Function installWindowsBinaryAtomically

pkg/npm/install.js:381–458

(sourceDir, destDir, verifier = verifyCandidate)

}

function installWindowsBinaryAtomically(sourceDir, destDir, verifier = verifyCandidate) {
  // Authenticate the source binary before it can contend for the cache.
  verifier(path.join(sourceDir, WINDOWS_BINARY_NAME));
  const lock = acquireWindowsBinaryLock(destDir);
  let operationError = null;
  try {
    // A contender may have completed while this process waited. Its executable
    // wins and is never moved or deleted.
    if (windowsBinaryReady(destDir, verifier)) return;

    const transaction = crypto.randomBytes(16).toString('hex');
    const stagedPaths = new Map();
    const stagedDigests = new Map();
    const backups = new Map();
    const publishedDigests = new Map();
    try {
      for (const name of [WINDOWS_BINARY_NAME]) {
        const staged = path.join(destDir, `.cbm-pair-stage-${transaction}-${name}`);
        fs.copyFileSync(path.join(sourceDir, name), staged, fs.constants.COPYFILE_EXCL);
        fs.chmodSync(staged, 0o755);
        stagedPaths.set(name, staged);
        stagedDigests.set(name, fileSha256(staged));
      }

      for (const name of [WINDOWS_BINARY_NAME]) {
        const target = path.join(destDir, name);
        const status = fs.lstatSync(target, { throwIfNoEntry: false });
        if (!status) continue;
        if (!status.isFile() || status.isSymbolicLink()) {
          throw new Error(`refusing unsafe Windows package-cache target: ${target}`);
        }
        const backup = path.join(destDir, `.cbm-pair-backup-${transaction}-${name}`);
        fs.renameSync(target, backup);
        backups.set(name, backup);
      }

      for (const name of [WINDOWS_BINARY_NAME]) {
        const target = path.join(destDir, name);
        fs.renameSync(stagedPaths.get(name), target);
        stagedPaths.delete(name);
        publishedDigests.set(name, stagedDigests.get(name));
      }
      if (!windowsBinaryReady(destDir, verifier)) {
        throw new Error('published Windows package-cache binary failed verification');
      }
      for (const backup of backups.values()) {
        try { fs.unlinkSync(backup); } catch (_) { /* valid binary is already committed */ }
      }
      return;
    } catch (err) {
      // If a non-cooperating contender nevertheless published a valid binary,
      // preserve that winner. Otherwise remove only our exact staged bytes and
      // restore the prior files when their target names are still absent.
      if (windowsBinaryReady(destDir, verifier)) {
        for (const backup of backups.values()) {
          try { fs.unlinkSync(backup); } catch (_) { /* winner remains authoritative */ }
        }
        return;