104 lines
3.7 KiB
JavaScript
104 lines
3.7 KiB
JavaScript
// This file replaces `index.js` in bundlers like webpack or Rollup,
|
||
// according to `browser` config in `package.json`.
|
||
|
||
import { urlAlphabet } from './url-alphabet/index.js'
|
||
|
||
if (true) {
|
||
// All bundlers will remove this block in the production bundle.
|
||
if (
|
||
typeof navigator !== 'undefined' &&
|
||
navigator.product === 'ReactNative' &&
|
||
typeof crypto === 'undefined'
|
||
) {
|
||
throw new Error(
|
||
'React Native does not have a built-in secure random generator. ' +
|
||
'If you don’t need unpredictable IDs use `nanoid/non-secure`. ' +
|
||
'For secure IDs, import `react-native-get-random-values` ' +
|
||
'before Nano ID.'
|
||
)
|
||
}
|
||
if (typeof msCrypto !== 'undefined' && typeof crypto === 'undefined') {
|
||
throw new Error(
|
||
'Import file with `if (!window.crypto) window.crypto = window.msCrypto`' +
|
||
' before importing Nano ID to fix IE 11 support'
|
||
)
|
||
}
|
||
if (typeof crypto === 'undefined') {
|
||
throw new Error(
|
||
'Your browser does not have secure random generator. ' +
|
||
'If you don’t need unpredictable IDs, you can use nanoid/non-secure.'
|
||
)
|
||
}
|
||
}
|
||
|
||
let random = bytes => crypto.getRandomValues(new Uint8Array(bytes))
|
||
|
||
let customRandom = (alphabet, size, getRandom) => {
|
||
// First, a bitmask is necessary to generate the ID. The bitmask makes bytes
|
||
// values closer to the alphabet size. The bitmask calculates the closest
|
||
// `2^31 - 1` number, which exceeds the alphabet size.
|
||
// For example, the bitmask for the alphabet size 30 is 31 (00011111).
|
||
// `Math.clz32` is not used, because it is not available in browsers.
|
||
let mask = (2 << (Math.log(alphabet.length - 1) / Math.LN2)) - 1
|
||
// Though, the bitmask solution is not perfect since the bytes exceeding
|
||
// the alphabet size are refused. Therefore, to reliably generate the ID,
|
||
// the random bytes redundancy has to be satisfied.
|
||
|
||
// Note: every hardware random generator call is performance expensive,
|
||
// because the system call for entropy collection takes a lot of time.
|
||
// So, to avoid additional system calls, extra bytes are requested in advance.
|
||
|
||
// Next, a step determines how many random bytes to generate.
|
||
// The number of random bytes gets decided upon the ID size, mask,
|
||
// alphabet size, and magic number 1.6 (using 1.6 peaks at performance
|
||
// according to benchmarks).
|
||
|
||
// `-~f => Math.ceil(f)` if f is a float
|
||
// `-~i => i + 1` if i is an integer
|
||
let step = -~((1.6 * mask * size) / alphabet.length)
|
||
|
||
return () => {
|
||
let id = ''
|
||
while (true) {
|
||
let bytes = getRandom(step)
|
||
// A compact alternative for `for (var i = 0; i < step; i++)`.
|
||
let j = step
|
||
while (j--) {
|
||
// Adding `|| ''` refuses a random byte that exceeds the alphabet size.
|
||
id += alphabet[bytes[j] & mask] || ''
|
||
if (id.length === size) return id
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
let customAlphabet = (alphabet, size) => customRandom(alphabet, size, random)
|
||
|
||
let nanoid = (size = 21) => {
|
||
let id = ''
|
||
let bytes = crypto.getRandomValues(new Uint8Array(size))
|
||
|
||
// A compact alternative for `for (var i = 0; i < step; i++)`.
|
||
while (size--) {
|
||
// It is incorrect to use bytes exceeding the alphabet size.
|
||
// The following mask reduces the random byte in the 0-255 value
|
||
// range to the 0-63 value range. Therefore, adding hacks, such
|
||
// as empty string fallback or magic numbers, is unneccessary because
|
||
// the bitmask trims bytes down to the alphabet size.
|
||
let byte = bytes[size] & 63
|
||
if (byte < 36) {
|
||
// `0-9a-z`
|
||
id += byte.toString(36)
|
||
} else if (byte < 62) {
|
||
// `A-Z`
|
||
id += (byte - 26).toString(36).toUpperCase()
|
||
} else if (byte < 63) {
|
||
id += '_'
|
||
} else {
|
||
id += '-'
|
||
}
|
||
}
|
||
return id
|
||
}
|
||
|
||
export { nanoid, customAlphabet, customRandom, urlAlphabet, random }
|