BitArray

Utility library for dealing with bit / byte arrays and converting between node Buffers and bitarrays.

Usage

var BitArray = require('node-bitarray')

Methods

BitArray

See: BitArray.factory for details on instantiation

BitArray.factory([bits], [length], [asOctet])

Return a new BitArray instance. Added for use in Array.map(), if a buffer is passed in, the asOctet will always be set to true.

• bits - 32bit integer, or buffer/array of 32bit integers (optional)
• length - zero fill the bitarray to the set length
• asOctet - ensure resulting array length is a multiple of 8 (optional, default false)

[255, 128].map(BitArray.factory).map(String) // [ '11111111', '00000001' ]

BitArray.parse([bits], [asOctet])

Convert a 32bit integer into a bit array, the asOctet will always be set to true if a Buffer is passed in.

• bits - 32bit integer, or buffer/array of 32bit integers (optional)
• asOctet - ensure resulting array length is a multiple of 8 (optional, default false)

BitArray.parse(255) // [1, 1, 1, 1, 1, 1, 1, 1]

BitArray.octet(array)

Zero fill an array until it represents an octet

• array - bit array

BitArray.octet([1, 0, 0]) // [1, 0, 0, 0, 0, 0, 0, 0]

BitArray.equals(bitarray, bitarray)

Perform an equality check on two BitArray instances

• bitarray - bit array to compare
• bitarray - bit array to compare

var a = new BitArray('0101')
  , b = new BitArray('0101')
  , c = new BitArray('10')

BitArray.equals(a, b) // true
BitArray.equals(b, c) // false

BitArray.fromBinary(string)

Create a new instance from a binary string

• string - binary string

var bits = BitArray.fromBinary('1001101')
bits.toJSON() // [1, 0, 1, 1, 0, 0, 1]

BitArray.fromOffsets(array)

Create a new instance from a offset positions of set bits

• string - binary string

var bits = BitArray.fromOffsets([0, 4, 2, 9])
bits.toJSON() // [1, 0, 1, 0, 1, 0, 0, 0, 0, 1]

BitArray.fromNumber(number)

Create a new instance from a base 10 number

• number - base 10 number

Aliases: [fromDecimal]

var bits = BitArray.fromNumber(15)
bits.toJSON() // [1, 1, 1, 1]

BitArray.fromHexadecimal(string)

Create a new instance from a hexadecimal string, case insensitive.

• string - hexadecimal string

Aliases: [fromHex]

var bits = BitArray.fromHex('Fa')
bits.toJSON() // [0, 1, 0, 1, 1, 1, 1, 1]

BitArray.from32Integer(number)

Create a new instance from a 32bit integer

• number - 32bit integer

var bits = BitArray.from32Integer(144)
bits.toJSON() // [1, 0, 0, 1, 0, 0, 0, 0]

BitArray.fromBuffer(buffer)

Create a new instance from a node buffer instance

• buffer - node buffer instance

Aliases: [fromRedis]

var buf = new Buffer([128, 144, 255])
  , bits = BitArray.fromBuffer(buf)

bits.toJSON() // [1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1]

BitArray.and(array1, [array2], [...])

Perform a bitwise AND operation on any number of bit arrays

• ... - any number of bit arrays

Alias: [intersect]

BitArray.and(
  [ 1, 0, 0, 1, 0, 0, 0, 1 ]
, [ 1, 0, 0, 0, 1, 0, 0, 1 ]
, [ 0, 1, 0, 0, 0, 1, 0, 1 ]
)
//[ 0, 0, 0, 0, 0, 0, 0, 1 ]

BitArray.toOffsets(array)

Find the offset indexes of all set bits

• array - bit array

BitArray.toOffsets([0, 0, 1, 0, 1]) // [2, 4]
new BitArray(144).toOffsets()       // [0, 3]

BitArray.toBuffer(bits)

BitArray.toNumber(bits)

Convert an array of bits to a base 10 number

Alias: [toDecimal]

BitArray.toNumber([1, 0, 1, 1, 0, 1]) // 45

BitArray.toHexadecimal(bits)

Convert an array of bits to a hex string. Results are lowercased.

Alias: [toHex]

BitArray.toHex([1, 0, 1, 1, 0, 1]) // '2d'

BitArray.or(array1, [array2], [...])

