// from https://github.com/jhiesey/to-arraybuffer/blob/6502d9850e70ba7935a7df4ad86b358fc216f9f0/index.js

// MIT License
// Copyright (c) 2016 John Hiesey
import {isBuffer} from 'buffer';
export default function (buf) {
  // If the buffer is backed by a Uint8Array, a faster version will work
  if (buf instanceof Uint8Array) {
    // If the buffer isn't a subarray, return the underlying ArrayBuffer
    if (buf.byteOffset === 0 && buf.byteLength === buf.buffer.byteLength) {
      return buf.buffer
    } else if (typeof buf.buffer.slice === 'function') {
      // Otherwise we need to get a proper copy
      return buf.buffer.slice(buf.byteOffset, buf.byteOffset + buf.byteLength)
    }
  }

  if (isBuffer(buf)) {
    // This is the slow version that will work with any Buffer
    // implementation (even in old browsers)
    var arrayCopy = new Uint8Array(buf.length)
    var len = buf.length
    for (var i = 0; i < len; i++) {
      arrayCopy[i] = buf[i]
    }
    return arrayCopy.buffer
  } else {
    throw new Error('Argument must be a Buffer')
  }
}