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node_modules/mongodb-core/lib/utils.js

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+'use strict';
+
+const crypto = require('crypto');
+const requireOptional = require('require_optional');
+
+/**
+ * Generate a UUIDv4
+ */
+const uuidV4 = () => {
+  const result = crypto.randomBytes(16);
+  result[6] = (result[6] & 0x0f) | 0x40;
+  result[8] = (result[8] & 0x3f) | 0x80;
+  return result;
+};
+
+/**
+ * Returns the duration calculated from two high resolution timers in milliseconds
+ *
+ * @param {Object} started A high resolution timestamp created from `process.hrtime()`
+ * @returns {Number} The duration in milliseconds
+ */
+const calculateDurationInMs = started => {
+  const hrtime = process.hrtime(started);
+  return (hrtime[0] * 1e9 + hrtime[1]) / 1e6;
+};
+
+/**
+ * Relays events for a given listener and emitter
+ *
+ * @param {EventEmitter} listener the EventEmitter to listen to the events from
+ * @param {EventEmitter} emitter the EventEmitter to relay the events to
+ */
+function relayEvents(listener, emitter, events) {
+  events.forEach(eventName => listener.on(eventName, event => emitter.emit(eventName, event)));
+}
+
+function retrieveKerberos() {
+  let kerberos;
+
+  try {
+    kerberos = requireOptional('kerberos');
+  } catch (err) {
+    if (err.code === 'MODULE_NOT_FOUND') {
+      throw new Error('The `kerberos` module was not found. Please install it and try again.');
+    }
+
+    throw err;
+  }
+
+  return kerberos;
+}
+
+// Throw an error if an attempt to use EJSON is made when it is not installed
+const noEJSONError = function() {
+  throw new Error('The `mongodb-extjson` module was not found. Please install it and try again.');
+};
+
+// Facilitate loading EJSON optionally
+function retrieveEJSON() {
+  let EJSON = null;
+  try {
+    EJSON = requireOptional('mongodb-extjson');
+  } catch (error) {} // eslint-disable-line
+  if (!EJSON) {
+    EJSON = {
+      parse: noEJSONError,
+      deserialize: noEJSONError,
+      serialize: noEJSONError,
+      stringify: noEJSONError,
+      setBSONModule: noEJSONError,
+      BSON: noEJSONError
+    };
+  }
+
+  return EJSON;
+}
+
+/*
+ * Checks that collation is supported by server.
+ *
+ * @param {Server} [server] to check against
+ * @param {object} [cmd] object where collation may be specified
+ * @param {function} [callback] callback function
+ * @return true if server does not support collation
+ */
+function collationNotSupported(server, cmd) {
+  return cmd && cmd.collation && server.ismaster && server.ismaster.maxWireVersion < 5;
+}
+
+module.exports = {
+  uuidV4,
+  calculateDurationInMs,
+  relayEvents,
+  collationNotSupported,
+  retrieveEJSON,
+  retrieveKerberos
+};