GeezerVison is showing github.com — JavaScript/prng-bytes.js at master · EntropyString/JavaScript

Expand file tree

prng-bytes.js

Copy path

More file actions

33 lines (28 loc) · 905 Bytes

Copy path

33 lines (28 loc) · 905 Bytes

Copy raw file

Download raw file

Open symbols panel

Edit and raw actions

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

}