1 files changed, 68 insertions, 0 deletions
diff --git a/pw_sync_freertos/public/pw_sync_freertos/mutex_inline.h b/pw_sync_freertos/public/pw_sync_freertos/mutex_inline.h
new file mode 100644
index 000000000..92f7c07d6
--- /dev/null
+++ b/pw_sync_freertos/public/pw_sync_freertos/mutex_inline.h
@@ -0,0 +1,68 @@
+// Copyright 2020 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+#pragma once
+
+#include "FreeRTOS.h"
+#include "pw_assert/light.h"
+#include "pw_interrupt/context.h"
+#include "pw_sync/mutex.h"
+#include "semphr.h"
+
+namespace pw::sync {
+namespace backend {
+
+static_assert(configUSE_MUTEXES != 0, "FreeRTOS mutexes aren't enabled.");
+
+static_assert(configSUPPORT_STATIC_ALLOCATION != 0,
+              "FreeRTOS static allocations are required for this backend.");
+
+}  // namespace backend
+
+inline Mutex::Mutex() : native_type_() {
+  const SemaphoreHandle_t handle = xSemaphoreCreateMutexStatic(&native_type_);
+  // This should never fail since the pointer provided was not null and it
+  // should return a pointer to the StaticSemaphore_t.
+  PW_DASSERT(handle == &native_type_);
+}
+
+inline Mutex::~Mutex() { vSemaphoreDelete(&native_type_); }
+
+inline void Mutex::lock() {
+  PW_ASSERT(!interrupt::InInterruptContext());
+#if INCLUDE_vTaskSuspend == 1  // This means portMAX_DELAY is indefinite.
+  const BaseType_t result = xSemaphoreTake(&native_type_, portMAX_DELAY);
+  PW_DASSERT(result == pdTRUE);
+#else
+  // In case we need to block for longer than the FreeRTOS delay can represent
+  // repeatedly hit take until success.
+  while (xSemaphoreTake(&native_type_, chrono::freertos::kMaxTimeout.count()) ==
+         pdFALSE) {
+  }
+#endif  // INCLUDE_vTaskSuspend
+}
+
+inline bool Mutex::try_lock() {
+  PW_ASSERT(!interrupt::InInterruptContext());
+  return xSemaphoreTake(&native_type_, 0) == pdTRUE;
+}
+
+inline void Mutex::unlock() {
+  PW_ASSERT(!interrupt::InInterruptContext());
+  // Unlocking only fails if it was not locked first.
+  PW_ASSERT(xSemaphoreGive(&native_type_) == pdTRUE);
+}
+
+inline Mutex::native_handle_type Mutex::native_handle() { return native_type_; }
+
+}  // namespace pw::sync