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# frozen_string_literal: true
require 'digest/sha2'
require_relative 'constants'
require_relative 'utils'
module Rack
# Automatically sets the etag header on all String bodies.
#
# The etag header is skipped if etag or last-modified headers are sent or if
# a sendfile body (body.responds_to :to_path) is given (since such cases
# should be handled by apache/nginx).
#
# On initialization, you can pass two parameters: a cache-control directive
# used when etag is absent and a directive when it is present. The first
# defaults to nil, while the second defaults to "max-age=0, private, must-revalidate"
class ETag
ETAG_STRING = Rack::ETAG
DEFAULT_CACHE_CONTROL = "max-age=0, private, must-revalidate"
def initialize(app, no_cache_control = nil, cache_control = DEFAULT_CACHE_CONTROL)
@app = app
@cache_control = cache_control
@no_cache_control = no_cache_control
end
def call(env)
status, headers, body = response = @app.call(env)
if etag_status?(status) && body.respond_to?(:to_ary) && !skip_caching?(headers)
body = body.to_ary
digest = digest_body(body)
headers[ETAG_STRING] = %(W/"#{digest}") if digest
# Body was modified, so we need to re-assign it:
response[2] = body
end
unless headers[CACHE_CONTROL]
if digest
headers[CACHE_CONTROL] = @cache_control if @cache_control
else
headers[CACHE_CONTROL] = @no_cache_control if @no_cache_control
end
end
response
end
private
def etag_status?(status)
status == 200 || status == 201
end
def skip_caching?(headers)
headers.key?(ETAG_STRING) || headers.key?('last-modified')
end
def digest_body(body)
digest = nil
body.each do |part|
(digest ||= Digest::SHA256.new) << part unless part.empty?
end
digest && digest.hexdigest.byteslice(0,32)
end
end
end
|
