GridStore()

Constructor

A class representation of a file stored in GridFS.

class GridStore()

Arguments:

• db (db) – A database instance to interact with.
• [id] (any) – optional unique id for this file
• [filename] (string) – optional filename for this file, no unique constrain on the field
• mode (string) – set the mode for this file.
• options (object) – optional properties to specify.

Returns:

gridstore

Modes

• “r” - read only. This is the default mode.
• “w” - write in truncate mode. Existing data will be overwriten.
• w+” - write in edit mode (append is not guaranteed for concurrent operations)

Options

• root {String}, root collection to use. Defaults to {GridStore.DEFAULT_ROOT_COLLECTION}.
• content_type {String}, mime type of the file. Defaults to {GridStore.DEFAULT_CONTENT_TYPE}.
• chunk_size {Number}, size for the chunk. Defaults to {Chunk.DEFAULT_CHUNK_SIZE}.
• metadata {Object}, arbitrary data the user wants to store.
• readPreference {String}, the prefered read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).
• w, {Number/String, > -1 || ‘majority’ || tag name} the write concern for the operation where < 1 is no acknowlegement of write and w >= 1, w = ‘majority’ or tag acknowledges the write
• wtimeout, {Number, 0} set the timeout for waiting for write concern to finish (combines with w option)
• fsync, (Boolean, default:false) write waits for fsync before returning, from MongoDB 2.6 on, fsync cannot be combined with journal
• j, (Boolean, default:false) write waits for journal sync before returning

Constants

Constant Name	Value	Description
GridStore.DEFAULT_ROOT_COLLECTION	‘fs’	The collection to be used for holding the files and chunks collection.
GridStore.DEFAULT_CONTENT_TYPE	‘binary/octet-stream’	Default file mime type
GridStore.IO_SEEK_SET	0	Seek mode where the given length is absolute.
GridStore.IO_SEEK_CUR	1	Seek mode where the given length is an offset to the current read/write head.
GridStore.IO_SEEK_END	2	Seek mode where the given length is an offset to the end of the file.

Properties

Returns the current chunksize of the file.

chunkSize number [Getter|Setter]

The md5 checksum for this file.

md5 number [Getter|Setter]

open

Opens the file from the database and initialize this object. Also creates a new one if file does not exist.

open(callback)

Arguments:

• callback (function) – this will be called after executing this method. The first parameter will contain an {Error} object and the second parameter will be null if an error occured. Otherwise, the first parameter will be null and the second will contain the reference to this object.

Returns:

null

Examples

A simple example showing how to save a file with a filename allowing for multiple files with the same name

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Create a file and open it var gridStore = new GridStore(db, new ObjectID(), "test_gs_getc_file", "w"); gridStore.open(function(err, gridStore) { // Write some content to the file gridStore.write(new Buffer("hello, world!", "utf8"), function(err, gridStore) { // Flush the file to GridFS gridStore.close(function(err, fileData) { assert.equal(null, err); // Create another file with same name and and save content to it gridStore = new GridStore(db, new ObjectID(), "test_gs_getc_file", "w"); gridStore.open(function(err, gridStore) { // Write some content to the file gridStore.write(new Buffer("hello, world!", "utf8"), function(err, gridStore) { // Flush the file to GridFS gridStore.close(function(err, fileData) { assert.equal(null, err); // Open the file in read mode using the filename var gridStore2 = new GridStore(db, "test_gs_getc_file", "r"); gridStore2.open(function(err, gridStore) { // Read first character and verify gridStore.getc(function(err, chr) { assert.equal('h', chr); // Open the file using an object id gridStore2 = new GridStore(db, fileData._id, "r"); gridStore2.open(function(err, gridStore) { // Read first character and verify gridStore.getc(function(err, chr) { assert.equal('h', chr); db.close(); }) }); }); }); }); }); }); }); }); }); }); 

