Mojo: Add a C++-style SharedBuffer API.

mojo/public/cpp/system/tests/core_unittest.cc

Index: mojo/public/cpp/system/tests/core_unittest.cc
diff --git a/mojo/public/cpp/system/tests/core_unittest.cc b/mojo/public/cpp/system/tests/core_unittest.cc
index b500be3be763d5b46a39334285a03acb70fa5827..9a956353d50cc41faef4ed4e236c6c865c2634cd 100644
--- a/mojo/public/cpp/system/tests/core_unittest.cc
+++ b/mojo/public/cpp/system/tests/core_unittest.cc
@@ -481,6 +481,47 @@ TEST(CoreCppTest, ScopedHandleMoveCtor) {
   EXPECT_FALSE(buffer2.is_valid());
 }
 
+TEST(CoreCppTest, BasicSharedBuffer) {
+  ScopedSharedBufferHandle h0;
+
+  // Create a shared buffer (|h0|).
+  {
+    SharedBuffer buffer(100);
+    h0 = std::move(buffer.handle);
+  }
+
+  // Map everything.
+  ScopedSharedBufferMapping mapping = h0->Map(100);
+  ASSERT_TRUE(mapping);
+  static_cast<char*>(mapping.get())[50] = 'x';
+
+  // Duplicate |h0| to |h1|.
+  ScopedSharedBufferHandle h1 =
+      h0->Clone(SharedBufferHandle::AccessMode::READ_ONLY);
+  ASSERT_TRUE(h1.is_valid());
+
+  // Close |h0|.
+  h0.reset();
+
+  // The mapping should still be good.
+  static_cast<char*>(mapping.get())[51] = 'y';
+
+  // Unmap it.
+  mapping.reset();
+
+  // Map half of |h1|.
+  mapping = h1->MapAtOffset(50, 50);
+  ASSERT_TRUE(mapping);
+
+  // It should have what we wrote.
+  EXPECT_EQ('x', static_cast<char*>(mapping.get())[0]);
+  EXPECT_EQ('y', static_cast<char*>(mapping.get())[1]);
+
+  // Unmap it.
+  mapping.reset();
+  h1.reset();
+}
+
 // TODO(vtl): Write data pipe tests.
 
 }  // namespace