Android: cleanup jni_android to minimize external dependencies.

content/browser/renderer_host/java/jni_helper.cc

+// Copyright (c) 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 "content/browser/renderer_host/java/jni_helper.h"
+
+#include <map>
+
+#include "base/android/jni_android.h"
+#include "base/lazy_instance.h"
+#include "base/threading/platform_thread.h"
+
+namespace {
+
+struct MethodIdentifier {
+  const char* class_name;
+  const char* method;
+  const char* jni_signature;
+
+  bool operator<(const MethodIdentifier& other) const {
+    int r = strcmp(class_name, other.class_name);
+    if (r < 0) {
+      return true;
+    } else if (r > 0) {
+      return false;
+    }
+
+    r = strcmp(method, other.method);
+    if (r < 0) {
+      return true;
+    } else if (r > 0) {
+      return false;
+    }
+
+    return strcmp(jni_signature, other.jni_signature) < 0;
+  }
+};
+
+typedef std::map<MethodIdentifier, jmethodID> MethodIDMap;
+
+const base::subtle::AtomicWord kUnlocked = 0;
+const base::subtle::AtomicWord kLocked = 1;
+base::subtle::AtomicWord g_method_id_map_lock = kUnlocked;
+
+base::LazyInstance<MethodIDMap> g_method_id_map = LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
+jmethodID GetMethodIDFromClassName(JNIEnv* env,
+                                   const char* class_name,
+                                   const char* method,
+                                   const char* jni_signature) {
+  MethodIdentifier key;
+  key.class_name = class_name;
+  key.method = method;
+  key.jni_signature = jni_signature;
+
+  MethodIDMap* map = g_method_id_map.Pointer();
+  bool found = false;
+
+  while (base::subtle::Acquire_CompareAndSwap(&g_method_id_map_lock,
+                                              kUnlocked,
+                                              kLocked) != kUnlocked) {
+    base::PlatformThread::YieldCurrentThread();
+  }
+  MethodIDMap::const_iterator iter = map->find(key);
+  if (iter != map->end()) {
+    found = true;
+  }
+  base::subtle::Release_Store(&g_method_id_map_lock, kUnlocked);
+
+  // Addition to the map does not invalidate this iterator.
+  if (found) {
+    return iter->second;
+  }
+
+  base::android::ScopedJavaLocalRef<jclass> clazz(
+      env, env->FindClass(class_name));
+  jmethodID id = base::android::MethodID::Get<
+      base::android::MethodID::TYPE_INSTANCE>(
+          env, clazz.obj(), method, jni_signature);
+
+  while (base::subtle::Acquire_CompareAndSwap(&g_method_id_map_lock,
+                                              kUnlocked,
+                                              kLocked) != kUnlocked) {
+    base::PlatformThread::YieldCurrentThread();
+  }
+  // Another thread may have populated the map already.
+  std::pair<MethodIDMap::const_iterator, bool> result =
+      map->insert(std::make_pair(key, id));
+  DCHECK_EQ(id, result.first->second);
+  base::subtle::Release_Store(&g_method_id_map_lock, kUnlocked);
+
+  return id;
+}