ART: Add GetClassSignature

Add support to retrieve the signature of a JNI class.

Add a test.

Bug: 31684578
Test: m test-art-host-run-test-912-classes
Change-Id: I1cf946996f9089cb5d41e93b4f1064193e9d6350
diff --git a/runtime/openjdkjvmti/ti_class.cc b/runtime/openjdkjvmti/ti_class.cc
new file mode 100644
index 0000000..de2076a
--- /dev/null
+++ b/runtime/openjdkjvmti/ti_class.cc
@@ -0,0 +1,73 @@
+/* Copyright (C) 2016 The Android Open Source Project
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This file implements interfaces from the file jvmti.h. This implementation
+ * is licensed under the same terms as the file jvmti.h.  The
+ * copyright and license information for the file jvmti.h follows.
+ *
+ * Copyright (c) 2003, 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#include "ti_class.h"
+
+#include "art_jvmti.h"
+#include "scoped_thread_state_change-inl.h"
+#include "thread-inl.h"
+
+namespace openjdkjvmti {
+
+jvmtiError ClassUtil::GetClassSignature(jvmtiEnv* env,
+                                         jclass jklass,
+                                         char** signature_ptr,
+                                         char** generic_ptr) {
+  art::ScopedObjectAccess soa(art::Thread::Current());
+  art::ObjPtr<art::mirror::Class> klass = soa.Decode<art::mirror::Class>(jklass);
+  if (klass == nullptr) {
+    return ERR(INVALID_CLASS);
+  }
+
+  JvmtiUniquePtr sig_copy;
+  if (signature_ptr != nullptr) {
+    std::string storage;
+    const char* descriptor = klass->GetDescriptor(&storage);
+
+    unsigned char* tmp;
+    jvmtiError ret = CopyString(env, descriptor, &tmp);
+    if (ret != ERR(NONE)) {
+      return ret;
+    }
+    sig_copy = MakeJvmtiUniquePtr(env, tmp);
+    *signature_ptr = reinterpret_cast<char*>(tmp);
+  }
+
+  // TODO: Support generic signature.
+  *generic_ptr = nullptr;
+
+  // Everything is fine, release the buffers.
+  sig_copy.release();
+
+  return ERR(NONE);
+}
+
+}  // namespace openjdkjvmti