Class: Archive::Zip::Codec::Deflate::Decompress

Inherits:
Zlib::ZReader show all
Defined in:
lib/archive/zip/codec/deflate.rb

Overview

Archive::Zip::Codec::Deflate::Decompress extends Zlib::ZReader in order to specify the standard Zlib options required by ZIP archives and to provide a close method which can optionally close the delegate IO-like object. In addition a convenience method is provided for generating DataDescriptor objects based on the data which is passed through this object.

Instances of this class should only be accessed via the Archive::Zip::Codec::Deflate#decompressor method.

Constant Summary

Constants inherited from Zlib::ZReader

Zlib::ZReader::DEFAULT_DELEGATE_READ_SIZE

Instance Attribute Summary collapse

Attributes inherited from Zlib::ZReader

#delegate, #delegate_read_size

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Zlib::ZReader

#compressed_size, #uncompressed_size

Constructor Details

#initialize(io) ⇒ Decompress

Creates a new instance of this class using io as a data source. io must be readable and provide a read method as IO does or errors will be raised when performing read operations. If io provides a rewind method, this class’ rewind method will be enabled.



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# File 'lib/archive/zip/codec/deflate.rb', line 118

def initialize(io)
  super(io, -Zlib::MAX_WBITS)
  @crc32 = 0
end

Instance Attribute Details

#crc32 ⇒ Object (readonly) Also known as: checksum

The CRC32 checksum of the uncompressed data read using this object.

NOTE: The contents of the internal read buffer are immediately processed any time the internal buffer is filled, so this checksum is only accurate if all data has been read out of this object.



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# File 'lib/archive/zip/codec/deflate.rb', line 128

def crc32
  @crc32
end

Class Method Details

.open(io) ⇒ Object

Creates a new instance of this class with the given arguments using #new and then passes the instance to the given block. The #close method is guaranteed to be called after the block completes.

Equivalent to #new if no block is given.



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# File 'lib/archive/zip/codec/deflate.rb', line 103

def self.open(io)
  inflate_io = new(io)
  return inflate_io unless block_given?

  begin
    yield(inflate_io)
  ensure
    inflate_io.close unless inflate_io.closed?
  end
end

Instance Method Details

#close(close_delegate = true) ⇒ Object

Closes this object so that further read operations will fail. If close_delegate is true, the delegate object used as a data source will also be closed using its close method.



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# File 'lib/archive/zip/codec/deflate.rb', line 134

def close(close_delegate = true)
  super()
  delegate.close if close_delegate
end

#data_descriptor ⇒ Object

Returns an instance of Archive::Zip::DataDescriptor with information regarding the data which has passed through this object from the delegate object. It is recommended to call the close method before calling this in order to ensure that no further read operations change the state of this object.



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# File 'lib/archive/zip/codec/deflate.rb', line 144

def data_descriptor
  DataDescriptor.new(crc32, compressed_size, uncompressed_size)
end

#unbuffered_read(length) ⇒ Object (private) 



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# File 'lib/archive/zip/codec/deflate.rb', line 150

def unbuffered_read(length)
  result = super(length)
  @crc32 = Zlib.crc32(result, @crc32)
  result
end

#unbuffered_seek(offset, whence = IO::SEEK_SET) ⇒ Object (private) 



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# File 'lib/archive/zip/codec/deflate.rb', line 156

def unbuffered_seek(offset, whence = IO::SEEK_SET)
  result = super(offset, whence)
  @crc32 = 0 if whence == IO::SEEK_SET
  result
end