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
operator <content::__anonf2be35e10111::MethodIdentifier22 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
GetMethodIDFromClassName(JNIEnv * env,const char * class_name,const char * method,const char * jni_signature)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
100