1 files changed, 109 insertions, 81 deletions

diff --git a/src/core/hle/kernel/kernel.h b/src/core/hle/kernel/kernel.h
index 27c406ad4..7f86fd07d 100644
--- a/src/core/hle/kernel/kernel.h
+++ b/src/core/hle/kernel/kernel.h
@@ -12,13 +12,17 @@
 typedef u32 Handle;
 typedef s32 Result;
 
+const Handle INVALID_HANDLE = 0;
+
 namespace Kernel {
 
-// From kernel.h. Declarations duplicated here to avoid a circular header dependency.
-class Thread;
-Thread* GetCurrentThread();
+// TODO: Verify code
+const ResultCode ERR_OUT_OF_HANDLES(ErrorDescription::OutOfMemory, ErrorModule::Kernel,
+        ErrorSummary::OutOfResource, ErrorLevel::Temporary);
+// TOOD: Verify code
+const ResultCode ERR_INVALID_HANDLE = InvalidHandle(ErrorModule::Kernel);
 
-enum KernelHandle {
+enum KernelHandle : Handle {
     CurrentThread   = 0xFFFF8000,
     CurrentProcess  = 0xFFFF8001,
 };
@@ -61,103 +65,127 @@ public:
         LOG_ERROR(Kernel, "(UNIMPLEMENTED)");
         return UnimplementedFunction(ErrorModule::Kernel);
     }
-};
 
-class HandleTable : NonCopyable {
-public:
-    HandleTable();
-    ~HandleTable() {}
+private:
+    friend void intrusive_ptr_add_ref(Object*);
+    friend void intrusive_ptr_release(Object*);
 
-    // Allocates a handle within the range and inserts the object into the map.
-    Handle Create(Object* obj, int range_bottom=INITIAL_NEXT_ID, int range_top=0x7FFFFFFF);
+    unsigned int ref_count = 0;
+};
 
-    static Object* CreateByIDType(int type);
+// Special functions that will later be used by boost::instrusive_ptr to do automatic ref-counting
+inline void intrusive_ptr_add_ref(Object* object) {
+    ++object->ref_count;
+}
 
-    template <class T>
-    void Destroy(Handle handle) {
-        if (Get<T>(handle)) {
-            occupied[handle - HANDLE_OFFSET] = false;
-            delete pool[handle - HANDLE_OFFSET];
-        }
+inline void intrusive_ptr_release(Object* object) {
+    if (--object->ref_count == 0) {
+        delete object;
     }
+}
 
-    bool IsValid(Handle handle) const;
+/**
+ * This class allows the creation of Handles, which are references to objects that can be tested
+ * for validity and looked up. Here they are used to pass references to kernel objects to/from the
+ * emulated process. it has been designed so that it follows the same handle format and has
+ * approximately the same restrictions as the handle manager in the CTR-OS.
+ *
+ * Handles contain two sub-fields: a slot index (bits 31:15) and a generation value (bits 14:0).
+ * The slot index is used to index into the arrays in this class to access the data corresponding
+ * to the Handle.
+ *
+ * To prevent accidental use of a freed Handle whose slot has already been reused, a global counter
+ * is kept and incremented every time a Handle is created. This is the Handle's "generation". The
+ * value of the counter is stored into the Handle as well as in the handle table (in the
+ * "generations" array). When looking up a handle, the Handle's generation must match with the
+ * value stored on the class, otherwise the Handle is considered invalid.
+ *
+ * To find free slots when allocating a Handle without needing to scan the entire object array, the
+ * generations field of unallocated slots is re-purposed as a linked list of indices to free slots.
+ * When a Handle is created, an index is popped off the list and used for the new Handle. When it
+ * is destroyed, it is again pushed onto the list to be re-used by the next allocation. It is
+ * likely that this allocation strategy differs from the one used in CTR-OS, but this hasn't been
+ * verified and isn't likely to cause any problems.
+ */
+class HandleTable final : NonCopyable {
+public:
+    HandleTable();
 
-    template <class T>
-    T* Get(Handle handle) {
-        if (handle == CurrentThread) {
-            return reinterpret_cast<T*>(GetCurrentThread());
-        }
+    /**
+     * Allocates a handle for the given object.
+     * @return The created Handle or one of the following errors:
+     *           - `ERR_OUT_OF_HANDLES`: the maximum number of handles has been exceeded.
+     */
+    ResultVal<Handle> Create(Object* obj);
 
