Adds TriState DIO functionality to the HAL (#835)

Adds a function to raw set the DIO direction. Also adds a C++ unsafe
function to enable fast setting of DIO direction.

hal/src/main/native/include/HAL/cpp/UnsafeDIO.h

@@ -0,0 +1,85 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) 2017 FIRST. All Rights Reserved.                             */
+/* Open Source Software - may be modified and shared by FRC teams. The code   */
+/* must be accompanied by the FIRST BSD license file in the root directory of */
+/* the project.                                                               */
+/*----------------------------------------------------------------------------*/
+
+#pragma once
+
+#include <support/mutex.h>
+
+#include "HAL/ChipObject.h"
+#include "HAL/Types.h"
+
+namespace hal {
+struct DIOSetProxy {
+  DIOSetProxy(const DIOSetProxy&) = delete;
+  DIOSetProxy(DIOSetProxy&&) = delete;
+  DIOSetProxy& operator=(const DIOSetProxy&) = delete;
+  DIOSetProxy& operator=(DIOSetProxy&&) = delete;
+
+  void SetOutputMode(int32_t* status) {
+    m_dio->writeOutputEnable(m_setOutputDirReg, status);
+  }
+
+  void SetInputMode(int32_t* status) {
+    m_dio->writeOutputEnable(m_unsetOutputDirReg, status);
+  }
+
+  void SetOutputTrue(int32_t* status) {
+    m_dio->writeDO(m_setOutputStateReg, status);
+  }
+
+  void SetOutputFalse(int32_t* status) {
+    m_dio->writeDO(m_unsetOutputStateReg, status);
+  }
+
+  tDIO::tOutputEnable m_setOutputDirReg;
+  tDIO::tOutputEnable m_unsetOutputDirReg;
+  tDIO::tDO m_setOutputStateReg;
+  tDIO::tDO m_unsetOutputStateReg;
+  tDIO* m_dio;
+};
+namespace detail {
+wpi::mutex& UnsafeGetDIOMutex();
+tDIO* UnsafeGetDigialSystem();
+int32_t ComputeDigitalMask(HAL_DigitalHandle handle, int32_t* status);
+}  // namespace detail
+
+/**
+ * Unsafe digital output set function
+ * This function can be used to perform fast and determinstically set digital
+ * outputs. This function holds the DIO lock, so calling anyting other then
+ * functions on the Proxy object passed as a parameter can deadlock your
+ * program.
+ *
+ */
+template <typename Functor>
+void UnsafeManipulateDIO(HAL_DigitalHandle handle, int32_t* status,
+                         Functor func) {
+  auto port = digitalChannelHandles->Get(handle, HAL_HandleEnum::DIO);
+  if (port == nullptr) {
+    *status = HAL_HANDLE_ERROR;
+    return;
+  }
+  wpi::mutex& dioMutex = detail::UnsafeGetDIOMutex();
+  tDIO* dSys = detail::UnsafeGetDigialSystem();
+  auto mask = detail::ComputeDigitalMask(handle, status);
+  if (status != 0) return;
+  std::lock_guard<wpi::mutex> lock(dioMutex);
+
+  tDIO::tOutputEnable enableOE = dSys->readOutputEnable(status);
+  enableOE.value |= mask;
+  auto disableOE = enableOE;
+  disableOE.value &= ~mask;
+  tDIO::tDO enableDO = dSys->readDO(status);
+  enableDO.value |= mask;
+  auto disableDO = enableDO;
+  disableDO.value &= ~mask;
+
+  DIOSetProxy dioData{enableOE, disableOE, enableDO, disableDO, dSys};
+  func(dioData);
+}
+
+}  // namespace hal