[mojo] Implement data pipe using a shared buffer.

mojo/edk/system/data_pipe_unittest.cc

Index: mojo/edk/system/data_pipe_unittest.cc
diff --git a/mojo/edk/system/data_pipe_unittest.cc b/mojo/edk/system/data_pipe_unittest.cc
index 6776a4f7a785bd81cd92fb777e10db368ba2a817..0526d9f50f7896651ca44d970add7ec54a2b05cc 100644
--- a/mojo/edk/system/data_pipe_unittest.cc
+++ b/mojo/edk/system/data_pipe_unittest.cc
@@ -367,6 +367,14 @@ TEST_F(DataPipeTest, BasicProducerWaiting) {
   ASSERT_EQ(123, elements[0]);
   ASSERT_EQ(-1, elements[1]);
 
+  // Wait until we can write.
+  hss = MojoHandleSignalsState();
+  ASSERT_EQ(MOJO_RESULT_OK, MojoWait(producer_, MOJO_HANDLE_SIGNAL_WRITABLE,
+                                     MOJO_DEADLINE_INDEFINITE, &hss));
+  EXPECT_EQ(MOJO_HANDLE_SIGNAL_WRITABLE, hss.satisfied_signals);
+  EXPECT_EQ(MOJO_HANDLE_SIGNAL_WRITABLE | MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+            hss.satisfiable_signals);
+
   // Try writing, using a two-phase write.
   void* buffer = nullptr;
   num_bytes = static_cast<uint32_t>(3u * sizeof(elements[0]));
@@ -392,6 +400,14 @@ TEST_F(DataPipeTest, BasicProducerWaiting) {
   ASSERT_EQ(MOJO_RESULT_OK, EndReadData(static_cast<uint32_t>(
                                         1u * sizeof(elements[0]))));
 
+  // Wait until we can write.
+  hss = MojoHandleSignalsState();
+  ASSERT_EQ(MOJO_RESULT_OK, MojoWait(producer_, MOJO_HANDLE_SIGNAL_WRITABLE,
+                                     MOJO_DEADLINE_INDEFINITE, &hss));
+  EXPECT_EQ(MOJO_HANDLE_SIGNAL_WRITABLE, hss.satisfied_signals);
+  EXPECT_EQ(MOJO_HANDLE_SIGNAL_WRITABLE | MOJO_HANDLE_SIGNAL_PEER_CLOSED,
+            hss.satisfiable_signals);
+
   // Write one element.
   elements[0] = 123;
   num_bytes = static_cast<uint32_t>(1u * sizeof(elements[0]));
@@ -562,7 +578,7 @@ TEST_F(DataPipeTest, BasicConsumerWaiting) {
   ASSERT_EQ(MOJO_RESULT_OK,
             MojoWait(consumer_, MOJO_HANDLE_SIGNAL_PEER_CLOSED,
                      MOJO_DEADLINE_INDEFINITE, &hss));
-  ASSERT_TRUE((hss.satisfied_signals & MOJO_HANDLE_SIGNAL_PEER_CLOSED) != 0);
+  ASSERT_NE(0u, hss.satisfied_signals & MOJO_HANDLE_SIGNAL_PEER_CLOSED);
   ASSERT_EQ(MOJO_HANDLE_SIGNAL_READABLE | MOJO_HANDLE_SIGNAL_PEER_CLOSED,
             hss.satisfiable_signals);