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