Add and document the new multipart code

The old undocumented API is removed entirely.

While a documentation exists for the new API, it will not
be considered set in stone until further testing has been
performed, and a file upload example has been added.

The new API should be a little more efficient than the
old API, especially with smaller messages.

test/http_SUITE_data/http_multipart.erl

@@ -8,22 +8,18 @@ init({_Transport, http}, Req, []) ->
 	{ok, Req, {}}.
 
 handle(Req, State) ->
-	{Result, Req2} = acc_multipart(Req),
+	{Result, Req2} = acc_multipart(Req, []),
 	{ok, Req3} = cowboy_req:reply(200, [], term_to_binary(Result), Req2),
 	{ok, Req3, State}.
 
 terminate(_, _, _) ->
 	ok.
 
-acc_multipart(Req) ->
-	acc_multipart(cowboy_req:multipart_data(Req), []).
-
-acc_multipart({headers, Headers, Req}, Acc) ->
-	acc_multipart(cowboy_req:multipart_data(Req), [{Headers, []}|Acc]);
-acc_multipart({body, Data, Req}, [{Headers, BodyAcc}|Acc]) ->
-	acc_multipart(cowboy_req:multipart_data(Req), [{Headers, [Data|BodyAcc]}|Acc]);
-acc_multipart({end_of_part, Req}, [{Headers, BodyAcc}|Acc]) ->
-	acc_multipart(cowboy_req:multipart_data(Req),
-		[{Headers, list_to_binary(lists:reverse(BodyAcc))}|Acc]);
-acc_multipart({eof, Req}, Acc) ->
-	{lists:reverse(Acc), Req}.
+acc_multipart(Req, Acc) ->
+	case cowboy_req:part(Req) of
+		{ok, Headers, Req2} ->
+			{ok, Body, Req3} = cowboy_req:part_body(Req2),
+			acc_multipart(Req3, [{Headers, Body}|Acc]);
+		{done, Req2} ->
+			{lists:reverse(Acc), Req2}
+	end.

test/http_SUITE_data/http_multipart_stream.erl

@@ -0,0 +1,34 @@
+%% Feel free to use, reuse and abuse the code in this file.
+
+-module(http_multipart_stream).
+-behaviour(cowboy_http_handler).
+-export([init/3, handle/2, terminate/3]).
+
+init(_, Req, []) ->
+	{ok, Req, undefined}.
+
+handle(Req, State) ->
+	Req2 = multipart(Req),
+	{ok, Req3} = cowboy_req:reply(200, Req2),
+	{ok, Req3, State}.
+
+terminate(_, _, _) ->
+	ok.
+
+multipart(Req) ->
+	case cowboy_req:part(Req) of
+		{ok, [{<<"content-length">>, BinLength}], Req2} ->
+			Length = list_to_integer(binary_to_list(BinLength)),
+			{Length, Req3} = stream_body(Req2, 0),
+			multipart(Req3);
+		{done, Req2} ->
+			Req2
+	end.
+
+stream_body(Req, N) ->
+	case cowboy_req:part_body(Req) of
+		{ok, Data, Req2} ->
+			{N + byte_size(Data), Req2};
+		{more, Data, Req2} ->
+			stream_body(Req2, N + byte_size(Data))
+	end.