Question: Integration a CRC32 check with BinData in a :check_value ? about bindata HOT 2 CLOSED

CRC32 checking is something that I'd like to add eventually as it is used in several file formats. It will have to wait until I've got a more complete verification system worked out. Thanks for the suggestion.

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BinData 1.6.0 adds :asserted_value which allows you to ensure a field contains an expected value.

Here's an example of implementing CRC32 checking. All the data to be included in the CRC32 check is wrapped inside a struct.

require 'bindata'
require 'zlib'

class A < BinData::Record
  endian :little

  int8 :qux
  struct :data do  # Only fields inside this struct are included in the CRC32
    string :foo, :length => 20
    int16  :bar
    int8   :baz
  end
  uint32 :crc32, :asserted_value => lambda { Zlib.crc32(data.to_binary_s) }
end

a = A.new(:qux => 3, :data => {:foo => "some string", :bar => -1, :baz => 42})
str = a.to_binary_s

p A.read(str)

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