From 40ad12e5bedb7f328328f5fb634203e3b84b9af9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sa=C3=BAl=20Ibarra=20Corretg=C3=A9?= <saghul@gmail.com>
Date: Fri, 4 Jul 2014 20:45:09 +0200
Subject: [PATCH] unix: return UV_EAGAIN if uv_try_write cannot write any data

---
 include/uv.h              |  5 +++--
 src/unix/stream.c         |  7 +++++--
 test/test-tcp-try-write.c | 12 +++++++-----
 3 files changed, 15 insertions(+), 9 deletions(-)

diff --git a/include/uv.h b/include/uv.h
index c21a51a5..d7dcb449 100644
--- a/include/uv.h
+++ b/include/uv.h
@@ -707,8 +707,9 @@ UV_EXTERN int uv_write2(uv_write_t* req,
  * Same as `uv_write()`, but won't queue write request if it can't be completed
  * immediately.
  * Will return either:
- * - >= 0: number of bytes written (can be less than the supplied buffer size)
- * - < 0: negative error code
+ * - > 0: number of bytes written (can be less than the supplied buffer size)
+ * - < 0: negative error code (UV_EAGAIN is returned if no data can be sent
+ *   immediately)
  */
 UV_EXTERN int uv_try_write(uv_stream_t* handle,
                            const uv_buf_t bufs[],
diff --git a/src/unix/stream.c b/src/unix/stream.c
index 85e958bd..db25187f 100644
--- a/src/unix/stream.c
+++ b/src/unix/stream.c
@@ -1374,7 +1374,7 @@ int uv_try_write(uv_stream_t* stream,
 
   /* Connecting or already writing some data */
   if (stream->connect_req != NULL || stream->write_queue_size != 0)
-    return 0;
+    return -EAGAIN;
 
   has_pollout = uv__io_active(&stream->io_watcher, UV__POLLOUT);
 
@@ -1404,7 +1404,10 @@ int uv_try_write(uv_stream_t* stream,
     uv__stream_osx_interrupt_select(stream);
   }
 
-  return (int) written;
+  if (written == 0)
+    return -EAGAIN;
+  else
+    return written;
 }
 
 
diff --git a/test/test-tcp-try-write.c b/test/test-tcp-try-write.c
index 00341e41..5523b7a1 100644
--- a/test/test-tcp-try-write.c
+++ b/test/test-tcp-try-write.c
@@ -63,12 +63,14 @@ static void connect_cb(uv_connect_t* req, int status) {
   do {
     buf = uv_buf_init(zeroes, sizeof(zeroes));
     r = uv_try_write((uv_stream_t*) &client, &buf, 1);
-    ASSERT(r >= 0);
-    bytes_written += r;
+    ASSERT(r > 0 || r == UV_EAGAIN);
+    if (r > 0) {
+      bytes_written += r;
 
-    /* Partial write */
-    if (r != (int) sizeof(zeroes))
-      break;
+      /* Partial write */
+      if (r != (int) sizeof(zeroes))
+        break;
+    }
   } while (1);
   uv_close((uv_handle_t*) &client, close_cb);
 }