api, login, auth

2 files changed, 2157 insertions, 0 deletions

diff --git a/node_modules/mongodb/lib/gridfs/chunk.js b/node_modules/mongodb/lib/gridfs/chunk.js
new file mode 100644
index 0000000..d276d72
--- /dev/null
+++ b/node_modules/mongodb/lib/gridfs/chunk.js
@@ -0,0 +1,236 @@
+'use strict';
+
+var Binary = require('../core').BSON.Binary,
+  ObjectID = require('../core').BSON.ObjectID;
+
+var Buffer = require('safe-buffer').Buffer;
+
+/**
+ * Class for representing a single chunk in GridFS.
+ *
+ * @class
+ *
+ * @param file {GridStore} The {@link GridStore} object holding this chunk.
+ * @param mongoObject {object} The mongo object representation of this chunk.
+ *
+ * @throws Error when the type of data field for {@link mongoObject} is not
+ *     supported. Currently supported types for data field are instances of
+ *     {@link String}, {@link Array}, {@link Binary} and {@link Binary}
+ *     from the bson module
+ *
+ * @see Chunk#buildMongoObject
+ */
+var Chunk = function(file, mongoObject, writeConcern) {
+  if (!(this instanceof Chunk)) return new Chunk(file, mongoObject);
+
+  this.file = file;
+  var mongoObjectFinal = mongoObject == null ? {} : mongoObject;
+  this.writeConcern = writeConcern || { w: 1 };
+  this.objectId = mongoObjectFinal._id == null ? new ObjectID() : mongoObjectFinal._id;
+  this.chunkNumber = mongoObjectFinal.n == null ? 0 : mongoObjectFinal.n;
+  this.data = new Binary();
+
+  if (typeof mongoObjectFinal.data === 'string') {
+    var buffer = Buffer.alloc(mongoObjectFinal.data.length);
+    buffer.write(mongoObjectFinal.data, 0, mongoObjectFinal.data.length, 'binary');
+    this.data = new Binary(buffer);
+  } else if (Array.isArray(mongoObjectFinal.data)) {
+    buffer = Buffer.alloc(mongoObjectFinal.data.length);
+    var data = mongoObjectFinal.data.join('');
+    buffer.write(data, 0, data.length, 'binary');
+    this.data = new Binary(buffer);
+  } else if (mongoObjectFinal.data && mongoObjectFinal.data._bsontype === 'Binary') {
+    this.data = mongoObjectFinal.data;
+  } else if (!Buffer.isBuffer(mongoObjectFinal.data) && !(mongoObjectFinal.data == null)) {
+    throw Error('Illegal chunk format');
+  }
+
+  // Update position
+  this.internalPosition = 0;
+};
+
+/**
+ * Writes a data to this object and advance the read/write head.
+ *
+ * @param data {string} the data to write
+ * @param callback {function(*, GridStore)} This will be called after executing
+ *     this method. The first parameter will contain null and the second one
+ *     will contain a reference to this object.
+ */
+Chunk.prototype.write = function(data, callback) {
+  this.data.write(data, this.internalPosition, data.length, 'binary');
+  this.internalPosition = this.data.length();
+  if (callback != null) return callback(null, this);
+  return this;
+};
+
+/**
+ * Reads data and advances the read/write head.
+ *
+ * @param length {number} The length of data to read.
+ *
+ * @return {string} The data read if the given length will not exceed the end of
+ *     the chunk. Returns an empty String otherwise.
+ */
+Chunk.prototype.read = function(length) {
+  // Default to full read if no index defined
+  length = length == null || length === 0 ? this.length() : length;
+
+  if (this.length() - this.internalPosition + 1 >= length) {
+    var data = this.data.read(this.internalPosition, length);
+    this.internalPosition = this.internalPosition + length;
+    return data;
+  } else {
+    return '';
+  }
+};
+
+Chunk.prototype.readSlice = function(length) {
+  if (this.length() - this.internalPosition >= length) {
+    var data = null;
+    if (this.data.buffer != null) {
+      //Pure BSON
+      data = this.data.buffer.slice(this.internalPosition, this.internalPosition + length);
+    } else {
+      //Native BSON
+      data = Buffer.alloc(length);
+      length = this.data.readInto(data, this.internalPosition);
+    }
+    this.internalPosition = this.internalPosition + length;
+    return data;
+  } else {
+    return null;
+  }
+};
+
+/**
+ * Checks if the read/write head is at the end.
+ *
+ * @return {boolean} Whether the read/write head has reached the end of this
+ *     chunk.
+ */
+Chunk.prototype.eof = function() {
+  return this.internalPosition === this.length() ? true : false;
+};
+
+/**
+ * Reads one character from the data of this chunk and advances the read/write
+ * head.
+ *
+ * @return {string} a single character data read if the the read/write head is
+ *     not at the end of the chunk. Returns an empty String otherwise.
+ */
+Chunk.prototype.getc = function() {
+  return this.read(1);
+};
+
+/**
+ * Clears the contents of the data in this chunk and resets the read/write head
+ * to the initial position.
+ */
+Chunk.prototype.rewind = function() {
+  this.internalPosition = 0;
+  this.data = new Binary();
+};
+
+/**
+ * Saves this chunk to the database. Also overwrites existing entries having the
+ * same id as this chunk.
+ *
+ * @param callback {function(*, GridStore)} This will be called after executing
+ *     this method. The first parameter will contain null and the second one
+ *     will contain a reference to this object.
+ */
+Chunk.prototype.save = function(options, callback) {
+  var self = this;
+  if (typeof options === 'function') {
+    callback = options;
+    options = {};
+  }
+
+  self.file.chunkCollection(function(err, collection) {
+    if (err) return callback(err);
+
+    // Merge the options
+    var writeOptions = { upsert: true };
+    for (var name in options) writeOptions[name] = options[name];
+    for (name in self.writeConcern) writeOptions[name] = self.writeConcern[name];
+
+    if (self.data.length() > 0) {
+      self.buildMongoObject(function(mongoObject) {
+        var options = { forceServerObjectId: true };
+        for (var name in self.writeConcern) {
+          options[name] = self.writeConcern[name];
+        }
+
+        collection.replaceOne({ _id: self.objectId }, mongoObject, writeOptions, function(err) {
+          callback(err, self);
+        });
+      });
+    } else {
+      callback(null, self);
+    }
+    // });
+  });
+};
+
+/**
+ * Creates a mongoDB object representation of this chunk.
+ *
+ * @param callback {function(Object)} This will be called after executing this
+ *     method. The object will be passed to the first parameter and will have
+ *     the structure:
+ *
+ *        <pre><code>
+ *        {
+ *          '_id' : , // {number} id for this chunk
+ *          'files_id' : , // {number} foreign key to the file collection
+ *          'n' : , // {number} chunk number
+ *          'data' : , // {bson#Binary} the chunk data itself
+ *        }
+ *        </code></pre>
+ *
+ * @see <a href="http://www.mongodb.org/display/DOCS/GridFS+Specification#GridFSSpecification-{{chunks}}">MongoDB GridFS Chunk Object Structure</a>
+ */
+Chunk.prototype.buildMongoObject = function(callback) {
+  var mongoObject = {
+    files_id: this.file.fileId,
+    n: this.chunkNumber,
+    data: this.data
+  };
+  // If we are saving using a specific ObjectId
+  if (this.objectId != null) mongoObject._id = this.objectId;
+
+  callback(mongoObject);
+};
+
+/**
+ * @return {number} the length of the data
+ */
+Chunk.prototype.length = function() {
+  return this.data.length();
+};
+
+/**
+ * The position of the read/write head
+ * @name position
+ * @lends Chunk#
+ * @field
+ */
+Object.defineProperty(Chunk.prototype, 'position', {
+  enumerable: true,
+  get: function() {
+    return this.internalPosition;
+  },
+  set: function(value) {
+    this.internalPosition = value;
+  }
+});
+
+/**
+ * The default chunk size
+ * @constant
+ */
+Chunk.DEFAULT_CHUNK_SIZE = 1024 * 255;
+
+module.exports = Chunk;
diff --git a/node_modules/mongodb/lib/gridfs/grid_store.js b/node_modules/mongodb/lib/gridfs/grid_store.js
new file mode 100644
index 0000000..a7c543a
--- /dev/null
+++ b/node_modules/mongodb/lib/gridfs/grid_store.js
@@ -0,0 +1,1921 @@
+'use strict';
+
+/**
+ * @fileOverview GridFS is a tool for MongoDB to store files to the database.
+ * Because of the restrictions of the object size the database can hold, a
+ * facility to split a file into several chunks is needed. The {@link GridStore}
+ * class offers a simplified api to interact with files while managing the
+ * chunks of split files behind the scenes. More information about GridFS can be
+ * found <a href="http://www.mongodb.org/display/DOCS/GridFS">here</a>.
