zorldo

Goofing around with Ebiten
git clone git://bsandro.tech/zorldo
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ctx_android.go (3174B)

      1 // Copyright 2015 The Go Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style
      3 // license that can be found in the LICENSE file.
      4 
      5 package mobileinit
      6 
      7 /*
      8 #include <jni.h>
      9 #include <stdlib.h>
     10 
     11 static char* lockJNI(JavaVM *vm, uintptr_t* envp, int* attachedp) {
     12 	JNIEnv* env;
     13 
     14 	if (vm == NULL) {
     15 		return "no current JVM";
     16 	}
     17 
     18 	*attachedp = 0;
     19 	switch ((*vm)->GetEnv(vm, (void**)&env, JNI_VERSION_1_6)) {
     20 	case JNI_OK:
     21 		break;
     22 	case JNI_EDETACHED:
     23 		if ((*vm)->AttachCurrentThread(vm, &env, 0) != 0) {
     24 			return "cannot attach to JVM";
     25 		}
     26 		*attachedp = 1;
     27 		break;
     28 	case JNI_EVERSION:
     29 		return "bad JNI version";
     30 	default:
     31 		return "unknown JNI error from GetEnv";
     32 	}
     33 
     34 	*envp = (uintptr_t)env;
     35 	return NULL;
     36 }
     37 
     38 static char* checkException(uintptr_t jnienv) {
     39 	jthrowable exc;
     40 	JNIEnv* env = (JNIEnv*)jnienv;
     41 
     42 	if (!(*env)->ExceptionCheck(env)) {
     43 		return NULL;
     44 	}
     45 
     46 	exc = (*env)->ExceptionOccurred(env);
     47 	(*env)->ExceptionClear(env);
     48 
     49 	jclass clazz = (*env)->FindClass(env, "java/lang/Throwable");
     50 	jmethodID toString = (*env)->GetMethodID(env, clazz, "toString", "()Ljava/lang/String;");
     51 	jobject msgStr = (*env)->CallObjectMethod(env, exc, toString);
     52 	return (char*)(*env)->GetStringUTFChars(env, msgStr, 0);
     53 }
     54 
     55 static void unlockJNI(JavaVM *vm) {
     56 	(*vm)->DetachCurrentThread(vm);
     57 }
     58 */
     59 import "C"
     60 
     61 import (
     62 	"errors"
     63 	"runtime"
     64 	"unsafe"
     65 )
     66 
     67 // currentVM is stored to initialize other cgo packages.
     68 //
     69 // As all the Go packages in a program form a single shared library,
     70 // there can only be one JNI_OnLoad function for initialization. In
     71 // OpenJDK there is JNI_GetCreatedJavaVMs, but this is not available
     72 // on android.
     73 var currentVM *C.JavaVM
     74 
     75 // currentCtx is Android's android.context.Context. May be NULL.
     76 var currentCtx C.jobject
     77 
     78 // SetCurrentContext populates the global Context object with the specified
     79 // current JavaVM instance (vm) and android.context.Context object (ctx).
     80 // The android.context.Context object must be a global reference.
     81 func SetCurrentContext(vm unsafe.Pointer, ctx uintptr) {
     82 	currentVM = (*C.JavaVM)(vm)
     83 	currentCtx = (C.jobject)(ctx)
     84 }
     85 
     86 // RunOnJVM runs fn on a new goroutine locked to an OS thread with a JNIEnv.
     87 //
     88 // RunOnJVM blocks until the call to fn is complete. Any Java
     89 // exception or failure to attach to the JVM is returned as an error.
     90 //
     91 // The function fn takes vm, the current JavaVM*,
     92 // env, the current JNIEnv*, and
     93 // ctx, a jobject representing the global android.context.Context.
     94 func RunOnJVM(fn func(vm, env, ctx uintptr) error) error {
     95 	errch := make(chan error)
     96 	go func() {
     97 		runtime.LockOSThread()
     98 		defer runtime.UnlockOSThread()
     99 
    100 		env := C.uintptr_t(0)
    101 		attached := C.int(0)
    102 		if errStr := C.lockJNI(currentVM, &env, &attached); errStr != nil {
    103 			errch <- errors.New(C.GoString(errStr))
    104 			return
    105 		}
    106 		if attached != 0 {
    107 			defer C.unlockJNI(currentVM)
    108 		}
    109 
    110 		vm := uintptr(unsafe.Pointer(currentVM))
    111 		if err := fn(vm, uintptr(env), uintptr(currentCtx)); err != nil {
    112 			errch <- err
    113 			return
    114 		}
    115 
    116 		if exc := C.checkException(env); exc != nil {
    117 			errch <- errors.New(C.GoString(exc))
    118 			C.free(unsafe.Pointer(exc))
    119 			return
    120 		}
    121 		errch <- nil
    122 	}()
    123 	return <-errch
    124 }