-        if (handle < HANDLE_OFFSET || handle >= HANDLE_OFFSET + MAX_COUNT || !occupied[handle - HANDLE_OFFSET]) {
-            if (handle != 0) {
-                LOG_ERROR(Kernel, "Bad object handle %08x", handle);
-            }
-            return nullptr;
-        } else {
-            Object* t = pool[handle - HANDLE_OFFSET];
-            if (t->GetHandleType() != T::HANDLE_TYPE) {
-                LOG_ERROR(Kernel, "Wrong object type for %08x", handle);
-                return nullptr;
-            }
-            return static_cast<T*>(t);
-        }
-    }
+    /**
+     * Returns a new handle that points to the same object as the passed in handle.
+     * @return The duplicated Handle or one of the following errors:
+     *           - `ERR_INVALID_HANDLE`: an invalid handle was passed in.
+     *           - Any errors returned by `Create()`.
+     */
+    ResultVal<Handle> Duplicate(Handle handle);
 
-    // ONLY use this when you know the handle is valid.
-    template <class T>
-    T *GetFast(Handle handle) {
-        if (handle == CurrentThread) {
-            return reinterpret_cast<T*>(GetCurrentThread());
-        }
+    /**
+     * Closes a handle, removing it from the table and decreasing the object's ref-count.
+     * @return `RESULT_SUCCESS` or one of the following errors:
+     *           - `ERR_INVALID_HANDLE`: an invalid handle was passed in.
+     */
+    ResultCode Close(Handle handle);
 
-        const Handle realHandle = handle - HANDLE_OFFSET;
-        _dbg_assert_(Kernel, realHandle >= 0 && realHandle < MAX_COUNT && occupied[realHandle]);
-        return static_cast<T*>(pool[realHandle]);
-    }
+    /// Checks if a handle is valid and points to an existing object.
+    bool IsValid(Handle handle) const;
 
-    template <class T, typename ArgT>
-    void Iterate(bool func(T*, ArgT), ArgT arg) {
-        int type = T::GetStaticIDType();
-        for (int i = 0; i < MAX_COUNT; i++)
-        {
-            if (!occupied[i])
-                continue;
-            T* t = static_cast<T*>(pool[i]);
-            if (t->GetIDType() == type) {
-                if (!func(t, arg))
-                    break;
-            }
-        }
-    }
+    /**
+     * Looks up a handle.
+     * @returns Pointer to the looked-up object, or `nullptr` if the handle is not valid.
+     */
+    Object* GetGeneric(Handle handle) const;
 
-    bool GetIDType(Handle handle, HandleType* type) const {
-        if ((handle < HANDLE_OFFSET) || (handle >= HANDLE_OFFSET + MAX_COUNT) ||
-                !occupied[handle - HANDLE_OFFSET]) {
-            LOG_ERROR(Kernel, "Bad object handle %08X", handle);
-            return false;
+    /**
+     * Looks up a handle while verifying its type.
+     * @returns Pointer to the looked-up object, or `nullptr` if the handle is not valid or its
+     *          type differs from the handle type `T::HANDLE_TYPE`.
+     */
+    template <class T>
+    T* Get(Handle handle) const {
+        Object* object = GetGeneric(handle);
+        if (object != nullptr && object->GetHandleType() == T::HANDLE_TYPE) {
+            return static_cast<T*>(object);
         }
-        Object* t = pool[handle - HANDLE_OFFSET];
-        *type = t->GetHandleType();
-        return true;
+        return nullptr;
     }
 
-    Object* &operator [](Handle handle);
-    void List();
+    /// Closes all handles held in this table.
     void Clear();
-    int GetCount() const;
 
 private:
+    /**
+     * This is the maximum limit of handles allowed per process in CTR-OS. It can be further
+     * reduced by ExHeader values, but this is not emulated here.
+     */
+    static const size_t MAX_COUNT = 4096;
+
+    static size_t GetSlot(Handle handle)    { return handle >> 15; }
+    static u16 GetGeneration(Handle handle) { return handle & 0x7FFF; }
+
+    /// Stores the Object referenced by the handle or null if the slot is empty.
+    std::array<Object*, MAX_COUNT> objects;
 
-    enum {
-        MAX_COUNT       = 0x1000,
-        HANDLE_OFFSET   = 0x100,
-        INITIAL_NEXT_ID = 0x10,
-    };
+    /**
+     * The value of `next_generation` when the handle was created, used to check for validity. For
+     * empty slots, contains the index of the next free slot in the list.
+     */
+    std::array<u16, MAX_COUNT> generations;
+
+    /**
+     * Global counter of the number of created handles. Stored in `generations` when a handle is
+     * created, and wraps around to 1 when it hits 0x8000.
+     */
+    u16 next_generation;
 
-    std::array<Object*, MAX_COUNT> pool;
-    std::array<bool, MAX_COUNT> occupied;
-    int next_id;
+    /// Head of the free slots linked list.
+    u16 next_free_slot;
 };
 
 extern HandleTable g_handle_table;