tjkoury / bitfield

A bitfield implementation using buffers, compliant with the BitTorrent spec.

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

• constructor

Properties

• buffer

Methods

• forEach
• get
• set

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