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require "zlib"
require "time" # for Time.httpdate
require 'rack/utils'
module Rack
# This middleware enables compression of http responses.
#
# Currently supported compression algorithms:
#
# * gzip
# * deflate
# * identity (no transformation)
#
# The middleware automatically detects when compression is supported
# and allowed. For example no transformation is made when a cache
# directive of 'no-transform' is present, or when the response status
# code is one that doesn't allow an entity body.
class Deflater
##
# Creates Rack::Deflater middleware.
#
# [app] rack app instance
# [options] hash of deflater options, i.e.
# 'if' - a lambda enabling / disabling deflation based on returned boolean value
# e.g use Rack::Deflater, :if => lambda { |env, status, headers, body| body.length > 512 }
# 'include' - a list of content types that should be compressed
def initialize(app, options = {})
@app = app
@condition = options[:if]
@compressible_types = options[:include]
end
def call(env)
status, headers, body = @app.call(env)
headers = Utils::HeaderHash.new(headers)
unless should_deflate?(env, status, headers, body)
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"
headers['Content-Encoding'] = "gzip"
headers.delete(CONTENT_LENGTH)
mtime = headers.key?("Last-Modified") ?
Time.httpdate(headers["Last-Modified"]) : Time.now
[status, headers, GzipStream.new(body, mtime)]
when "deflate"
headers['Content-Encoding'] = "deflate"
headers.delete(CONTENT_LENGTH)
[status, headers, DeflateStream.new(body)]
when "identity"
[status, headers, body]
when nil
message = "An acceptable encoding for the requested resource #{request.fullpath} could not be found."
bp = Rack::BodyProxy.new([message]) { body.close if body.respond_to?(:close) }
[406, {CONTENT_TYPE => "text/plain", CONTENT_LENGTH => message.length.to_s}, bp]
end
end
class GzipStream
def initialize(body, mtime)
@body = body
@mtime = mtime
@closed = false
end
def each(&block)
@writer = block
gzip =::Zlib::GzipWriter.new(self)
gzip.mtime = @mtime
@body.each { |part|
gzip.write(part)
gzip.flush
}
ensure
gzip.close
@writer = nil
end
def write(data)
@writer.call(data)
end
def close
return if @closed
@closed = true
@body.close if @body.respond_to?(:close)
end
end
class DeflateStream
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
]
def initialize(body)
@body = body
@closed = false
end
def each
deflator = ::Zlib::Deflate.new(*DEFLATE_ARGS)
@body.each { |part| yield deflator.deflate(part, Zlib::SYNC_FLUSH) }
yield deflator.finish
nil
ensure
deflator.close
end
def close
return if @closed
@closed = true
@body.close if @body.respond_to?(:close)
end
end
private
def should_deflate?(env, status, headers, body)
# 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/ ||
(headers['Content-Encoding'] && headers['Content-Encoding'] !~ /\bidentity\b/)
return false
end
# Skip if @compressible_types are given and does not include request's content type
return false if @compressible_types && !(headers.has_key?('Content-Type') && @compressible_types.include?(headers['Content-Type'][/[^;]*/]))
# Skip if @condition lambda is given and evaluates to false
return false if @condition && !@condition.call(env, status, headers, body)
true
end
end
end