86 lines · 2.7 KB
| 1 | import { describe, it, expect } from 'vitest'; |
| 2 | import { applyDelta, readOfsOffset } from '../delta.js'; |
| 3 | |
| 4 | const encoder = new TextEncoder(); |
| 5 | |
| 6 | describe('applyDelta', () => { |
| 7 | it('should apply an insert-only delta', () => { |
| 8 | const base = encoder.encode('hello'); |
| 9 | // Delta: source size 5, target size 11, insert "hello world" |
| 10 | const delta = new Uint8Array([ |
| 11 | 5, // source size: 5 |
| 12 | 11, // target size: 11 |
| 13 | 11, // insert 11 bytes |
| 14 | ...encoder.encode('hello world'), |
| 15 | ]); |
| 16 | |
| 17 | const result = applyDelta(base, delta); |
| 18 | expect(new TextDecoder().decode(result)).toBe('hello world'); |
| 19 | }); |
| 20 | |
| 21 | it('should apply a copy-only delta', () => { |
| 22 | const base = encoder.encode('hello world'); |
| 23 | // Delta: source size 11, target size 5, copy 5 bytes from offset 0 |
| 24 | const delta = new Uint8Array([ |
| 25 | 11, // source size: 11 |
| 26 | 5, // target size: 5 |
| 27 | 0x80 | 0x01 | 0x10, // copy: offset byte + size byte present |
| 28 | 0, // offset: 0 |
| 29 | 5, // size: 5 |
| 30 | ]); |
| 31 | |
| 32 | const result = applyDelta(base, delta); |
| 33 | expect(new TextDecoder().decode(result)).toBe('hello'); |
| 34 | }); |
| 35 | |
| 36 | it('should apply a mixed copy+insert delta', () => { |
| 37 | const base = encoder.encode('hello world'); |
| 38 | // Copy "hello" (5 bytes from offset 0), then insert " there" |
| 39 | const delta = new Uint8Array([ |
| 40 | 11, // source size: 11 |
| 41 | 11, // target size: 11 ("hello there") |
| 42 | // Copy instruction: offset=0, size=5 |
| 43 | 0x80 | 0x01 | 0x10, |
| 44 | 0, // offset: 0 |
| 45 | 5, // size: 5 |
| 46 | // Insert instruction: 6 bytes " there" |
| 47 | 6, |
| 48 | ...encoder.encode(' there'), |
| 49 | ]); |
| 50 | |
| 51 | const result = applyDelta(base, delta); |
| 52 | expect(new TextDecoder().decode(result)).toBe('hello there'); |
| 53 | }); |
| 54 | |
| 55 | it('should throw on source size mismatch', () => { |
| 56 | const base = encoder.encode('hi'); |
| 57 | const delta = new Uint8Array([ |
| 58 | 10, // says source is 10 bytes |
| 59 | 5, |
| 60 | 5, |
| 61 | ...encoder.encode('hello'), |
| 62 | ]); |
| 63 | |
| 64 | expect(() => applyDelta(base, delta)).toThrow('source size mismatch'); |
| 65 | }); |
| 66 | }); |
| 67 | |
| 68 | describe('readOfsOffset', () => { |
| 69 | it('should read a single-byte offset', () => { |
| 70 | const buf = new Uint8Array([42]); |
| 71 | const { value, bytesRead } = readOfsOffset(buf, 0); |
| 72 | expect(value).toBe(42); |
| 73 | expect(bytesRead).toBe(1); |
| 74 | }); |
| 75 | |
| 76 | it('should read a multi-byte offset', () => { |
| 77 | // First byte: 0x80 | 0x01 = 129 (continuation bit set, value = 1) |
| 78 | // Second byte: 0x00 (value = 0) |
| 79 | // Decoded: ((1 + 1) << 7) | 0 = 256 |
| 80 | const buf = new Uint8Array([0x81, 0x00]); |
| 81 | const { value, bytesRead } = readOfsOffset(buf, 0); |
| 82 | expect(value).toBe(256); |
| 83 | expect(bytesRead).toBe(2); |
| 84 | }); |
| 85 | }); |
| 86 |