Restore Readable#buffered and add Buffered#buffered.

Fixes compatibility with `async-http-cache`.

lib/protocol/http/body/buffered.rb

@@ -52,6 +52,13 @@ def initialize(chunks = [], length = nil)
 
 				attr :chunks
 
+				# A rewindable body wraps some other body. Convert it to a buffered body. The buffered body will share the same chunks as the rewindable body.
+				#
+				# @returns [Buffered] the buffered body.
+				def buffered
+					self.class.new(@chunks)
+				end
+
 				def finish
 					self
 				end
@@ -64,7 +71,7 @@ def close(error = nil)
 				end
 
 				def clear
-					@chunks.clear
+					@chunks = []
 					@length = 0
 					@index = 0
 				end

lib/protocol/http/body/readable.rb

@@ -11,9 +11,9 @@ module Body
 			#
 			# Typically, you'd override `#read` to return chunks of data.
 			#
-			# I n general, you read chunks of data from a body until it is empty and returns `nil`. Upon reading `nil`, the body is considered consumed and should not be read from again.
+			# In general, you read chunks of data from a body until it is empty and returns `nil`. Upon reading `nil`, the body is considered consumed and should not be read from again.
 			#
-			# Reading can also fail, for example if the body represents a streaming upload, and the connection is lost. In this case, the body will raise some kind of error.
+			# Reading can also fail, for example if the body represents a streaming upload, and the connection is lost. In this case, `#read` will raise some kind of error.
 			#
 			# If you don't want to read from a stream, and instead want to close it immediately, you can call `close` on the body. If the body is already completely consumed, `close` will do nothing, but if there is still data to be read, it will cause the underlying stream to be reset (and possibly closed).
 			class Readable
@@ -50,6 +50,15 @@ def rewind
 					false
 				end
 
+				# Return a buffered representation of this body.
+				#
+				# This method must return a buffered body if `#rewindable?`.
+				#
+				# @returns [Buffered | Nil] The buffered body.
+				def buffered
+					nil
+				end
+
 				# The total length of the body, if known.
 				# @returns [Integer | Nil] The total length of the body, or `nil` if the length is unknown.
 				def length

lib/protocol/http/body/wrapper.rb

@@ -42,6 +42,10 @@ def ready?
 					@body.ready?
 				end
 
+				def buffered
+					@body.buffered
+				end
+
 				def rewind
 					@body.rewind
 				end

test/protocol/http/body/buffered.rb

@@ -131,6 +131,23 @@
 		end
 	end
 
+	with "#buffered" do
+		let(:buffered_body) {body.buffered}
+
+		it "returns a buffered body" do
+			expect(buffered_body).to be_a(subject)
+			expect(buffered_body.read).to be == "Hello"
+			expect(buffered_body.read).to be == "World"
+		end
+
+		it "doesn't affect the original body" do
+			expect(buffered_body.join).to be == "HelloWorld"
+
+			expect(buffered_body).to be(:empty?)
+			expect(body).not.to be(:empty?)
+		end
+	end
+
 	with "#each" do
 		with "a block" do
 			it "iterates over chunks" do