+ *
+ * @example
+ * const MongoClient = require('mongodb').MongoClient;
+ * const GridStore = require('mongodb').GridStore;
+ * const ObjectID = require('mongodb').ObjectID;
+ * const test = require('assert');
+ * // Connection url
+ * const url = 'mongodb://localhost:27017';
+ * // Database Name
+ * const dbName = 'test';
+ * // Connect using MongoClient
+ * MongoClient.connect(url, function(err, client) {
+ *   const db = client.db(dbName);
+ *   const gridStore = new GridStore(db, null, "w");
+ *   gridStore.open(function(err, gridStore) {
+ *     gridStore.write("hello world!", function(err, gridStore) {
+ *       gridStore.close(function(err, result) {
+ *         // Let's read the file using object Id
+ *         GridStore.read(db, result._id, function(err, data) {
+ *           test.equal('hello world!', data);
+ *           client.close();
+ *           test.done();
+ *         });
+ *       });
+ *     });
+ *   });
+ * });
+ */
+const Chunk = require('./chunk');
+const ObjectID = require('../core').BSON.ObjectID;
+const ReadPreference = require('../core').ReadPreference;
+const Buffer = require('safe-buffer').Buffer;
+const fs = require('fs');
+const f = require('util').format;
+const util = require('util');
+const MongoError = require('../core').MongoError;
+const inherits = util.inherits;
+const Duplex = require('stream').Duplex;
+const shallowClone = require('../utils').shallowClone;
+const executeLegacyOperation = require('../utils').executeLegacyOperation;
+const deprecate = require('util').deprecate;
+
+var REFERENCE_BY_FILENAME = 0,
+  REFERENCE_BY_ID = 1;
+
+const deprecationFn = deprecate(() => {},
+'GridStore is deprecated, and will be removed in a future version. Please use GridFSBucket instead');
+
+/**
+ * Namespace provided by the core module
+ * @external Duplex
+ */
+
+/**
+ * Create a new GridStore instance
+ *
+ * Modes
+ *  - **"r"** - read only. This is the default mode.
+ *  - **"w"** - write in truncate mode. Existing data will be overwritten.
+ *
+ * @class
+ * @param {Db} db A database instance to interact with.
+ * @param {object} [id] optional unique id for this file
+ * @param {string} [filename] optional filename for this file, no unique constrain on the field
+ * @param {string} mode set the mode for this file.
+ * @param {object} [options] Optional settings.
+ * @param {(number|string)} [options.w] The write concern.
+ * @param {number} [options.wtimeout] The write concern timeout.
+ * @param {boolean} [options.j=false] Specify a journal write concern.
+ * @param {boolean} [options.fsync=false] Specify a file sync write concern.
+ * @param {string} [options.root] Root collection to use. Defaults to **{GridStore.DEFAULT_ROOT_COLLECTION}**.
+ * @param {string} [options.content_type] MIME type of the file. Defaults to **{GridStore.DEFAULT_CONTENT_TYPE}**.
+ * @param {number} [options.chunk_size=261120] Size for the chunk. Defaults to **{Chunk.DEFAULT_CHUNK_SIZE}**.
+ * @param {object} [options.metadata] Arbitrary data the user wants to store.
+ * @param {object} [options.promiseLibrary] A Promise library class the application wishes to use such as Bluebird, must be ES6 compatible
+ * @param {(ReadPreference|string)} [options.readPreference] The preferred read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).
+ * @property {number} chunkSize Get the gridstore chunk size.
+ * @property {number} md5 The md5 checksum for this file.
+ * @property {number} chunkNumber The current chunk number the gridstore has materialized into memory
+ * @return {GridStore} a GridStore instance.
+ * @deprecated Use GridFSBucket API instead
+ */
+var GridStore = function GridStore(db, id, filename, mode, options) {
+  deprecationFn();
+  if (!(this instanceof GridStore)) return new GridStore(db, id, filename, mode, options);
+  this.db = db;
+
+  // Handle options
+  if (typeof options === 'undefined') options = {};
+  // Handle mode
+  if (typeof mode === 'undefined') {
+    mode = filename;
+    filename = undefined;
+  } else if (typeof mode === 'object') {
+    options = mode;
+    mode = filename;
+    filename = undefined;
+  }
+
+  if (id && id._bsontype === 'ObjectID') {
+    this.referenceBy = REFERENCE_BY_ID;
+    this.fileId = id;
+    this.filename = filename;
+  } else if (typeof filename === 'undefined') {
+    this.referenceBy = REFERENCE_BY_FILENAME;
+    this.filename = id;
+    if (mode.indexOf('w') != null) {
+      this.fileId = new ObjectID();
+    }
+  } else {
+    this.referenceBy = REFERENCE_BY_ID;
+    this.fileId = id;
+    this.filename = filename;
+  }
+
+  // Set up the rest
+  this.mode = mode == null ? 'r' : mode;
+  this.options = options || {};
+
+  // Opened
+  this.isOpen = false;
+
+  // Set the root if overridden
+  this.root =
+    this.options['root'] == null ? GridStore.DEFAULT_ROOT_COLLECTION : this.options['root'];
+  this.position = 0;
+  this.readPreference =
+    this.options.readPreference || db.options.readPreference || ReadPreference.primary;
+  this.writeConcern = _getWriteConcern(db, this.options);
+  // Set default chunk size
+  this.internalChunkSize =
+    this.options['chunkSize'] == null ? Chunk.DEFAULT_CHUNK_SIZE : this.options['chunkSize'];
+
+  // Get the promiseLibrary
+  var promiseLibrary = this.options.promiseLibrary || Promise;
+
+  // Set the promiseLibrary
+  this.promiseLibrary = promiseLibrary;
+
+  Object.defineProperty(this, 'chunkSize', {
+    enumerable: true,
+    get: function() {
+      return this.internalChunkSize;
+    },
+    set: function(value) {
+      if (!(this.mode[0] === 'w' && this.position === 0 && this.uploadDate == null)) {
+        // eslint-disable-next-line no-self-assign
+        this.internalChunkSize = this.internalChunkSize;
+      } else {
+        this.internalChunkSize = value;
+      }
+    }
+  });
+
+  Object.defineProperty(this, 'md5', {
+    enumerable: true,
+    get: function() {
+      return this.internalMd5;
+    }
+  });
+
+  Object.defineProperty(this, 'chunkNumber', {
+    enumerable: true,
+    get: function() {
+      return this.currentChunk && this.currentChunk.chunkNumber
+        ? this.currentChunk.chunkNumber
+        : null;
+    }
+  });
+};
+
+/**
+ * The callback format for the Gridstore.open method
+ * @callback GridStore~openCallback
+ * @param {MongoError} error An error instance representing the error during the execution.
+ * @param {GridStore} gridStore The GridStore instance if the open method was successful.
+ */
+
+/**
+ * Opens the file from the database and initialize this object. Also creates a
+ * new one if file does not exist.
+ *
+ * @method
+ * @param {object} [options] Optional settings
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~openCallback} [callback] this will be called after executing this method
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.open = function(options, callback) {
+  if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
+  if (this.mode !== 'w' && this.mode !== 'w+' && this.mode !== 'r') {
+    throw MongoError.create({ message: 'Illegal mode ' + this.mode, driver: true });
+  }
+
+  return executeLegacyOperation(this.db.s.topology, open, [this, options, callback], {
+    skipSessions: true
+  });
+};
+
+var open = function(self, options, callback) {
+  // Get the write concern
+  var writeConcern = _getWriteConcern(self.db, self.options);
+
+  // If we are writing we need to ensure we have the right indexes for md5's
+  if (self.mode === 'w' || self.mode === 'w+') {
+    // Get files collection
+    var collection = self.collection();
+    // Put index on filename
+    collection.ensureIndex([['filename', 1]], writeConcern, function() {
+      // Get chunk collection
+      var chunkCollection = self.chunkCollection();
+      // Make an unique index for compatibility with mongo-cxx-driver:legacy
+      var chunkIndexOptions = shallowClone(writeConcern);
+      chunkIndexOptions.unique = true;
+      // Ensure index on chunk collection
+      chunkCollection.ensureIndex(
+        [
+          ['files_id', 1],
+          ['n', 1]
+        ],
+        chunkIndexOptions,
+        function() {
+          // Open the connection
+          _open(self, writeConcern, function(err, r) {
+            if (err) return callback(err);
+            self.isOpen = true;
+            callback(err, r);
+          });
+        }
+      );
+    });
+  } else {
+    // Open the gridstore
+    _open(self, writeConcern, function(err, r) {
+      if (err) return callback(err);
+      self.isOpen = true;
+      callback(err, r);
+    });
+  }
+};
+
+/**
+ * Verify if the file is at EOF.
