Class: Mongo::GridIO

Inherits:
Object show all
Includes:
WriteConcern
Defined in:
lib/mongo/gridfs/grid_io.rb

Overview

GridIO objects represent files in the GridFS specification. This class manages the reading and writing of file chunks and metadata.

Constant Summary

DEFAULT_CHUNK_SIZE =
255 * 1024
DEFAULT_CONTENT_TYPE =
'binary/octet-stream'
PROTECTED_ATTRS =
[:files_id, :file_length, :client_md5, :server_md5]

Constants included from WriteConcern

WriteConcern::DEFAULT_WRITE_CONCERN, WriteConcern::VALID_KEYS

Instance Attribute Summary (collapse)

Attributes included from WriteConcern

#legacy_write_concern

Instance Method Summary (collapse)

Methods included from WriteConcern

#get_write_concern, gle?, #write_concern_from_legacy

Constructor Details

- (GridIO) initialize(files, chunks, filename, mode, opts = {})

Create a new GridIO object. Note that most users will not need to use this class directly; the Grid and GridFileSystem classes will instantiate this class

Parameters:

  • files (Mongo::Collection)

    a collection for storing file metadata.

  • chunks (Mongo::Collection)

    a collection for storing file chunks.

  • filename (String)

    the name of the file to open or write.

  • mode (String)

    ‘r’ or ‘w’ or reading or creating a file.

  • opts (Hash) (defaults to: {})

    a customizable set of options

Options Hash (opts):

  • :query (Hash)

    a query selector used when opening the file in ‘r’ mode.

  • :query_opts (Hash)

    any query options to be used when opening the file in ‘r’ mode.

  • :fs_name (String)

    the file system prefix.

  • (261120) (Integer)

    :chunk_size size of file chunks in bytes.

  • :metadata (Hash) — default: {}

    any additional data to store with the file.

  • :_id (ObjectId) — default: ObjectId

    a unique id for the file to be use in lieu of an automatically generated one.

  • :content_type (String) — default: 'binary/octet-stream'

    If no content type is specified, the content type will may be inferred from the filename extension if the mime-types gem can be loaded. Otherwise, the content type ‘binary/octet-stream’ will be used.

  • :w (String, Integer, Symbol) — default: 1

    Set the write concern

    Notes on write concern:

    When :w > 0, the chunks sent to the server
    will be validated using an md5 hash. If validation fails, an exception will be raised.


54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
# File 'lib/mongo/gridfs/grid_io.rb', line 54

def initialize(files, chunks, filename, mode, opts={})
  @files          = files
  @chunks         = chunks
  @filename       = filename
  @mode           = mode
  opts            = opts.dup
  @query          = opts.delete(:query) || {}
  @query_opts     = opts.delete(:query_opts) || {}
  @fs_name        = opts.delete(:fs_name) || Grid::DEFAULT_FS_NAME
  @write_concern  = get_write_concern(opts)
  @local_md5      = Digest::MD5.new if Mongo::WriteConcern.gle?(@write_concern)
  @custom_attrs   = {}

  case @mode
    when 'r' then init_read
    when 'w' then init_write(opts)
    else
      raise GridError, "Invalid file mode #{@mode}. Mode should be 'r' or 'w'."
  end
end

Instance Attribute Details

- (Object) chunk_size (readonly)

Returns the value of attribute chunk_size



28
29
30
# File 'lib/mongo/gridfs/grid_io.rb', line 28

def chunk_size
  @chunk_size
end

- (Object) client_md5 (readonly)

Returns the value of attribute client_md5



28
29
30
# File 'lib/mongo/gridfs/grid_io.rb', line 28

def client_md5
  @client_md5
end

- (Object) content_type (readonly)

Returns the value of attribute content_type



28
29
30
# File 'lib/mongo/gridfs/grid_io.rb', line 28

def content_type
  @content_type
end

- (Object) file_length (readonly)

Returns the value of attribute file_length



28
29
30
# File 'lib/mongo/gridfs/grid_io.rb', line 28

def file_length
  @file_length
end

- (Object) file_position (readonly)

Returns the value of attribute file_position



28
29
30
# File 'lib/mongo/gridfs/grid_io.rb', line 28

def file_position
  @file_position
end

- (Object) filename (readonly)

Returns the value of attribute filename



28
29
30
# File 'lib/mongo/gridfs/grid_io.rb', line 28

def filename
  @filename
end

- (Object) files_id (readonly)

Returns the value of attribute files_id



28
29
30
# File 'lib/mongo/gridfs/grid_io.rb', line 28

def files_id
  @files_id
end

- (Object) metadata (readonly)

Returns the value of attribute metadata



28
29
30
# File 'lib/mongo/gridfs/grid_io.rb', line 28

def 
  @metadata
end

- (Object) server_md5 (readonly)

Returns the value of attribute server_md5



28
29
30
# File 'lib/mongo/gridfs/grid_io.rb', line 28

def server_md5
  @server_md5
end

- (Object) upload_date (readonly)

Returns the value of attribute upload_date



28
29
30
# File 'lib/mongo/gridfs/grid_io.rb', line 28

def upload_date
  @upload_date
end

Instance Method Details

- (Object) [](key)



75
76
77
# File 'lib/mongo/gridfs/grid_io.rb', line 75

def [](key)
  @custom_attrs[key] || instance_variable_get("@#{key.to_s}")
end

- (Object) []=(key, value)



79
80
81
82
83
84
85
86
# File 'lib/mongo/gridfs/grid_io.rb', line 79

def []=(key, value)
  if PROTECTED_ATTRS.include?(key.to_sym)
    warn "Attempting to overwrite protected value."
    return nil
  else
    @custom_attrs[key] = value
  end
end

- (BSON::ObjectId) close

Creates or updates the document from the files collection that stores the chunks' metadata. The file becomes available only after this method has been called.

