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require "zlib"
require "stringio"
require "time" # for Time.httpdate
require 'rack/utils'
module Rack
class Deflater
def initialize(app)
@app = app
end
def call(env)
status, headers, body = @app.call(env)
headers = Utils::HeaderHash.new(headers)
# Skip compressing empty entity body responses and responses with
# no-transform set.
if Utils::STATUS_WITH_NO_ENTITY_BODY.include?(status) ||
headers['Cache-Control'].to_s =~ /\bno-transform\b/
return [status, headers, body]
end
request = Request.new(env)
encoding = Utils.select_best_encoding(%w(gzip deflate identity),
request.accept_encoding)
# Set the Vary HTTP header.
vary = headers["Vary"].to_s.split(",").map { |v| v.strip }
unless vary.include?("*") || vary.include?("Accept-Encoding")
headers["Vary"] = vary.push("Accept-Encoding").join(",")
end
case encoding
when "gzip"
mtime = headers.key?("Last-Modified") ?
Time.httpdate(headers["Last-Modified"]) : Time.now
body = self.class.gzip(body, mtime)
headers = headers.merge("Content-Encoding" => "gzip", "Content-Length" => body.length.to_s)
[status, headers, [body]]
when "deflate"
body = self.class.deflate(body)
headers = headers.merge("Content-Encoding" => "deflate", "Content-Length" => body.length.to_s)
[status, headers, [body]]
when "identity"
[status, headers, body]
when nil
message = ["An acceptable encoding for the requested resource #{request.fullpath} could not be found."]
[406, {"Content-Type" => "text/plain", "Content-Length" => message[0].length.to_s}, message]
end
end
def self.gzip(body, mtime)
io = StringIO.new
gzip = Zlib::GzipWriter.new(io)
gzip.mtime = mtime
# TODO: Add streaming
body.each { |part| gzip << part }
gzip.close
return io.string
end
DEFLATE_ARGS = [
Zlib::DEFAULT_COMPRESSION,
# drop the zlib header which causes both Safari and IE to choke
-Zlib::MAX_WBITS,
Zlib::DEF_MEM_LEVEL,
Zlib::DEFAULT_STRATEGY
]
# Loosely based on Mongrel's Deflate handler
def self.deflate(body)
deflater = Zlib::Deflate.new(*DEFLATE_ARGS)
# TODO: Add streaming
body.each { |part| deflater << part }
return deflater.finish
end
end
end
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