Class: FlashHeader

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

Overview

Read and parses the headers of an SWF file.

Examples:

header = FlashHeader.new('dog_on_skateboard.swf')
header.size #=> 5234

header = FlashHeader.new
# You can feed it any object that supports the read method
header.file = StringIO.new(flash_data)
header.read_header
header.width #=> 640
header.height #=> 480

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(filename = nil) ⇒ FlashHeader

Initialize a new FlashHeader instance. This reads the file and parses the header.

filename: A filename for a shockwave flash file (optional).



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# File 'lib/flash_header.rb', line 26

def initialize(filename=nil)
  @header = {}
  unless filename.nil?
    @file = File.open filename
    begin
      read_header
    ensure
      @file.close
    end
  end
end

Dynamic Method Handling

This class handles dynamic methods through the method_missing method

#method_missing(m, *a) ⇒ Object

Adds method access to the headers; signature, version, size, width and height.



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# File 'lib/flash_header.rb', line 73

def method_missing(m, *a)
  if @header.has_key?(m.to_sym)
    @header[m.to_sym]
  else
    super
  end
end

Instance Attribute Details

#file ⇒ Object

An open IO object to read the headers from.



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# File 'lib/flash_header.rb', line 19

def file
  @file
end

#header ⇒ Object (readonly)

Reader for the instance variable that holds all the header values



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# File 'lib/flash_header.rb', line 21

def header
  @header
end

Instance Method Details

#compressed? ⇒ Boolean

Returns true if the file was compressed, otherwise it returns false

Returns:

  • (Boolean) 


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# File 'lib/flash_header.rb', line 68

def compressed?
  @header[:signature][0..0] == 'C'
end

#read_header ⇒ Object

Read the header of the initialized file



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# File 'lib/flash_header.rb', line 39

def read_header
  temp = @file.read
  # Signature is three ASCII bytes, CWS or FWS
  @header[:signature] = temp[0..2]
  # Version is one byte version number
  @header[:version] = temp[3]
  # Size is LE byte order BE bit order
  @header[:size] = temp[4..7].unpack('C*').reverse.inject(0) do |t,i|
    (t << 8) + i
  end
  # Chop off the header part we just parsed
  if compressed?
    temp = Zlib::Inflate.inflate temp[8..-1]
  else
    temp = temp[8..-1]
  end
  return if temp.empty?
  
  # First 5 bits are the number of bits for the RECT structure
  nbits = temp[0] >> 3
  # 5 bits + 4 times nbits, byte aligned
  nbytes = ((5 + nbits*4) / 8.0).ceil
  bytes = BitUnpacker.uunpack(temp[0..nbytes], nbits, 4, 5)
  @header[:width] = bytes[1] / 20
  @header[:heigth] = bytes[3] / 20
  # TODO: support for framerate and the other thing
end