Class: DRM::Wrapper

Inherits:
Object
  • Object
show all
Defined in:
lib/drm/wrapper.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(length, mime_type) ⇒ Wrapper

new wrapper for a contents file the file has length bytes and its MIME type is mime_type



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# File 'lib/drm/wrapper.rb', line 4

def initialize(length, mime_type)
  @filekey = DRM::Metadata.new_filekey
  @metadata = DRM::Metadata.new_for_file length, mime_type
end

Instance Attribute Details

#filekey ⇒ Object (readonly)

the key used to wrap the file



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# File 'lib/drm/wrapper.rb', line 10

def filekey
  @filekey
end

#metadata ⇒ Object (readonly)

the DRM metadata for the wrapped file



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# File 'lib/drm/wrapper.rb', line 12

def metadata
  @metadata
end

Instance Method Details

#wrap(read_proc, write_proc) ⇒ Object

wraps a content file with DRM protection read_proc(length, offset) reads length bytes at offset from the file to be wrapped write_proc(data) appends the given data to the file containing the wrapped content



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# File 'lib/drm/wrapper.rb', line 17

def wrap(read_proc, write_proc)
  # push the metadata
  metadata_str = @metadata.to_yaml_str
  metadata_lenstr = [metadata_str.length].pack('N')
  write_proc.call metadata_lenstr
  write_proc.call metadata_str
  
  # push the data
  block_size = @metadata.block_size
  length = @metadata.length
  in_offset = 0    
  0.upto(@metadata.blocks - 1) do |block_index|
    # read
    read_size = (block_size <= length - in_offset) ? block_size : length - in_offset
    block_data = read_proc.call read_size, in_offset
    in_offset += read_size
    # encrypt
    subkey = @metadata.subkey_from_filekey(metadata.subkey_index(block_index), @filekey)
    crypted_data = @metadata.encrypt_block block_data, block_index, subkey
    # write
    write_proc.call crypted_data
  end
end