77 lines
2.6 KiB
JavaScript
77 lines
2.6 KiB
JavaScript
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/** Largest accepted session message, including the encoded command result. */
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export const MAX_CLI_SESSION_FRAME_BYTES = 64 * 1024 * 1024;
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/** Length-prefixed JSON frame shared by the session parent and worker. */
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export const encodeCliSessionFrame = (value) => {
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const body = Buffer.from(JSON.stringify(value));
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if (body.length > MAX_CLI_SESSION_FRAME_BYTES) {
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throw new Error(
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`CLI session frame is ${body.length} bytes; the limit is ${MAX_CLI_SESSION_FRAME_BYTES}`,
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);
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}
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const frame = Buffer.allocUnsafe(4 + body.length);
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frame.writeUInt32BE(body.length, 0);
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body.copy(frame, 4);
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return frame;
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};
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const frameLimitError = (length) =>
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new Error(
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`CLI session frame is ${length} bytes; the limit is ${MAX_CLI_SESSION_FRAME_BYTES}`,
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);
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/** Read a big-endian length from the start of a chunk list without joining it. */
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const readFrameLength = (chunks) => {
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const first = chunks[0];
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if (first.length >= 4) return first.readUInt32BE(0);
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const header = Buffer.allocUnsafe(4);
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let offset = 0;
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for (const chunk of chunks) {
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const take = Math.min(chunk.length, 4 - offset);
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chunk.copy(header, offset, 0, take);
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offset += take;
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if (offset === 4) break;
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}
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return header.readUInt32BE(0);
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};
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/**
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* Parse complete frames from a byte stream. An oversized or malformed frame
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* fails the reader instead of resynchronizing on a later length. Incomplete
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* chunks stay separate until one whole frame is buffered, then that frame is
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* joined once.
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*/
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export const createCliSessionFrameReader = (onFrame) => {
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/** @type {Buffer[]} */
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const chunks = [];
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let buffered = 0;
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return (chunk) => {
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const bytes = Buffer.isBuffer(chunk) ? chunk : Buffer.from(chunk);
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chunks.push(bytes);
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buffered += bytes.length;
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if (buffered < 4) return;
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const length = readFrameLength(chunks);
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if (length > MAX_CLI_SESSION_FRAME_BYTES) throw frameLimitError(length);
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if (buffered < 4 + length) return;
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const pending = Buffer.concat(chunks);
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let offset = 0;
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try {
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while (offset + 4 <= pending.length) {
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const frameLength = pending.readUInt32BE(offset);
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if (frameLength > MAX_CLI_SESSION_FRAME_BYTES) {
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throw frameLimitError(frameLength);
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}
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const frameEnd = offset + 4 + frameLength;
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if (frameEnd > pending.length) break;
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const body = pending.toString("utf8", offset + 4, frameEnd);
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offset = frameEnd;
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onFrame(JSON.parse(body));
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}
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} finally {
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const rest = pending.subarray(offset);
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chunks.length = 0;
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buffered = rest.length;
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if (rest.length > 0) chunks.push(Buffer.from(rest));
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}
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};
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};
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