new GridFS example

examples/gridfs.rb

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+$LOAD_PATH[0,0] = File.join(File.dirname(__FILE__), '..', 'lib')
+require 'mongo'
+require 'mongo/gridfs'
+
+include XGen::Mongo::Driver
+include XGen::Mongo::GridFS
+
+host = ENV['MONGO_RUBY_DRIVER_HOST'] || 'localhost'
+port = ENV['MONGO_RUBY_DRIVER_PORT'] || XGen::Mongo::Driver::Mongo::DEFAULT_PORT
+
+puts "Connecting to #{host}:#{port}"
+db = Mongo.new(host, port).db('ruby-mongo-examples')
+
+def dump(db, fname)
+  GridStore.open(db, fname, 'r') { |f| puts f.read }
+end
+
+# Write a new file
+GridStore.open(db, 'foobar', 'w') { |f| f.write("hello, world!") }
+
+# Read it and print out the contents
+dump(db, 'foobar')                 # defined above
+
+# Append more data
+GridStore.open(db, 'foobar', 'w+') { |f| f.write("\n"); f.puts "line two" }
+dump(db, 'foobar')
+
+# Overwrite
+GridStore.open(db, 'foobar', 'w') { |f| f.puts "hello, sailor!" }
+dump(db, 'foobar')
+
+# File existence tests
+puts "File 'foobar' exists: #{GridStore.exist?(db, 'foobar')}"
+puts "File 'does-not-exist' exists: #{GridStore.exist?(db, 'does-not-exist')}"
+
+# Read with offset (uses seek)
+puts GridStore.read(db, 'foobar', 6, 7)
+
+# Rewind/seek/tell
+GridStore.open(db, 'foobar', 'w') { |f|
+  f.write "hello, world!"
+  f.rewind
+  f.write "xyzzz"
+  puts f.tell                   # => 5
+  f.seek(4)
+  f.write('y')
+}
+dump(db, 'foobar')              # => 'xyzzy'
+
+# Unlink (delete)
+GridStore.unlink(db, 'foobar')
+puts "File 'foobar' exists after delete: #{GridStore.exist?(db, 'foobar')}"
+
+# Metadata
+GridStore.open(db, 'foobar', 'w') { |f| f.write("hello, world!") }
+GridStore.open(db, 'foobar', 'r') { |f|
+  puts f.content_type
+  puts f.upload_date
+  puts f.chunk_size
+  puts f.metadata.inspect
+}
+
+# Add some metadata; change content type
+GridStore.open(db, 'foobar', 'w+') { |f|
+  f.content_type = 'text/xml'
+  f.metadata = {'a' => 1}
+}
+# Print it
+GridStore.open(db, 'foobar', 'r') { |f|
+  puts f.content_type
+  puts f.upload_date
+  puts f.chunk_size
+  puts f.metadata.inspect
+}
+
+# You can also set metadata when initially writing the file. Setting :root
+# means that the file and its chunks are stored in a different root
+# collection: instead of gridfs.files and gridfs.chunks, here we use
+# my_files.files and my_files.chunks.
+GridStore.open(db, 'foobar', 'w',
+               :content_type => 'text/plain',
+               :metadata => {'a' => 1},
+               :chunk_size => 1024 * 4,
+               :root => 'my_files') { |f|
+  f.puts 'hello, world'
+}
+