Function downloadHop

pkg/npm/install.js:110–172

(url, dest, maxBytes)

}

function downloadHop(url, dest, maxBytes) {
  return new Promise((resolve, reject) => {
    let settled = false;
    let response = null;
    let timer = null;

    function finish(err, result) {
      if (settled) return;
      settled = true;
      if (timer) clearTimeout(timer);
      if (err) reject(err);
      else resolve(result);
    }

    const req = https.get(url, (res) => {
      response = res;
      res.on('error', (err) => finish(err));
      const redirectCodes = new Set([301, 302, 303, 307, 308]);
      if (redirectCodes.has(res.statusCode)) {
        const location = res.headers.location;
        if (!location) {
          res.destroy();
          finish(new Error(`Redirect with no location for ${url}`));
          return;
        }
        let next;
        try {
          next = validateUrl(new URL(location, url).href);
        } catch (err) {
          res.destroy();
          finish(err);
          return;
        }
        res.destroy();
        finish(null, { redirect: next });
        return;
      }
      if (res.statusCode !== 200) {
        res.destroy();
        finish(new Error(`HTTP ${res.statusCode} for ${url}`));
        return;
      }

      let received = 0;
      res.on('data', (chunk) => {
        received += chunk.length;
        if (maxBytes && received > maxBytes) {
          res.destroy(new Error(`Download exceeds the ${maxBytes}-byte safety limit`));
        }
      });
      const file = fs.createWriteStream(dest, { flags: 'w' });
      pipeline(res, file, (err) => {
        finish(err, { redirect: null });
      });
    });
    req.on('error', (err) => finish(err));
    timer = setTimeout(() => {
      const err = new Error(`Download hop timed out after ${DOWNLOAD_HOP_TIMEOUT_MS} ms: ${url}`);