A simple example showing opening a file using a filename, writing to it and saving it.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Create a new instance of the gridstore var gridStore = new GridStore(db, 'ourexamplefiletowrite.txt', 'w'); // Open the file gridStore.open(function(err, gridStore) { // Write some data to the file gridStore.write('bar', function(err, gridStore) { assert.equal(null, err); // Close (Flushes the data to MongoDB) gridStore.close(function(err, result) { assert.equal(null, err); // Verify that the file exists GridStore.exist(db, 'ourexamplefiletowrite.txt', function(err, result) { assert.equal(null, err); assert.equal(true, result); db.close(); }); }); }); }); }); 

A simple example showing opening a file using an ObjectID, writing to it and saving it.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Our file ID var fileId = new ObjectID(); // Create a new instance of the gridstore var gridStore = new GridStore(db, fileId, 'w'); // Open the file gridStore.open(function(err, gridStore) { // Write some data to the file gridStore.write('bar', function(err, gridStore) { assert.equal(null, err); // Close (Flushes the data to MongoDB) gridStore.close(function(err, result) { assert.equal(null, err); // Verify that the file exists GridStore.exist(db, fileId, function(err, result) { assert.equal(null, err); assert.equal(true, result); db.close(); }); }); }); }); }); 

writeFile

Stores a file from the file system to the GridFS database.

writeFile(file, callback)

Arguments:

• file (string) – the file to store.
• callback (function) – this will be called after this method is executed. The first parameter will be null and the the second will contain the reference to this object.

Returns:

null

Examples

A simple example showing how to write a file to Gridstore using file location path.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Our file ID var fileId = new ObjectID(); // Open a new file var gridStore = new GridStore(db, fileId, 'w'); // Read the filesize of file on disk (provide your own) var fileSize = fs.statSync('./test/tests/functional/gridstore/test_gs_weird_bug.png').size; // Read the buffered data for comparision reasons var data = fs.readFileSync('./test/tests/functional/gridstore/test_gs_weird_bug.png'); // Open the new file gridStore.open(function(err, gridStore) { // Write the file to gridFS gridStore.writeFile('./test/tests/functional/gridstore/test_gs_weird_bug.png', function(err, doc) { // Read back all the written content and verify the correctness GridStore.read(db, fileId, function(err, fileData) { assert.equal(data.toString('base64'), fileData.toString('base64')) assert.equal(fileSize, fileData.length); db.close(); }); }); }); }); 

A simple example showing how to write a file to Gridstore using a file handle.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Our file ID var fileId = new ObjectID(); // Open a new file var gridStore = new GridStore(db, fileId, 'w'); // Read the filesize of file on disk (provide your own) var fileSize = fs.statSync('./test/tests/functional/gridstore/test_gs_weird_bug.png').size; // Read the buffered data for comparision reasons var data = fs.readFileSync('./test/tests/functional/gridstore/test_gs_weird_bug.png'); // Open a file handle for reading the file var fd = fs.openSync('./test/tests/functional/gridstore/test_gs_weird_bug.png', 'r', 0666); // Open the new file gridStore.open(function(err, gridStore) { // Write the file to gridFS using the file handle gridStore.writeFile(fd, function(err, doc) { // Read back all the written content and verify the correctness GridStore.read(db, fileId, function(err, fileData) { assert.equal(data.toString('base64'), fileData.toString('base64')); assert.equal(fileSize, fileData.length); db.close(); }); }); }); }); 

close

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+”.

close(callback)

Arguments:

• callback (function) – this will be called after executing this method. Passes an {Error} object to the first parameter and null to the second if an error occured. Otherwise, passes null to the first and a reference to this object to the second.

Returns:

null

Examples

A simple example showing how to use the write command with strings and Buffers.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Our file ID var fileId = new ObjectID(); // Open a new file var gridStore = new GridStore(db, fileId, 'w'); // Open the new file gridStore.open(function(err, gridStore) { // Write a text string gridStore.write('Hello world', function(err, gridStore) { // Close the gridStore.close(function(err, result) { assert.equal(err, null); db.close(); }); }); }); }); 

chunkCollection

Retrieve this file’s chunks collection.

chunkCollection(callback)

Arguments:

• callback (function) – this will be called after executing this method. An exception object will be passed to the first parameter when an error occured or null otherwise. A new {Collection} object will be passed to the second parameter if no error occured.

