Support for GridFS append mode

lib/mongo/gridfs/grid_io.rb

@@ -53,8 +53,9 @@ def initialize(files, chunks, filename, mode, opts={})
       case @mode
         when 'r' then init_read
         when 'w' then init_write(opts)
+        when 'a' then init_append(opts)
         else
-          raise GridError, "Invalid file mode #{@mode}. Mode should be 'r' or 'w'."
+          raise GridError, "Invalid file mode #{@mode}. Mode should be 'r', 'w' or 'a'."
       end
     end
 
@@ -98,7 +99,8 @@ def read(length=nil)
     # @return [Integer]
     #   the number of bytes written.
     def write(io)
-      raise GridError, "file not opened for write" unless @mode[0] == ?w
+      raise GridError, "file not opened for write" unless @mode[0] == ?w or @mode[0] == ?a
+
       if io.is_a? String
         if Mongo::WriteConcern.gle?(@write_concern)
           @local_md5.update(io)
@@ -216,13 +218,27 @@ def getc
     # on GridIO#open is passed a block. Otherwise, it must be called manually.
     #
     # @return [BSON::ObjectId]
+    #def close
+    #  if @current_chunk['n'].zero? && @chunk_position.zero?
+    #    warn "Warning: Storing a file with zero length."
+    #  end
+    #  @upload_date = Time.now.utc
+    #  object = to_mongo_object
+    #  id = @files.update({_id: object['_id']}, object, {upsert: true})
+    #  id
+    #end
     def close
-      if @mode[0] == ?w
+      if @mode[0] == ?w or @mode[0] == ?a
         if @current_chunk['n'].zero? && @chunk_position.zero?
           warn "Warning: Storing a file with zero length."
         end
         @upload_date = Time.now.utc
-        id = @files.insert(to_mongo_object)
+        if @mode[0] == ?w
+          id = @files.insert(to_mongo_object)
+        elsif @mode[0] == ?a
+          object = to_mongo_object
+          id = @files.update({:_id => object['_id']}, object, {:upsert => true})
+        end
       end
       id
     end
@@ -267,7 +283,7 @@ def save_chunk(chunk)
 
     def get_chunk(n)
       chunk = @chunks.find({'files_id' => @files_id, 'n' => n}).next_document
-      @chunk_position = 0
+      @chunk_position = (@mode == ?a ? chunk['data'].size : 0) unless chunk.nil?
       chunk
     end
 
@@ -420,7 +436,41 @@ def init_write(opts)
       @current_chunk = create_chunk(0)
       @file_position = 0
     end
+
+    # Initialize the class for appending to a file.
+    def init_append(opts)
+      doc = @files.find(@query, @query_opts).next_document
+      return init_write(opts) unless doc
+
+      opts = doc.dup
+
+      @files_id     = opts.delete('_id')
+      @content_type = opts.delete('contentType')
+      @chunk_size   = opts.delete('chunkSize')
+      @upload_date  = opts.delete('uploadDate')
+      @aliases      = opts.delete('aliases')
+      @file_length  = opts.delete('length')
+      @metadata     = opts.delete('metadata')
+      @md5          = opts.delete('md5')
+      @filename     = opts.delete('filename')
+      @custom_attrs = opts
+
+      # recalculate the md5 of the previous chunks
+      if Mongo::WriteConcern.gle?(@write_concern)
+        @current_chunk = get_chunk(0)
+        @file_position = 0
+        @local_md5 = Digest::MD5.new
+        @local_md5.update(read_all)
+      end
 
+      # position at the end of the file (last chunk)
+      last_chunk = @file_length / @chunk_size
+      @current_chunk = get_chunk(last_chunk)
+      chunk = get_chunk(last_chunk-1) if @current_chunk.nil?
+      @current_chunk ||= create_chunk(last_chunk)
+      @file_position = @chunk_size * last_chunk + @current_chunk['data'].size
+    end
+
     def check_existing_file
       if @files.find_one('_id' => @files_id)
         raise GridError, "Attempting to overwrite with Grid#put. You must delete the file first."
@@ -448,6 +498,7 @@ def get_md5
       md5_command['filemd5'] = @files_id
       md5_command['root']    = @fs_name
       @server_md5 = @files.db.command(md5_command)['md5']
+
       if Mongo::WriteConcern.gle?(@write_concern)
         @client_md5 = @local_md5.hexdigest
         if @local_md5 == @server_md5

test/functional/grid_io_test.rb

@@ -151,6 +151,43 @@ class GridIOTest < Test::Unit::TestCase
       end
     end
 
+    context "Appending" do
+      setup do
+        @filename = 'test'
+        @length = nil
+        @times = 2
+      end
+
+      should "correctly append two chunks" do
+
+        @times.times do |t|
+          file = GridIO.new(@files, @chunks, @filename, 'a')
+          file.write "#{t}" * 100
+          file.close
+        end
+
+        file = GridIO.new(@files, @chunks, @filename, 'r')
+        data = file.read
+        file.close
+
+        assert_equal data, @times.times.map {|i| "#{i}" * 100}.join
+      end
+
+      should "append two chunks of exactly chunk_size" do
+        @times.times do |t|
+          file = GridIO.new(@files, @chunks, @filename, 'a')
+          file.write "#{t}" * file.chunk_size
+          file.close
+        end
+
+        file = GridIO.new(@files, @chunks, @filename, 'r')
+        data = file.read
+        file.close
+
+        assert_equal data, @times.times.map {|i| "#{i}" * file.chunk_size}.join
+      end
+    end
+
     context "Seeking" do
       setup do
         @filename = 'test'