From 2c335dbc7ae1a1724d715e051cc49cc3298fe8fb Mon Sep 17 00:00:00 2001 From: Tatsuhiro Tsujikawa Date: Sun, 26 Oct 2014 18:34:39 +0900 Subject: [PATCH] Add more comment about local window size adjustment --- lib/nghttp2_helper.c | 35 +++++++++++++++++++++++++++++++---- 1 file changed, 31 insertions(+), 4 deletions(-) diff --git a/lib/nghttp2_helper.c b/lib/nghttp2_helper.c index 87410a96..bb2342b4 100644 --- a/lib/nghttp2_helper.c +++ b/lib/nghttp2_helper.c @@ -163,6 +163,32 @@ void nghttp2_downcase(uint8_t *s, size_t len) } } +/* + * local_window_size + * ^ * + * | * recv_window_size + * | * * ^ + * | * * | + * 0+++++++++ + * | * * \ + * | * * | This rage is hidden in flow control. But it must be + * v * * / kept in order to restore it when window size is enlarged. + * recv_reduction + * (+ for negative direction) + * + * recv_window_size could be negative if we decrease + * local_window_size more than recv_window_size: + * + * local_window_size + * ^ * + * | * + * | * + * 0++++++++ + * | * ^ recv_window_size (negative) + * | * | + * v * * + * recv_reduction + */ int nghttp2_adjust_local_window_size(int32_t *local_window_size_ptr, int32_t *recv_window_size_ptr, int32_t *recv_reduction_ptr, @@ -188,10 +214,11 @@ int nghttp2_adjust_local_window_size(int32_t *local_window_size_ptr, if(*recv_window_size_ptr < 0) { *recv_window_size_ptr += recv_reduction_diff; } else { - /* If *recv_window_size_ptr > 0, then those bytes are - considered to be backed to the remote peer (by - WINDOW_UPDATE with the adjusted *delta_ptr), so it is - effectively 0 now. */ + /* If *recv_window_size_ptr > 0, then those bytes are going to + be backed to the remote peer (by WINDOW_UPDATE with the + adjusted *delta_ptr), so it is effectively 0 now. We set + to *recv_reduction_diff, because caller does not take into + account it in *delta_ptr. */ *recv_window_size_ptr = recv_reduction_diff; } /* recv_reduction_diff must be paied from *delta_ptr, since it