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/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include <sys/cdefs.h>
#include <stdbool.h>
__BEGIN_DECLS
/*
* The JNI invocation API exists to allow a choice of library responsible for managing virtual
* machines.
*/
/*
* Opaque structure used to hold JNI invocation internal state.
*/
struct JniInvocationImpl;
/*
* Creates an instance of a JniInvocationImpl.
*/
struct JniInvocationImpl* JniInvocationCreate();
/*
* Associates a library with a JniInvocationImpl instance. The library should export C symbols for
* JNI_GetDefaultJavaVMInitArgs, JNI_CreateJavaVM and JNI_GetDefaultJavaVMInitArgs.
*
* The specified |library| should be the filename of a shared library. The |library| is opened with
* dlopen(3).
*
* If there is an error opening the specified |library|, then function will fallback to the
* default library "libart.so". If the fallback library is successfully used then a warning is
* written to the Android log buffer. Use of the fallback library is not considered an error.
*
* If the fallback library cannot be opened or the expected symbols are not found in the library
* opened, then an error message is written to the Android log buffer and the function returns 0.
*
* Returns true on success, false otherwise.
*/
bool JniInvocationInit(struct JniInvocationImpl* instance, const char* library);
/*
* Release resources associated with JniInvocationImpl instance.
*/
void JniInvocationDestroy(struct JniInvocationImpl* instance);
/*
* Gets the default library for JNI invocation. The default library is "libart.so". This value may
* be overridden for debuggable builds using the persist.sys.dalvik.vm.lib.2 system property.
*
* The |library| argument is the preferred library to use on debuggable builds (when
* ro.debuggable=1). If the |library| argument is nullptr, then the system preferred value will be
* queried from persist.sys.dalvik.vm.lib.2 if the caller has provided |buffer| argument.
*
* The |buffer| argument is used for reading system properties in debuggable builds. It is
* optional, but should be provisioned to be PROP_VALUE_MAX bytes if provided to ensure it is
* large enough to hold a system property.
*
* Returns the filename of the invocation library determined from the inputs and system
* properties. The returned value may be |library|, |buffer|, or a pointer to a string constant
* "libart.so".
*/
const char* JniInvocationGetLibrary(const char* library, char* buffer);
__END_DECLS
#ifdef __cplusplus
// JniInvocation adds a layer of indirection for applications using
// the JNI invocation API to allow the JNI implementation to be
// selected dynamically. Apps can specify a specific implementation to
// be used by calling InitJniInvocation. If this is not done, the
// library will chosen based on the value of Android system property
// persist.sys.dalvik.vm.lib on the device, and otherwise fall back to
// a hard-coded default implementation.
class JniInvocation final {
public:
JniInvocation() {
impl_ = JniInvocationCreate();
}
~JniInvocation() {
JniInvocationDestroy(impl_);
}
// Initialize JNI invocation API. library should specify a valid
// shared library for opening via dlopen providing a JNI invocation
// implementation, or null to allow defaulting via
// persist.sys.dalvik.vm.lib.
bool Init(const char* library) {
return JniInvocationInit(impl_, library) != 0;
}
// Exposes which library is actually loaded from the given name. The
// buffer of size PROPERTY_VALUE_MAX will be used to load the system
// property for the default library, if necessary. If no buffer is
// provided, the fallback value will be used.
static const char* GetLibrary(const char* library, char* buffer) {
return JniInvocationGetLibrary(library, buffer);
}
private:
JniInvocation(const JniInvocation&) = delete;
JniInvocation& operator=(const JniInvocation&) = delete;
JniInvocationImpl* impl_;
};
#endif // __cplusplus
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