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bitfield

A simple bitfield, compliant with the BitTorrent spec.

npm install bitfield

Example

import Bitfield from "bitfield";

const field = new Bitfield(256); // Create a bitfield with 256 bits.

field.set(128); // Set the 128th bit.
field.set(128, true); // Same as above.

field.get(128); // `true`
field.get(200); // `false` (all values are initialised to `false`)
field.get(1e3); // `false` (out-of-bounds is also false)

field.set(128, false); // Set the 128th bit to 0 again.

field.buffer; // The buffer used by the bitfield.

Class: BitField

Constructors

Properties

Methods

Constructors

constructor

+ new BitField(data?: number | Uint8Array, opts?: BitFieldOptions): BitField

Parameters:

Name Type Default value Description
data number | Uint8Array 0 Either a number representing the maximum number of supported bytes, or a Uint8Array.
opts? { grow: number } { grow: 0 }

grow:

If you set an index that is out-of-bounds, the bitfield will automatically grow so that the bitfield is big enough to contain the given index, up to the given size (in bit).

If you want the Bitfield to grow indefinitely, pass Infinity.

Returns: BitField

Properties

buffer

• buffer: Uint8Array

The internal storage of the bitfield.

Methods

forEach

▸ forEach(fn: (bit: boolean, index: number) => void, start?: number, end?: number): void

Loop through the bits in the bitfield.

Parameters:

Name Type Default value Description
fn (bit: boolean, index: number) => void - Function to be called with the bit value and index.
start number 0 Index of the first bit to look at.
end number this.buffer.length * 8 Index of the first bit that should no longer be considered.

Returns: void

get

▸ get(i: number): boolean

Get a particular bit.

Parameters:

Name Type Description
i number Bit index to retrieve.

Returns: boolean

A boolean indicating whether the ith bit is set.

set

▸ set(i: number, value?: boolean): void

Set a particular bit.

Will grow the underlying array if the bit is out of bounds and the grow option is set.

Parameters:

Name Type Default value Description
i number - Bit index to set.
value boolean true Value to set the bit to. Defaults to true.

Returns: void

setAll

▸ setAll(array: ArrayLike<boolean>, offset?: number): void

Set the bits in the bitfield to the values in the given array.

Parameters:

Name Type Default value Description
array ArrayLike<boolean> - Array of booleans to set the bits to.
offset number 0 Index of the first bit to set.

Returns: void

License

MIT