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Implements locking in C++ DriverStation, and adds double buffering to DS Thread (#25)

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Currently, about 5ms of every 20ms loop the DS thread would hold
the mutex, while grabbing data. During this time, and call to grab
joystick data would be blocked. This change grabs the joystick data
to a cache, and then grabs the mutex and moves the data references
around. This is much more efficient then the old code, and gives
teams more of their teleop loop time back for use.

Another major change this does is use preallocated arrays when entering
the JNI. Previously every JNI DS call would allocate an entire new array.
With a GC'd language where those arrays go on the heap, thats a problem,
and creates tons of garbage. That garbage is no longer created anymore,
as all arrays and byte buffers sent to JNI in the DS are preallocated.

In addition, GetJoystickName was always returning joystick 0 data, which
this fixes.
This commit is contained in:
Thad House
2016-05-21 00:41:15 -07:00
committed by Peter Johnson
parent 0965d60a71
commit a4f0c4fbe0
5 changed files with 274 additions and 131 deletions
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30
wpilibj/src/athena/cpp/lib/FRCNetworkCommunicationsLibrary.cpp
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@@ -142,37 +142,47 @@ Java_edu_wpi_first_wpilibj_communication_FRCNetworkCommunicationsLibrary_NativeH
/*
* Class: edu_wpi_first_wpilibj_communication_FRCNetworkCommunicationsLibrary
* Method: HALGetJoystickAxes
* Signature: (B)[S
* Signature: (B[S)B
*/
JNIEXPORT jshortArray JNICALL
JNIEXPORT jbyte JNICALL
Java_edu_wpi_first_wpilibj_communication_FRCNetworkCommunicationsLibrary_HALGetJoystickAxes(
JNIEnv *env, jclass, jbyte joystickNum) {
JNIEnv * env, jclass, jbyte joystickNum, jshortArray axesArray) {
NETCOMM_LOG(logDEBUG) << "Calling HALJoystickAxes";
HALJoystickAxes axes;
HALGetJoystickAxes(joystickNum, &axes);
jshortArray axesArray = env->NewShortArray(axes.count);
jsize javaSize = env->GetArrayLength(axesArray);
if (axes.count > javaSize)
{
ThrowIllegalArgumentException(env, "Native array size larger then passed in java array size");
}
env->SetShortArrayRegion(axesArray, 0, axes.count, axes.axes);
return axesArray;
return axes.count;
}
/*
* Class: edu_wpi_first_wpilibj_communication_FRCNetworkCommunicationsLibrary
* Method: HALGetJoystickPOVs
* Signature: (B)[S
* Signature: (B[S)B
*/
JNIEXPORT jshortArray JNICALL
JNIEXPORT jbyte JNICALL
Java_edu_wpi_first_wpilibj_communication_FRCNetworkCommunicationsLibrary_HALGetJoystickPOVs(
JNIEnv *env, jclass, jbyte joystickNum) {
JNIEnv * env, jclass, jbyte joystickNum, jshortArray povsArray) {
NETCOMM_LOG(logDEBUG) << "Calling HALJoystickPOVs";
HALJoystickPOVs povs;
HALGetJoystickPOVs(joystickNum, &povs);
jshortArray povsArray = env->NewShortArray(povs.count);
jsize javaSize = env->GetArrayLength(povsArray);
if (povs.count > javaSize)
{
ThrowIllegalArgumentException(env, "Native array size larger then passed in java array size");
}
env->SetShortArrayRegion(povsArray, 0, povs.count, povs.povs);
return povsArray;
return povs.count;
}
/*