feat(packages/stdlib): add bit vector tool

packages/stdlib/src/bits/vector/index.test.ts

@@ -0,0 +1,57 @@
+import { describe, it, expect } from 'vitest';
+import { BitVector } from '.';
+
+describe('BitVector', () => {
+  it('should initialize with the correct size', () => {
+    const size = 16;
+    const expectedSize = Math.ceil(size / 8);
+    const bitVector = new BitVector(size);
+
+    expect(bitVector.length).toBe(expectedSize);
+  });
+
+  it('should set and get bits correctly', () => {
+    const bitVector = new BitVector(16);
+    bitVector.setBit(5);
+    
+    expect(bitVector.getBit(5)).toBe(true);
+    expect(bitVector.getBit(4)).toBe(false);
+  });
+
+  it('should clear bits correctly', () => {
+    const bitVector = new BitVector(16);
+    bitVector.setBit(5);
+
+    expect(bitVector.getBit(5)).toBe(true);
+
+    bitVector.clearBit(5);
+
+    expect(bitVector.getBit(5)).toBe(false);
+  });
+
+  it('should find the previous bit correctly', () => {
+    const bitVector = new BitVector(100);
+    const indices = [99, 88, 66, 65, 64, 63, 15, 14, 1, 0];
+    const result = [];
+    indices.forEach(index => bitVector.setBit(index));
+    
+    for (let i = bitVector.previousBit(100); i !== -1; i = bitVector.previousBit(i)) {
+      result.push(i);
+    }
+
+    expect(result).toEqual(indices);
+  });
+
+  it('should return -1 when no previous bit is found', () => {
+    const bitVector = new BitVector(16);
+
+    expect(bitVector.previousBit(0)).toBe(-1);
+  });
+
+  it('should throw RangeError when previousBit is called with an unreachable value', () => {
+    const bitVector = new BitVector(16);
+    bitVector.setBit(5);
+
+    expect(() => bitVector.previousBit(24)).toThrow(new RangeError('Unreachable value'));
+  });
+});

packages/stdlib/src/bits/vector/index.ts

@@ -0,0 +1,61 @@
+export interface BitVector {
+  getBit(index: number): boolean;
+  setBit(index: number): void;
+  clearBit(index: number): void;
+  previousBit(index: number): number;
+}
+
+/**
+ * @name BitVector
+ * @category Bits
+ * @description A bit vector is a vector of bits that can be used to store a collection of bits
+ * 
+ * @since 0.0.3
+ */
+export class BitVector extends Uint8Array implements BitVector {
+  constructor(size: number) {
+    super(Math.ceil(size / 8));
+  }
+
+  getBit(index: number) {
+    const value = this[index >> 3]! & (1 << (index & 7));
+    return value !== 0;
+  }
+
+  setBit(index: number) {
+    this[index >> 3]! |= 1 << (index & 7);
+  }
+
+  clearBit(index: number): void {
+    this[index >> 3]! &= ~(1 << (index & 7));
+  }
+
+  previousBit(index: number): number {
+    while (index !== ((index >> 3) << 3)) {
+      --index;
+
+      if (this.getBit(index)) {
+        return index;
+      }
+    }
+
+    let byteIndex = (index >> 3) - 1;
+
+    while (byteIndex >= 0 && this[byteIndex] === 0)
+      --byteIndex;
+
+    if (byteIndex < 0)
+      return -1;
+
+    index = (byteIndex << 3) + 7;
+
+    while (index >= (byteIndex << 3)) {
+      if (this.getBit(index))
+        return index;
+
+      --index;
+    }
+
+    throw new RangeError('Unreachable value');
+  }
+}