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fix: bitstring improvement and test coverage (#270)
Signed-off-by: Francisco Javier Ribo Labrador <elribonazo@gmail.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,56 +1,87 @@ | ||
| import { base64url } from 'multiformats/bases/base64'; | ||
| import { gzip, ungzip } from 'pako'; | ||
|
|
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| export class Bitstring { | ||
| bits: Uint8Array; | ||
| length: number; | ||
| leftToRightIndexing: boolean; | ||
|
|
||
| constructor({ | ||
| buffer, | ||
| leftToRightIndexing | ||
| }: { | ||
| buffer: Uint8Array; | ||
| public bits: Uint8Array; | ||
| public length: number; | ||
| private leftToRightIndexing: boolean; | ||
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| constructor(options: { | ||
| length?: number; | ||
| buffer?: Uint8Array; | ||
| leftToRightIndexing?: boolean; | ||
| }) { | ||
| if (!buffer) { | ||
| littleEndianBits?: boolean; | ||
| } = {}) { | ||
| const { length, buffer, leftToRightIndexing, littleEndianBits } = options; | ||
|
|
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| if (length && buffer) { | ||
| throw new Error('Only one of "length" or "buffer" must be given.'); | ||
| } | ||
| this.bits = new Uint8Array(buffer.buffer); | ||
| this.length = buffer.length * 8; | ||
| this.leftToRightIndexing = leftToRightIndexing ?? false; | ||
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| if (littleEndianBits !== undefined) { | ||
| if (leftToRightIndexing !== undefined) { | ||
| throw new Error( | ||
| 'Using both "littleEndianBits" and "leftToRightIndexing" is not allowed.' | ||
| ); | ||
| } | ||
| this.leftToRightIndexing = littleEndianBits; | ||
| } else { | ||
| this.leftToRightIndexing = leftToRightIndexing ?? true; | ||
| } | ||
|
|
||
| if (length) { | ||
| this.bits = new Uint8Array(Math.ceil(length / 8)); | ||
| this.length = length; | ||
| } else if (buffer) { | ||
| this.bits = new Uint8Array(buffer.buffer); | ||
| this.length = buffer.length * 8; | ||
| } else { | ||
| throw new Error('Either "length" or "buffer" must be provided.'); | ||
| } | ||
| } | ||
|
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| set(position: number, on: boolean): void { | ||
| const { length, leftToRightIndexing } = this; | ||
| const { index, bit } = _parsePosition(position, length, leftToRightIndexing); | ||
| const { index, bit } = this.parsePosition(position); | ||
| if (on) { | ||
| this.bits[index] |= bit; | ||
| } else { | ||
| this.bits[index] &= 0xff ^ bit; | ||
| this.bits[index] &= 0xFF ^ bit; | ||
| } | ||
| } | ||
|
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| get(position: number): boolean { | ||
| const { length, leftToRightIndexing } = this; | ||
| const { index, bit } = _parsePosition(position, length, leftToRightIndexing); | ||
| const { index, bit } = this.parsePosition(position); | ||
| return !!(this.bits[index] & bit); | ||
| } | ||
|
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| async encodeBits(): Promise<string> { | ||
| return base64url.baseEncode(gzip(this.bits)); | ||
| } | ||
|
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| static async decodeBits(encoded: string): Promise<Uint8Array> { | ||
| return ungzip(base64url.baseDecode(encoded)); | ||
| } | ||
|
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| async compressBits(): Promise<Uint8Array> { | ||
| return gzip(this.bits); | ||
| } | ||
|
|
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| static async uncompressBits(compressed: Uint8Array): Promise<Uint8Array> { | ||
| return ungzip(compressed); | ||
| } | ||
|
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| private parsePosition(position: number): { index: number; bit: number } { | ||
