export function readElements()

in modules/serialize/src/read_element.ts [32:80]

• 36 lines of code
• 7 McCabe index (conditional complexity)

export function readElements(
  elementCount: number,
  fieldsPerElement: number,
  buffer: Uint8Array,
  readPos = 0
) {
  /* Uint8Array is a view on top of the underlying ArrayBuffer.
   * This means that raw underlying memory stored in the ArrayBuffer
   * may be larger than the Uint8Array.  This is especially true of
   * the Node.js Buffer object.  The offset and length *must* be
   * passed to the DataView otherwise I will get unexpected results.
   */
  const dataView = new DataView(
    buffer.buffer,
    buffer.byteOffset,
    buffer.byteLength
  )
  const elements = []

  /* Precondition: readPos must be non-negative and within the byte length of the buffer given. */
  needs(
    readPos >= 0 && dataView.byteLength >= readPos,
    'readPos out of bounds.'
  )

  /* Precondition: elementCount and fieldsPerElement must be non-negative. */
  needs(
    elementCount >= 0 && fieldsPerElement >= 0,
    'elementCount and fieldsPerElement must be positive.'
  )

  while (elementCount--) {
    const element = []
    let fieldCount = fieldsPerElement
    while (fieldCount--) {
      /* Check for early return (Postcondition): Enough data must exist to read the Uint16 length value. */
      if (readPos + 2 > dataView.byteLength) return false
      const length = dataView.getUint16(readPos, false) // big endian
      readPos += 2
      /* Check for early return (Postcondition): Enough data must exist length of the value. */
      if (readPos + length > dataView.byteLength) return false
      const fieldBinary = buffer.slice(readPos, readPos + length)
      element.push(fieldBinary)
      readPos += length
    }
    elements.push(element)
  }
  return { elements, readPos }
}