fast-bitset

fast-bitset

A fast bitset with some nice methods.

##Features

• Outperforms all other bitset packages in terms of speed and space
• All bit operations execute in O(1) time (does not iterate through bits)
• Useful methods for graph algorithms
• Any array that stores booleans can safely be replaced by a bitset for improved speed
• Uses 64x less space than a nontyped array

##Installation npm install fast-bitset --save

##License MIT

##API

• BitSet
  • new BitSet(nBitsOrKey)
  • .get(idx) ⇒ boolean
  • .set(idx) ⇒ boolean
  • .setRange(from, to) ⇒ boolean
  • .unset(idx) ⇒ boolean
  • .unsetRange(from, to) ⇒ boolean
  • .toggle(idx) ⇒ boolean
  • .toggleRange(from, to) ⇒ boolean
  • .clear() ⇒ boolean
  • .clone() ⇒ BitSet
  • .dehydrate() ⇒ string
  • .and(bsOrIdx) ⇒ BitSet
  • .or(bsOrIdx) ⇒ BitSet
  • .xor(bsOrIdx) ⇒ BitSet
  • .forEach(func)
  • .getCardinality() ⇒ number
  • .getIndices() ⇒ Array
  • .isSubsetOf(bitset) ⇒ Boolean
  • .isEmpty() ⇒ boolean
  • .isEqual(bs) ⇒ boolean
  • .toString() ⇒ string
  • .ffs(_startWord) ⇒ number
  • .ffz(_startWord) ⇒ number
  • .fls(_startWord) ⇒ number
  • .flz(_startWord) ⇒ number
  • .nextSetBit(idx) ⇒ number
  • .nextUnsetBit(idx) ⇒ number
  • .previousSetBit(idx) ⇒ number
  • .previousUnsetBit(idx) ⇒ number

new BitSet(nBitsOrKey)

Create a new bitset. Accepts either the maximum number of bits, or a dehydrated bitset

Param	Type	Description
nBitsOrKey	number | string	Number of bits in the set or dehydrated bitset. For speed and space concerns, the initial number of bits cannot be increased.

bitSet.get(idx) ⇒ boolean

Check whether a bit at a specific index is set

Kind: instance method of BitSet
Returns: boolean - true if bit is set, else false

Param	Type	Description
idx	number	the position of a single bit to check

bitSet.set(idx) ⇒ boolean

Set a single bit

Kind: instance method of BitSet
Returns: boolean - true if set was successful, else false

Param	Type	Description
idx	number	the position of a single bit to set

bitSet.setRange(from, to) ⇒ boolean

Set a range of bits

Kind: instance method of BitSet
Returns: boolean - true if set was successful, else false

Param	Type	Description
from	number	the starting index of the range to set
to	number	the ending index of the range to set

bitSet.unset(idx) ⇒ boolean

Unset a single bit

Kind: instance method of BitSet
Returns: boolean - true if set was successful, else false

Param	Type	Description
idx	number	the position of a single bit to unset

bitSet.unsetRange(from, to) ⇒ boolean

Unset a range of bits

Kind: instance method of BitSet
Returns: boolean - true if set was successful, else false

Param	Type	Description
from	number	the starting index of the range to unset
to	number	the ending index of the range to unset

bitSet.toggle(idx) ⇒ boolean

Toggle a single bit

Kind: instance method of BitSet
Returns: boolean - true if set was successful, else false

Param	Type	Description
idx	number	the position of a single bit to toggle

bitSet.toggleRange(from, to) ⇒ boolean

Toggle a range of bits

Kind: instance method of BitSet
Returns: boolean - true if set was successful, else false

Param	Type	Description
from	number	the starting index of the range to toggle
to	number	the ending index of the range to toggle

bitSet.clear() ⇒ boolean

Clear an entire bitset

Kind: instance method of BitSet
Returns: boolean - true

bitSet.clone() ⇒ BitSet

Clone a bitset

Kind: instance method of BitSet
Returns: BitSet - an copy (by value) of the calling bitset

bitSet.dehydrate() ⇒ string

Turn the bitset into a comma separated string that skips leading & trailing 0 words. Ends with the number of leading 0s and MAX_BIT. Useful if you need the bitset to be an object key (eg dynamic programming). Can rehydrate by passing the result into the constructor

Kind: instance method of BitSet
Returns: string - representation of the bitset

bitSet.and(bsOrIdx) ⇒ BitSet

Perform a bitwise AND on 2 bitsets or 1 bitset and 1 index. Both bitsets must have the same number of words, no length check is performed to prevent and overflow.

Kind: instance method of BitSet
Returns: BitSet - a new bitset that is the bitwise AND of the two

Param	Type	Description
bsOrIdx	BitSet | Number	a bitset or single index to check (useful for LP, DP problems)

bitSet.or(bsOrIdx) ⇒ BitSet

Perform a bitwise OR on 2 bitsets or 1 bitset and 1 index. Both bitsets must have the same number of words, no length check is performed to prevent and overflow.