| if (position < 0 || position >= this.length) { | ||
| throw new Error( | ||
| `Position "${position}" is out of range "0-${this.length - 1}".` | ||
| ); | ||
| } | ||
|
|
||
| } | ||
| const index = Math.floor(position / 8); | ||
| const rem = position % 8; | ||
| const shift = this.leftToRightIndexing ? 7 - rem : rem; | ||
| const bit = 1 << shift; | ||
|
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||
| function _parsePosition( | ||
| position: number, | ||
| length: number, | ||
| leftToRightIndexing: boolean | ||
| ): { index: number; bit: number } { | ||
| if (position >= length) { | ||
| throw new Error( | ||
| `Position "${position}" is out of range "0-${length - 1}".` | ||
| ); | ||
| return { index, bit }; | ||
| } | ||
| const index = Math.floor(position / 8); | ||
| const rem = position % 8; | ||
| const shift = leftToRightIndexing ? 7 - rem : rem; | ||
| const bit = 1 << shift; | ||
| return { index, bit }; | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,67 @@ | ||
| import { expect } from 'chai'; | ||
| import { Bitstring } from '../../src/pollux/utils/Bitstring'; | ||
|
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| describe('Bitstring', () => { | ||
| describe('constructor', () => { | ||
| it('should create a Bitstring with all indexes false for [0, 0]', () => { | ||
| const buffer = new Uint8Array([0, 0]); | ||
| const bitstring = new Bitstring({ buffer }); | ||
| for (let i = 0; i < 16; i++) { | ||
| expect(bitstring.get(i)).to.be.false; | ||
| } | ||
| }); | ||
|
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| it('should create a Bitstring with indexes 0, 14, 15 true for [128,3]', () => { | ||
| const buffer = Uint8Array.from([128, 3]); | ||
| const bitstring = new Bitstring({ buffer }); | ||
| const validIndexes = [0, 14, 15]; | ||
| for (let i = 0; i < 16; i++) { | ||
| const bitstringIndex = bitstring.get(i); | ||
| if (validIndexes.includes(i)) { | ||
| console.log("Index should be true ", i) | ||
| expect(bitstringIndex).to.be.true; | ||
| } else { | ||
| console.log("Index should be false ", i) | ||
| expect(bitstringIndex).to.be.false; | ||
| } | ||
| } | ||
| }); | ||
|
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| it('should create a Bitstring with indexes 6 true for [2,0]', () => { | ||
| const buffer = Uint8Array.from([2, 0]); | ||
| const bitstring = new Bitstring({ buffer }); | ||
| const validIndexes = [6]; | ||
| for (let i = 0; i < 16; i++) { | ||
| const bitstringIndex = bitstring.get(i); | ||
| if (validIndexes.includes(i)) { | ||
| console.log("Index should be true ", i) | ||
| expect(bitstringIndex).to.be.true; | ||
| } else { | ||
| console.log("Index should be false ", i) | ||
| expect(bitstringIndex).to.be.false; | ||
| } | ||
| } | ||
| }); | ||
|
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| it('should set a bit to true on default instance', async () => { | ||
| const buffer = Uint8Array.from([0b00000000]); | ||
| const bitstring = new Bitstring({ buffer }); | ||
| bitstring.set(4, true); | ||
| expect(bitstring.get(0)).to.equal(false); | ||
| expect(bitstring.get(1)).to.equal(false); | ||
| expect(bitstring.get(2)).to.equal(false); | ||
| expect(bitstring.get(3)).to.equal(false); | ||
| expect(bitstring.get(4)).to.equal(true); | ||
| expect(bitstring.get(5)).to.equal(false); | ||
| expect(bitstring.get(6)).to.equal(false); | ||
| expect(bitstring.get(7)).to.equal(false); | ||
| expect(bitstring.bits).to.have.length(1); | ||
| expect(bitstring.length).to.equal(8); | ||
| // left-to-right bit order | ||
| expect(bitstring.bits[0]).to.equal(0b00001000); | ||
| }); | ||
|
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| }); | ||
|
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|
|
||
| }); |
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