2 files changed, 126 insertions, 0 deletions

diff --git a/src/core/hle/kernel/semaphore.cpp b/src/core/hle/kernel/semaphore.cpp
new file mode 100644
index 000000000..6f56da8a9
--- /dev/null
+++ b/src/core/hle/kernel/semaphore.cpp
@@ -0,0 +1,94 @@
+// Copyright 2014 Citra Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#include <queue>
+
+#include "common/common.h"
+
+#include "core/hle/kernel/kernel.h"
+#include "core/hle/kernel/semaphore.h"
+#include "core/hle/kernel/thread.h"
+
+namespace Kernel {
+
+class Semaphore : public Object {
+public:
+    std::string GetTypeName() const override { return "Semaphore"; }
+    std::string GetName() const override { return name; }
+
+    static Kernel::HandleType GetStaticHandleType() { return Kernel::HandleType::Semaphore; }
+    Kernel::HandleType GetHandleType() const override { return Kernel::HandleType::Semaphore; }
+
+    u32 max_count;                              ///< Maximum number of simultaneous holders the semaphore can have
+    u32 available_count;                        ///< Number of free slots left in the semaphore
+    std::queue<Handle> waiting_threads;         ///< Threads that are waiting for the semaphore
+    std::string name;                           ///< Name of semaphore (optional)
+
+    /**
+     * Tests whether a semaphore still has free slots
+     * @return Whether the semaphore is available
+     */
+    bool IsAvailable() const {
+        return available_count > 0;
+    }
+
+    ResultVal<bool> WaitSynchronization() override {
+        bool wait = !IsAvailable();
+
+        if (wait) {
+            Kernel::WaitCurrentThread(WAITTYPE_SEMA, GetHandle());
+            waiting_threads.push(GetCurrentThreadHandle());
+        } else {
+            --available_count;
+        }
+
+        return MakeResult<bool>(wait);
+    }
+};
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+ResultCode CreateSemaphore(Handle* handle, u32 initial_count, 
+    u32 max_count, const std::string& name) {
+
+    if (initial_count > max_count)
+        return ResultCode(ErrorDescription::InvalidCombination, ErrorModule::Kernel,
+                          ErrorSummary::WrongArgument, ErrorLevel::Permanent);
+
+    Semaphore* semaphore = new Semaphore;
+    *handle = g_object_pool.Create(semaphore);
+
+    // When the semaphore is created, some slots are reserved for other threads,
+    // and the rest is reserved for the caller thread
+    semaphore->max_count = max_count;
+    semaphore->available_count = initial_count;
+    semaphore->name = name;
+
+    return RESULT_SUCCESS;
+}
+
+ResultCode ReleaseSemaphore(s32* count, Handle handle, s32 release_count) {
+    Semaphore* semaphore = g_object_pool.Get<Semaphore>(handle);
+    if (semaphore == nullptr)
+        return InvalidHandle(ErrorModule::Kernel);
+
+    if (semaphore->max_count - semaphore->available_count < release_count)
+        return ResultCode(ErrorDescription::OutOfRange, ErrorModule::Kernel, 
+                          ErrorSummary::InvalidArgument, ErrorLevel::Permanent);
+
+    *count = semaphore->available_count;
+    semaphore->available_count += release_count;
+
+    // Notify some of the threads that the semaphore has been released
+    // stop once the semaphore is full again or there are no more waiting threads
+    while (!semaphore->waiting_threads.empty() && semaphore->IsAvailable()) {
+        Kernel::ResumeThreadFromWait(semaphore->waiting_threads.front());
+        semaphore->waiting_threads.pop();
+        --semaphore->available_count;
+    }
+
+    return RESULT_SUCCESS;
+}
+
+} // namespace
diff --git a/src/core/hle/kernel/semaphore.h b/src/core/hle/kernel/semaphore.h
new file mode 100644
index 000000000..f0075fdb8
--- /dev/null
+++ b/src/core/hle/kernel/semaphore.h
@@ -0,0 +1,32 @@
+// Copyright 2014 Citra Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include "common/common_types.h"
+
+#include "core/hle/kernel/kernel.h"
+
+namespace Kernel {
+
+/**
+ * Creates a semaphore.
+ * @param handle Pointer to the handle of the newly created object
+ * @param initial_count Number of slots reserved for other threads
+ * @param max_count Maximum number of slots the semaphore can have
+ * @param name Optional name of semaphore
+ * @return ResultCode of the error
+ */
+ResultCode CreateSemaphore(Handle* handle, u32 initial_count, u32 max_count, const std::string& name = "Unknown");
+
+/**
+ * Releases a certain number of slots from a semaphore.
+ * @param count The number of free slots the semaphore had before this call
+ * @param handle The handle of the semaphore to release
+ * @param release_count The number of slots to release
+ * @return ResultCode of the error
+ */
+ResultCode ReleaseSemaphore(s32* count, Handle handle, s32 release_count);
+
+} // namespace