Returns:

null

Examples

A simple example showing how to access the chunks collection object.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Our file ID var fileId = new ObjectID(); // Open a new file var gridStore = new GridStore(db, fileId, 'w'); // Open the new file gridStore.open(function(err, gridStore) { // Access the Chunk collection gridStore.chunkCollection(function(err, collection) { assert.equal(err, null); db.close(); }); }); }); 

unlink

Deletes all the chunks of this file in the database.

unlink(callback)

Arguments:

• callback (function) – this will be called after this method executes. Passes null to the first and true to the second argument.

Returns:

null

Examples

A simple example showing how to use the instance level unlink command to delete a gridstore item.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Our file ID var fileId = new ObjectID(); // Open a new file var gridStore = new GridStore(db, fileId, 'w'); // Open the new file gridStore.open(function(err, gridStore) { // Write a text string gridStore.write('Hello world', function(err, gridStore) { // Close the gridStore.close(function(err, result) { assert.equal(err, null); // Open the file again and unlin it new GridStore(db, fileId, 'r').open(function(err, gridStore) { // Unlink the file gridStore.unlink(function(err, result) { assert.equal(null, err); // Verify that the file no longer exists GridStore.exist(db, fileId, function(err, result) { assert.equal(null, err); assert.equal(false, result); db.close(); }); }); }); }); }); }); }); 

collection

Retrieves the file collection associated with this object.

collection(callback)

Arguments:

• callback (function) – this will be called after executing this method. An exception object will be passed to the first parameter when an error occured or null otherwise. A new {Collection} object will be passed to the second parameter if no error occured.

Returns:

null

Examples

A simple example showing how to access the files collection object.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Our file ID var fileId = new ObjectID(); // Open a new file var gridStore = new GridStore(db, fileId, 'w'); // Open the new file gridStore.open(function(err, gridStore) { // Access the Chunk collection gridStore.collection(function(err, collection) { assert.equal(err, null); db.close(); }); }); }); 

readlines

Reads the data of this file.

readlines([separator], callback)

Arguments:

• [separator] (string) – the character to be recognized as the newline separator.
• callback (function) – This will be called after this method is executed. The first parameter will be null and the second parameter will contain an array of strings representing the entire data, each element representing a line including the separator character.

Returns:

null

Examples

A simple example showing reading back using readlines to split the text into lines by the seperator provided.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Our file ID var fileId = new ObjectID(); // Open a new file var gridStore = new GridStore(db, fileId, 'w'); // Open the new file gridStore.open(function(err, gridStore) { // Write one line to gridStore gridStore.puts("line one", function(err, gridStore) { // Write second line to gridStore gridStore.puts("line two", function(err, gridStore) { // Write third line to gridStore gridStore.puts("line three", function(err, gridStore) { // Flush file to disk gridStore.close(function(err, result) { // Open file for reading gridStore = new GridStore(db, fileId, 'r'); gridStore.open(function(err, gridStore) { // Read all the lines and verify correctness gridStore.readlines(function(err, lines) { assert.deepEqual(["line one\n", "line two\n", "line three\n"], lines); db.close(); }); }); }); }); }); }); }); }); 

rewind

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.

rewind(callback)

Arguments:

• callback (function) – 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.

