Changeset 0c6b92a for imaps-frontend/node_modules/nanoid/async/index.js

Timestamp:

12/12/24 17:06:06 (5 weeks ago)

Author:

stefan toskovski <stefantoska84@…>

Branches:

main

Parents:

d565449

Message:

Pred finalna verzija

File:

• imaps-frontend/node_modules/nanoid/async/index.js (modified) (2 diffs)

imaps-frontend/node_modules/nanoid/async/index.js

@@ -1 +1 @@
 import crypto from 'crypto'
+
 import { urlAlphabet } from '../url-alphabet/index.js'
+
+// `crypto.randomFill()` is a little faster than `crypto.randomBytes()`,
+// because it is possible to use in combination with `Buffer.allocUnsafe()`.
 let random = bytes =>
   new Promise((resolve, reject) => {
+    // `Buffer.allocUnsafe()` is faster because it doesn’t flush the memory.
+    // Memory flushing is unnecessary since the buffer allocation itself resets
+    // the memory with the new bytes.
     crypto.randomFill(Buffer.allocUnsafe(bytes), (err, buf) => {
       if (err) {
@@ -11 +18 @@
     })
   })
+
 let customAlphabet = (alphabet, defaultSize = 21) => {
+  // 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).
   let mask = (2 << (31 - Math.clz32((alphabet.length - 1) | 1))) - 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).
   let step = Math.ceil((1.6 * mask * defaultSize) / alphabet.length)
+
   let tick = (id, size = defaultSize) =>
     random(step).then(bytes => {
+      // A compact alternative for `for (var i = 0; i < step; i++)`.
       let i = step
       while (i--) {
+        // Adding `|| ''` refuses a random byte that exceeds the alphabet size.
         id += alphabet[bytes[i] & mask] || ''
-        if (id.length === size) return id
+        if (id.length >= size) return id
       }
       return tick(id, size)
     })
+
   return size => tick('', size)
 }
+
 let nanoid = (size = 21) =>
-  random(size).then(bytes => {
+  random((size |= 0)).then(bytes => {
     let id = ''
+    // 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.
       id += urlAlphabet[bytes[size] & 63]
     }
     return id
   })
+
 export { nanoid, customAlphabet, random }