Adds new handle structure and type for vendors (#297)

hal/include/HAL/handles/HandlesInternal.h

@@ -42,7 +42,8 @@ enum class HAL_HandleEnum {
   Encoder = 13,
   Compressor = 14,
   Solenoid = 15,
-  AnalogGyro = 16
+  AnalogGyro = 16,
+  Vendor = 17
 };
 
 static inline int16_t getHandleIndex(HAL_Handle handle) {

hal/include/HAL/handles/IndexedClassedHandleResource.h

@@ -0,0 +1,111 @@
+/*----------------------------------------------------------------------------*/
+/* Copyright (c) FIRST 2016. 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 <stdint.h>
+
+#include <memory>
+#include <vector>
+
+#include "HAL/Errors.h"
+#include "HAL/Types.h"
+#include "HAL/cpp/make_unique.h"
+#include "HAL/cpp/priority_mutex.h"
+#include "HAL/handles/HandlesInternal.h"
+
+namespace hal {
+
+/**
+ * The IndexedClassedHandleResource class is a way to track handles. This
+ * version
+ * allows a limited number of handles that are allocated by index.
+ * Because they are allocated by index, each individual index holds its own
+ * mutex, which reduces contention heavily.]
+ *
+ * @tparam THandle The Handle Type (Must be typedefed from HAL_Handle)
+ * @tparam TStruct The struct type held by this resource
+ * @tparam size The number of resources allowed to be allocated
+ * @tparam enumValue The type value stored in the handle
+ *
+ */
+template <typename THandle, typename TStruct, int16_t size,
+          HAL_HandleEnum enumValue>
+class IndexedClassedHandleResource {
+  friend class IndexedClassedHandleResourceTest;
+
+ public:
+  IndexedClassedHandleResource(const IndexedClassedHandleResource&) = delete;
+  IndexedClassedHandleResource operator=(const IndexedClassedHandleResource&) =
+      delete;
+  IndexedClassedHandleResource();
+  THandle Allocate(int16_t index, std::shared_ptr<TStruct> toSet,
+                   int32_t* status);
+  std::shared_ptr<TStruct> Get(THandle handle);
+  void Free(THandle handle);
+
+ private:
+  // Dynamic array to shrink HAL file size.
+  std::unique_ptr<std::shared_ptr<TStruct>[]> m_structures;
+  std::unique_ptr<priority_mutex[]> m_handleMutexes;
+};
+
+template <typename THandle, typename TStruct, int16_t size,
+          HAL_HandleEnum enumValue>
+IndexedClassedHandleResource<THandle, TStruct, size,
+                             enumValue>::IndexedClassedHandleResource() {
+  m_structures = std::make_unique<std::shared_ptr<TStruct>[]>(size);
+  m_handleMutexes = std::make_unique<priority_mutex[]>(size);
+}
+
+template <typename THandle, typename TStruct, int16_t size,
+          HAL_HandleEnum enumValue>
+THandle
+IndexedClassedHandleResource<THandle, TStruct, size, enumValue>::Allocate(
+    int16_t index, std::shared_ptr<TStruct> toSet, int32_t* status) {
+  // don't aquire the lock if we can fail early.
+  if (index < 0 || index >= size) {
+    *status = RESOURCE_OUT_OF_RANGE;
+    return HAL_kInvalidHandle;
+  }
+  std::lock_guard<priority_mutex> sync(m_handleMutexes[index]);
+  // check for allocation, otherwise allocate and return a valid handle
+  if (m_structures[index] != nullptr) {
+    *status = RESOURCE_IS_ALLOCATED;
+    return HAL_kInvalidHandle;
+  }
+  m_structures[index] = toSet;
+  return static_cast<THandle>(hal::createHandle(index, enumValue));
+}
+
+template <typename THandle, typename TStruct, int16_t size,
+          HAL_HandleEnum enumValue>
+std::shared_ptr<TStruct> IndexedClassedHandleResource<
+    THandle, TStruct, size, enumValue>::Get(THandle handle) {
+  // get handle index, and fail early if index out of range or wrong handle
+  int16_t index = getHandleTypedIndex(handle, enumValue);
+  if (index < 0 || index >= size) {
+    return nullptr;
+  }
+  std::lock_guard<priority_mutex> sync(m_handleMutexes[index]);
+  // return structure. Null will propogate correctly, so no need to manually
+  // check.
+  return m_structures[index];
+}
+
+template <typename THandle, typename TStruct, int16_t size,
+          HAL_HandleEnum enumValue>
+void IndexedClassedHandleResource<THandle, TStruct, size, enumValue>::Free(
+    THandle handle) {
+  // get handle index, and fail early if index out of range or wrong handle
+  int16_t index = getHandleTypedIndex(handle, enumValue);
+  if (index < 0 || index >= size) return;
+  // lock and deallocated handle
+  std::lock_guard<priority_mutex> sync(m_handleMutexes[index]);
+  m_structures[index].reset();
+}
+}  // namespace hal