+ *
+ * @method
+ * @return {boolean} true if the read/write head is at the end of this file.
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.eof = function() {
+  return this.position === this.length ? true : false;
+};
+
+/**
+ * The callback result format.
+ * @callback GridStore~resultCallback
+ * @param {object} [options] Optional settings
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {MongoError} error An error instance representing the error during the execution.
+ * @param {object} result The result from the callback.
+ */
+
+/**
+ * Retrieves a single character from this file.
+ *
+ * @method
+ * @param {GridStore~resultCallback} [callback] this gets called after this method is executed. Passes null to the first parameter and the character read to the second or null to the second if the read/write head is at the end of the file.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.getc = function(options, callback) {
+  if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
+  return executeLegacyOperation(this.db.s.topology, getc, [this, options, callback], {
+    skipSessions: true
+  });
+};
+
+var getc = function(self, options, callback) {
+  if (self.eof()) {
+    callback(null, null);
+  } else if (self.currentChunk.eof()) {
+    nthChunk(self, self.currentChunk.chunkNumber + 1, function(err, chunk) {
+      self.currentChunk = chunk;
+      self.position = self.position + 1;
+      callback(err, self.currentChunk.getc());
+    });
+  } else {
+    self.position = self.position + 1;
+    callback(null, self.currentChunk.getc());
+  }
+};
+
+/**
+ * Writes a string to the file with a newline character appended at the end if
+ * the given string does not have one.
+ *
+ * @method
+ * @param {string} string the string to write.
+ * @param {object} [options] Optional settings
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~resultCallback} [callback] this will be called after executing this method. The first parameter will contain null and the second one will contain a reference to this object.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.puts = function(string, options, callback) {
+  if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
+  var finalString = string.match(/\n$/) == null ? string + '\n' : string;
+  return executeLegacyOperation(
+    this.db.s.topology,
+    this.write.bind(this),
+    [finalString, options, callback],
+    { skipSessions: true }
+  );
+};
+
+/**
+ * Return a modified Readable stream including a possible transform method.
+ *
+ * @method
+ * @return {GridStoreStream}
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.stream = function() {
+  return new GridStoreStream(this);
+};
+
+/**
+ * Writes some data. This method will work properly only if initialized with mode "w" or "w+".
+ *
+ * @method
+ * @param {(string|Buffer)} data the data to write.
+ * @param {boolean} [close] closes this file after writing if set to true.
+ * @param {object} [options] Optional settings
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~resultCallback} [callback] this will be called after executing this method. The first parameter will contain null and the second one will contain a reference to this object.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.write = function write(data, close, options, callback) {
+  if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
+  return executeLegacyOperation(
+    this.db.s.topology,
+    _writeNormal,
+    [this, data, close, options, callback],
+    { skipSessions: true }
+  );
+};
+
+/**
+ * Handles the destroy part of a stream
+ *
+ * @method
+ * @result {null}
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.destroy = function destroy() {
+  // close and do not emit any more events. queued data is not sent.
+  if (!this.writable) return;
+  this.readable = false;
+  if (this.writable) {
+    this.writable = false;
+    this._q.length = 0;
+    this.emit('close');
+  }
+};
+
+/**
+ * Stores a file from the file system to the GridFS database.
+ *
+ * @method
+ * @param {(string|Buffer|FileHandle)} file the file to store.
+ * @param {object} [options] Optional settings
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~resultCallback} [callback] this will be called after executing this method. The first parameter will contain null and the second one will contain a reference to this object.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.writeFile = function(file, options, callback) {
+  if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
+  return executeLegacyOperation(this.db.s.topology, writeFile, [this, file, options, callback], {
+    skipSessions: true
+  });
+};
+
+var writeFile = function(self, file, options, callback) {
+  if (typeof file === 'string') {
+    fs.open(file, 'r', function(err, fd) {
+      if (err) return callback(err);
+      self.writeFile(fd, callback);
+    });
+    return;
+  }
+
+  self.open(function(err, self) {
+    if (err) return callback(err, self);
+
+    fs.fstat(file, function(err, stats) {
+      if (err) return callback(err, self);
+
+      var offset = 0;
+      var index = 0;
+
+      // Write a chunk
+      var writeChunk = function() {
+        // Allocate the buffer
+        var _buffer = Buffer.alloc(self.chunkSize);
+        // Read the file
+        fs.read(file, _buffer, 0, _buffer.length, offset, function(err, bytesRead, data) {
+          if (err) return callback(err, self);
+
+          offset = offset + bytesRead;
+
+          // Create a new chunk for the data
+          var chunk = new Chunk(self, { n: index++ }, self.writeConcern);
+          chunk.write(data.slice(0, bytesRead), function(err, chunk) {
+            if (err) return callback(err, self);
+
+            chunk.save({}, function(err) {
+              if (err) return callback(err, self);
+
+              self.position = self.position + bytesRead;
+
+              // Point to current chunk
+              self.currentChunk = chunk;
+
+              if (offset >= stats.size) {
+                fs.close(file, function(err) {
+                  if (err) return callback(err);
+
+                  self.close(function(err) {
+                    if (err) return callback(err, self);
+                    return callback(null, self);
+                  });
+                });
+              } else {
+                return process.nextTick(writeChunk);
+              }
+            });
+          });
+        });
+      };
+
+      // Process the first write
+      process.nextTick(writeChunk);
+    });
+  });
+};
+
+/**
+ * Saves this file to the database. This will overwrite the old entry if it
+ * already exists. This will work properly only if mode was initialized to
+ * "w" or "w+".
+ *
+ * @method
+ * @param {object} [options] Optional settings
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~resultCallback} [callback] this will be called after executing this method. The first parameter will contain null and the second one will contain a reference to this object.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.close = function(options, callback) {
+  if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
+  return executeLegacyOperation(this.db.s.topology, close, [this, options, callback], {
+    skipSessions: true
+  });
+};
+
+var close = function(self, options, callback) {
+  if (self.mode[0] === 'w') {
+    // Set up options
+    options = Object.assign({}, self.writeConcern, options);
+
+    if (self.currentChunk != null && self.currentChunk.position > 0) {
+      self.currentChunk.save({}, function(err) {
+        if (err && typeof callback === 'function') return callback(err);
+
+        self.collection(function(err, files) {
+          if (err && typeof callback === 'function') return callback(err);
+
+          // Build the mongo object
+          if (self.uploadDate != null) {
+            buildMongoObject(self, function(err, mongoObject) {
+              if (err) {
+                if (typeof callback === 'function') return callback(err);
+                else throw err;
+              }
+
+              files.save(mongoObject, options, function(err) {
+                if (typeof callback === 'function') callback(err, mongoObject);
+              });
+            });
+          } else {
+            self.uploadDate = new Date();
+            buildMongoObject(self, function(err, mongoObject) {
+              if (err) {
+                if (typeof callback === 'function') return callback(err);
+                else throw err;
+              }
+
+              files.save(mongoObject, options, function(err) {
+                if (typeof callback === 'function') callback(err, mongoObject);
+              });
+            });
+          }
+        });
+      });
+    } else {
+      self.collection(function(err, files) {
+        if (err && typeof callback === 'function') return callback(err);
+
+        self.uploadDate = new Date();
+        buildMongoObject(self, function(err, mongoObject) {
+          if (err) {
+            if (typeof callback === 'function') return callback(err);
+            else throw err;
+          }
+
+          files.save(mongoObject, options, function(err) {
+            if (typeof callback === 'function') callback(err, mongoObject);
+          });
+        });
+      });
+    }
+  } else if (self.mode[0] === 'r') {
+    if (typeof callback === 'function') callback(null, null);
+  } else {
+    if (typeof callback === 'function')
+      callback(MongoError.create({ message: f('Illegal mode %s', self.mode), driver: true }));
+  }
+};
+
+/**
+ * The collection callback format.
+ * @callback GridStore~collectionCallback
+ * @param {MongoError} error An error instance representing the error during the execution.
+ * @param {Collection} collection The collection from the command execution.
+ */
+
+/**
+ * Retrieve this file's chunks collection.
+ *
+ * @method
+ * @param {GridStore~collectionCallback} callback the command callback.
+ * @return {Collection}
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.chunkCollection = function(callback) {
+  if (typeof callback === 'function') return this.db.collection(this.root + '.chunks', callback);
+  return this.db.collection(this.root + '.chunks');
+};
+
+/**
+ * Deletes all the chunks of this file in the database.
