fix(receive): a receive 0 should immediately return, not block

The fix is slightly more complex because reading from a closed
socket should still return a closed-error.

fixes: #427
fixes: https://github.com/ledgetech/lua-resty-http/pull/313

1 files changed, 1 insertions, 0 deletions

diff --git a/src/wsocket.c b/src/wsocket.c
index d3af9d4..86c6994 100644
--- a/src/wsocket.c
+++ b/src/wsocket.c
@@ -247,6 +247,7 @@ int socket_recv(p_socket ps, char *data, size_t count, size_t *got,
     int err, prev = IO_DONE;
     *got = 0;
     if (*ps == SOCKET_INVALID) return IO_CLOSED;
+    if (count == 0) return IO_DONE;
     for ( ;; ) {
         int taken = recv(*ps, data, (int) count, 0);
         if (taken > 0) {