This method will be invoked automatically when on GridIO#open is passed a block. Otherwise, it must be called manually.

Returns:



231
232
233
234
235
236
237
238
239
240
# File 'lib/mongo/gridfs/grid_io.rb', line 231

def close
  if @mode[0] == ?w
    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)
  end
  id
end

- (Mongo::GridIO) each { ... }

Read a chunk of the data from the file and yield it to the given block.

Note that this method reads from the current file position.

Yields:

  • Yields on chunk per iteration as defined by this file’s chunk size.

Returns:



251
252
253
254
255
256
257
258
# File 'lib/mongo/gridfs/grid_io.rb', line 251

def each
  return read_all unless block_given?
  while chunk = read(chunk_size)
    yield chunk
    break if chunk.empty?
  end
  self
end

- (Boolean) eof Also known as: eof?

Return a boolean indicating whether the position pointer is at the end of the file.

Returns:

  • (Boolean)

Raises:



185
186
187
188
# File 'lib/mongo/gridfs/grid_io.rb', line 185

def eof
  raise GridError, "file not opened for read #{@mode}" unless @mode[0] == ?r
  @file_position >= @file_length
end

- (String) getc

Return the next byte from the GridFS file.

Returns:



219
220
221
# File 'lib/mongo/gridfs/grid_io.rb', line 219

def getc
  read_length(1)
end

- (String) gets(separator = "\n", length = nil)

Return the next line from a GridFS file. This probably makes sense only if you're storing plain text. This method has a somewhat tricky API, which it inherits from Ruby's StringIO#gets.

Parameters:

  • separator (String, Integer) (defaults to: "\n")

    or length. If a separator, read up to the separator. If a length, read the length number of bytes. If nil, read the entire file.

  • length (Integer) (defaults to: nil)

    If a separator is provided, then read until either finding the separator or passing over the length number of bytes.

Returns:



204
205
206
207
208
209
210
211
212
213
214
# File 'lib/mongo/gridfs/grid_io.rb', line 204

def gets(separator="\n", length=nil)
  if separator.nil?
    read_all
  elsif separator.is_a?(Integer)
    read_length(separator)
  elsif separator.length > 1
    read_to_string(separator, length)
  else
    read_to_character(separator, length)
  end
end

- (Object) inspect



260
261
262
# File 'lib/mongo/gridfs/grid_io.rb', line 260

def inspect
  "#<GridIO _id: #{@files_id}>"
end

- (String) read(length = nil) Also known as: data

Read the data from the file. If a length if specified, will read from the current file position.

Parameters:

  • length (Integer) (defaults to: nil)

Returns:

  • (String)

    the data in the file



95
96
97
98
99
100
101
102
103
104
# File 'lib/mongo/gridfs/grid_io.rb', line 95

def read(length=nil)
  return '' if @file_length.zero?
  if length == 0
    return ''
  elsif length.nil? && @file_position.zero?
    read_all
  else
    read_length(length)
  end
end

- (Integer) rewind

Rewind the file. This is equivalent to seeking to the zeroth position.

Returns:

  • (Integer)

    the position of the file after rewinding (always zero).

Raises:



176
177
178
179
# File 'lib/mongo/gridfs/grid_io.rb', line 176

def rewind
  raise GridError, "file not opened for read" unless @mode[0] == ?r
  seek(0)
end

- (Integer) seek(pos, whence = IO::SEEK_SET)

Position the file pointer at the provided location.

Parameters:

  • pos (Integer)

    the number of bytes to advance the file pointer. this can be a negative number.

  • whence (Integer) (defaults to: IO::SEEK_SET)

    one of IO::SEEK_CUR, IO::SEEK_END, or IO::SEEK_SET

Returns:

  • (Integer)

    the new file position

Raises:



144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
# File 'lib/mongo/gridfs/grid_io.rb', line 144

def seek(pos, whence=IO::SEEK_SET)
  raise GridError, "Seek is only allowed in read mode." unless @mode == 'r'
  target_pos = case whence
               when IO::SEEK_CUR
                 @file_position + pos
               when IO::SEEK_END
                 @file_length + pos
               when IO::SEEK_SET
                 pos
               end

  new_chunk_number = (target_pos / @chunk_size).to_i
  if new_chunk_number != @current_chunk['n']
    save_chunk(@current_chunk) if @mode[0] == ?w
    @current_chunk = get_chunk(new_chunk_number)
  end
  @file_position  = target_pos
  @chunk_position = @file_position % @chunk_size
  @file_position
end

- (Integer) tell Also known as: pos

The current position of the file.

Returns:

  • (Integer)


168
169
170
# File 'lib/mongo/gridfs/grid_io.rb', line 168

def tell
  @file_position
end

- (Integer) write(io)

Write the given string (binary) data to the file.

Parameters:

  • io (String)

    the data to write.

Returns:

  • (Integer)

    the number of bytes written.

Raises:



112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
# File 'lib/mongo/gridfs/grid_io.rb', line 112

def write(io)
  raise GridError, "file not opened for write" unless @mode[0] == ?w
  if io.is_a? String
    if Mongo::WriteConcern.gle?(@write_concern)
      @local_md5.update(io)
    end
    write_string(io)
  else
    length = 0
    if Mongo::WriteConcern.gle?(@write_concern)
      while(string = io.read(@chunk_size))
        @local_md5.update(string)
        length += write_string(string)
      end
    else
      while(string = io.read(@chunk_size))
        length += write_string(string)
      end
    end
    length
  end
end