remove if the if condition by assigning function statically

[KrishnaPG]

The crypto availability is being checked every time randomBytes method is called here

This if else condition checking can be done just once at the beginning, and assign the correct function to a variable, something like below:

const randomBytes = (typeof crypto !== 'undefined') ? randomCrypto : randomMath;

let bufIdx = uuid.BUFFER_SIZE;
function randomCrypto(n) {
      if ((++bufIdx + n) > uuid.BUFFER_SIZE) {
        bufIdx = 0;
        if (crypto.getRandomValues) {
          buf = new Uint8Array(uuid.BUFFER_SIZE);
          crypto.getRandomValues(bytes);
        } else if (crypto.randomBytes) {
          buf = crypto.randomBytes(uuid.BUFFER_SIZE);
        } else {
          throw new Error('Non-standard crypto library');
        }
      }
      return buf.slice(bufIdx, bufIdx + n);
}
function randomMath(n) { 
      r = [];
      for (i = 0; i < n; i++) {
        r.push(getRandomInt(0, 255));
      }
      return r;
}

This further improves the performance.

[jchook]

Hey thanks very much for your thoughtful suggestion.

I tried the changes and didn't see any material performance gains. However, in testing, I did find a bug! So ultimately I think it was a big win.

[KrishnaPG]

The performance gains will not be visible at the code level. They will be at the energy consumption level of the underlying CPUs, as the if-else branching logic affects the Processor cache pipeline, especially when the processors have branch-prediction logic built-in. If you want to measure the performance at the code level, then try with RDTSC performance counters.

[jchook]

Interesting.

What do you think of this PR? #6

[KrishnaPG]

Looks fine to me, except for one small thing:

At Line 76, the else condition for randomBytesMath may need to be outside the if (typeof crypto !== 'undefined'), since it should get executed even when crypto === undefined. Currently it looks like it will not run if crypto is undefined.

[KrishnaPG]

Also, It would be great if nacl is supported, if possible.
Ref: Best Practices of Security

TweetNACL

nacl.randomBytes internally picks up the right method based on the current platform.

[jchook]

I got around to implementing this performance fix in #11 and also exposed uuid.randomBytes() so you can override it with TweetNACL. Thanks again for the great suggestions.