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Copy pathentropy-string.js
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209 lines (175 loc) · 5.51 KB
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const { csprngBytes } = require('./csprng-bytes')
const { prngBytes } = require('./prng-bytes')
const { CharSet } = require('./charSet')
const BITS_PER_BYTE = 8
const {
ceil, floor, log2, round
} = Math
const charset64 = new CharSet('ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_')
const charset32 = new CharSet('2346789bdfghjmnpqrtBDFGHJLMNPQRT')
const charset16 = new CharSet('0123456789abcdef')
const charset8 = new CharSet('01234567')
const charset4 = new CharSet('ATCG')
const charset2 = new CharSet('01')
const stringWithBytes = (bytes, bitLen, charset) => {
if (bitLen <= 0) { return '' }
const { bitsPerChar } = charset
const count = ceil(bitLen / bitsPerChar)
if (count <= 0) { return '' }
const need = ceil(count * (bitsPerChar / BITS_PER_BYTE))
if (bytes.length < need) {
throw new Error(`Insufficient bytes: need ${need} and got ${bytes.length}`)
}
const { ndxFn, charsPerChunk, chars } = charset
const chunks = floor(count / charsPerChunk)
const partials = count % charsPerChunk
let string = ''
for (let chunk = 0; chunk < chunks; chunk += 1) {
for (let slice = 0; slice < charsPerChunk; slice += 1) {
const ndx = ndxFn(chunk, slice, bytes)
string += chars[ndx]
}
}
for (let slice = 0; slice < partials; slice += 1) {
const ndx = ndxFn(chunks, slice, bytes)
string += chars[ndx]
}
return string
}
const entropyBits = (total, risk) => {
if (total === 0) { return 0 }
let N
if (total < 1000) {
N = log2(total) + log2(total - 1)
} else {
N = 2 * log2(total)
}
return (N + log2(risk)) - 1
}
class Entropy {
constructor(params = { bits: 128, charset: charset32 }) {
if (params !== undefined) {
if (!(params instanceof Object)) {
throw new Error('Invalid argument for Entropy constructor: Expect params object')
}
if (params.bits === undefined
&& params.charset === undefined
&& params.total === undefined
&& params.risk === undefined
&& params.prng === undefined) {
throw new Error('Invalid Entropy params')
}
if (params.bits !== undefined) {
if (typeof params.bits !== 'number') {
throw new Error('Invalid Entropy params: non-numeric bits')
}
if (params.bits < 0) {
throw new Error('Invalid Entropy params: negative bits')
}
}
if (params.total !== undefined) {
if (typeof params.total !== 'number') {
throw new Error('Invalid Entropy params: non-numeric total')
}
if (params.total < 1) {
throw new Error('Invalid Entropy params: non-positive total')
}
}
if (params.risk !== undefined) {
if (typeof params.risk !== 'number') {
throw new Error('Invalid Entropy params: non-numeric risk')
}
if (params.risk < 1) {
throw new Error('Invalid Entropy params: non-positive risk')
}
}
if (params.risk !== undefined && typeof params.risk !== 'number') {
throw new Error('Invalid Entropy params: non-numeric risk')
}
if ((params.total !== undefined && params.risk === undefined)
|| (params.total === undefined && params.risk !== undefined)) {
throw new Error('Invalid Entropy params: total and risk must be paired')
}
if (params.bits !== undefined
&& (params.total !== undefined || params.risk !== undefined)) {
throw new Error('Invalid Entropy params: bits with total and/or risk')
}
}
let bitLen
if (params.bits) {
bitLen = round(params.bits)
} else if (params.total && params.risk) {
bitLen = round(entropyBits(params.total, params.risk))
} else {
bitLen = 128
}
let charset
if (params.charset instanceof CharSet) {
const { charset: cs } = params
charset = cs
} else if ((typeof params.charset === 'string' || params.charset instanceof String)) {
charset = new CharSet(params.charset)
} else {
charset = charset32
}
this.charset = charset
this.bitLen = bitLen
this.prng = params.prng || false
}
static bits(total, risk) { return entropyBits(total, risk) }
smallID(charset = this.charset) {
return this.string(29, charset)
}
mediumID(charset = this.charset) {
return this.string(69, charset)
}
largeID(charset = this.charset) {
return this.string(99, charset)
}
sessionID(charset = this.charset) {
return this.string(128, charset)
}
token(charset = this.charset) {
return this.string(256, charset)
}
string(bitLen = this.bitLen, charset = this.charset) {
const bytesNeeded = charset.bytesNeeded(bitLen)
const bytes = this.prng ? prngBytes(bytesNeeded) : csprngBytes(bytesNeeded)
return this.stringWithBytes(bytes, bitLen, charset)
}
stringWithBytes(
bytes,
bitLen = this.bitLen, charset = this.charset
) {
return stringWithBytes(bytes, bitLen, charset)
}
bytesNeeded(bitLen = this.bitLen, charset = this.charset) {
return charset.bytesNeeded(bitLen)
}
chars() {
return this.charset.chars
}
bits() {
return this.bitLen
}
use(charset) {
if (!(charset instanceof CharSet)) { throw new Error('Invalid CharSet') }
this.charset = charset
}
useChars(chars) {
if (!(typeof chars === 'string' || chars instanceof String)) {
throw new Error('Invalid chars: Must be string')
}
this.use(new CharSet(chars))
}
}
module.exports = {
CharSet,
Entropy,
charset2,
charset4,
charset8,
charset16,
charset32,
charset64
}