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Android: move and group JNIEnv helper functions
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@1bsyl
1bsyl committed Jan 11, 2019
1 parent 7f34783 commit 7b42f03
Showing 1 changed file with 88 additions and 94 deletions.
182 changes: 88 additions & 94 deletions src/core/android/SDL_android.c
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Expand Up @@ -46,12 +46,6 @@
#include <sys/types.h>
#include <unistd.h>
#include <dlfcn.h>
/* #define LOG_TAG "SDL_android" */
/* #define LOGI(...) __android_log_print(ANDROID_LOG_INFO,LOG_TAG,__VA_ARGS__) */
/* #define LOGE(...) __android_log_print(ANDROID_LOG_ERROR,LOG_TAG,__VA_ARGS__) */
#define LOGI(...) do {} while (0)
#define LOGE(...) do {} while (0)


#define SDL_JAVA_PREFIX org_libsdl_app
#define CONCAT1(prefix, class, function) CONCAT2(prefix, class, function)
Expand Down Expand Up @@ -212,7 +206,6 @@ JNIEXPORT jint JNICALL SDL_JAVA_CONTROLLER_INTERFACE(nativeRemoveHaptic)(
/* Uncomment this to log messages entering and exiting methods in this file */
/* #define DEBUG_JNI */

static void Android_JNI_ThreadDestroyed(void *);
static void checkJNIReady(void);

/*******************************************************************************
Expand Down Expand Up @@ -293,13 +286,95 @@ static SDL_bool bHasNewData;

static SDL_bool bHasEnvironmentVariables = SDL_FALSE;


static int Android_JNI_SetEnv(JNIEnv *env);

/*******************************************************************************
Functions called by JNI
*******************************************************************************/

/* From http://developer.android.com/guide/practices/jni.html
* All threads are Linux threads, scheduled by the kernel.
* They're usually started from managed code (using Thread.start), but they can also be created elsewhere and then
* attached to the JavaVM. For example, a thread started with pthread_create can be attached with the
* JNI AttachCurrentThread or AttachCurrentThreadAsDaemon functions. Until a thread is attached, it has no JNIEnv,
* and cannot make JNI calls.
* Attaching a natively-created thread causes a java.lang.Thread object to be constructed and added to the "main"
* ThreadGroup, making it visible to the debugger. Calling AttachCurrentThread on an already-attached thread
* is a no-op.
* Note: You can call this function any number of times for the same thread, there's no harm in it
*/

/* From http://developer.android.com/guide/practices/jni.html
* Threads attached through JNI must call DetachCurrentThread before they exit. If coding this directly is awkward,
* in Android 2.0 (Eclair) and higher you can use pthread_key_create to define a destructor function that will be
* called before the thread exits, and call DetachCurrentThread from there. (Use that key with pthread_setspecific
* to store the JNIEnv in thread-local-storage; that way it'll be passed into your destructor as the argument.)
* Note: The destructor is not called unless the stored value is != NULL
* Note: You can call this function any number of times for the same thread, there's no harm in it
* (except for some lost CPU cycles)
*/

/* Set local storage value */
static int
Android_JNI_SetEnv(JNIEnv *env) {
int status = pthread_setspecific(mThreadKey, env);
if (status < 0) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "Failed pthread_setspecific() in Android_JNI_SetEnv() (err=%d)", status);
}
return status;
}

/* Get local storage value */
JNIEnv* Android_JNI_GetEnv(void)
{
/* Get JNIEnv from the Thread local storage */
JNIEnv *env = pthread_getspecific(mThreadKey);
if (env == NULL) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "JNIEnv is NULL. Call Android_JNI_SetupThread() first.");
}

return env;
}

/* Set up an external thread for using JNI with Android_JNI_GetEnv() */
int Android_JNI_SetupThread(void)
{
JNIEnv *env;
int status;

/* There should be a JVM */
if (mJavaVM == NULL) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "Failed, there is no JavaVM");
return 0;
}

/* Attach the current thread to the JVM and get a JNIEnv.
* It will be detached by pthread_create destructor 'Android_JNI_ThreadDestroyed' */
status = (*mJavaVM)->AttachCurrentThread(mJavaVM, &env, NULL);
if (status < 0) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "Failed to attach current thread (err=%d)", status);
return 0;
}

/* Save JNIEnv into the Thread local storage */
if (Android_JNI_SetEnv(env) < 0) {
return 0;
}

return 1;
}

/* Destructor called for each thread where mThreadKey is not NULL */
static void
Android_JNI_ThreadDestroyed(void *value)
{
/* The thread is being destroyed, detach it from the Java VM and set the mThreadKey value to NULL as required */
JNIEnv *env = (JNIEnv *) value;
if (env != NULL) {
(*mJavaVM)->DetachCurrentThread(mJavaVM);
Android_JNI_SetEnv(NULL);
}
}