Returns:

null

Examples

A simple example showing how to rewind and overwrite the file.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Our file ID var fileId = new ObjectID(); // Create a new file var gridStore = new GridStore(db, fileId, "w"); // Open the file gridStore.open(function(err, gridStore) { // Write to the file gridStore.write("hello, world!", function(err, gridStore) { // Flush the file to disk gridStore.close(function(err, result) { // Reopen the file gridStore = new GridStore(db, fileId, "w"); gridStore.open(function(err, gridStore) { // Write some more text to the file gridStore.write('some text is inserted here', function(err, gridStore) { // Let's rewind to truncate the file gridStore.rewind(function(err, gridStore) { // Write something from the start gridStore.write('abc', function(err, gridStore) { // Flush the data to mongodb gridStore.close(function(err, result) { // Verify that the new data was written GridStore.read(db, fileId, function(err, data) { assert.equal("abc", data); db.close(); }); }); }); }); }); }); }); }); }); }); 

read

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)

read([length][, buffer], callback)

Arguments:

• [length] (number) – the number of characters to read. Reads all the characters from the read/write head to the EOF if not specified.
• [buffer] (string) – a string to hold temporary data. This is used for storing the string data read so far when recursively calling this method.
• callback (function) – this will be called after this method is executed. null will be passed to the first parameter and a string containing the contents of the buffer concatenated with the contents read from this file will be passed to the second.

Returns:

null

Examples

A simple example showing the usage of the read method.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Read in the content of a file var data = fs.readFileSync('./test/tests/functional/gridstore/iya_logo_final_bw.jpg'); // Create a new file var gs = new GridStore(db, "test", "w"); // Open the file gs.open(function(err, gs) { // Write the file to GridFS gs.write(data, function(err, gs) { // Flush to the GridFS gs.close(function(err, gs) { // Define the file we wish to read var gs2 = new GridStore(db, "test", "r"); // Open the file gs2.open(function(err, gs) { // Set the pointer of the read head to the start of the gridstored file gs2.seek(0, function() { // Read the entire file gs2.read(function(err, data2) { // Compare the file content against the orgiinal assert.equal(data.toString('base64'), data2.toString('base64')); db.close(); }); }); }); }); }); }); }); 

tell

Retrieves the position of the read/write head of this file.

tell(callback)

Arguments:

• callback (function) – This gets called after this method terminates. null is passed to the first parameter and the position is passed to the second.

Returns:

null

Examples

A simple example showing the usage of the tell method.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Create a new file var gridStore = new GridStore(db, "test_gs_tell", "w"); // Open the file gridStore.open(function(err, gridStore) { // Write a string to the file gridStore.write("hello, world!", function(err, gridStore) { // Flush the file to GridFS gridStore.close(function(err, result) { // Open the file in read only mode var gridStore2 = new GridStore(db, "test_gs_tell", "r"); gridStore2.open(function(err, gridStore) { // Read the first 5 characters gridStore.read(5, function(err, data) { assert.equal("hello", data); // Get the current position of the read head gridStore.tell(function(err, position) { assert.equal(5, position); db.close(); }); }); }); }); }); }); }); 

seek

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.

seek([position][, seekLocation], callback)

Arguments:

• [position] (number) – the position to seek to
• [seekLocation] (number) – seek mode. Use one of the Seek Location modes.
• callback (function) – 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.

Returns:

