#
# File:: md5.rb
# Description:: MD5 digest utility class.
#
# Author:: David Muir <david.muir@rockstarnorth.com>
# Date:: 15 September 2008
#

#-----------------------------------------------------------------------------
# Uses
#-----------------------------------------------------------------------------
require 'digest/md5'

#-----------------------------------------------------------------------------
# Implementation
#-----------------------------------------------------------------------------
module Pipeline
module Util

	#
	# == Description
	# MD5 digest utility class.  This class contains a few methods to ease
	# generating MD5 digest checksums for files either read in a single 
	# chunk or read in specific sized chunks.
	#
	class MD5
		CHUNK_128K 	= ( 128 * 1024 )
		CHUNK_256K 	= ( 256 * 1024 )
		CHUNK_512K 	= ( 512 * 1024 )
		CHUNK_1M 	= ( 1 * 1024 * 1024 )
		CHUNK_2M	= ( 2 * 1024 * 1024 )
		CHUNK_4M	= ( 4 * 1024 * 1024 )
		CHUNK_8M	= ( 8 * 1024 * 1024 )
		CHUNK_16M	= ( 16 * 1024 * 1024 )
		CHUNK_32M	= ( 32 * 1024 * 1024 )
	
		#
		# Return the MD5 digest string for a given file. 
		#
		def MD5::digest( filename, chunk_size = CHUNK_4M, mode = 'rb' )
			throw IOError.new( "File #{filename} does not exist, or is not readable." ) \
				unless ( ::File::exists?( filename ) and ::File::readable?( filename ) )
			
			MD5::md5( filename, chunk_size, mode ).digest()
		end
		
		#
		# Return the MD5 hexdigest string for a given file.
		#
		def MD5::hexdigest( filename, chunk_size = CHUNK_4M, mode = 'rb' )
			throw IOError.new( "File #{filename} does not exist, or is not readable." ) \
				unless ( ::File::exists?( filename ) and ::File::readable?( filename ) )
			
			MD5::md5( filename, chunk_size, mode ).hexdigest()
		end
		
		#
		# Return the Digest::MD5 object for a given file with the MD5 checksum
		# pre-calculated.
		#
		def MD5::md5( filename, chunk_size = CHUNK_4M, mode = 'rb' )
			throw IOError.new( "File #{filename} does not exist, or is not readable." ) \
				unless ( ::File::exists?( filename ) and ::File::readable?( filename ) )
			
			md5 = Digest::MD5.new()
			::File.open( filename, mode ) do |fp|
				
				while ( not fp.eof ) do
					data = fp.read( chunk_size )
					md5 << data
				end
			end	
			md5	
		end
	end

end # Util module
end # Pipeline module

# md5.rb