Permalink
253 lines (209 sloc) 5.13 KB
require 'zlib'
require 'stringio'
##
# Provides a unified callback interface to decompression libraries.
module EventMachine::HttpDecoders
class DecoderError < StandardError
end
class << self
def accepted_encodings
DECODERS.inject([]) { |r, d| r + d.encoding_names }
end
def decoder_for_encoding(encoding)
DECODERS.each { |d|
return d if d.encoding_names.include? encoding
}
nil
end
end
class Base
def self.encoding_names
name = to_s.split('::').last.downcase
[name]
end
##
# chunk_callback:: [Block] To handle a decompressed chunk
def initialize(&chunk_callback)
@chunk_callback = chunk_callback
end
def <<(compressed)
return unless compressed && compressed.size > 0
decompressed = decompress(compressed)
receive_decompressed decompressed
end
def finalize!
decompressed = finalize
receive_decompressed decompressed
end
private
def receive_decompressed(decompressed)
if decompressed && decompressed.size > 0
@chunk_callback.call(decompressed)
end
end
protected
##
# Must return a part of decompressed
def decompress(compressed)
nil
end
##
# May return last part
def finalize
nil
end
end
class Deflate < Base
def decompress(compressed)
begin
@zstream ||= Zlib::Inflate.new(-Zlib::MAX_WBITS)
@zstream.inflate(compressed)
rescue Zlib::Error
raise DecoderError
end
end
def finalize
return nil unless @zstream
begin
r = @zstream.inflate(nil)
@zstream.close
r
rescue Zlib::Error
raise DecoderError
end
end
end
##
# Partial implementation of RFC 1952 to extract the deflate stream from a gzip file
class GZipHeader
def initialize
@state = :begin
@data = ""
@pos = 0
end
def finished?
@state == :finish
end
def read(n, buffer)
if (@pos + n) <= @data.size
buffer << @data[@pos..(@pos + n - 1)]
@pos += n
return true
else
return false
end
end
def readbyte
if (@pos + 1) <= @data.size
@pos += 1
@data.getbyte(@pos - 1)
end
end
def eof?
@pos >= @data.size
end
def extract_stream(compressed)
@data << compressed
while !eof? && !finished?
buffer = ""
case @state
when :begin
break if !read(10, buffer)
if buffer.getbyte(0) != 0x1f || buffer.getbyte(1) != 0x8b
raise DecoderError.new("magic header not found")
end
if buffer.getbyte(2) != 0x08
raise DecoderError.new("unknown compression method")
end
@flags = buffer.getbyte(3)
if (@flags & 0xe0).nonzero?
raise DecoderError.new("unknown header flags set")
end
# We don't care about these values, I'm leaving the code for reference
# @time = buffer[4..7].unpack("V")[0] # little-endian uint32
# @extra_flags = buffer.getbyte(8)
# @os = buffer.getbyte(9)
@state = :extra_length
when :extra_length
if (@flags & 0x04).nonzero?
break if !read(2, buffer)
@extra_length = buffer.unpack("v")[0] # little-endian uint16
@state = :extra
else
@state = :extra
end
when :extra
if (@flags & 0x04).nonzero?
break if read(@extra_length, buffer)
@state = :name
else
@state = :name
end
when :name
if (@flags & 0x08).nonzero?
while !(buffer = readbyte).nil?
if buffer == 0
@state = :comment
break
end
end
else
@state = :comment
end
when :comment
if (@flags & 0x10).nonzero?
while !(buffer = readbyte).nil?
if buffer == 0
@state = :hcrc
break
end
end
else
@state = :hcrc
end
when :hcrc
if (@flags & 0x02).nonzero?
break if !read(2, buffer)
@state = :finish
else
@state = :finish
end
end
end
if finished?
compressed[(@pos - (@data.length - compressed.length))..-1]
else
""
end
end
end
class GZip < Base
def self.encoding_names
%w(gzip compressed)
end
def decompress(compressed)
@header ||= GZipHeader.new
if !@header.finished?
compressed = @header.extract_stream(compressed)
end
@zstream ||= Zlib::Inflate.new(-Zlib::MAX_WBITS)
@zstream.inflate(compressed)
rescue Zlib::Error
raise DecoderError
end
def finalize
if @zstream
if !@zstream.finished?
r = @zstream.finish
end
@zstream.close
r
else
nil
end
rescue Zlib::Error
raise DecoderError
end
end
DECODERS = [Deflate, GZip]
end