null

Examples

A simple example showing the usage of the seek method.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Create a file and open it var gridStore = new GridStore(db, "test_gs_seek_with_buffer", "w"); gridStore.open(function(err, gridStore) { // Write some content to the file gridStore.write(new Buffer("hello, world!", "utf8"), function(err, gridStore) { // Flush the file to GridFS gridStore.close(function(result) { // Open the file in read mode var gridStore2 = new GridStore(db, "test_gs_seek_with_buffer", "r"); gridStore2.open(function(err, gridStore) { // Seek to start gridStore.seek(0, function(err, gridStore) { // Read first character and verify gridStore.getc(function(err, chr) { assert.equal('h', chr); }); }); }); // Open the file in read mode var gridStore3 = new GridStore(db, "test_gs_seek_with_buffer", "r"); gridStore3.open(function(err, gridStore) { // Seek to 7 characters from the beginning off the file and verify gridStore.seek(7, function(err, gridStore) { gridStore.getc(function(err, chr) { assert.equal('w', chr); }); }); }); // Open the file in read mode var gridStore5 = new GridStore(db, "test_gs_seek_with_buffer", "r"); gridStore5.open(function(err, gridStore) { // Seek to -1 characters from the end off the file and verify gridStore.seek(-1, GridStore.IO_SEEK_END, function(err, gridStore) { gridStore.getc(function(err, chr) { assert.equal('!', chr); }); }); }); // Open the file in read mode var gridStore6 = new GridStore(db, "test_gs_seek_with_buffer", "r"); gridStore6.open(function(err, gridStore) { // Seek to -6 characters from the end off the file and verify gridStore.seek(-6, GridStore.IO_SEEK_END, function(err, gridStore) { gridStore.getc(function(err, chr) { assert.equal('w', chr); }); }); }); // Open the file in read mode var gridStore7 = new GridStore(db, "test_gs_seek_with_buffer", "r"); gridStore7.open(function(err, gridStore) { // Seek forward 7 characters from the current read position and verify gridStore.seek(7, GridStore.IO_SEEK_CUR, function(err, gridStore) { gridStore.getc(function(err, chr) { assert.equal('w', chr); // Seek forward -1 characters from the current read position and verify gridStore.seek(-1, GridStore.IO_SEEK_CUR, function(err, gridStore) { gridStore.getc(function(err, chr) { assert.equal('w', chr); // Seek forward -4 characters from the current read position and verify gridStore.seek(-4, GridStore.IO_SEEK_CUR, function(err, gridStore) { gridStore.getc(function(err, chr) { assert.equal('o', chr); // Seek forward 3 characters from the current read position and verify gridStore.seek(3, GridStore.IO_SEEK_CUR, function(err, gridStore) { gridStore.getc(function(err, chr) { assert.equal('o', chr); db.close(); }); }); }); }); }); }); }); }); }); }); }); }); }); 

eof

Verify if the file is at EOF.

eof()

Returns:boolean true if the read/write head is at the end of this file.

Examples

A simple example showing the usage of the eof method.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Open the file in write mode var gridStore = new GridStore(db, 'test_gs_empty_file_eof', "w"); gridStore.open(function(err, gridStore) { // Flush the empty file to GridFS gridStore.close(function(err, gridStore) { // Open the file in read mode var gridStore2 = new GridStore(db, 'test_gs_empty_file_eof', "r"); gridStore2.open(function(err, gridStore) { // Verify that we are at the end of the file assert.equal(true, gridStore.eof()); db.close(); }) }); }); }); 

getc

Retrieves a single character from this file.

getc(callback)

Arguments:

• callback (function) – 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.

Returns:

null

Examples

A simple example showing the usage of the seek method.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Create a file and open it var gridStore = new GridStore(db, "test_gs_getc_file", "w"); gridStore.open(function(err, gridStore) { // Write some content to the file gridStore.write(new Buffer("hello, world!", "utf8"), function(err, gridStore) { // Flush the file to GridFS gridStore.close(function(result) { // Open the file in read mode var gridStore2 = new GridStore(db, "test_gs_getc_file", "r"); gridStore2.open(function(err, gridStore) { // Read first character and verify gridStore.getc(function(err, chr) { assert.equal('h', chr); db.close(); }); }); }); }); }); }); 

puts

Writes a string to the file with a newline character appended at the end if the given string does not have one.

puts(string, callback)

Arguments:

• string (string) – the string to write.
• callback (function) – 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.

Returns:

null

Examples

A simple example showing the usage of the puts method.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Open a file for writing var gridStore = new GridStore(db, "test_gs_puts_and_readlines", "w"); gridStore.open(function(err, gridStore) { // Write a line to the file using the puts method gridStore.puts("line one", function(err, gridStore) { // Flush the file to GridFS gridStore.close(function(err, result) { // Read in the entire contents GridStore.read(db, 'test_gs_puts_and_readlines', function(err, data) { assert.equal("line one\n", data.toString()); db.close(); }); }); }); }); }); 

stream

Returns read stream based on this GridStore file

Events

• data {function(item) {}} the data event triggers when a document is ready.
• end {function() {}} the end event triggers when there is no more documents available.
• close {function() {}} the close event triggers when the stream is closed.
• error {function(err) {}} the error event triggers if an error happens.