+ *
+ * @method
+ * @param {object} [options] Optional settings
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~resultCallback} [callback] the command callback.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.unlink = function(options, callback) {
+  if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
+  return executeLegacyOperation(this.db.s.topology, unlink, [this, options, callback], {
+    skipSessions: true
+  });
+};
+
+var unlink = function(self, options, callback) {
+  deleteChunks(self, function(err) {
+    if (err !== null) {
+      err.message = 'at deleteChunks: ' + err.message;
+      return callback(err);
+    }
+
+    self.collection(function(err, collection) {
+      if (err !== null) {
+        err.message = 'at collection: ' + err.message;
+        return callback(err);
+      }
+
+      collection.remove({ _id: self.fileId }, self.writeConcern, function(err) {
+        callback(err, self);
+      });
+    });
+  });
+};
+
+/**
+ * Retrieves the file collection associated with this object.
+ *
+ * @method
+ * @param {GridStore~collectionCallback} callback the command callback.
+ * @return {Collection}
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.collection = function(callback) {
+  if (typeof callback === 'function') this.db.collection(this.root + '.files', callback);
+  return this.db.collection(this.root + '.files');
+};
+
+/**
+ * The readlines callback format.
+ * @callback GridStore~readlinesCallback
+ * @param {MongoError} error An error instance representing the error during the execution.
+ * @param {string[]} strings The array of strings returned.
+ */
+
+/**
+ * Read the entire file as a list of strings splitting by the provided separator.
+ *
+ * @method
+ * @param {string} [separator] The character to be recognized as the newline separator.
+ * @param {object} [options] Optional settings
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~readlinesCallback} [callback] the command callback.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.readlines = function(separator, options, callback) {
+  var args = Array.prototype.slice.call(arguments, 0);
+  callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
+  separator = args.length ? args.shift() : '\n';
+  separator = separator || '\n';
+  options = args.length ? args.shift() : {};
+
+  return executeLegacyOperation(
+    this.db.s.topology,
+    readlines,
+    [this, separator, options, callback],
+    { skipSessions: true }
+  );
+};
+
+var readlines = function(self, separator, options, callback) {
+  self.read(function(err, data) {
+    if (err) return callback(err);
+
+    var items = data.toString().split(separator);
+    items = items.length > 0 ? items.splice(0, items.length - 1) : [];
+    for (var i = 0; i < items.length; i++) {
+      items[i] = items[i] + separator;
+    }
+
+    callback(null, items);
+  });
+};
+
+/**
+ * Deletes all the chunks of this file in the database if mode was set to "w" or
+ * "w+" and resets the read/write head to the initial position.
+ *
+ * @method
+ * @param {object} [options] Optional settings
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~resultCallback} [callback] this will be called after executing this method. The first parameter will contain null and the second one will contain a reference to this object.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.rewind = function(options, callback) {
+  if (typeof options === 'function') (callback = options), (options = {});
+  options = options || {};
+
+  return executeLegacyOperation(this.db.s.topology, rewind, [this, options, callback], {
+    skipSessions: true
+  });
+};
+
+var rewind = function(self, options, callback) {
+  if (self.currentChunk.chunkNumber !== 0) {
+    if (self.mode[0] === 'w') {
+      deleteChunks(self, function(err) {
+        if (err) return callback(err);
+        self.currentChunk = new Chunk(self, { n: 0 }, self.writeConcern);
+        self.position = 0;
+        callback(null, self);
+      });
+    } else {
+      self.currentChunk(0, function(err, chunk) {
+        if (err) return callback(err);
+        self.currentChunk = chunk;
+        self.currentChunk.rewind();
+        self.position = 0;
+        callback(null, self);
+      });
+    }
+  } else {
+    self.currentChunk.rewind();
+    self.position = 0;
+    callback(null, self);
+  }
+};
+
+/**
+ * The read callback format.
+ * @callback GridStore~readCallback
+ * @param {MongoError} error An error instance representing the error during the execution.
+ * @param {Buffer} data The data read from the GridStore object
+ */
+
+/**
+ * Retrieves the contents of this file and advances the read/write head. Works with Buffers only.
+ *
+ * There are 3 signatures for this method:
+ *
+ * (callback)
+ * (length, callback)
+ * (length, buffer, callback)
+ *
+ * @method
+ * @param {number} [length] the number of characters to read. Reads all the characters from the read/write head to the EOF if not specified.
+ * @param {(string|Buffer)} [buffer] a string to hold temporary data. This is used for storing the string data read so far when recursively calling this method.
+ * @param {object} [options] Optional settings
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~readCallback} [callback] the command callback.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.read = function(length, buffer, options, callback) {
+  var args = Array.prototype.slice.call(arguments, 0);
+  callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
+  length = args.length ? args.shift() : null;
+  buffer = args.length ? args.shift() : null;
+  options = args.length ? args.shift() : {};
+
+  return executeLegacyOperation(
+    this.db.s.topology,
+    read,
+    [this, length, buffer, options, callback],
+    { skipSessions: true }
+  );
+};
+
+var read = function(self, length, buffer, options, callback) {
+  // The data is a c-terminated string and thus the length - 1
+  var finalLength = length == null ? self.length - self.position : length;
+  var finalBuffer = buffer == null ? Buffer.alloc(finalLength) : buffer;
+  // Add a index to buffer to keep track of writing position or apply current index
+  finalBuffer._index = buffer != null && buffer._index != null ? buffer._index : 0;
+
+  if (self.currentChunk.length() - self.currentChunk.position + finalBuffer._index >= finalLength) {
+    var slice = self.currentChunk.readSlice(finalLength - finalBuffer._index);
+    // Copy content to final buffer
+    slice.copy(finalBuffer, finalBuffer._index);
+    // Update internal position
+    self.position = self.position + finalBuffer.length;
+    // Check if we don't have a file at all
+    if (finalLength === 0 && finalBuffer.length === 0)
+      return callback(MongoError.create({ message: 'File does not exist', driver: true }), null);
+    // Else return data
+    return callback(null, finalBuffer);
+  }
+
+  // Read the next chunk
+  slice = self.currentChunk.readSlice(self.currentChunk.length() - self.currentChunk.position);
+  // Copy content to final buffer
+  slice.copy(finalBuffer, finalBuffer._index);
+  // Update index position
+  finalBuffer._index += slice.length;
+
+  // Load next chunk and read more
+  nthChunk(self, self.currentChunk.chunkNumber + 1, function(err, chunk) {
+    if (err) return callback(err);
+
+    if (chunk.length() > 0) {
+      self.currentChunk = chunk;
+      self.read(length, finalBuffer, callback);
+    } else {
+      if (finalBuffer._index > 0) {
+        callback(null, finalBuffer);
+      } else {
+        callback(
+          MongoError.create({
+            message: 'no chunks found for file, possibly corrupt',
+            driver: true
+          }),
+          null
+        );
+      }
+    }
+  });
+};
+
+/**
+ * The tell callback format.
+ * @callback GridStore~tellCallback
+ * @param {MongoError} error An error instance representing the error during the execution.
+ * @param {number} position The current read position in the GridStore.
+ */
+
+/**
+ * Retrieves the position of the read/write head of this file.
+ *
+ * @method
+ * @param {number} [length] the number of characters to read. Reads all the characters from the read/write head to the EOF if not specified.
+ * @param {(string|Buffer)} [buffer] a string to hold temporary data. This is used for storing the string data read so far when recursively calling this method.
+ * @param {object} [options] Optional settings
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~tellCallback} [callback] the command callback.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.tell = function(callback) {
+  var self = this;
+  // We provided a callback leg
+  if (typeof callback === 'function') return callback(null, this.position);
+  // Return promise
+  return new self.promiseLibrary(function(resolve) {
+    resolve(self.position);
+  });
+};
+
+/**
+ * The tell callback format.
+ * @callback GridStore~gridStoreCallback
+ * @param {MongoError} error An error instance representing the error during the execution.
+ * @param {GridStore} gridStore The gridStore.
+ */
+
+/**
+ * Moves the read/write head to a new location.
+ *
+ * There are 3 signatures for this method
+ *
+ * Seek Location Modes
+ *  - **GridStore.IO_SEEK_SET**, **(default)** set the position from the start of the file.
+ *  - **GridStore.IO_SEEK_CUR**, set the position from the current position in the file.
+ *  - **GridStore.IO_SEEK_END**, set the position from the end of the file.
+ *
+ * @method
+ * @param {number} [position] the position to seek to
+ * @param {number} [seekLocation] seek mode. Use one of the Seek Location modes.
