Add a buffered Tempfile setup

similar to zip_tricks "next" branch

lib/zipline.rb

@@ -2,7 +2,8 @@
 require "zipline/version"
 require 'zip_tricks'
 require "zipline/zip_generator"
-require "zipline/chunked"
+require "zipline/chunked_body"
+require "zipline/tempfile_body"
 
 # class MyController < ApplicationController
 #   include Zipline
@@ -31,7 +32,10 @@ def zipline(files, zipname = 'zipline.zip', **kwargs_for_new)
 
       # Here it would be good natured to to read and save the ZIP into a tempfile, and serve it from there.
       # Rack has a Rack::TempfileReaper middleware which could be used for that etc. Maybe one day.
-      self.response_body = zip_generator
+      tempfile_body = Zipline::TempfileBody.new(request.env, zip_generator)
+      headers["Content-Length"] = tempfile_body.size.to_s
+      headers["X-Zipline-Output"] = "buffered"
+      self.response_body = tempfile_body
     else
       # Disable buffering for both nginx and Google Load Balancer, see
       # https://cloud.google.com/appengine/docs/flexible/how-requests-are-handled?tab=python#x-accel-buffering
@@ -43,6 +47,7 @@ def zipline(files, zipname = 'zipline.zip', **kwargs_for_new)
 
       # and send out in chunked encoding
       headers["Transfer-Encoding"] = "chunked"
+      headers["X-Zipline-Output"] = "streamed"
       self.response_body = Zipline::Chunked.new(zip_generator)
     end
   end

lib/zipline/tempfile_body.rb

@@ -0,0 +1,50 @@
+# Contains a file handle which can be closed once the response finishes sending.
+# It supports `to_path` so that `Rack::Sendfile` can intercept it
+class Zipline::TempfileBody
+  TEMPFILE_NAME_PREFIX = "zipline-tf-body-"
+  attr_reader :tempfile
+
+  # @param body[#each] the enumerable that yields bytes, usually a `RackBody`.
+  #   The `body` will be read in full immediately and closed.
+  def initialize(env, body)
+    @tempfile = Tempfile.new(TEMPFILE_NAME_PREFIX)
+    # Rack::TempfileReaper calls close! on tempfiles which get buffered
+    # We wil assume that it works fine with Rack::Sendfile (i.e. the path
+    # to the file getting served gets used before we unlink the tempfile)
+    env['rack.tempfiles'] ||= []
+    env['rack.tempfiles'] << @tempfile
+
+    @tempfile.binmode
+
+    body.each { |bytes| @tempfile << bytes }
+    body.close if body.respond_to?(:close)
+
+    @tempfile.flush
+  end
+
+  # Returns the size of the contained `Tempfile` so that a correct
+  # Content-Length header can be set
+  #
+  # @return [Integer]
+  def size
+    @tempfile.size
+  end
+
+  # Returns the path to the `Tempfile`, so that Rack::Sendfile can send this response
+  # using the downstream webserver
+  #
+  # @return [String]
+  def to_path
+    @tempfile.to_path
+  end
+
+  # Stream the file's contents if `Rack::Sendfile` isn't present.
+  #
+  # @return [void]
+  def each
+    @tempfile.rewind
+    while chunk = @tempfile.read(16384)
+      yield chunk
+    end
+  end
+end