Address some review comments

Addressed comments in dex cache and class table. Added class table
test.

Test: mm test-art-host-gtest-class_table_test -j20

Change-Id: I3ec0282247187acb1ec7af25b309501f001a1c3e
diff --git a/runtime/class_table_test.cc b/runtime/class_table_test.cc
new file mode 100644
index 0000000..f1248eb
--- /dev/null
+++ b/runtime/class_table_test.cc
@@ -0,0 +1,163 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "class_table-inl.h"
+
+#include "art_field-inl.h"
+#include "art_method-inl.h"
+#include "class_linker-inl.h"
+#include "common_runtime_test.h"
+#include "dex_file.h"
+#include "gc/accounting/card_table-inl.h"
+#include "gc/heap.h"
+#include "handle_scope-inl.h"
+#include "mirror/class-inl.h"
+#include "obj_ptr.h"
+#include "scoped_thread_state_change-inl.h"
+
+namespace art {
+namespace mirror {
+
+class CollectRootVisitor {
+ public:
+  CollectRootVisitor() {}
+
+  template <class MirrorType>
+  ALWAYS_INLINE void VisitRootIfNonNull(GcRoot<MirrorType>& root) const
+      REQUIRES_SHARED(Locks::mutator_lock_) {
+    if (!root.IsNull()) {
+      VisitRoot(root);
+    }
+  }
+
+  template <class MirrorType>
+  ALWAYS_INLINE void VisitRootIfNonNull(mirror::CompressedReference<MirrorType>* root) const
+      REQUIRES_SHARED(Locks::mutator_lock_) {
+    if (!root->IsNull()) {
+      VisitRoot(root);
+    }
+  }
+
+  template <class MirrorType>
+  void VisitRoot(GcRoot<MirrorType>& root) const REQUIRES_SHARED(Locks::mutator_lock_) {
+    VisitRoot(root.AddressWithoutBarrier());
+  }
+
+  template <class MirrorType>
+  void VisitRoot(mirror::CompressedReference<MirrorType>* root) const
+      REQUIRES_SHARED(Locks::mutator_lock_) {
+    roots_.insert(root->AsMirrorPtr());
+  }
+
+  mutable std::set<mirror::Object*> roots_;
+};
+
+
+class ClassTableTest : public CommonRuntimeTest {};
+
+TEST_F(ClassTableTest, ClassTable) {
+  ScopedObjectAccess soa(Thread::Current());
+  jobject jclass_loader = LoadDex("XandY");
+  VariableSizedHandleScope hs(soa.Self());
+  Handle<ClassLoader> class_loader(hs.NewHandle(soa.Decode<ClassLoader>(jclass_loader)));
+  const char* descriptor_x = "LX;";
+  const char* descriptor_y = "LY;";
+  Handle<mirror::Class> h_X(
+      hs.NewHandle(class_linker_->FindClass(soa.Self(), descriptor_x, class_loader)));
+  Handle<mirror::Class> h_Y(
+      hs.NewHandle(class_linker_->FindClass(soa.Self(), descriptor_y, class_loader)));
+  Handle<mirror::Object> obj_X = hs.NewHandle(h_X->AllocObject(soa.Self()));
+  ASSERT_TRUE(obj_X.Get() != nullptr);
+  ClassTable table;
+  EXPECT_EQ(table.NumZygoteClasses(class_loader.Get()), 0u);
+  EXPECT_EQ(table.NumNonZygoteClasses(class_loader.Get()), 0u);
+
+  // Add h_X to the class table.
+  table.Insert(h_X.Get());
+  EXPECT_EQ(table.LookupByDescriptor(h_X.Get()), h_X.Get());
+  EXPECT_EQ(table.Lookup(descriptor_x, ComputeModifiedUtf8Hash(descriptor_x)), h_X.Get());
