const { ceil, random } = Math
const BITS_PER_BYTE = 8
const endianByteNum = (() => {
const buf32 = new Uint32Array(1)
const buf8 = new Uint8Array(buf32.buffer)
buf32[0] = 0xff
return (buf8[0] === 0xff) ? [2, 3, 4, 5, 6, 7] : [0, 1, 2, 3, 6, 7]
})()
const prngBytes = (count) => {
const BYTES_USED_PER_RANDOM_CALL = 6
const randCount = ceil(count / BYTES_USED_PER_RANDOM_CALL)
const buffer = new ArrayBuffer(count)
const dataView = new DataView(new ArrayBuffer(BITS_PER_BYTE))
for (let rNum = 0; rNum < randCount; rNum += 1) {
dataView.setFloat64(0, random())
for (let n = 0; n < BYTES_USED_PER_RANDOM_CALL; n += 1) {
const fByteNum = endianByteNum[n]
const bByteNum = (rNum * BYTES_USED_PER_RANDOM_CALL) + n
if (bByteNum < count) {
buffer[bByteNum] = dataView.getUint8(fByteNum)
}
}
}
return buffer
}
module.exports = {
prngBytes
}