stream(autoclose)

Arguments:

• autoclose (boolean) – if true current GridStore will be closed when EOF and ‘close’ event will be fired

Returns:

null

Examples

A simple example showing the usage of the stream method.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Open a file for reading var gridStoreR = new GridStore(db, "test_gs_read_stream", "r"); // Open a file for writing var gridStoreW = new GridStore(db, "test_gs_read_stream", "w"); // Read in the data of a file var data = fs.readFileSync("./test/tests/functional/gridstore/test_gs_weird_bug.png"); var readLen = 0; var gotEnd = 0; // Open the file we are writting to gridStoreW.open(function(err, gs) { // Write the file content gs.write(data, function(err, gs) { // Flush the file to GridFS gs.close(function(err, result) { // Open the read file gridStoreR.open(function(err, gs) { // Create a stream to the file var stream = gs.stream(true); // Register events stream.on("data", function(chunk) { // Record the length of the file readLen += chunk.length; }); stream.on("end", function() { // Record the end was called ++gotEnd; }); stream.on("close", function() { // Verify the correctness of the read data assert.equal(data.length, readLen); assert.equal(1, gotEnd); db.close(); }); }); }); }); }); }); 

A simple example showing how to pipe a file stream through from gridfs to a file

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Open a file for writing var gridStoreWrite = new GridStore(db, "test_gs_read_stream_pipe", "w", {chunkSize:1024}); gridStoreWrite.writeFile("./test/tests/functional/gridstore/test_gs_weird_bug.png", function(err, result) { // Ensure we correctly returning a Gridstore object assert.ok(typeof result.close == 'function'); // Open the gridStore for reading and pipe to a file var gridStore = new GridStore(db, "test_gs_read_stream_pipe", "r"); gridStore.open(function(err, gridStore) { // Create a file write stream var fileStream = fs.createWriteStream("./test_gs_weird_bug_streamed.tmp"); // Grab the read stream var stream = gridStore.stream(true); // When the stream is finished close the database fileStream.on("close", function(err) { // Read the original content var originalData = fs.readFileSync("./test/tests/functional/gridstore/test_gs_weird_bug.png"); // Ensure we are doing writing before attempting to open the file fs.readFile("./test_gs_weird_bug_streamed.tmp", function(err, streamedData) { // Compare the data for(var i = 0; i < originalData.length; i++) { assert.equal(originalData[i], streamedData[i]) } // Close the database db.close(); }); }) // Pipe out the data stream.pipe(fileStream); }) }) }); 

GridStore.exist

Checks if a file exists in the database.

Options

• readPreference {String}, the prefered read preference (ReadPreference.PRIMARY, ReadPreference.PRIMARY_PREFERRED, ReadPreference.SECONDARY, ReadPreference.SECONDARY_PREFERRED, ReadPreference.NEAREST).

GridStore.exist(db, name[, rootCollection], callback)

Arguments:

• db (db) – the database to query.
• name (string) – the name of the file to look for.
• [rootCollection] (string) – the root collection that holds the files and chunks collection. Defaults to {GridStore.DEFAULT_ROOT_COLLECTION}.
• callback (function) – this will be called after this method executes. Passes null to the first and passes true to the second if the file exists and false otherwise.

Returns:

null

Examples

A simple example showing the usage of the Gridstore.exist method.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Open a file for writing var gridStore = new GridStore(db, null, "w"); gridStore.open(function(err, gridStore) { assert.equal(null, err); // Writing some content to the file gridStore.write("hello world!", function(err, gridStore) { assert.equal(null, err); // Flush the file to GridFS gridStore.close(function(err, result) { assert.equal(null, err); // Check if the file exists using the id returned from the close function GridStore.exist(db, result._id, function(err, result) { assert.equal(null, err); assert.equal(true, result); }) // Show that the file does not exist for a random ObjectID GridStore.exist(db, new ObjectID(), function(err, result) { assert.equal(null, err); assert.equal(false, result); }); // Show that the file does not exist for a different file root GridStore.exist(db, result._id, 'another_root', function(err, result) { assert.equal(null, err); assert.equal(false, result); db.close(); }); }); }); }); }); 

GridStore.list

Gets the list of files stored in the GridFS.