/* Creation of local storage mThreadKey */
static void
Android_JNI_CreateKey()
{
Expand All @@ -309,7 +384,7 @@ Android_JNI_CreateKey()
}
}

static void
static void
Android_JNI_CreateKey_once()
{
int status = pthread_once(&key_once, Android_JNI_CreateKey);
Expand Down Expand Up @@ -576,7 +651,7 @@ JNIEXPORT int JNICALL SDL_JAVA_INTERFACE(nativeRunMain)(JNIEnv *env, jclass cls,
}
(*env)->ReleaseStringUTFChars(env, library, library_file);

/* This is a Java thread, it doesn't need to be Detached from the JVM.
/* This is a Java thread, it doesn't need to be Detached from the JVM.
* Set to mThreadKey value to NULL not to call pthread_create destructor 'Android_JNI_ThreadDestroyed' */
Android_JNI_SetEnv(NULL);

Expand Down Expand Up @@ -888,7 +963,7 @@ JNIEXPORT void JNICALL SDL_JAVA_INTERFACE(nativeQuit)(

str = SDL_GetError();
if (str && str[0]) {
__android_log_print(ANDROID_LOG_VERBOSE, "SDL", "SDLActivity thread ends (error=%s)", str);
__android_log_print(ANDROID_LOG_ERROR, "SDL", "SDLActivity thread ends (error=%s)", str);
} else {
__android_log_print(ANDROID_LOG_VERBOSE, "SDL", "SDLActivity thread ends");
}
Expand Down Expand Up @@ -1141,87 +1216,6 @@ SDL_bool Android_JNI_GetAccelerometerValues(float values[3])
return retval;
}

static void Android_JNI_ThreadDestroyed(void *value)
{
/* The thread is being destroyed, detach it from the Java VM and set the mThreadKey value to NULL as required */
JNIEnv *env = (JNIEnv *) value;
if (env != NULL) {
(*mJavaVM)->DetachCurrentThread(mJavaVM);
Android_JNI_SetEnv(NULL);
}
}

static int Android_JNI_SetEnv(JNIEnv *env) {
int status = pthread_setspecific(mThreadKey, env);
if (status < 0) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "Failed pthread_setspecific() in Android_JNI_SetEnv() (err=%d)", status);
}
return status;
}

JNIEnv* Android_JNI_GetEnv(void)
{
/* From http://developer.android.com/guide/practices/jni.html
* All threads are Linux threads, scheduled by the kernel.
* They're usually started from managed code (using Thread.start), but they can also be created elsewhere and then
* attached to the JavaVM. For example, a thread started with pthread_create can be attached with the
* JNI AttachCurrentThread or AttachCurrentThreadAsDaemon functions. Until a thread is attached, it has no JNIEnv,
* and cannot make JNI calls.
* Attaching a natively-created thread causes a java.lang.Thread object to be constructed and added to the "main"
* ThreadGroup, making it visible to the debugger. Calling AttachCurrentThread on an already-attached thread
* is a no-op.
* Note: You can call this function any number of times for the same thread, there's no harm in it
*/

/* From http://developer.android.com/guide/practices/jni.html
* Threads attached through JNI must call DetachCurrentThread before they exit. If coding this directly is awkward,
* in Android 2.0 (Eclair) and higher you can use pthread_key_create to define a destructor function that will be
* called before the thread exits, and call DetachCurrentThread from there. (Use that key with pthread_setspecific
* to store the JNIEnv in thread-local-storage; that way it'll be passed into your destructor as the argument.)
* Note: The destructor is not called unless the stored value is != NULL
* Note: You can call this function any number of times for the same thread, there's no harm in it
* (except for some lost CPU cycles)
*/



/* Get JNIEnv from the Thread local storage */
JNIEnv *env = pthread_getspecific(mThreadKey);
if (env == NULL) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "JNIEnv is NULL. Call Android_JNI_SetupThread() first.");
}

return env;
}

int Android_JNI_SetupThread(void)
{
JNIEnv *env;
int status;

/* There should be a JVM */
if (mJavaVM == NULL) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "Failed, there is no JavaVM");
return 0;
}

/* Attach the current thread to the JVM and get a JNIEnv.
* It will be detached by pthread_create destructor 'Android_JNI_ThreadDestroyed'
*/
status = (*mJavaVM)->AttachCurrentThread(mJavaVM, &env, NULL);
if (status < 0) {
__android_log_print(ANDROID_LOG_ERROR, "SDL", "Failed to attach current thread (err=%d)", status);
return 0;
}

/* Save JNIEnv into the Thread local storage */
if (Android_JNI_SetEnv(env) < 0) {
return 0;
}

return 1;
}

/*
* Audio support
*/
Expand Down

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