+ * @param {object} [options] Optional settings
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~gridStoreCallback} [callback] the command callback.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.prototype.seek = function(position, seekLocation, options, callback) {
+  var args = Array.prototype.slice.call(arguments, 1);
+  callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
+  seekLocation = args.length ? args.shift() : null;
+  options = args.length ? args.shift() : {};
+
+  return executeLegacyOperation(
+    this.db.s.topology,
+    seek,
+    [this, position, seekLocation, options, callback],
+    { skipSessions: true }
+  );
+};
+
+var seek = function(self, position, seekLocation, options, callback) {
+  // Seek only supports read mode
+  if (self.mode !== 'r') {
+    return callback(
+      MongoError.create({ message: 'seek is only supported for mode r', driver: true })
+    );
+  }
+
+  var seekLocationFinal = seekLocation == null ? GridStore.IO_SEEK_SET : seekLocation;
+  var finalPosition = position;
+  var targetPosition = 0;
+
+  // Calculate the position
+  if (seekLocationFinal === GridStore.IO_SEEK_CUR) {
+    targetPosition = self.position + finalPosition;
+  } else if (seekLocationFinal === GridStore.IO_SEEK_END) {
+    targetPosition = self.length + finalPosition;
+  } else {
+    targetPosition = finalPosition;
+  }
+
+  // Get the chunk
+  var newChunkNumber = Math.floor(targetPosition / self.chunkSize);
+  var seekChunk = function() {
+    nthChunk(self, newChunkNumber, function(err, chunk) {
+      if (err) return callback(err, null);
+      if (chunk == null) return callback(new Error('no chunk found'));
+
+      // Set the current chunk
+      self.currentChunk = chunk;
+      self.position = targetPosition;
+      self.currentChunk.position = self.position % self.chunkSize;
+      callback(err, self);
+    });
+  };
+
+  seekChunk();
+};
+
+/**
+ * @ignore
+ */
+var _open = function(self, options, callback) {
+  var collection = self.collection();
+  // Create the query
+  var query =
+    self.referenceBy === REFERENCE_BY_ID ? { _id: self.fileId } : { filename: self.filename };
+  query = null == self.fileId && self.filename == null ? null : query;
+  options.readPreference = self.readPreference;
+
+  // Fetch the chunks
+  if (query != null) {
+    collection.findOne(query, options, function(err, doc) {
+      if (err) {
+        return error(err);
+      }
+
+      // Check if the collection for the files exists otherwise prepare the new one
+      if (doc != null) {
+        self.fileId = doc._id;
+        // Prefer a new filename over the existing one if this is a write
+        self.filename =
+          self.mode === 'r' || self.filename === undefined ? doc.filename : self.filename;
+        self.contentType = doc.contentType;
+        self.internalChunkSize = doc.chunkSize;
+        self.uploadDate = doc.uploadDate;
+        self.aliases = doc.aliases;
+        self.length = doc.length;
+        self.metadata = doc.metadata;
+        self.internalMd5 = doc.md5;
+      } else if (self.mode !== 'r') {
+        self.fileId = self.fileId == null ? new ObjectID() : self.fileId;
+        self.contentType = GridStore.DEFAULT_CONTENT_TYPE;
+        self.internalChunkSize =
+          self.internalChunkSize == null ? Chunk.DEFAULT_CHUNK_SIZE : self.internalChunkSize;
+        self.length = 0;
+      } else {
+        self.length = 0;
+        var txtId = self.fileId._bsontype === 'ObjectID' ? self.fileId.toHexString() : self.fileId;
+        return error(
+          MongoError.create({
+            message: f(
+              'file with id %s not opened for writing',
+              self.referenceBy === REFERENCE_BY_ID ? txtId : self.filename
+            ),
+            driver: true
+          }),
+          self
+        );
+      }
+
+      // Process the mode of the object
+      if (self.mode === 'r') {
+        nthChunk(self, 0, options, function(err, chunk) {
+          if (err) return error(err);
+          self.currentChunk = chunk;
+          self.position = 0;
+          callback(null, self);
+        });
+      } else if (self.mode === 'w' && doc) {
+        // Delete any existing chunks
+        deleteChunks(self, options, function(err) {
+          if (err) return error(err);
+          self.currentChunk = new Chunk(self, { n: 0 }, self.writeConcern);
+          self.contentType =
+            self.options['content_type'] == null ? self.contentType : self.options['content_type'];
+          self.internalChunkSize =
+            self.options['chunk_size'] == null
+              ? self.internalChunkSize
+              : self.options['chunk_size'];
+          self.metadata =
+            self.options['metadata'] == null ? self.metadata : self.options['metadata'];
+          self.aliases = self.options['aliases'] == null ? self.aliases : self.options['aliases'];
+          self.position = 0;
+          callback(null, self);
+        });
+      } else if (self.mode === 'w') {
+        self.currentChunk = new Chunk(self, { n: 0 }, self.writeConcern);
+        self.contentType =
+          self.options['content_type'] == null ? self.contentType : self.options['content_type'];
+        self.internalChunkSize =
+          self.options['chunk_size'] == null ? self.internalChunkSize : self.options['chunk_size'];
+        self.metadata = self.options['metadata'] == null ? self.metadata : self.options['metadata'];
+        self.aliases = self.options['aliases'] == null ? self.aliases : self.options['aliases'];
+        self.position = 0;
+        callback(null, self);
+      } else if (self.mode === 'w+') {
+        nthChunk(self, lastChunkNumber(self), options, function(err, chunk) {
+          if (err) return error(err);
+          // Set the current chunk
+          self.currentChunk = chunk == null ? new Chunk(self, { n: 0 }, self.writeConcern) : chunk;
+          self.currentChunk.position = self.currentChunk.data.length();
+          self.metadata =
+            self.options['metadata'] == null ? self.metadata : self.options['metadata'];
+          self.aliases = self.options['aliases'] == null ? self.aliases : self.options['aliases'];
+          self.position = self.length;
+          callback(null, self);
+        });
+      }
+    });
+  } else {
+    // Write only mode
+    self.fileId = null == self.fileId ? new ObjectID() : self.fileId;
+    self.contentType = GridStore.DEFAULT_CONTENT_TYPE;
+    self.internalChunkSize =
+      self.internalChunkSize == null ? Chunk.DEFAULT_CHUNK_SIZE : self.internalChunkSize;
+    self.length = 0;
+
+    // No file exists set up write mode
+    if (self.mode === 'w') {
+      // Delete any existing chunks
+      deleteChunks(self, options, function(err) {
+        if (err) return error(err);
+        self.currentChunk = new Chunk(self, { n: 0 }, self.writeConcern);
+        self.contentType =
+          self.options['content_type'] == null ? self.contentType : self.options['content_type'];
+        self.internalChunkSize =
+          self.options['chunk_size'] == null ? self.internalChunkSize : self.options['chunk_size'];
+        self.metadata = self.options['metadata'] == null ? self.metadata : self.options['metadata'];
+        self.aliases = self.options['aliases'] == null ? self.aliases : self.options['aliases'];
+        self.position = 0;
+        callback(null, self);
+      });
+    } else if (self.mode === 'w+') {
+      nthChunk(self, lastChunkNumber(self), options, function(err, chunk) {
+        if (err) return error(err);
+        // Set the current chunk
+        self.currentChunk = chunk == null ? new Chunk(self, { n: 0 }, self.writeConcern) : chunk;
+        self.currentChunk.position = self.currentChunk.data.length();
+        self.metadata = self.options['metadata'] == null ? self.metadata : self.options['metadata'];
+        self.aliases = self.options['aliases'] == null ? self.aliases : self.options['aliases'];
+        self.position = self.length;
+        callback(null, self);
+      });
+    }
+  }
+
+  // only pass error to callback once
+  function error(err) {
+    if (error.err) return;
+    callback((error.err = err));
+  }
+};
+
+/**
+ * @ignore
+ */
+var writeBuffer = function(self, buffer, close, callback) {
+  if (typeof close === 'function') {
+    callback = close;
+    close = null;
+  }
+  var finalClose = typeof close === 'boolean' ? close : false;
+
+  if (self.mode !== 'w') {
+    callback(
+      MongoError.create({
+        message: f(
+          'file with id %s not opened for writing',
+          self.referenceBy === REFERENCE_BY_ID ? self.referenceBy : self.filename
+        ),
+        driver: true
+      }),
+      null
+    );
+  } else {
+    if (self.currentChunk.position + buffer.length >= self.chunkSize) {
+      // Write out the current Chunk and then keep writing until we have less data left than a chunkSize left
+      // to a new chunk (recursively)
+      var previousChunkNumber = self.currentChunk.chunkNumber;
+      var leftOverDataSize = self.chunkSize - self.currentChunk.position;
+      var firstChunkData = buffer.slice(0, leftOverDataSize);
+      var leftOverData = buffer.slice(leftOverDataSize);
+      // A list of chunks to write out
+      var chunksToWrite = [self.currentChunk.write(firstChunkData)];
+      // If we have more data left than the chunk size let's keep writing new chunks
+      while (leftOverData.length >= self.chunkSize) {
+        // Create a new chunk and write to it
+        var newChunk = new Chunk(self, { n: previousChunkNumber + 1 }, self.writeConcern);
+        firstChunkData = leftOverData.slice(0, self.chunkSize);
+        leftOverData = leftOverData.slice(self.chunkSize);
+        // Update chunk number
+        previousChunkNumber = previousChunkNumber + 1;
+        // Write data
+        newChunk.write(firstChunkData);
+        // Push chunk to save list
+        chunksToWrite.push(newChunk);
+      }
+
+      // Set current chunk with remaining data
+      self.currentChunk = new Chunk(self, { n: previousChunkNumber + 1 }, self.writeConcern);
+      // If we have left over data write it
+      if (leftOverData.length > 0) self.currentChunk.write(leftOverData);
+
+      // Update the position for the gridstore
+      self.position = self.position + buffer.length;
+      // Total number of chunks to write
+      var numberOfChunksToWrite = chunksToWrite.length;
+
+      for (var i = 0; i < chunksToWrite.length; i++) {
+        chunksToWrite[i].save({}, function(err) {
+          if (err) return callback(err);
+
+          numberOfChunksToWrite = numberOfChunksToWrite - 1;
+
+          if (numberOfChunksToWrite <= 0) {
+            // We care closing the file before returning
+            if (finalClose) {
+              return self.close(function(err) {
+                callback(err, self);
+              });
+            }
+
+            // Return normally
+            return callback(null, self);
+          }
+        });
+      }
+    } else {
+      // Update the position for the gridstore
+      self.position = self.position + buffer.length;
+      // We have less data than the chunk size just write it and callback
+      self.currentChunk.write(buffer);
+      // We care closing the file before returning
+      if (finalClose) {
+        return self.close(function(err) {
+          callback(err, self);
+        });
+      }
+      // Return normally
+      return callback(null, self);
+    }
+  }
+};
+
+/**
+ * Creates a mongoDB object representation of this object.
