content/browser/android/java/jni_helper.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "content/browser/android/java/jni_helper.h"
   6
   7 #include <map>
   8
   9 #include "base/android/jni_android.h"
  10 #include "base/lazy_instance.h"
  11 #include "base/threading/platform_thread.h"
  12
  13 namespace content {
  14
  15 namespace {
  16
  17 struct MethodIdentifier {
  18   const char* class_name;
  19   const char* method;
  20   const char* jni_signature;
  21
  22   bool operator<(const MethodIdentifier& other) const {
  23     int r = strcmp(class_name, other.class_name);
  24     if (r < 0) {
  25       return true;
  26     } else if (r > 0) {
  27       return false;
  28     }
  29
  30     r = strcmp(method, other.method);
  31     if (r < 0) {
  32       return true;
  33     } else if (r > 0) {
  34       return false;
  35     }
  36
  37     return strcmp(jni_signature, other.jni_signature) < 0;
  38   }
  39 };
  40
  41 typedef std::map<MethodIdentifier, jmethodID> MethodIDMap;
  42
  43 const base::subtle::AtomicWord kUnlocked = 0;
  44 const base::subtle::AtomicWord kLocked = 1;
  45 base::subtle::AtomicWord g_method_id_map_lock = kUnlocked;
  46
  47 base::LazyInstance<MethodIDMap> g_method_id_map = LAZY_INSTANCE_INITIALIZER;
  48
  49 }  // namespace
  50
  51 jmethodID GetMethodIDFromClassName(JNIEnv* env,
  52                                    const char* class_name,
  53                                    const char* method,
  54                                    const char* jni_signature) {
  55   MethodIdentifier key;
  56   key.class_name = class_name;
  57   key.method = method;
  58   key.jni_signature = jni_signature;
  59
  60   MethodIDMap* map = g_method_id_map.Pointer();
  61   bool found = false;
  62
  63   while (base::subtle::Acquire_CompareAndSwap(&g_method_id_map_lock,
  64                                               kUnlocked,
  65                                               kLocked) != kUnlocked) {
  66     base::PlatformThread::YieldCurrentThread();
  67   }
  68   MethodIDMap::const_iterator iter = map->find(key);
  69   if (iter != map->end()) {
  70     found = true;
  71   }
  72   base::subtle::Release_Store(&g_method_id_map_lock, kUnlocked);
  73
  74   // Addition to the map does not invalidate this iterator.
  75   if (found) {
  76     return iter->second;
  77   }
  78
  79   base::android::ScopedJavaLocalRef<jclass> clazz(
  80       env, env->FindClass(class_name));
  81   jmethodID id = base::android::MethodID::Get<
  82       base::android::MethodID::TYPE_INSTANCE>(
  83           env, clazz.obj(), method, jni_signature);
  84
  85   while (base::subtle::Acquire_CompareAndSwap(&g_method_id_map_lock,
  86                                               kUnlocked,
  87                                               kLocked) != kUnlocked) {
  88     base::PlatformThread::YieldCurrentThread();
  89   }
  90   // Another thread may have populated the map already.
  91   std::pair<MethodIDMap::const_iterator, bool> result =
  92       map->insert(std::make_pair(key, id));
  93   DCHECK_EQ(id, result.first->second);
  94   base::subtle::Release_Store(&g_method_id_map_lock, kUnlocked);
  95
  96   return id;
  97 }
  98
  99 }  // namespace content