GridStore.list(db[, rootCollection], callback)

Arguments:

• db (db) – the database to query.
• [rootCollection] (string) – the root collection that holds the files and chunks collection. Defaults to {GridStore.DEFAULT_ROOT_COLLECTION}.
• callback (function) – this will be called after this method executes. Passes null to the first and passes an array of strings containing the names of the files.

Returns:

null

Examples

A simple example showing the usage of the eof method.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Our file id var fileId = new ObjectID(); // Open a file for writing var gridStore = new GridStore(db, fileId, "foobar2", "w"); gridStore.open(function(err, gridStore) { // Write some content to the file gridStore.write("hello world!", function(err, gridStore) { // Flush to GridFS gridStore.close(function(err, result) { // List the existing files GridStore.list(db, function(err, items) { var found = false; items.forEach(function(filename) { if(filename == 'foobar2') found = true; }); assert.ok(items.length >= 1); assert.ok(found); }); // List the existing files but return only the file ids GridStore.list(db, {id:true}, function(err, items) { var found = false; items.forEach(function(id) { assert.ok(typeof id == 'object'); }); assert.ok(items.length >= 1); }); // List the existing files in a specific root collection GridStore.list(db, 'fs', function(err, items) { var found = false; items.forEach(function(filename) { if(filename == 'foobar2') found = true; }); assert.ok(items.length >= 1); assert.ok(found); }); // List the existing files in a different root collection where the file is not located GridStore.list(db, 'my_fs', function(err, items) { var found = false; items.forEach(function(filename) { if(filename == 'foobar2') found = true; }); assert.ok(items.length >= 0); assert.ok(!found); // Specify seperate id var fileId2 = new ObjectID(); // Write another file to GridFS var gridStore2 = new GridStore(db, fileId2, "foobar3", "w"); gridStore2.open(function(err, gridStore) { // Write the content gridStore2.write('my file', function(err, gridStore) { // Flush to GridFS gridStore.close(function(err, result) { // List all the available files and verify that our files are there GridStore.list(db, function(err, items) { var found = false; var found2 = false; items.forEach(function(filename) { if(filename == 'foobar2') found = true; if(filename == 'foobar3') found2 = true; }); assert.ok(items.length >= 2); assert.ok(found); assert.ok(found2); db.close(); }); }); }); }); }); }); }); }); }); 

GridStore.read

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)

GridStore.read(db, name[, length][, offset][, options], callback)

Arguments:

• db (db) – the database to query.
• name (string) – the name of the file.
• [length] (number) – the size of data to read.
• [offset] (number) – the offset from the head of the file of which to start reading from.
• [options] (object) – the options for the file.
• callback (function) – this will be called after this method executes. A string with an error message will be passed to the first parameter when the length and offset combination exceeds the length of the file while an Error object will be passed if other forms of error occured, otherwise, a string is passed. The second parameter will contain the data read if successful or null if an error occured.

Returns:

null

Examples

A simple example showing the usage of the read method.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Create a new file var gridStore = new GridStore(db, null, "w"); // Read in the content from a file, replace with your own var data = fs.readFileSync("./test/tests/functional/gridstore/test_gs_weird_bug.png"); // Open the file gridStore.open(function(err, gridStore) { // Write the binary file data to GridFS gridStore.write(data, function(err, gridStore) { // Flush the remaining data to GridFS gridStore.close(function(err, result) { // Read in the whole file and check that it's the same content GridStore.read(db, result._id, function(err, fileData) { assert.equal(data.length, fileData.length); db.close(); }); }); }); }); }); 

GridStore.readlines

Reads the data of this file.

