Add some unit tests for mojo's Buffer classes.

mojo/public/tests/buffer_unittest.cc

+// Copyright 2013 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/bindings/lib/bindings_serialization.h"
+#include "mojo/public/bindings/lib/buffer.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace mojo {
+namespace test {
+
+bool IsZero(void* p_buf, size_t size) {
+  char* buf = reinterpret_cast<char*>(p_buf);
+  for (size_t i = 0; i < size; ++i) {
+    if (buf[i] != 0)
+      return false;
+  }
+  return true;
+}
+
+// Tests small and large allocations in ScratchBuffer.
+TEST(ScratchBufferTest, Basic) {
+  // Test that a small allocation is placed on the stack.
+  ScratchBuffer buf;
+  void* small = buf.Allocate(10);
+  EXPECT_TRUE(small >= &buf && small < (&buf + sizeof(buf)));
+  EXPECT_TRUE(IsZero(small, 10));
+
+  // Large allocations won't be on the stack.
+  void* large = buf.Allocate(100*1024);
+  EXPECT_TRUE(IsZero(large, 100*1024));
+  EXPECT_FALSE(large >= &buf && large < (&buf + sizeof(buf)));
+
+  // But another small allocation should be back on the stack.
+  // TODO(mpcomplete): but it isn't. We can fix that easily enough.
+  small = buf.Allocate(10);
+  EXPECT_TRUE(IsZero(small, 10));
+  //EXPECT_TRUE(small >= &buf && small < (&buf + sizeof(buf)));
+}
+
+// Tests that FixedBuffer allocates memory aligned to 8 byte boundaries.
+TEST(FixedBufferTest, Alignment) {
+  FixedBuffer buf(internal::Align(10) * 2);
+  ASSERT_EQ(buf.size(), 16u * 2);
+
+  void* a = buf.Allocate(10);
+  ASSERT_TRUE(a);
+  EXPECT_TRUE(IsZero(a, 10));
+  EXPECT_EQ(0, reinterpret_cast<ptrdiff_t>(a) % 8);
+
+  void* b = buf.Allocate(10);
+  ASSERT_TRUE(b);
+  EXPECT_TRUE(IsZero(b, 10));
+  EXPECT_EQ(0, reinterpret_cast<ptrdiff_t>(b) % 8);
+
+  // Any more allocations would result in an assert, but we can't test that.
+}
+
+// Tests that FixedBuffer::Leak passes ownership to the caller.
+TEST(FixedBufferTest, Leak) {
+  void* ptr = NULL;
+  void* buf_ptr = NULL;
+  {
+    FixedBuffer buf(8);
+    ASSERT_EQ(8u, buf.size());
+
+    ptr = buf.Allocate(8);
+    ASSERT_TRUE(ptr);
+    void* buf_ptr = buf.Leak();
+
+    // The buffer should point to the first element allocated.
+    // TODO(mpcomplete): Is this a reasonable expectation?
+    EXPECT_EQ(ptr, buf_ptr);
+
+    // The FixedBuffer should be empty now.
+    EXPECT_EQ(0u, buf.size());
+    EXPECT_FALSE(buf.Leak());
+  }
+
+  // Since we called Leak, ptr is still writable after FixedBuffer went out of
+  // scope.
+  memset(ptr, 1, 8);
+  free(buf_ptr);
+}
+
+}  // namespace test
+}  // namespace mojo