Class: PDF::Reader::Filter::Flate

Inherits:
Object
  • Object
show all
Defined in:
lib/pdf/reader/filter/flate.rb

Overview

implementation of the Flate (zlib) stream filter

Instance Method Summary collapse

Constructor Details

#initialize(options = {}) ⇒ Flate

Returns a new instance of Flate.



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# File 'lib/pdf/reader/filter/flate.rb', line 10

def initialize(options = {})
  @options = options
end

Instance Method Details

#filter(data) ⇒ Object

Decode the specified data with the Zlib compression algorithm



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# File 'lib/pdf/reader/filter/flate.rb', line 16

def filter(data)
  deflated = nil
  begin
    deflated = Zlib::Inflate.new.inflate(data)
  rescue Zlib::DataError => e
    # by default, Ruby's Zlib assumes the data it's inflating
    # is RFC1951 deflated data, wrapped in a RFC1951 zlib container.
    # If that fails, then use an undocumented 'feature' to attempt to inflate
    # the data as a raw RFC1951 stream.
    #
    # See
    # - http://blade.nagaokaut.ac.jp/cgi-bin/scat.rb/ruby/ruby-talk/243545
    # - http://www.gzip.org/zlib/zlib_faq.html#faq38
    deflated = Zlib::Inflate.new(-Zlib::MAX_WBITS).inflate(data)
  end
  Depredict.new(@options).filter(deflated)
rescue Exception => e
  # Oops, there was a problem inflating the stream
  raise MalformedPDFError,
    "Error occured while inflating a compressed stream (#{e.class.to_s}: #{e.to_s})"
end