GridStore.readlines(db, name[, separator][, options], callback)

Arguments:

• db (db) – the database to query.
• name (string) – the name of the file.
• [separator] (string) – the character to be recognized as the newline separator.
• [options] (object) – file options.
• callback (function) – this will be called after this method is executed. The first parameter will be null and the second parameter will contain an array of strings representing the entire data, each element representing a line including the separator character.

Returns:

null

Examples

A simple example showing reading back using readlines to split the text into lines by the seperator provided.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Our file ID var fileId = new ObjectID(); // Open a new file var gridStore = new GridStore(db, fileId, 'w'); // Open the new file gridStore.open(function(err, gridStore) { // Write one line to gridStore gridStore.puts("line one", function(err, gridStore) { // Write second line to gridStore gridStore.puts("line two", function(err, gridStore) { // Write third line to gridStore gridStore.puts("line three", function(err, gridStore) { // Flush file to disk gridStore.close(function(err, result) { // Read back all the lines GridStore.readlines(db, fileId, function(err, lines) { assert.deepEqual(["line one\n", "line two\n", "line three\n"], lines); db.close(); }); }); }); }); }); }); }); 

GridStore.unlink

Deletes the chunks and metadata information of a file from GridFS.

GridStore.unlink(db, names[, options])

Arguments:

• db (db) – the database to interact with.
• names (string) – the name/names of the files to delete.
• [options] (object) – the options for the files.

Returns:

null

Examples

A simple example showing the usage of the GridStore.unlink method.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Open a new file for writing var gridStore = new GridStore(db, "test_gs_unlink", "w"); gridStore.open(function(err, gridStore) { // Write some content gridStore.write("hello, world!", function(err, gridStore) { // Flush file to GridFS gridStore.close(function(err, result) { // Verify the existance of the fs.files document db.collection('fs.files', function(err, collection) { collection.count(function(err, count) { assert.equal(1, count); }) }); // Verify the existance of the fs.chunks chunk document db.collection('fs.chunks', function(err, collection) { collection.count(function(err, count) { assert.equal(1, count); // Unlink the file (removing it) GridStore.unlink(db, 'test_gs_unlink', function(err, gridStore) { // Verify that fs.files document is gone db.collection('fs.files', function(err, collection) { collection.count(function(err, count) { assert.equal(0, count); }) }); // Verify that fs.chunks chunk documents are gone db.collection('fs.chunks', function(err, collection) { collection.count(function(err, count) { assert.equal(0, count); db.close(); }) }); }); }) }); }); }); }); }); 

write

Writes some data. This method will work properly only if initialized with mode “w” or “w+”.

write(data[, close], callback)

Arguments:

• data (string) – the data to write.
• [close] (boolean) – closes this file after writing if set to true.
• callback (function) – 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.

Returns:

null

Examples

A simple example showing how to use the write command with strings and Buffers.

var Db = require('mongodb').Db, MongoClient = require('mongodb').MongoClient, Server = require('mongodb').Server, ReplSetServers = require('mongodb').ReplSetServers, ObjectID = require('mongodb').ObjectID, Binary = require('mongodb').Binary, GridStore = require('mongodb').GridStore, Grid = require('mongodb').Grid, Code = require('mongodb').Code, BSON = require('mongodb').pure().BSON, assert = require('assert'); var db = new Db('test', new Server('localhost', 27017)); // Establish connection to db db.open(function(err, db) { // Our file ID var fileId = new ObjectID(); // Open a new file var gridStore = new GridStore(db, fileId, 'w'); // Open the new file gridStore.open(function(err, gridStore) { // Write a text string gridStore.write('Hello world', function(err, gridStore) { // Write a buffer gridStore.write(new Buffer('Buffer Hello world'), function(err, gridStore) { // Close the gridStore.close(function(err, result) { // Read back all the written content and verify the correctness GridStore.read(db, fileId, function(err, fileData) { assert.equal('Hello worldBuffer Hello world', fileData.toString()); db.close(); }); }); }); }); }); });