bizzleandClaude Opus 4.8
4036ad5839
Brings the share build up to date with the main project: QTI .zip export and optional direct Canvas API push, plus the Canvas settings card. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
100 lines
3.8 KiB
JavaScript
100 lines
3.8 KiB
JavaScript
// lib/canvas/zip.js — minimal, zero-dependency ZIP writer (STORE method, no compression).
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// Canvas accepts uncompressed QTI packages, so we skip DEFLATE entirely and avoid any
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// dependency. Output is a standard .zip as a Uint8Array. Deterministic (fixed timestamps).
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const CRC_TABLE = (() => {
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const t = new Uint32Array(256);
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for (let n = 0; n < 256; n++) {
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let c = n;
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for (let k = 0; k < 8; k++) c = c & 1 ? 0xedb88320 ^ (c >>> 1) : c >>> 1;
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t[n] = c >>> 0;
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}
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return t;
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})();
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// CRC-32 (IEEE 802.3). crc32 of "123456789" === 0xCBF43926 (unit-test anchor).
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export function crc32(bytes) {
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let c = 0xffffffff;
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for (let i = 0; i < bytes.length; i++) c = CRC_TABLE[(c ^ bytes[i]) & 0xff] ^ (c >>> 8);
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return (c ^ 0xffffffff) >>> 0;
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}
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const enc = new TextEncoder();
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const toBytes = (data) => (typeof data === "string" ? enc.encode(data) : data);
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// files: [{ name: string, data: string|Uint8Array }] -> Uint8Array (.zip bytes)
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export function storeZip(files) {
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const DOS_TIME = 0;
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const DOS_DATE = 0x0021; // 1980-01-01, deterministic
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const chunks = [];
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const central = [];
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let offset = 0;
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for (const f of files) {
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const nameBytes = enc.encode(f.name);
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const data = toBytes(f.data);
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const crc = crc32(data);
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const local = new Uint8Array(30 + nameBytes.length);
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const lv = new DataView(local.buffer);
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lv.setUint32(0, 0x04034b50, true); // local file header signature
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lv.setUint16(4, 20, true); // version needed to extract
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lv.setUint16(6, 0x0800, true); // flags: bit 11 = UTF-8 filenames
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lv.setUint16(8, 0, true); // compression method 0 = store
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lv.setUint16(10, DOS_TIME, true);
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lv.setUint16(12, DOS_DATE, true);
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lv.setUint32(14, crc, true);
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lv.setUint32(18, data.length, true); // compressed size (== uncompressed for store)
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lv.setUint32(22, data.length, true); // uncompressed size
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lv.setUint16(26, nameBytes.length, true);
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lv.setUint16(28, 0, true); // extra field length
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local.set(nameBytes, 30);
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chunks.push(local, data);
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const cd = new Uint8Array(46 + nameBytes.length);
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const cv = new DataView(cd.buffer);
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cv.setUint32(0, 0x02014b50, true); // central directory header signature
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cv.setUint16(4, 20, true); // version made by
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cv.setUint16(6, 20, true); // version needed
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cv.setUint16(8, 0x0800, true);
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cv.setUint16(10, 0, true); // method
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cv.setUint16(12, DOS_TIME, true);
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cv.setUint16(14, DOS_DATE, true);
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cv.setUint32(16, crc, true);
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cv.setUint32(20, data.length, true);
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cv.setUint32(24, data.length, true);
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cv.setUint16(28, nameBytes.length, true);
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cv.setUint16(30, 0, true); // extra length
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cv.setUint16(32, 0, true); // comment length
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cv.setUint16(34, 0, true); // disk number start
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cv.setUint16(36, 0, true); // internal attributes
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cv.setUint32(38, 0, true); // external attributes
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cv.setUint32(42, offset, true); // relative offset of local header
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cd.set(nameBytes, 46);
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central.push(cd);
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offset += local.length + data.length;
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}
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const centralStart = offset;
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let centralSize = 0;
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for (const cd of central) { chunks.push(cd); centralSize += cd.length; }
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const eocd = new Uint8Array(22);
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const ev = new DataView(eocd.buffer);
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ev.setUint32(0, 0x06054b50, true); // end of central directory signature
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ev.setUint16(8, central.length, true); // entries on this disk
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ev.setUint16(10, central.length, true); // total entries
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ev.setUint32(12, centralSize, true);
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ev.setUint32(16, centralStart, true);
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ev.setUint16(20, 0, true); // comment length
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chunks.push(eocd);
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let total = 0;
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for (const c of chunks) total += c.length;
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const out = new Uint8Array(total);
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let p = 0;
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for (const c of chunks) { out.set(c, p); p += c.length; }
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return out;
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}
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