339 lines
11 KiB
Ruby
339 lines
11 KiB
Ruby
# --
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# Copyright (C) 2008-2010 10gen Inc.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# ++
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require 'digest/md5'
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begin
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require 'mime/types'
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rescue LoadError
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end
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module Mongo
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# GridIO objects represent files in the GridFS specification. This class
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# manages the reading and writing of file chunks and metadata.
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class GridIO
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DEFAULT_CHUNK_SIZE = 256 * 1024
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DEFAULT_CONTENT_TYPE = 'binary/octet-stream'
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attr_reader :content_type, :chunk_size, :upload_date, :files_id, :filename,
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:metadata, :server_md5, :client_md5
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# Create a new GridIO object. Note that most users will not need to use this class directly;
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# the Grid and GridFileSystem classes will instantiate this class
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#
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# @param [Mongo::Collection] files a collection for storing file metadata.
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# @param [Mongo::Collection] chunks a collection for storing file chunks.
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# @param [String] filename the name of the file to open or write.
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# @param [String] mode 'r' or 'w' or reading or creating a file.
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#
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# @option opts [Hash] :query a query selector used when opening the file in 'r' mode.
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# @option opts [Hash] :query_opts any query options to be used when opening the file in 'r' mode.
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# @option opts [String] :fs_name the file system prefix.
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# @options opts [Integer] (262144) :chunk_size size of file chunks in bytes.
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# @options opts [Hash] :metadata ({}) any additional data to store with the file.
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# @options opts [ObjectID] :_id (ObjectID) a unique id for
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# the file to be use in lieu of an automatically generated one.
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# @options opts [String] :content_type ('binary/octet-stream') If no content type is specified,
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# the content type will may be inferred from the filename extension if the mime-types gem can be
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# loaded. Otherwise, the content type 'binary/octet-stream' will be used.
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# @options opts [Boolean] :safe (false) When safe mode is enabled, the chunks sent to the server
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# will be validated using an md5 hash. If validation fails, an exception will be raised.
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def initialize(files, chunks, filename, mode, opts={})
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@files = files
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@chunks = chunks
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@filename = filename
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@mode = mode
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@query = opts[:query] || {}
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@query_opts = opts[:query_opts] || {}
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@fs_name = opts[:fs_name] || Grid::DEFAULT_FS_NAME
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@safe = opts[:safe] || false
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@local_md5 = Digest::MD5.new if @safe
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case @mode
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when 'r' then init_read
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when 'w' then init_write(opts)
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else
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raise GridError, "Invalid file mode #{@mode}. Mode should be 'r' or 'w'."
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end
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end
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# Read the data from the file. If a length if specified, will read from the
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# current file position.
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#
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# @param [Integer] length
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#
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# @return [String]
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# the data in the file
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def read(length=nil)
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if length == 0
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return ''
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elsif length.nil? && @file_position.zero?
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read_all
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else
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read_length(length)
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end
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end
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alias_method :data, :read
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# Write the given string (binary) data to the file.
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#
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# @param [String] string
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# the data to write
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#
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# @return [Integer]
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# the number of bytes written.
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def write(io)
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raise GridError, "file not opened for write" unless @mode[0] == ?w
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if io.is_a? String
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if @safe
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@local_md5.update(io)
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end
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write_string(io)
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else
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length = 0
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if @safe
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while(string = io.read(@chunk_size))
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@local_md5.update(string)
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length += write_string(string)
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end
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else
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while(string = io.read(@chunk_size))
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length += write_string(string)
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end
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end
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length
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end
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end
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# Position the file pointer at the provided location.
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#
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# @param [Integer] pos
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# the number of bytes to advance the file pointer. this can be a negative
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# number.
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# @param [Integer] whence
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# one of IO::SEEK_CUR, IO::SEEK_END, or IO::SEEK_SET
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#
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# @return [Integer] the new file position
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def seek(pos, whence=IO::SEEK_SET)
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raise GridError, "Seek is only allowed in read mode." unless @mode == 'r'
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target_pos = case whence
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when IO::SEEK_CUR
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@file_position + pos
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when IO::SEEK_END
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@file_length + pos
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when IO::SEEK_SET
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pos
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end
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new_chunk_number = (target_pos / @chunk_size).to_i
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if new_chunk_number != @current_chunk['n']
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save_chunk(@current_chunk) if @mode[0] == ?w
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@current_chunk = get_chunk(new_chunk_number)
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end
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@file_position = target_pos
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@chunk_position = @file_position % @chunk_size
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@file_position
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end
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# The current position of the file.
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#
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# @return [Integer]
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def tell
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@file_position
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end
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# Creates or updates the document from the files collection that
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# stores the chunks' metadata. The file becomes available only after
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# this method has been called.
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#
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# This method will be invoked automatically when
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# on GridIO#open is passed a block. Otherwise, it must be called manually.
