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1 // Copyright (c) 2012 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 #ifndef BASE_ANDROID_JNI_ANDROID_H_
6 #define BASE_ANDROID_JNI_ANDROID_H_
7 
8 #include <jni.h>
9 #include <sys/types.h>
10 
11 #include <string>
12 
13 #include "base/android/scoped_java_ref.h"
14 #include "base/atomicops.h"
15 #include "base/base_export.h"
16 #include "base/compiler_specific.h"
17 #include "base/debug/debugging_buildflags.h"
18 #include "base/debug/stack_trace.h"
19 #include "base/macros.h"
20 
21 #if BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
22 
23 // When profiling is enabled (enable_profiling=true) this macro is added to
24 // all generated JNI stubs so that it becomes the last thing that runs before
25 // control goes into Java.
26 //
27 // This macro saves stack frame pointer of the current function. Saved value
28 // used later by JNI_LINK_SAVED_FRAME_POINTER.
29 #define JNI_SAVE_FRAME_POINTER \
30   base::android::JNIStackFrameSaver jni_frame_saver(__builtin_frame_address(0))
31 
32 // When profiling is enabled (enable_profiling=true) this macro is added to
33 // all generated JNI callbacks so that it becomes the first thing that runs
34 // after control returns from Java.
35 //
36 // This macro links stack frame of the current function to the stack frame
37 // saved by JNI_SAVE_FRAME_POINTER, allowing frame-based unwinding
38 // (used by the heap profiler) to produce complete traces.
39 #define JNI_LINK_SAVED_FRAME_POINTER                    \
40   base::debug::ScopedStackFrameLinker jni_frame_linker( \
41       __builtin_frame_address(0),                       \
42       base::android::JNIStackFrameSaver::SavedFrame())
43 
44 #else
45 
46 // Frame-based stack unwinding is not supported, do nothing.
47 #define JNI_SAVE_FRAME_POINTER
48 #define JNI_LINK_SAVED_FRAME_POINTER
49 
50 #endif  // BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
51 
52 namespace base {
53 namespace android {
54 
55 // Used to mark symbols to be exported in a shared library's symbol table.
56 #define JNI_EXPORT __attribute__ ((visibility("default")))
57 
58 // Contains the registration method information for initializing JNI bindings.
59 struct RegistrationMethod {
60   const char* name;
61   bool (*func)(JNIEnv* env);
62 };
63 
64 // Attaches the current thread to the VM (if necessary) and return the JNIEnv*.
65 BASE_EXPORT JNIEnv* AttachCurrentThread();
66 
67 // Same to AttachCurrentThread except that thread name will be set to
68 // |thread_name| if it is the first call. Otherwise, thread_name won't be
69 // changed. AttachCurrentThread() doesn't regard underlying platform thread
70 // name, but just resets it to "Thread-???". This function should be called
71 // right after new thread is created if it is important to keep thread name.
72 BASE_EXPORT JNIEnv* AttachCurrentThreadWithName(const std::string& thread_name);
73 
74 // Detaches the current thread from VM if it is attached.
75 BASE_EXPORT void DetachFromVM();
76 
77 // Initializes the global JVM.
78 BASE_EXPORT void InitVM(JavaVM* vm);
79 
80 // Returns true if the global JVM has been initialized.
81 BASE_EXPORT bool IsVMInitialized();
82 
83 // Initializes the global ClassLoader used by the GetClass and LazyGetClass
84 // methods. This is needed because JNI will use the base ClassLoader when there
85 // is no Java code on the stack. The base ClassLoader doesn't know about any of
86 // the application classes and will fail to lookup anything other than system
87 // classes.
88 BASE_EXPORT void InitReplacementClassLoader(
89     JNIEnv* env,
90     const JavaRef<jobject>& class_loader);
91 
92 // Finds the class named |class_name| and returns it.
93 // Use this method instead of invoking directly the JNI FindClass method (to
94 // prevent leaking local references).
95 // This method triggers a fatal assertion if the class could not be found.
96 // Use HasClass if you need to check whether the class exists.
97 BASE_EXPORT ScopedJavaLocalRef<jclass> GetClass(JNIEnv* env,
98                                                 const char* class_name);
99 
100 // The method will initialize |atomic_class_id| to contain a global ref to the
101 // class. And will return that ref on subsequent calls.  It's the caller's
102 // responsibility to release the ref when it is no longer needed.
103 // The caller is responsible to zero-initialize |atomic_method_id|.
104 // It's fine to simultaneously call this on multiple threads referencing the
105 // same |atomic_method_id|.
106 BASE_EXPORT jclass LazyGetClass(
107     JNIEnv* env,
108     const char* class_name,
109     base::subtle::AtomicWord* atomic_class_id);
110 
111 // This class is a wrapper for JNIEnv Get(Static)MethodID.
112 class BASE_EXPORT MethodID {
113  public:
114   enum Type {
115     TYPE_STATIC,
116     TYPE_INSTANCE,
117   };
118 
119   // Returns the method ID for the method with the specified name and signature.
120   // This method triggers a fatal assertion if the method could not be found.
121   template<Type type>
122   static jmethodID Get(JNIEnv* env,
123                        jclass clazz,
124                        const char* method_name,
125                        const char* jni_signature);
126 
127   // The caller is responsible to zero-initialize |atomic_method_id|.
128   // It's fine to simultaneously call this on multiple threads referencing the
129   // same |atomic_method_id|.
130   template<Type type>
131   static jmethodID LazyGet(JNIEnv* env,
132                            jclass clazz,
133                            const char* method_name,
134                            const char* jni_signature,
135                            base::subtle::AtomicWord* atomic_method_id);
136 };
137 
138 // Returns true if an exception is pending in the provided JNIEnv*.
139 BASE_EXPORT bool HasException(JNIEnv* env);
140 
141 // If an exception is pending in the provided JNIEnv*, this function clears it
142 // and returns true.
143 BASE_EXPORT bool ClearException(JNIEnv* env);
144 
145 // This function will call CHECK() macro if there's any pending exception.
146 BASE_EXPORT void CheckException(JNIEnv* env);
147 
148 // This returns a string representation of the java stack trace.
149 BASE_EXPORT std::string GetJavaExceptionInfo(JNIEnv* env,
150                                              jthrowable java_throwable);
151 
152 #if BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
153 
154 // Saves caller's PC and stack frame in a thread-local variable.
155 // Implemented only when profiling is enabled (enable_profiling=true).
156 class BASE_EXPORT JNIStackFrameSaver {
157  public:
158   JNIStackFrameSaver(void* current_fp);
159   ~JNIStackFrameSaver();
160   static void* SavedFrame();
161 
162  private:
163   void* previous_fp_;
164 
165   DISALLOW_COPY_AND_ASSIGN(JNIStackFrameSaver);
166 };
167 
168 #endif  // BUILDFLAG(CAN_UNWIND_WITH_FRAME_POINTERS)
169 
170 }  // namespace android
171 }  // namespace base
172 
173 #endif  // BASE_ANDROID_JNI_ANDROID_H_
174