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MIRROR: javascript for 🐜's, a tiny runtime with big ambitions ant.themackabu.dev
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123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687import { HttpError } from './errors';
export async function readZipText(zip: ArrayBuffer, wantedName: string): Promise<string> { const fileBytes = await readZipEntry(zip, wantedName); return new TextDecoder().decode(fileBytes);}
export async function readZipEntry(zip: ArrayBuffer, wantedName: string): Promise<Uint8Array> { const bytes = new Uint8Array(zip); const view = new DataView(zip); const eocd = findEndOfCentralDirectory(view); ensureZipRange(view, eocd, 22, 'end of central directory'); const entries = view.getUint16(eocd + 10, true); let cursor = view.getUint32(eocd + 16, true); let match: { compressed: Uint8Array; method: number } | undefined;
for (let i = 0; i < entries; i++) { ensureZipRange(view, cursor, 46, 'central directory header'); if (view.getUint32(cursor, true) !== 0x02014b50) { throw new HttpError('invalid zip central directory', 502); }
const method = view.getUint16(cursor + 10, true); const compressedSize = view.getUint32(cursor + 20, true); const filenameLength = view.getUint16(cursor + 28, true); const extraLength = view.getUint16(cursor + 30, true); const commentLength = view.getUint16(cursor + 32, true); const localOffset = view.getUint32(cursor + 42, true); const entryEnd = cursor + 46 + filenameLength + extraLength + commentLength; ensureZipRange(view, cursor, entryEnd - cursor, 'central directory entry'); const name = new TextDecoder().decode(bytes.slice(cursor + 46, cursor + 46 + filenameLength));
if (name === wantedName || name.endsWith(`/${wantedName}`)) { if (match) { throw new HttpError(`zip entry ambiguous: ${wantedName}`, 502); } ensureZipRange(view, localOffset, 30, 'local file header'); if (view.getUint32(localOffset, true) !== 0x04034b50) { throw new HttpError('invalid zip local header', 502); } const localNameLength = view.getUint16(localOffset + 26, true); const localExtraLength = view.getUint16(localOffset + 28, true); const dataStart = localOffset + 30 + localNameLength + localExtraLength; ensureZipRange(view, localOffset, dataStart - localOffset, 'local file entry'); ensureZipRange(view, dataStart, compressedSize, 'zip entry data'); const compressed = bytes.slice(dataStart, dataStart + compressedSize); match = { compressed, method }; }
cursor = entryEnd; }
if (match) return decompressZipEntry(match.compressed, match.method); throw new HttpError(`zip entry not found: ${wantedName}`, 502);}
function ensureZipRange(view: DataView, offset: number, len: number, label: string): void { if (offset < 0 || len < 0 || offset > view.byteLength || offset + len > view.byteLength) { throw new HttpError(`invalid zip: ${label} outside archive bounds`, 502); }}
async function decompressZipEntry(bytes: Uint8Array, method: number): Promise<Uint8Array> { if (method === 0) return bytes; if (method !== 8) throw new HttpError(`unsupported zip compression method: ${method}`, 502);
const input = new ReadableStream<Uint8Array>({ start(controller) { controller.enqueue(bytes); controller.close(); }, }); const stream = (input as ReadableStream<BufferSource>).pipeThrough( new DecompressionStream('deflate-raw'), ); const buffer = await new Response(stream).arrayBuffer(); return new Uint8Array(buffer);}
function findEndOfCentralDirectory(view: DataView): number { const min = Math.max(0, view.byteLength - 0xffff - 22); for (let cursor = view.byteLength - 22; cursor >= min; cursor--) { if (view.getUint32(cursor, true) === 0x06054b50) return cursor; } throw new HttpError('invalid zip: missing end of central directory', 502);}