Repository files navigation

BitSet.js is an infiniteBit-Array (aka bit vector, bit string, bit set) implementation in JavaScript. Infinite means that if you invert a bit vector, the leading ones get remembered. As far as I can tell, BitSet.js is the only library which has this feature. It is also heavily benchmarked against other implementations and is the most performant implementation to date.

letbs=newBitSet;bs.set(128,1);// Set bit at position 128console.log(bs.toString(16));// Print out a hex dump with one bit set

letbs=newBitSet;bs.flip(0,62).flip(29,35);letstr=bs.toString();if(str==="111111111111111111111111111000000011111111111111111111111111111"){console.log("YES!");}

letbs=newBitSet;bs.setRange(10,18,1);// Set a 1 between 10 and 18, inclusive

If you want to store user permissions in your database and use BitSet for the bit twiddling, you can start with the following Linux-style snippet:

letP_READ=2;// Bit posletP_WRITE=1;letP_EXEC=0;letuser=newBitSet;user.set(P_READ);// Give read permsuser.set(P_WRITE);// Give write permsletgroup=newBitSet(P_READ);letworld=newBitSet(P_EXEC);console.log("0"+user.toString(8)+group.toString(8)+world.toString(8));

npm install bitset

<scriptsrc="bitset.js"></script><script>console.log(BitSet("111"));</script>

<scriptsrc="require.js"></script><script>requirejs(['bitset.js'],function(BitSet){console.log(BitSet("1111"));});</script>

The defaultBitSet constructor accepts a single value of one the following types :

• String
  • Binary strings :new BitSet("010101")
  • Binary strings with prefix :new BitSet("0b010101")
  • Hexadecimal strings with prefixnew BitSet("0xaffe")
• Array
  • The values of the array are the indices to be set to 1 :new BitSet([1,12,9])
• Uint8Array
  • A binary representation in 8 bit form
• Number
  • A binary value
• BitSet
  • A BitSet object, which get copied over

The data type Mixed can be either a BitSet object, a String or an integer representing a native bitset with 31 bits.

Mutable; Sets value 0 or 1 to indexndx of the bitset

Gets the value at index ndx

Mutable; Helper function for set, to set an entire range to a given value

Mutable; Sets a portion of a given bitset to zero

• If no param is given, the whole bitset gets cleared
• If one param is given, the bit at this index gets cleared
• If two params are given, the range is cleared

Immutable; Extracts a portion of a given bitset as a new bitset

• If no param is given, the bitset is getting cloned
• If one param is given, the index is used as offset
• If two params are given, the range is returned as new BitSet

Mutable; Toggles a portion of a given bitset

• If no param is given, the bitset is inverted
• If one param is given, the bit at the index is toggled
• If two params are given, the bits in the given range are toggled

Immutable; Calculates the bitwise complement

Immutable; Calculates the bitwise intersection of two bitsets

Immutable; Calculates the bitwise union of two bitsets

Immutable; Calculates the bitwise xor between two bitsets

Immutable; Calculates the bitwise difference of two bitsets (this is not the nand operation!)

Immutable; Clones the actual object

Returns an array with all indexes set in the bitset

Returns a string representation with respect to the base

Calculates the number of bits set

Calculates the most significant bit (the left most)

Calculates the number of trailing zeros (zeros on the right). If all digits are zero,Infinity is returned, since BitSet.js is an arbitrary large bit vector implementation.

Calculates the least significant bit (the right most)

Checks if the bitset has all bits set to zero

Checks if two bitsets are the same

Alternative constructor to pass with a binary string

Alternative constructor to pass a hex string

Create a random BitSet with a maximum length of n bits

ABitSet object is iterable. The iterator gets all bits up to the most significant bit. If no bits are set, the iteration stops immediately.

letbs=BitSet.Random(55);for(letbofbs){console.log(b);}

Note: If the bitset is inverted so that all leading bits are 1, the iterator must be stopped by the user!

As every library I publish, BitSet.js is also built to be as small as possible after compressing it with Google Closure Compiler in advanced mode. Thus the coding style orientates a little on maxing-out the compression rate. Please make sure you keep this style if you plan to extend the library.

After cloning the Git repository run:

npm installnpm run build

Testing the source against the shipped test suite is as easy as

npm run test

Copyright (c) 2024,Robert EiseleLicensed under the MIT license.