[wpiutil] Add synchronization primitives

These enable more consistent use of synchronization across the
native libraries.  Users can create Event and Semaphore primitives, but
in addition, libraries can set up any handle as an Event-type signal.

wpiutil/src/main/java/edu/wpi/first/util/WPIUtilJNI.java

@@ -63,4 +63,63 @@ public final class WPIUtilJNI {
   public static native void addPortForwarder(int port, String remoteHost, int remotePort);
 
   public static native void removePortForwarder(int port);
+
+  public static native int createEvent(boolean manualReset, boolean initialState);
+
+  public static native void destroyEvent(int eventHandle);
+
+  public static native void setEvent(int eventHandle);
+
+  public static native void resetEvent(int eventHandle);
+
+  public static native int createSemaphore(int initialCount, int maximumCount);
+
+  public static native void destroySemaphore(int semHandle);
+
+  public static native boolean releaseSemaphore(int semHandle, int releaseCount);
+
+  /**
+   * Waits for an handle to be signaled.
+   *
+   * @param handle handle to wait on
+   * @throws InterruptedException on failure (e.g. object was destroyed)
+   */
+  public static native void waitForObject(int handle) throws InterruptedException;
+
+  /**
+   * Waits for an handle to be signaled, with timeout.
+   *
+   * @param handle handle to wait on
+   * @param timeout timeout in seconds
+   * @return True if timeout reached without handle being signaled
+   * @throws InterruptedException on failure (e.g. object was destroyed)
+   */
+  public static native boolean waitForObjectTimeout(int handle, double timeout)
+      throws InterruptedException;
+
+  /**
+   * Waits for one or more handles to be signaled.
+   *
+   * <p>Invalid handles are treated as signaled; the returned array will have the handle error bit
+   * set for any invalid handles.
+   *
+   * @param handles array of handles to wait on
+   * @return array of signaled handles
+   * @throws InterruptedException on failure (e.g. no objects were signaled)
+   */
+  public static native int[] waitForObjects(int[] handles) throws InterruptedException;
+
+  /**
+   * Waits for one or more handles to be signaled, with timeout.
+   *
+   * <p>Invalid handles are treated as signaled; the returned array will have the handle error bit
+   * set for any invalid handles.
+   *
+   * @param handles array of handles to wait on
+   * @param timeout timeout in seconds
+   * @return array of signaled handles; empty if timeout reached without any handle being signaled
+   * @throws InterruptedException on failure (e.g. no objects were signaled and no timeout)
+   */
+  public static native int[] waitForObjectsTimeout(int[] handles, double timeout)
+      throws InterruptedException;
 }