Changeset 0c6b92a for imaps-frontend/node_modules/nanoid/async/index.browser.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/async/index.browser.cjs (modified) (3 diffs)

imaps-frontend/node_modules/nanoid/async/index.browser.cjs

@@ -1 +1 @@
 let random = async bytes => crypto.getRandomValues(new Uint8Array(bytes))
+
 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).
+  // `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 * defaultSize) / alphabet.length)
+
   return async (size = defaultSize) => {
     let id = ''
     while (true) {
       let bytes = crypto.getRandomValues(new Uint8Array(step))
-      let i = step
+      // A compact alternative for `for (var i = 0; i < step; i++)`.
+      let i = step | 0
       while (i--) {
+        // Adding `|| ''` refuses a random byte that exceeds the alphabet size.
         id += alphabet[bytes[i] & mask] || ''
         if (id.length === size) return id
@@ -15 +39 @@
   }
 }
+
 let nanoid = async (size = 21) => {
   let id = ''
-  let bytes = crypto.getRandomValues(new Uint8Array(size))
+  let bytes = crypto.getRandomValues(new Uint8Array((size |= 0)))
+
+  // 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) {
@@ -32 +66 @@
   return id
 }
+
 module.exports = { nanoid, customAlphabet, random }