| 1 | import pako from "pako"; |
| 2 | |
| 3 | /** zlib-deflate (RFC 1950), the format git uses for loose objects and pack entries. */ |
| 4 | export function deflate(data: Uint8Array): Uint8Array { |
| 5 | return pako.deflate(data); |
| 6 | } |
| 7 | |
| 8 | export function inflate(data: Uint8Array): Uint8Array { |
| 9 | return pako.inflate(data); |
| 10 | } |
| 11 | |
| 12 | /** |
| 13 | * Inflate one zlib stream that starts at `offset` inside `data`, and report how |
| 14 | * many input bytes it consumed. Pack files concatenate zlib streams without |
| 15 | * lengths, so the consumed count is how we find the next entry. |
| 16 | */ |
| 17 | export function inflateAt(data: Uint8Array, offset: number, expectedSize?: number): { out: Uint8Array; consumed: number } { |
| 18 | const inflator = new pako.Inflate() as pako.Inflate & { ended: boolean }; |
| 19 | if (expectedSize !== undefined) { |
| 20 | // Stop as soon as the output passes the size the pack declared, so a small zlib stream |
| 21 | // can't be made to inflate to gigabytes. |
| 22 | const keep = inflator.onData.bind(inflator); |
| 23 | let produced = 0; |
| 24 | inflator.onData = (chunk) => { |
| 25 | produced += (chunk as Uint8Array).length; |
| 26 | if (produced > expectedSize) throw new Error(`object at ${offset} is larger than its declared size (${expectedSize} bytes)`); |
| 27 | keep(chunk); |
| 28 | }; |
| 29 | } |
| 30 | // Feed in bounded windows so a huge trailing buffer is not copied repeatedly. |
| 31 | const window = Math.max(64 * 1024, expectedSize ? expectedSize + 1024 : 0); |
| 32 | let pos = offset; |
| 33 | while (!inflator.ended && pos < data.length) { |
| 34 | const end = Math.min(data.length, pos + window); |
| 35 | inflator.push(data.subarray(pos, end), false); |
| 36 | if (inflator.err) throw new Error(`zlib error at ${offset}: ${inflator.msg}`); |
| 37 | pos = end; |
| 38 | } |
| 39 | if (!inflator.ended) throw new Error(`truncated zlib stream at offset ${offset}`); |
| 40 | const strm = (inflator as unknown as { strm: { avail_in: number } }).strm; |
| 41 | const consumed = pos - offset - strm.avail_in; |
| 42 | const out = inflator.result as Uint8Array; |
| 43 | return { out: out ?? new Uint8Array(0), consumed }; |
| 44 | } |