https://github.com/mikolalysenko/bit-twiddle

Bit twidling hacks for node.js
https://github.com/mikolalysenko/bit-twiddle

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Bit twidling hacks for node.js

• Host: GitHub
• URL: https://github.com/mikolalysenko/bit-twiddle
• Owner: mikolalysenko
• License: mit
• Created: 2013-01-15T19:52:52.000Z (almost 12 years ago)
• Default Branch: master
• Last Pushed: 2017-07-05T20:02:11.000Z (over 7 years ago)
• Last Synced: 2024-10-19T00:19:23.487Z (2 months ago)
• Language: JavaScript
• Size: 557 KB
• Stars: 54
• Watchers: 7
• Forks: 5
• Open Issues: 0
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
bit-twiddle

===========

This is a collection of miscellaneous bit twiddling hacks ported to JavaScript, mostly taken from here:

* [Stanford Bit Twiddling Hacks](http://graphics.stanford.edu/~seander/bithacks.html)

[![testling badge](https://ci.testling.com/mikolalysenko/bit-twiddle.png)](https://ci.testling.com/mikolalysenko/bit-twiddle)

[![build status](https://secure.travis-ci.org/mikolalysenko/bit-twiddle.png)](http://travis-ci.org/mikolalysenko/bit-twiddle)

Install

=======

Via npm:

    npm install bit-twiddle

# API

### `sign(v)`

Computes the sign of the integer v.  Returns:

* -1 if v < 0

*  0 if v === 0

* +1 if v > 0

### `abs(v)`

Returns the absolute value of the integer v

### `min(x,y)`

Computes the minimum of integers x and y

### `max(x,y)`

Computes the maximum of integers x and y

### `isPow2(v)`

Returns `true` if v is a power of 2, otherwise false.

### `log2(v)`

Returns an integer approximation of the log-base 2 of v

### `log10(v)`

Returns log base 10 of v.

### `popCount(v)`

Counts the number of bits set in v

###  `countTrailingZeros(v)`

Counts the number of trailing zeros.

### `nextPow2(v)`

Rounds v up to the next power of 2.

### `prevPow2(v)`

Rounds v down to the previous power of 2.

### `parity(v)`

Computes the parity of the bits in v.

### `reverse(v)`

Reverses the bits of v.

### `interleave2(x,y)`

Interleaves a pair of 16 bit integers.  Useful for fast quadtree style indexing.  (See wiki: http://en.wikipedia.org/wiki/Z-order_curve )

### `deinterleave2(v, n)`

Deinterleaves the bits of v, returns the nth part.  If both x and y are 16 bit, then it is true that:

```javascript

deinterleave2(interleave2(x,y), 0) === x

deinterleave2(interleave2(x,y), 1) === y

```

    

### `interleave3(x,y,z)`

Interleaves a triple of 10 bit integers.  Useful for fast octree indexing.

### `deinterleave3(v, n)`

Same deal as `deinterleave2`, only for triples instead of pairs

### `nextCombination(x)`

Returns next combination ordered colexicographically.

Acknowledgements

================

Code is ported from Sean Eron Anderson's public domain bit twiddling hacks page.  http://graphics.stanford.edu/~seander/bithacks.html

JavaScript implementation (c) 2013 Mikola Lysenko.  MIT License