Kind: instance method of BitSet
Returns: BitSet - a new bitset that is the bitwise OR of the two

Param	Type	Description
bsOrIdx	BitSet | Number	a bitset or single index to check (useful for LP, DP problems)

bitSet.xor(bsOrIdx) ⇒ BitSet

Perform a bitwise XOR on 2 bitsets or 1 bitset and 1 index. Both bitsets must have the same number of words, no length check is performed to prevent and overflow.

Kind: instance method of BitSet
Returns: BitSet - a new bitset that is the bitwise XOR of the two

Param	Type	Description
bsOrIdx	BitSet | Number	a bitset or single index to check (useful for LP, DP problems)

bitSet.forEach(func)

Run a custom function on every set bit. Faster than iterating over the entire bitset with a get() Source code includes a nice pattern to follow if you need to break the for-loop early

Kind: instance method of BitSet

Param	Type	Description
func	function	the function to pass the next set bit to

bitSet.getCardinality() ⇒ number

Get the cardinality (count of set bits) for the entire bitset

Kind: instance method of BitSet
Returns: number - cardinality

bitSet.getIndices() ⇒ Array

Get the indices of all set bits. Useful for debugging, uses forEach internally

Kind: instance method of BitSet
Returns: Array - Indices of all set bits

bitSet.isSubsetOf(bs) ⇒ Boolean

Checks if one bitset is subset of another. Same thing can be done using and operation and equality check, but then new BitSet would be created, and if one is only interested in yes/no information it would be a waste of memory and additional GC strain.

Kind: instance method of BitSet
Returns: Boolean - true if provided bitset is a subset of this bitset, false otherwise

Param	Type	Description
bs	BitSet	a bitset to check

bitSet.isEmpty() ⇒ boolean

Quickly determine if a bitset is empty

Kind: instance method of BitSet
Returns: boolean - true if the entire bitset is empty, else false

bitSet.isEqual(bs) ⇒ boolean

Quickly determine if both bitsets are equal (faster than checking if the XOR of the two is === 0). Both bitsets must have the same number of words, no length check is performed to prevent and overflow.

Kind: instance method of BitSet
Returns: boolean - true if the entire bitset is empty, else false

Param	Type
bs	BitSet

bitSet.toString() ⇒ string

Get a string representation of the entire bitset, including leading 0s (useful for debugging)

Kind: instance method of BitSet
Returns: string - a base 2 representation of the entire bitset

bitSet.ffs(_startWord) ⇒ number

Find first set bit (useful for processing queues, breadth-first tree searches, etc.)

Kind: instance method of BitSet
Returns: number - the index of the first set bit in the bitset, or -1 if not found

Param	Type	Description
_startWord	number	the word to start with (only used internally by nextSetBit)

bitSet.ffz(_startWord) ⇒ number

Find first zero (unset bit)

Kind: instance method of BitSet
Returns: number - the index of the first unset bit in the bitset, or -1 if not found

Param	Type	Description
_startWord	number	the word to start with (only used internally by nextUnsetBit)

bitSet.fls(_startWord) ⇒ number

Find last set bit

Kind: instance method of BitSet
Returns: number - the index of the last set bit in the bitset, or -1 if not found

Param	Type	Description
_startWord	number	the word to start with (only used internally by previousSetBit)

bitSet.flz(_startWord) ⇒ number

Find last zero (unset bit)

Kind: instance method of BitSet
Returns: number - the index of the last unset bit in the bitset, or -1 if not found

Param	Type	Description
_startWord	number	the word to start with (only used internally by previousUnsetBit)

bitSet.nextSetBit(idx) ⇒ number

Find first set bit, starting at a given index

Kind: instance method of BitSet
Returns: number - the index of the next set bit >= idx, or -1 if not found

Param	Type	Description
idx	number	the starting index for the next set bit

bitSet.nextUnsetBit(idx) ⇒ number

Find first unset bit, starting at a given index

Kind: instance method of BitSet
Returns: number - the index of the next unset bit >= idx, or -1 if not found

Param	Type	Description
idx	number	the starting index for the next unset bit

bitSet.previousSetBit(idx) ⇒ number

Find last set bit, up to a given index

Kind: instance method of BitSet
Returns: number - the index of the next unset bit <= idx, or -1 if not found

Param	Type	Description
idx	number	the starting index for the next unset bit (going in reverse)

bitSet.previousUnsetBit(idx) ⇒ number

Find last unset bit, up to a given index

Kind: instance method of BitSet
Returns: number - the index of the next unset bit <= idx, or -1 if not found

Param	Type	Description
idx	number	the starting index for the next unset bit (going in reverse)