All files / lib/serialize readTlvs.ts

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import { BufferReader } from '@node-dlc/bufio';
 
/**
 * Reads TLVs from a reader until the entire stream is processed. The handler is
 * responsible for doing something with the data bytes.
 * @param reader
 * @param handler
 */
export function readTlvs(
  reader: BufferReader,
  handler: (type: bigint, value: BufferReader) => boolean,
): void {
  let lastType: bigint;
  while (!reader.eof) {
    const type = reader.readBigSize();
    const len = reader.readBigSize();
    const value = reader.readBytes(Number(len));
    const valueReader = new BufferReader(value);
 
    Iif (type <= lastType) {
      throw new Error('Invalid TLV stream');
    }
 
    const isEven = type % BigInt(2) === BigInt(0);
    const wasHandled = handler(type, valueReader);
 
    Iif (!wasHandled && isEven) {
      throw new Error('Unknown even type');
    }
 
    Iif (wasHandled && !valueReader.eof) {
      throw new Error('Non-canonical length');
    }
 
    lastType = type;
  }
}