copyFrom()

in backend/encoding.js [1091:1123]

• 27 lines of code
• 14 McCabe index (conditional complexity)

  copyFrom(decoder, options = {}) {
    if (!(decoder instanceof BooleanDecoder)) {
      throw new TypeError('incompatible type of decoder')
    }

    const { count } = options
    let remaining = (typeof count === 'number' ? count : Number.MAX_SAFE_INTEGER)
    if (count && remaining > 0 && decoder.done) throw new RangeError(`cannot copy ${count} values`)
    if (remaining === 0 || decoder.done) return

    // Copy one value to bring decoder and encoder state into sync, then finish that value's repetitions
    this.appendValue(decoder.readValue())
    remaining--
    const firstCopy = Math.min(decoder.count, remaining)
    this.count += firstCopy
    decoder.count -= firstCopy
    remaining -= firstCopy

    while (remaining > 0 && !decoder.done) {
      decoder.count = decoder.readUint53()
      if (decoder.count === 0) throw new RangeError('Zero-length runs are not allowed')
      decoder.lastValue = !decoder.lastValue
      this.appendUint53(this.count)

      const numCopied = Math.min(decoder.count, remaining)
      this.count = numCopied
      this.lastValue = decoder.lastValue
      decoder.count -= numCopied
      remaining -= numCopied
    }

    if (count && remaining > 0 && decoder.done) throw new RangeError(`cannot copy ${count} values`)
  }