bit-twiddle

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

Stanford Bit Twiddling Hacks

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:

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.

bit-twiddle

bit-twiddle

Install

API

`sign(v)`

`abs(v)`

`min(x,y)`

`max(x,y)`

`isPow2(v)`

`log2(v)`

`log10(v)`

`popCount(v)`

`countTrailingZeros(v)`

`nextPow2(v)`

`prevPow2(v)`

`parity(v)`

`reverse(v)`

`interleave2(x,y)`

`deinterleave2(v, n)`

`interleave3(x,y,z)`

`deinterleave3(v, n)`

`nextCombination(x)`

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Dependencies

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