+ *
+ *        <pre><code>
+ *        {
+ *          '_id' : , // {number} id for this file
+ *          'filename' : , // {string} name for this file
+ *          'contentType' : , // {string} mime type for this file
+ *          'length' : , // {number} size of this file?
+ *          'chunksize' : , // {number} chunk size used by this file
+ *          'uploadDate' : , // {Date}
+ *          'aliases' : , // {array of string}
+ *          'metadata' : , // {string}
+ *        }
+ *        </code></pre>
+ *
+ * @ignore
+ */
+var buildMongoObject = function(self, callback) {
+  // Calcuate the length
+  var mongoObject = {
+    _id: self.fileId,
+    filename: self.filename,
+    contentType: self.contentType,
+    length: self.position ? self.position : 0,
+    chunkSize: self.chunkSize,
+    uploadDate: self.uploadDate,
+    aliases: self.aliases,
+    metadata: self.metadata
+  };
+
+  var md5Command = { filemd5: self.fileId, root: self.root };
+  self.db.command(md5Command, function(err, results) {
+    if (err) return callback(err);
+
+    mongoObject.md5 = results.md5;
+    callback(null, mongoObject);
+  });
+};
+
+/**
+ * Gets the nth chunk of this file.
+ * @ignore
+ */
+var nthChunk = function(self, chunkNumber, options, callback) {
+  if (typeof options === 'function') {
+    callback = options;
+    options = {};
+  }
+
+  options = options || self.writeConcern;
+  options.readPreference = self.readPreference;
+  // Get the nth chunk
+  self
+    .chunkCollection()
+    .findOne({ files_id: self.fileId, n: chunkNumber }, options, function(err, chunk) {
+      if (err) return callback(err);
+
+      var finalChunk = chunk == null ? {} : chunk;
+      callback(null, new Chunk(self, finalChunk, self.writeConcern));
+    });
+};
+
+/**
+ * @ignore
+ */
+var lastChunkNumber = function(self) {
+  return Math.floor((self.length ? self.length - 1 : 0) / self.chunkSize);
+};
+
+/**
+ * Deletes all the chunks of this file in the database.
+ *
+ * @ignore
+ */
+var deleteChunks = function(self, options, callback) {
+  if (typeof options === 'function') {
+    callback = options;
+    options = {};
+  }
+
+  options = options || self.writeConcern;
+
+  if (self.fileId != null) {
+    self.chunkCollection().remove({ files_id: self.fileId }, options, function(err) {
+      if (err) return callback(err, false);
+      callback(null, true);
+    });
+  } else {
+    callback(null, true);
+  }
+};
+
+/**
+ * The collection to be used for holding the files and chunks collection.
+ *
+ * @classconstant DEFAULT_ROOT_COLLECTION
+ */
+GridStore.DEFAULT_ROOT_COLLECTION = 'fs';
+
+/**
+ * Default file mime type
+ *
+ * @classconstant DEFAULT_CONTENT_TYPE
+ */
+GridStore.DEFAULT_CONTENT_TYPE = 'binary/octet-stream';
+
+/**
+ * Seek mode where the given length is absolute.
+ *
+ * @classconstant IO_SEEK_SET
+ */
+GridStore.IO_SEEK_SET = 0;
+
+/**
+ * Seek mode where the given length is an offset to the current read/write head.
+ *
+ * @classconstant IO_SEEK_CUR
+ */
+GridStore.IO_SEEK_CUR = 1;
+
+/**
+ * Seek mode where the given length is an offset to the end of the file.
+ *
+ * @classconstant IO_SEEK_END
+ */
+GridStore.IO_SEEK_END = 2;
+
+/**
+ * Checks if a file exists in the database.
+ *
+ * @method
+ * @static
+ * @param {Db} db the database to query.
+ * @param {string} name The name of the file to look for.
+ * @param {string} [rootCollection] The root collection that holds the files and chunks collection. Defaults to **{GridStore.DEFAULT_ROOT_COLLECTION}**.
+ * @param {object} [options] Optional settings.
+ * @param {(ReadPreference|string)} [options.readPreference] The preferred read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).
+ * @param {object} [options.promiseLibrary] A Promise library class the application wishes to use such as Bluebird, must be ES6 compatible
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~resultCallback} [callback] result from exists.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.exist = function(db, fileIdObject, rootCollection, options, callback) {
+  var args = Array.prototype.slice.call(arguments, 2);
+  callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
+  rootCollection = args.length ? args.shift() : null;
+  options = args.length ? args.shift() : {};
+  options = options || {};
+
+  return executeLegacyOperation(
+    db.s.topology,
+    exists,
+    [db, fileIdObject, rootCollection, options, callback],
+    { skipSessions: true }
+  );
+};
+
+var exists = function(db, fileIdObject, rootCollection, options, callback) {
+  // Establish read preference
+  var readPreference = options.readPreference || ReadPreference.PRIMARY;
+  // Fetch collection
+  var rootCollectionFinal =
+    rootCollection != null ? rootCollection : GridStore.DEFAULT_ROOT_COLLECTION;
+  db.collection(rootCollectionFinal + '.files', function(err, collection) {
+    if (err) return callback(err);
+
+    // Build query
+    var query =
+      typeof fileIdObject === 'string' ||
+      Object.prototype.toString.call(fileIdObject) === '[object RegExp]'
+        ? { filename: fileIdObject }
+        : { _id: fileIdObject }; // Attempt to locate file
+
+    // We have a specific query
+    if (
+      fileIdObject != null &&
+      typeof fileIdObject === 'object' &&
+      Object.prototype.toString.call(fileIdObject) !== '[object RegExp]'
+    ) {
+      query = fileIdObject;
+    }
+
+    // Check if the entry exists
+    collection.findOne(query, { readPreference: readPreference }, function(err, item) {
+      if (err) return callback(err);
+      callback(null, item == null ? false : true);
+    });
+  });
+};
+
+/**
+ * Gets the list of files stored in the GridFS.
+ *
+ * @method
+ * @static
+ * @param {Db} db the database to query.
+ * @param {string} [rootCollection] The root collection that holds the files and chunks collection. Defaults to **{GridStore.DEFAULT_ROOT_COLLECTION}**.
+ * @param {object} [options] Optional settings.
+ * @param {(ReadPreference|string)} [options.readPreference] The preferred read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).
