1 files changed, 126 insertions, 0 deletions
diff --git a/src/core/hle/kernel/handle_table.h b/src/core/hle/kernel/handle_table.h
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+++ b/src/core/hle/kernel/handle_table.h
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+// Copyright 2014 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <array>
+#include <cstddef>
+#include "common/common_types.h"
+#include "core/hle/kernel/kernel.h"
+#include "core/hle/result.h"
+
+namespace Kernel {
+
+enum KernelHandle : Handle {
+    CurrentThread = 0xFFFF8000,
+    CurrentProcess = 0xFFFF8001,
+};
+
+/**
+ * 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();
+
+    /**
+     * 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(SharedPtr<Object> obj);
+
+    /**
+     * 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);
+
+    /**
+     * 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);
+
+    /// Checks if a handle is valid and points to an existing object.
+    bool IsValid(Handle handle) const;
+
+    /**
+     * Looks up a handle.
+     * @return Pointer to the looked-up object, or `nullptr` if the handle is not valid.
+     */
+    SharedPtr<Object> GetGeneric(Handle handle) const;
+
+    /**
+     * Looks up a handle while verifying its type.
+     * @return Pointer to the looked-up object, or `nullptr` if the handle is not valid or its
+     *         type differs from the requested one.
+     */
+    template <class T>
+    SharedPtr<T> Get(Handle handle) const {
+        return DynamicObjectCast<T>(GetGeneric(handle));
+    }
+
+    /// Closes all handles held in this table.
+    void Clear();
+
+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 u16 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<SharedPtr<Object>, MAX_COUNT> objects;
+
+    /**
+     * 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;
+
+    /// Head of the free slots linked list.
+    u16 next_free_slot;
+};
+
+extern HandleTable g_handle_table;
+
+} // namespace