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#
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# @return [True]
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def close
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if @mode[0] == ?w
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@upload_date = Time.now.utc
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@files.insert(to_mongo_object)
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end
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true
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end
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def inspect
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"#<GridIO _id: #{@files_id}>"
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end
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private
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def create_chunk(n)
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chunk = OrderedHash.new
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chunk['_id'] = Mongo::ObjectID.new
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chunk['n'] = n
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chunk['files_id'] = @files_id
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chunk['data'] = ''
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@chunk_position = 0
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chunk
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end
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def save_chunk(chunk)
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@chunks.insert(chunk)
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end
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def get_chunk(n)
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chunk = @chunks.find({'files_id' => @files_id, 'n' => n}).next_document
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@chunk_position = 0
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chunk
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end
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def last_chunk_number
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(@file_length / @chunk_size).to_i
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end
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# Read a file in its entirety.
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def read_all
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buf = ''
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while true
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buf << @current_chunk['data'].to_s
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@current_chunk = get_chunk(@current_chunk['n'] + 1)
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break unless @current_chunk
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end
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buf
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end
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# Read a file incrementally.
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def read_length(length)
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cache_chunk_data
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remaining = (@file_length - @file_position)
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to_read = length > remaining ? remaining : length
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return nil unless remaining > 0
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buf = ''
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while to_read > 0
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if @chunk_position == @chunk_data_length
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@current_chunk = get_chunk(@current_chunk['n'] + 1)
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cache_chunk_data
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end
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chunk_remainder = @chunk_data_length - @chunk_position
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size = (to_read >= chunk_remainder) ? chunk_remainder : to_read
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buf << @current_chunk_data[@chunk_position, size]
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to_read -= size
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@chunk_position += size
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@file_position += size
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end
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buf
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end
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def cache_chunk_data
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@current_chunk_data = @current_chunk['data'].to_s
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if @current_chunk_data.respond_to?(:force_encoding)
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@current_chunk_data.force_encoding("binary")
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end
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@chunk_data_length = @current_chunk['data'].length
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end
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def write_string(string)
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# Since Ruby 1.9.1 doesn't necessarily store one character per byte.
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if string.respond_to?(:force_encoding)
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string.force_encoding("binary")
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end
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to_write = string.length
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while (to_write > 0) do
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if @current_chunk && @chunk_position == @chunk_size
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next_chunk_number = @current_chunk['n'] + 1
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@current_chunk = create_chunk(next_chunk_number)
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end
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chunk_available = @chunk_size - @chunk_position
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step_size = (to_write > chunk_available) ? chunk_available : to_write
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@current_chunk['data'] = Binary.new((@current_chunk['data'].to_s << string[-to_write, step_size]).unpack("c*"))
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@chunk_position += step_size
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to_write -= step_size
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save_chunk(@current_chunk)
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end
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string.length - to_write
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end
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# Initialize the class for reading a file.
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def init_read
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doc = @files.find(@query, @query_opts).next_document
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raise GridError, "Could not open file matching #{@query.inspect} #{@query_opts.inspect}" unless doc
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@files_id = doc['_id']
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@content_type = doc['contentType']
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@chunk_size = doc['chunkSize']
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@upload_date = doc['uploadDate']
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@aliases = doc['aliases']
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@file_length = doc['length']
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@metadata = doc['metadata']
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@md5 = doc['md5']
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@filename = doc['filename']
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@current_chunk = get_chunk(0)
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@file_position = 0
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end
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# Initialize the class for writing a file.
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def init_write(opts)
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@files_id = opts[:_id] || Mongo::ObjectID.new
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@content_type = opts[:content_type] || (defined? MIME) && get_content_type || DEFAULT_CONTENT_TYPE
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@chunk_size = opts[:chunk_size] || DEFAULT_CHUNK_SIZE
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@file_length = 0
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@metadata = opts[:metadata] if opts[:metadata]
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@current_chunk = create_chunk(0)
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@file_position = 0
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end
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def to_mongo_object
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h = OrderedHash.new
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h['_id'] = @files_id
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h['filename'] = @filename
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h['contentType'] = @content_type
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h['length'] = @current_chunk ? @current_chunk['n'] * @chunk_size + @chunk_position : 0
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h['chunkSize'] = @chunk_size
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h['uploadDate'] = @upload_date
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h['aliases'] = @aliases
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h['metadata'] = @metadata
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h['md5'] = get_md5
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h
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end
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# Get a server-side md5 and validate against the client if running in safe mode.
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def get_md5
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md5_command = OrderedHash.new
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md5_command['filemd5'] = @files_id
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md5_command['root'] = @fs_name
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@server_md5 = @files.db.command(md5_command)['md5']
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if @safe
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@client_md5 = @local_md5.hexdigest
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if @local_md5 != @server_md5
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raise @local_md5 != @server_md5, "File on server failed MD5 check"
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end
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else
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@server_md5
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end
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end
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# Determine the content type based on the filename.
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def get_content_type
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if @filename
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if types = MIME::Types.type_for(@filename)
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types.first.simplified unless types.empty?
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end
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end
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end
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end
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end
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