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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package mobileinit
/*
#include <jni.h>
#include <stdlib.h>
static char* lockJNI(JavaVM *vm, uintptr_t* envp, int* attachedp) {
JNIEnv* env;
if (vm == NULL) {
return "no current JVM";
}
*attachedp = 0;
switch ((*vm)->GetEnv(vm, (void**)&env, JNI_VERSION_1_6)) {
case JNI_OK:
break;
case JNI_EDETACHED:
if ((*vm)->AttachCurrentThread(vm, &env, 0) != 0) {
return "cannot attach to JVM";
}
*attachedp = 1;
break;
case JNI_EVERSION:
return "bad JNI version";
default:
return "unknown JNI error from GetEnv";
}
*envp = (uintptr_t)env;
return NULL;
}
static char* checkException(uintptr_t jnienv) {
jthrowable exc;
JNIEnv* env = (JNIEnv*)jnienv;
if (!(*env)->ExceptionCheck(env)) {
return NULL;
}
exc = (*env)->ExceptionOccurred(env);
(*env)->ExceptionClear(env);
jclass clazz = (*env)->FindClass(env, "java/lang/Throwable");
jmethodID toString = (*env)->GetMethodID(env, clazz, "toString", "()Ljava/lang/String;");
jobject msgStr = (*env)->CallObjectMethod(env, exc, toString);
return (char*)(*env)->GetStringUTFChars(env, msgStr, 0);
}
static void unlockJNI(JavaVM *vm) {
(*vm)->DetachCurrentThread(vm);
}
*/
import "C"
import (
"errors"
"runtime"
"unsafe"
)
// currentVM is stored to initialize other cgo packages.
//
// As all the Go packages in a program form a single shared library,
// there can only be one JNI_OnLoad function for initialization. In
// OpenJDK there is JNI_GetCreatedJavaVMs, but this is not available
// on android.
var currentVM *C.JavaVM
// currentCtx is Android's android.context.Context. May be NULL.
var currentCtx C.jobject
// SetCurrentContext populates the global Context object with the specified
// current JavaVM instance (vm) and android.context.Context object (ctx).
// The android.context.Context object must be a global reference.
func SetCurrentContext(vm unsafe.Pointer, ctx uintptr) {
currentVM = (*C.JavaVM)(vm)
currentCtx = (C.jobject)(ctx)
}
// RunOnJVM runs fn on a new goroutine locked to an OS thread with a JNIEnv.
//
// RunOnJVM blocks until the call to fn is complete. Any Java
// exception or failure to attach to the JVM is returned as an error.
//
// The function fn takes vm, the current JavaVM*,
// env, the current JNIEnv*, and
// ctx, a jobject representing the global android.context.Context.
func RunOnJVM(fn func(vm, env, ctx uintptr) error) error {
errch := make(chan error)
go func() {
runtime.LockOSThread()
defer runtime.UnlockOSThread()
env := C.uintptr_t(0)
attached := C.int(0)
if errStr := C.lockJNI(currentVM, &env, &attached); errStr != nil {
errch <- errors.New(C.GoString(errStr))
return
}
if attached != 0 {
defer C.unlockJNI(currentVM)
}
vm := uintptr(unsafe.Pointer(currentVM))
if err := fn(vm, uintptr(env), uintptr(currentCtx)); err != nil {
errch <- err
return
}
if exc := C.checkException(env); exc != nil {
errch <- errors.New(C.GoString(exc))
C.free(unsafe.Pointer(exc))
return
}
errch <- nil
}()
return <-errch
}
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