let acc = 0;
    let header = input[acc++];

    if (header < 0x80) {
      return [header, acc];
    } else if (header < 0x90) {
      let len = header & 15;
      let [data, readBytes] = decodeObjectEntries(input.slice(acc), len, pos + acc);
      return [data, acc + readBytes];
    } else if (header < 0xa0) {
      let len = header & 15;
      let [data, readBytes] = decodeArrayItems(input.slice(acc), len);
      return [data, acc + readBytes];
    } else if (header < 0xc0) {
      let len = 0x1f & header;
      let str = textDecoder.decode(input.slice(acc, acc + len));
      return [str, acc + len];
    } else if (header === 0xc0) {
      return [null, acc];
    } else if (header === 0xc1) {