module ChunkyPNG::Chunk

def self.read(io)

Returns:
  • (ChunkyPNG::Chung::Base) - The loaded chunk instance.

Parameters:
  • io (IO, #read) -- The IO stream to read from. 
def self.read(io)
  length, type = io.read(8).unpack('Na4')
  content      = io.read(length)
  crc          = io.read(4).unpack('N').first
  verify_crc!(type, content, crc)
  CHUNK_TYPES.fetch(type, Generic).read(type, content)
end

def self.verify_crc!(type, content, found_crc)

Raises:
  • (RuntimeError) - An exception is raised if the found CRC value

Parameters:
  • content (Fixnum) -- The chunk's content.
  • content (String) -- The chunk's content.
  • type (String) -- The chunk's type. 
def self.verify_crc!(type, content, found_crc)
  expected_crc = Zlib.crc32(content, Zlib.crc32(type))
  raise "Chuck CRC mismatch!" if found_crc != expected_crc
end