+  EXPECT_EQ(table.Lookup("NOT_THERE", ComputeModifiedUtf8Hash("NOT_THERE")), nullptr);
+  EXPECT_EQ(table.NumZygoteClasses(class_loader.Get()), 0u);
+  EXPECT_EQ(table.NumNonZygoteClasses(class_loader.Get()), 1u);
+
+  // Create the zygote snapshot and ensure the accounting is correct.
+  table.FreezeSnapshot();
+  EXPECT_EQ(table.NumZygoteClasses(class_loader.Get()), 1u);
+  EXPECT_EQ(table.NumNonZygoteClasses(class_loader.Get()), 0u);
+
+  // Test inserting and related lookup functions.
+  EXPECT_EQ(table.LookupByDescriptor(h_Y.Get()), nullptr);
+  EXPECT_FALSE(table.Contains(h_Y.Get()));
+  table.Insert(h_Y.Get());
+  EXPECT_EQ(table.LookupByDescriptor(h_X.Get()), h_X.Get());
+  EXPECT_EQ(table.LookupByDescriptor(h_Y.Get()), h_Y.Get());
+  EXPECT_TRUE(table.Contains(h_X.Get()));
+  EXPECT_TRUE(table.Contains(h_Y.Get()));
+
+  EXPECT_EQ(table.NumZygoteClasses(class_loader.Get()), 1u);
+  EXPECT_EQ(table.NumNonZygoteClasses(class_loader.Get()), 1u);
+
+  // Test adding / clearing strong roots.
+  EXPECT_TRUE(table.InsertStrongRoot(obj_X.Get()));
+  EXPECT_FALSE(table.InsertStrongRoot(obj_X.Get()));
+  table.ClearStrongRoots();
+  EXPECT_TRUE(table.InsertStrongRoot(obj_X.Get()));
+
+  // Collect all the roots and make sure there is nothing missing.
+  CollectRootVisitor roots;
+  table.VisitRoots(roots);
+  EXPECT_TRUE(roots.roots_.find(h_X.Get()) != roots.roots_.end());
+  EXPECT_TRUE(roots.roots_.find(h_Y.Get()) != roots.roots_.end());
+  EXPECT_TRUE(roots.roots_.find(obj_X.Get()) != roots.roots_.end());
+
+  // Checks that vising only classes works.
+  std::set<mirror::Class*> classes;
+  table.Visit([&classes](ObjPtr<mirror::Class> klass) REQUIRES_SHARED(Locks::mutator_lock_) {
+    classes.insert(klass.Ptr());
+    return true;
+  });
+  EXPECT_TRUE(classes.find(h_X.Get()) != classes.end());
+  EXPECT_TRUE(classes.find(h_Y.Get()) != classes.end());
+  EXPECT_EQ(classes.size(), 2u);
+  classes.clear();
+  table.Visit([&classes](ObjPtr<mirror::Class> klass) REQUIRES_SHARED(Locks::mutator_lock_) {
+    classes.insert(klass.Ptr());
+    // Return false to exit the Visit early.
+    return false;
+  });
+  EXPECT_EQ(classes.size(), 1u);
+
+  // Test remove.
+  table.Remove(descriptor_x);
+  EXPECT_FALSE(table.Contains(h_X.Get()));
+
+  // Test that WriteToMemory and ReadFromMemory work.
+  table.Insert(h_X.Get());
+  const size_t count = table.WriteToMemory(nullptr);
+  std::unique_ptr<uint8_t[]> buffer(new uint8_t[count]());
+  ASSERT_EQ(table.WriteToMemory(&buffer[0]), count);
+  ClassTable table2;
+  size_t count2 = table2.ReadFromMemory(&buffer[0]);
+  EXPECT_EQ(count, count2);
+  // Strong roots are not serialized, only classes.
+  EXPECT_TRUE(table2.Contains(h_X.Get()));
+  EXPECT_TRUE(table2.Contains(h_Y.Get()));
+
+  // TODO: Add tests for UpdateClass, InsertOatFile.
+}
+
+}  // namespace mirror
+}  // namespace art