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 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));
  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));
  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();
          });
        });
      });
    });
  });

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));
  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();
                      })
                    });
                  });
                });
              });
            });
          });
        });
      });
    });
  });

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));
  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/functional/data/test_gs_weird_bug.png').size;
    // Read the buffered data for comparision reasons
    var data = fs.readFileSync('./test/functional/data/test_gs_weird_bug.png');

    // Open the new file
    gridStore.open(function(err, gridStore) {

      // Write the file to gridFS
      gridStore.writeFile('./test/functional/data/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));
  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/functional/data/test_gs_weird_bug.png').size;
    // Read the buffered data for comparision reasons
    var data = fs.readFileSync('./test/functional/data/test_gs_weird_bug.png');

    // Open a file handle for reading the file
    var fd = fs.openSync('./test/functional/data/test_gs_weird_bug.png', 'r', parseInt('0666',8));

    // 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));
  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));
  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();
      });
    });
  });

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));
  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));
  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));
  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));
  db.open(function(err, db) {
    // Read in the content of a file
    var data = fs.readFileSync('./test/functional/data/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));
  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));
  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));
  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));
  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));
  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));
  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/functional/data/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();

            // Register events
            stream.on("data", function(chunk) {
              // Record the length of the file
              readLen += chunk.length;
            });

            stream.on("end", function() {
              // Verify the correctness of the read data
              assert.equal(data.length, readLen);
              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));
  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/functional/data/test_gs_weird_bug.png", function(err, result) {
      assert.equal(null, err);
      assert.ok(result != null);
      // 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();
        // When the stream is finished close the database
        fileStream.on("close", function(err) {
          // Read the original content
          var originalData = fs.readFileSync("./test/functional/data/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));
  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));
  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));
  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/functional/data/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));
  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();
              });
            });
          });
        });
      });
    });
  });

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));
  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();
            });
          });
        });
      });
    });
  });

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