Perform a bitwise OR operation on any number of bit arrays

• ... - any number of bit arrays

Alias: [union]

BitArray.and(
  [ 1, 0, 0, 1, 0, 0, 0, 1 ]
, [ 1, 0, 0, 0, 1, 0, 0, 1 ]
, [ 0, 1, 0, 0, 0, 1, 0, 1 ]
)
//[ 1, 1, 0, 1, 1, 1, 0, 1 ]

BitArray.xor(array1, [array2], [...])

Perform a bitwise XOR operation on any number of bit arrays

• ... - any number of bit arrays

Alias: [difference]

BitArray.xor(
  [ 1, 0, 0, 1, 0, 0, 0, 1 ]
, [ 1, 0, 0, 0, 1, 0, 0, 1 ]
, [ 0, 1, 0, 0, 0, 1, 0, 1 ]
)
//[ 0, 1, 0, 1, 1, 1, 0, 1 ]

BitArray.not(array)

Perform a bitwise NOT operation on a single array

• array - single bit array to flip

Alias: [reverse]

BitArray.not(
  [ 1, 0, 0, 1, 0, 0, 0, 1 ]
)
//[ 0, 1, 1, 0, 1, 1, 1, 0 ]

BitArray.bitcount(32bit)

Find the cardinality of a bit array, 32bit integer, or buffer of 32bit ints

• bits - 32bit integer, buffer of 32bit integers, or bit array

Alias: [count, cardinality, population]

BitArray.cardinality(144)              // 2
BitArray.population(128)               // 1
BitArray.count(new Buffer([255, 128])) // 9
BitArray.bitcount([0,1,1,0,1])         // 3

instance.set(index, value)

Set the value of the bit array at the given index / offset

• index - offset position to set value
• value - bit val (1 / 0)

new BitArray().set(2, 1) // bits: [0, 0, 1]

instance.get(index)

Get the value of the bit array at the given index / offset

• index - offset position to get

new BitArray(144).get(3) // 1

instance.fill(offset)

Zero fill the current bits to the given offset

• offset - zero fill the current bits to the given offset

new BitArray().fill(5) // bits: [0, 0, 0, 0, 0, 0]

instance.bitcount()

Get the bitcount of the current bits

Alias: [count, cardinality, population]

new BitArray(255).cardinality() // 8

instance.toString()

Get the binary representation of the current bits, can also be used in string coercion.

new BitArray(128).toString() // '00000001'
[new BitArray(255)].join('') // '11111111'

instance.valueOf()

Get the base 10 number representing the current bits, can also be used in number coercion.

Alias: [toNumber, toDecimal]

new BitArray(144).valueOf() // 9
1 + new BitArray(255)       // 256

instance.toJSON()

Get a copy of the current bit array

Alias: [toArray, toBits]

new BitArray(128).toJSON() // [1,0,0,0,0,0,0,0]

instance.toBuffer()

Convert the current bit array to a node Buffer

new BitArray(new Buffer([128, 255])).toBuffer() // <Buffer 80 ff>

instance.toOffsets()

Convert the current bit array to an offset array

new BitArray(new Buffer([128, 255])).toOffsets() // [0, 8, 9, 10, 11, 12, 13, 14, 15]

instance.copy()

Create and return a copy of the current BitArray

Aliases: [clone]

var bits = new BitArray(255)
  , bits2 = bits.clone()

BitArray.equals(bits, bits2) // true
bits === bits2               // false

instance.reset()

Reset the current bits, if a length was supplied to the constructor it will be used.

Aliases: [clear]

var bits = new BitArray(144, 16)
bits.toString() // '000000000001001'

instance.equals(bitarray)

Determine if the instance is equal to another instance

• bitarray - instance to compare

var a = new BitArray(1)          // [1]
  , b = new BitArray(2)          // [1, 0]
  , c = new BitArray().set(0, 1) // [1]

a.equals(b) // false
a.equals(c) // true

instance.length

Get the length of the current bit array

new BitArray().length           // 0
new BitArray([128, 255]).length // 16

Install

With npm

npm install node-bitarray

License

(The MIT License)

Copyright (c) 2013 Beau Sorensen [email protected]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the 'Software'), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.