nm_componentize_qjs.js

//! componentize-qjs Native Messaging host
//! guest271314, andreiltd (https://github.com/andreiltd), 6-13-2026
//! https://github.com/andreiltd/issues/1
//! Based on https://github.com/guest271314/native-messaging-webassembly/nm_javy.js

import stdin from "wasi:cli/stdin@0.2.6";
import stdout from "wasi:cli/stdout@0.2.6";

const MAX_IN = 64 * 1024 * 1024;
const WRITE_CHUNK = 4096;
const FRAME = 1024 * 1024;
const COMMA = 0x2c, OPEN = 0x5b, CLOSE = 0x5d;

function readExact(input, n) {
  const out = new Uint8Array(n);
  let off = 0;
  while (off < n) {
    let chunk;
    try {
      chunk = input.blockingRead(n - off);
    } catch (e) {
      if (e && e.payload && e.payload.tag === "closed" && off === 0) {
        return null;
      }
      throw e;
    }
    if (chunk.length === 0) {
      if (off === 0) return null;
      throw new Error(`stdin closed after ${off} of ${n} bytes`);
    }
    out.set(chunk, off);
    off += chunk.length;
  }
  return out;
}

function readMessage(input) {
  const header = readExact(input, 4);
  if (header === null) return null;
  const len = new DataView(header.buffer).getUint32(0, true);
  if (len > MAX_IN) throw new Error(`message of ${len} bytes exceeds 64 MiB`);
  return len === 0 ? new Uint8Array(0) : readExact(input, len);
}

function writeAll(output, data) {
  for (let off = 0; off < data.length; off += WRITE_CHUNK) {
    output.blockingWriteAndFlush(data.subarray(off, off + WRITE_CHUNK));
  }
}

function writeFrame(output, body) {
  const frame = new Uint8Array(4 + body.length);
  new DataView(frame.buffer).setUint32(0, body.length, true);
  frame.set(body, 4);
  writeAll(output, frame);
}

function sendMessage(output, msg) {
  if (msg.length <= FRAME) {
    writeFrame(output, msg);
    return;
  }
  for (let i = 1, end = msg.length - 1; i < end;) {
    let j = i + FRAME - 16;
    if (j >= end) j = end;
    else {
      const c = msg.indexOf(COMMA, j);
      j = c === -1 ? end : c;
    }
    const body = new Uint8Array(2 + (j - i));
    body[0] = OPEN;
    body.set(msg.subarray(i, j), 1);
    body[body.length - 1] = CLOSE;
    writeFrame(output, body);
    i = j + 1;
  }
}

export const run = {
  run() {
    const input = stdin.getStdin();
    const output = stdout.getStdout();
    for (let msg; (msg = readMessage(input)) !== null;) {
      sendMessage(output, msg);
    }
    return { tag: "ok" };
  },
};