+ * @param {object} [options.promiseLibrary] A Promise library class the application wishes to use such as Bluebird, must be ES6 compatible
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~resultCallback} [callback] result from exists.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.list = function(db, rootCollection, options, callback) {
+  var args = Array.prototype.slice.call(arguments, 1);
+  callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
+  rootCollection = args.length ? args.shift() : null;
+  options = args.length ? args.shift() : {};
+  options = options || {};
+
+  return executeLegacyOperation(db.s.topology, list, [db, rootCollection, options, callback], {
+    skipSessions: true
+  });
+};
+
+var list = function(db, rootCollection, options, callback) {
+  // Ensure we have correct values
+  if (rootCollection != null && typeof rootCollection === 'object') {
+    options = rootCollection;
+    rootCollection = null;
+  }
+
+  // Establish read preference
+  var readPreference = options.readPreference || ReadPreference.primary;
+  // Check if we are returning by id not filename
+  var byId = options['id'] != null ? options['id'] : false;
+  // Fetch item
+  var rootCollectionFinal =
+    rootCollection != null ? rootCollection : GridStore.DEFAULT_ROOT_COLLECTION;
+  var items = [];
+  db.collection(rootCollectionFinal + '.files', function(err, collection) {
+    if (err) return callback(err);
+
+    collection.find({}, { readPreference: readPreference }, function(err, cursor) {
+      if (err) return callback(err);
+
+      cursor.each(function(err, item) {
+        if (item != null) {
+          items.push(byId ? item._id : item.filename);
+        } else {
+          callback(err, items);
+        }
+      });
+    });
+  });
+};
+
+/**
+ * Reads the contents of a file.
+ *
+ * This method has the following signatures
+ *
+ * (db, name, callback)
+ * (db, name, length, callback)
+ * (db, name, length, offset, callback)
+ * (db, name, length, offset, options, callback)
+ *
+ * @method
+ * @static
+ * @param {Db} db the database to query.
+ * @param {string} name The name of the file.
+ * @param {number} [length] The size of data to read.
+ * @param {number} [offset] The offset from the head of the file of which to start reading from.
+ * @param {object} [options] Optional settings.
+ * @param {(ReadPreference|string)} [options.readPreference] The preferred read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).
+ * @param {object} [options.promiseLibrary] A Promise library class the application wishes to use such as Bluebird, must be ES6 compatible
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~readCallback} [callback] the command callback.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.read = function(db, name, length, offset, options, callback) {
+  var args = Array.prototype.slice.call(arguments, 2);
+  callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
+  length = args.length ? args.shift() : null;
+  offset = args.length ? args.shift() : null;
+  options = args.length ? args.shift() : null;
+  options = options || {};
+
+  return executeLegacyOperation(
+    db.s.topology,
+    readStatic,
+    [db, name, length, offset, options, callback],
+    { skipSessions: true }
+  );
+};
+
+var readStatic = function(db, name, length, offset, options, callback) {
+  new GridStore(db, name, 'r', options).open(function(err, gridStore) {
+    if (err) return callback(err);
+    // Make sure we are not reading out of bounds
+    if (offset && offset >= gridStore.length)
+      return callback('offset larger than size of file', null);
+    if (length && length > gridStore.length)
+      return callback('length is larger than the size of the file', null);
+    if (offset && length && offset + length > gridStore.length)
+      return callback('offset and length is larger than the size of the file', null);
+
+    if (offset != null) {
+      gridStore.seek(offset, function(err, gridStore) {
+        if (err) return callback(err);
+        gridStore.read(length, callback);
+      });
+    } else {
+      gridStore.read(length, callback);
+    }
+  });
+};
+
+/**
+ * Read the entire file as a list of strings splitting by the provided separator.
+ *
+ * @method
+ * @static
+ * @param {Db} db the database to query.
+ * @param {(String|object)} name the name of the file.
+ * @param {string} [separator] The character to be recognized as the newline separator.
+ * @param {object} [options] Optional settings.
+ * @param {(ReadPreference|string)} [options.readPreference] The preferred read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).
+ * @param {object} [options.promiseLibrary] A Promise library class the application wishes to use such as Bluebird, must be ES6 compatible
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~readlinesCallback} [callback] the command callback.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.readlines = function(db, name, separator, options, callback) {
+  var args = Array.prototype.slice.call(arguments, 2);
+  callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
+  separator = args.length ? args.shift() : null;
+  options = args.length ? args.shift() : null;
+  options = options || {};
+
+  return executeLegacyOperation(
+    db.s.topology,
+    readlinesStatic,
+    [db, name, separator, options, callback],
+    { skipSessions: true }
+  );
+};
+
+var readlinesStatic = function(db, name, separator, options, callback) {
+  var finalSeperator = separator == null ? '\n' : separator;
+  new GridStore(db, name, 'r', options).open(function(err, gridStore) {
+    if (err) return callback(err);
+    gridStore.readlines(finalSeperator, callback);
+  });
+};
+
+/**
+ * Deletes the chunks and metadata information of a file from GridFS.
+ *
+ * @method
+ * @static
+ * @param {Db} db The database to query.
+ * @param {(string|array)} names The name/names of the files to delete.
+ * @param {object} [options] Optional settings.
+ * @param {object} [options.promiseLibrary] A Promise library class the application wishes to use such as Bluebird, must be ES6 compatible
+ * @param {ClientSession} [options.session] optional session to use for this operation
+ * @param {GridStore~resultCallback} [callback] the command callback.
+ * @return {Promise} returns Promise if no callback passed
+ * @deprecated Use GridFSBucket API instead
+ */
+GridStore.unlink = function(db, names, options, callback) {
+  var args = Array.prototype.slice.call(arguments, 2);
+  callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
+  options = args.length ? args.shift() : {};
+  options = options || {};
+
+  return executeLegacyOperation(db.s.topology, unlinkStatic, [this, db, names, options, callback], {
+    skipSessions: true
+  });
+};
+
+var unlinkStatic = function(self, db, names, options, callback) {
+  // Get the write concern
+  var writeConcern = _getWriteConcern(db, options);
+
+  // List of names
+  if (names.constructor === Array) {
+    var tc = 0;
+    for (var i = 0; i < names.length; i++) {
+      ++tc;
+      GridStore.unlink(db, names[i], options, function() {
+        if (--tc === 0) {
+          callback(null, self);
+        }
+      });
+    }
+  } else {
+    new GridStore(db, names, 'w', options).open(function(err, gridStore) {
+      if (err) return callback(err);
+      deleteChunks(gridStore, function(err) {
+        if (err) return callback(err);
+        gridStore.collection(function(err, collection) {
+          if (err) return callback(err);
+          collection.remove({ _id: gridStore.fileId }, writeConcern, function(err) {
+            callback(err, self);
+          });
+        });
+      });
+    });
+  }
+};
+
+/**
+ *  @ignore
+ */
+var _writeNormal = function(self, data, close, options, callback) {
+  // If we have a buffer write it using the writeBuffer method
+  if (Buffer.isBuffer(data)) {
+    return writeBuffer(self, data, close, callback);
+  } else {
+    return writeBuffer(self, Buffer.from(data, 'binary'), close, callback);
+  }
+};
+
+/**
+ * @ignore
+ */
+var _setWriteConcernHash = function(options) {
+  var finalOptions = {};
+  if (options.w != null) finalOptions.w = options.w;
+  if (options.journal === true) finalOptions.j = options.journal;
+  if (options.j === true) finalOptions.j = options.j;
+  if (options.fsync === true) finalOptions.fsync = options.fsync;
+  if (options.wtimeout != null) finalOptions.wtimeout = options.wtimeout;
+  return finalOptions;
+};
+
+/**
+ * @ignore
+ */
+var _getWriteConcern = function(self, options) {
+  // Final options
+  var finalOptions = { w: 1 };
+  options = options || {};
+
+  // Local options verification
+  if (
+    options.w != null ||
+    typeof options.j === 'boolean' ||
+    typeof options.journal === 'boolean' ||
+    typeof options.fsync === 'boolean'
+  ) {
+    finalOptions = _setWriteConcernHash(options);
+  } else if (options.safe != null && typeof options.safe === 'object') {
+    finalOptions = _setWriteConcernHash(options.safe);
+  } else if (typeof options.safe === 'boolean') {
+    finalOptions = { w: options.safe ? 1 : 0 };
+  } else if (
+    self.options.w != null ||
+    typeof self.options.j === 'boolean' ||
+    typeof self.options.journal === 'boolean' ||
+    typeof self.options.fsync === 'boolean'
+  ) {
+    finalOptions = _setWriteConcernHash(self.options);
+  } else if (
+    self.safe &&
+    (self.safe.w != null ||
+      typeof self.safe.j === 'boolean' ||
+      typeof self.safe.journal === 'boolean' ||
+      typeof self.safe.fsync === 'boolean')
+  ) {
+    finalOptions = _setWriteConcernHash(self.safe);
+  } else if (typeof self.safe === 'boolean') {
+    finalOptions = { w: self.safe ? 1 : 0 };
+  }
+
+  // Ensure we don't have an invalid combination of write concerns
+  if (
+    finalOptions.w < 1 &&
+    (finalOptions.journal === true || finalOptions.j === true || finalOptions.fsync === true)
+  )
+    throw MongoError.create({
+      message: 'No acknowledgement using w < 1 cannot be combined with journal:true or fsync:true',
+      driver: true
+    });
+
+  // Return the options
+  return finalOptions;
+};
+
+/**
+ * Create a new GridStoreStream instance (INTERNAL TYPE, do not instantiate directly)
+ *
+ * @class
+ * @extends external:Duplex
+ * @return {GridStoreStream} a GridStoreStream instance.
