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

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/index.cjs (modified) (3 diffs)

imaps-frontend/node_modules/nanoid/index.cjs

@@ -1 +1 @@
 let crypto = require('crypto')
+
 let { urlAlphabet } = require('./url-alphabet/index.cjs')
+
+// It is best to make fewer, larger requests to the crypto module to
+// avoid system call overhead. So, random numbers are generated in a
+// pool. The pool is a Buffer that is larger than the initial random
+// request size by this multiplier. The pool is enlarged if subsequent
+// requests exceed the maximum buffer size.
 const POOL_SIZE_MULTIPLIER = 128
 let pool, poolOffset
+
 let fillPool = bytes => {
   if (!pool || pool.length < bytes) {
@@ -14 +22 @@
   poolOffset += bytes
 }
+
 let random = bytes => {
-  fillPool((bytes -= 0))
+  // `|=` convert `bytes` to number to prevent `valueOf` abusing and pool pollution
+  fillPool((bytes |= 0))
   return pool.subarray(poolOffset - bytes, poolOffset)
 }
+
 let customRandom = (alphabet, defaultSize, 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).
   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)
+
   return (size = defaultSize) => {
     let id = ''
     while (true) {
       let bytes = getRandom(step)
+      // A compact alternative for `for (let 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
@@ -33 +63 @@
   }
 }
+
 let customAlphabet = (alphabet, size = 21) =>
   customRandom(alphabet, size, random)
+
 let nanoid = (size = 21) => {
-  fillPool((size -= 0))
+  // `|=` convert `size` to number to prevent `valueOf` abusing and pool pollution
+  fillPool((size |= 0))
   let id = ''
+  // We are reading directly from the random pool to avoid creating new array
   for (let i = poolOffset - size; i < poolOffset; i++) {
+    // 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[pool[i] & 63]
   }
   return id
 }
+
 module.exports = { nanoid, customAlphabet, customRandom, urlAlphabet, random }