Refactor nghttp2_adjust_local_window_size

lib/nghttp2_helper.c

@@ -172,40 +172,45 @@ int nghttp2_adjust_local_window_size(int32_t *local_window_size_ptr,
                                      int32_t *recv_reduction_ptr,
                                      int32_t *delta_ptr) {
   if (*delta_ptr > 0) {
+    int32_t recv_reduction_delta;
+    int32_t delta;
     int32_t new_recv_window_size =
         nghttp2_max(0, *recv_window_size_ptr) - *delta_ptr;
-    if (new_recv_window_size < 0) {
+
+    if (new_recv_window_size >= 0) {
+      *recv_window_size_ptr = new_recv_window_size;
+      return 0;
+    }
+
+    delta = -new_recv_window_size;
+
     /* The delta size is strictly more than received bytes. Increase
-         local_window_size by that difference. */
-      int32_t recv_reduction_diff;
-      if (*local_window_size_ptr >
-          NGHTTP2_MAX_WINDOW_SIZE + new_recv_window_size) {
+       local_window_size by that difference |delta|. */
+    if (*local_window_size_ptr > NGHTTP2_MAX_WINDOW_SIZE - delta) {
       return NGHTTP2_ERR_FLOW_CONTROL;
     }
-      *local_window_size_ptr -= new_recv_window_size;
+    *local_window_size_ptr += delta;
     /* If there is recv_reduction due to earlier window_size
        reduction, we have to adjust it too. */
-      recv_reduction_diff =
-          nghttp2_min(*recv_reduction_ptr, -new_recv_window_size);
-      *recv_reduction_ptr -= recv_reduction_diff;
+    recv_reduction_delta = nghttp2_min(*recv_reduction_ptr, delta);
+    *recv_reduction_ptr -= recv_reduction_delta;
     if (*recv_window_size_ptr < 0) {
-        *recv_window_size_ptr += recv_reduction_diff;
+      *recv_window_size_ptr += recv_reduction_delta;
     } else {
       /* 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
+         be returned to the remote peer (by WINDOW_UPDATE with the
+         adjusted *delta_ptr), so it is effectively 0 now.  We set to
+         *recv_reduction_delta, because caller does not take into
          account it in *delta_ptr. */
-        *recv_window_size_ptr = recv_reduction_diff;
+      *recv_window_size_ptr = recv_reduction_delta;
     }
-      /* recv_reduction_diff must be paied from *delta_ptr, since it
+    /* recv_reduction_delta must be paied from *delta_ptr, since it
        was added in window size reduction (see below). */
-      *delta_ptr -= recv_reduction_diff;
-    } else {
-      *recv_window_size_ptr = new_recv_window_size;
-    }
+    *delta_ptr -= recv_reduction_delta;
+
     return 0;
-  } else {
+  }
+
   if (*local_window_size_ptr + *delta_ptr < 0 ||
       *recv_window_size_ptr < INT32_MIN - *delta_ptr ||
       *recv_reduction_ptr > INT32_MAX + *delta_ptr) {
@@ -219,7 +224,7 @@ int nghttp2_adjust_local_window_size(int32_t *local_window_size_ptr,
   *recv_window_size_ptr += *delta_ptr;
   *recv_reduction_ptr -= *delta_ptr;
   *delta_ptr = 0;
-  }
+
   return 0;
 }