+ * @deprecated Use GridFSBucket API instead
+ */
+var GridStoreStream = function(gs) {
+  // Initialize the duplex stream
+  Duplex.call(this);
+
+  // Get the gridstore
+  this.gs = gs;
+
+  // End called
+  this.endCalled = false;
+
+  // If we have a seek
+  this.totalBytesToRead = this.gs.length - this.gs.position;
+  this.seekPosition = this.gs.position;
+};
+
+//
+// Inherit duplex
+inherits(GridStoreStream, Duplex);
+
+GridStoreStream.prototype._pipe = GridStoreStream.prototype.pipe;
+
+// Set up override
+GridStoreStream.prototype.pipe = function(destination) {
+  var self = this;
+
+  // Only open gridstore if not already open
+  if (!self.gs.isOpen) {
+    self.gs.open(function(err) {
+      if (err) return self.emit('error', err);
+      self.totalBytesToRead = self.gs.length - self.gs.position;
+      self._pipe.apply(self, [destination]);
+    });
+  } else {
+    self.totalBytesToRead = self.gs.length - self.gs.position;
+    self._pipe.apply(self, [destination]);
+  }
+
+  return destination;
+};
+
+// Called by stream
+GridStoreStream.prototype._read = function() {
+  var self = this;
+
+  var read = function() {
+    // Read data
+    self.gs.read(length, function(err, buffer) {
+      if (err && !self.endCalled) return self.emit('error', err);
+
+      // Stream is closed
+      if (self.endCalled || buffer == null) return self.push(null);
+      // Remove bytes read
+      if (buffer.length <= self.totalBytesToRead) {
+        self.totalBytesToRead = self.totalBytesToRead - buffer.length;
+        self.push(buffer);
+      } else if (buffer.length > self.totalBytesToRead) {
+        self.totalBytesToRead = self.totalBytesToRead - buffer._index;
+        self.push(buffer.slice(0, buffer._index));
+      }
+
+      // Finished reading
+      if (self.totalBytesToRead <= 0) {
+        self.endCalled = true;
+      }
+    });
+  };
+
+  // Set read length
+  var length =
+    self.gs.length < self.gs.chunkSize ? self.gs.length - self.seekPosition : self.gs.chunkSize;
+  if (!self.gs.isOpen) {
+    self.gs.open(function(err) {
+      self.totalBytesToRead = self.gs.length - self.gs.position;
+      if (err) return self.emit('error', err);
+      read();
+    });
+  } else {
+    read();
+  }
+};
+
+GridStoreStream.prototype.destroy = function() {
+  this.pause();
+  this.endCalled = true;
+  this.gs.close();
+  this.emit('end');
+};
+
+GridStoreStream.prototype.write = function(chunk) {
+  var self = this;
+  if (self.endCalled)
+    return self.emit(
+      'error',
+      MongoError.create({ message: 'attempting to write to stream after end called', driver: true })
+    );
+  // Do we have to open the gridstore
+  if (!self.gs.isOpen) {
+    self.gs.open(function() {
+      self.gs.isOpen = true;
+      self.gs.write(chunk, function() {
+        process.nextTick(function() {
+          self.emit('drain');
+        });
+      });
+    });
+    return false;
+  } else {
+    self.gs.write(chunk, function() {
+      self.emit('drain');
+    });
+    return true;
+  }
+};
+
+GridStoreStream.prototype.end = function(chunk, encoding, callback) {
+  var self = this;
+  var args = Array.prototype.slice.call(arguments, 0);
+  callback = typeof args[args.length - 1] === 'function' ? args.pop() : undefined;
+  chunk = args.length ? args.shift() : null;
+  encoding = args.length ? args.shift() : null;
+  self.endCalled = true;
+
+  if (chunk) {
+    self.gs.write(chunk, function() {
+      self.gs.close(function() {
+        if (typeof callback === 'function') callback();
+        self.emit('end');
+      });
+    });
+  }
+
+  self.gs.close(function() {
+    if (typeof callback === 'function') callback();
+    self.emit('end');
+  });
+};
+
+/**
+ * The read() method pulls some data out of the internal buffer and returns it. If there is no data available, then it will return null.
+ * @function external:Duplex#read
+ * @param {number} size Optional argument to specify how much data to read.
+ * @return {(String | Buffer | null)}
+ */
+
+/**
+ * Call this function to cause the stream to return strings of the specified encoding instead of Buffer objects.
+ * @function external:Duplex#setEncoding
+ * @param {string} encoding The encoding to use.
+ * @return {null}
+ */
+
+/**
+ * This method will cause the readable stream to resume emitting data events.
+ * @function external:Duplex#resume
+ * @return {null}
+ */
+
+/**
+ * This method will cause a stream in flowing-mode to stop emitting data events. Any data that becomes available will remain in the internal buffer.
+ * @function external:Duplex#pause
+ * @return {null}
+ */
+
+/**
+ * This method pulls all the data out of a readable stream, and writes it to the supplied destination, automatically managing the flow so that the destination is not overwhelmed by a fast readable stream.
+ * @function external:Duplex#pipe
+ * @param {Writable} destination The destination for writing data
+ * @param {object} [options] Pipe options
+ * @return {null}
+ */
+
+/**
+ * This method will remove the hooks set up for a previous pipe() call.
+ * @function external:Duplex#unpipe
+ * @param {Writable} [destination] The destination for writing data
+ * @return {null}
+ */
+
+/**
+ * This is useful in certain cases where a stream is being consumed by a parser, which needs to "un-consume" some data that it has optimistically pulled out of the source, so that the stream can be passed on to some other party.
+ * @function external:Duplex#unshift
+ * @param {(Buffer|string)} chunk Chunk of data to unshift onto the read queue.
+ * @return {null}
+ */
+
+/**
+ * Versions of Node prior to v0.10 had streams that did not implement the entire Streams API as it is today. (See "Compatibility" below for more information.)
+ * @function external:Duplex#wrap
+ * @param {Stream} stream An "old style" readable stream.
+ * @return {null}
+ */
+
+/**
+ * This method writes some data to the underlying system, and calls the supplied callback once the data has been fully handled.
+ * @function external:Duplex#write
+ * @param {(string|Buffer)} chunk The data to write
+ * @param {string} encoding The encoding, if chunk is a String
+ * @param {function} callback Callback for when this chunk of data is flushed
+ * @return {boolean}
+ */
+
+/**
+ * Call this method when no more data will be written to the stream. If supplied, the callback is attached as a listener on the finish event.
+ * @function external:Duplex#end
+ * @param {(string|Buffer)} chunk The data to write
+ * @param {string} encoding The encoding, if chunk is a String
+ * @param {function} callback Callback for when this chunk of data is flushed
+ * @return {null}
+ */
+
+/**
+ * GridStoreStream stream data event, fired for each document in the cursor.
+ *
+ * @event GridStoreStream#data
+ * @type {object}
+ */
+
+/**
+ * GridStoreStream stream end event
+ *
+ * @event GridStoreStream#end
+ * @type {null}
+ */
+
+/**
+ * GridStoreStream stream close event
+ *
+ * @event GridStoreStream#close
+ * @type {null}
+ */
+
+/**
+ * GridStoreStream stream readable event
+ *
+ * @event GridStoreStream#readable
+ * @type {null}
+ */
+
+/**
+ * GridStoreStream stream drain event
+ *
+ * @event GridStoreStream#drain
+ * @type {null}
+ */
+
+/**
+ * GridStoreStream stream finish event
+ *
+ * @event GridStoreStream#finish
+ * @type {null}
+ */
+
+/**
+ * GridStoreStream stream pipe event
+ *
+ * @event GridStoreStream#pipe
+ * @type {null}
+ */
+
+/**
+ * GridStoreStream stream unpipe event
+ *
+ * @event GridStoreStream#unpipe
+ * @type {null}
+ */
+
+/**
+ * GridStoreStream stream error event
+ *
+ * @event GridStoreStream#error
+ * @type {null}
+ */
+
+/**
+ * @ignore
+ */
+module.exports = GridStore;