|  | // Copyright 2014 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/android/java/jni_helper.h" | 
|  |  | 
|  | #include <map> | 
|  |  | 
|  | #include "base/android/jni_android.h" | 
|  | #include "base/lazy_instance.h" | 
|  | #include "base/threading/platform_thread.h" | 
|  |  | 
|  | namespace content { | 
|  |  | 
|  | 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; | 
|  | } | 
|  |  | 
|  | }  // namespace content |