Mojo C bindings library pt1: MojomBuffer

mojo/public/c/bindings/tests/buffer_unittest.cc

Index: mojo/public/c/bindings/tests/buffer_unittest.cc
diff --git a/mojo/public/c/bindings/tests/buffer_unittest.cc b/mojo/public/c/bindings/tests/buffer_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..014a7988b85e43dddcc6f549dfe3b0301e90f16c
--- /dev/null
+++ b/mojo/public/c/bindings/tests/buffer_unittest.cc
@@ -0,0 +1,38 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "mojo/public/c/bindings/buffer.h"
+#include "testing/gtest/include/gtest/gtest.h"

[viettrungluu, 2016/06/15 15:00:58]

nit: blank line above

[vardhan, 2016/06/15 15:48:00]

Done.

+
+namespace {
+
+TEST(MojomBufferTest, Alignment) {
+  char buffer[100];
+  struct MojomBuffer mbuf = {
+      buffer, sizeof(buffer),
+      0,  // num_bytes_used
+  };
+
+  // This should actually allocate 8 bytes:
+  EXPECT_EQ(buffer, MojomBuffer_Allocate(&mbuf, 6));
+  EXPECT_EQ(8ul, mbuf.num_bytes_used);
+  // The start of the next buffer is buffer + 8 bytes:
+  EXPECT_EQ(buffer + 8, MojomBuffer_Allocate(&mbuf, 6));
+  EXPECT_EQ(16ul, mbuf.num_bytes_used);
+}

[viettrungluu, 2016/06/15 15:00:58]

You should test that allocating things that are already a multiple of 8 in size
don't result in larger allocations.

[vardhan, 2016/06/15 15:48:00]

Done.

+
+TEST(MojomBufferTest, Failure) {

[viettrungluu, 2016/06/15 15:00:58]

You should really test the subtle part, namely the overflow logic.

[vardhan, 2016/06/15 15:48:00]

Done.

+  char buffer[100];
+  struct MojomBuffer mbuf = {
+      buffer, sizeof(buffer),
+      0,  // num_bytes_used
+  };
+
+  // Allocate too much space.
+  EXPECT_EQ(NULL, MojomBuffer_Allocate(&mbuf, sizeof(buffer) + 10));
+  // Allocating 0 bytes should fail as well.

[viettrungluu, 2016/06/15 15:00:58]

Why should it necessarily be a failure?

[vardhan, 2016/06/15 15:48:00]

(see other comment)

+  EXPECT_EQ(NULL, MojomBuffer_Allocate(&mbuf, 0));
+}
+
+}  // namespace