bitfield

A simple bitfield, compliant with the BitTorrent spec.

npm install bitfield

#### Example

``js
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

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- constructor

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- buffer

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- forEach
- get
- set

Constructors

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\+ 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

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• buffer: Uint8Array

The internal storage of the bitfield.

Methods

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▸ 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

---

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▸ 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.

---

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▸ 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

---

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

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

#### Parameters:

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

Returns: void

License

MIT