117 lines
4.4 KiB
C++
117 lines
4.4 KiB
C++
// Copyright 2014 Citra Emulator Project
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// Licensed under GPLv2 or any later version
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// Refer to the license.txt file included.
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#pragma once
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#include <array>
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#include <cstddef>
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#include "common/common_types.h"
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#include "core/hle/kernel/object.h"
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#include "core/hle/result.h"
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namespace Kernel {
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enum KernelHandle : Handle {
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InvalidHandle = 0,
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CurrentThread = 0xFFFF8000,
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CurrentProcess = 0xFFFF8001,
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};
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/**
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* This class allows the creation of Handles, which are references to objects that can be tested
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* for validity and looked up. Here they are used to pass references to kernel objects to/from the
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* emulated process. it has been designed so that it follows the same handle format and has
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* approximately the same restrictions as the handle manager in the CTR-OS.
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*
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* Handles contain two sub-fields: a slot index (bits 31:15) and a generation value (bits 14:0).
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* The slot index is used to index into the arrays in this class to access the data corresponding
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* to the Handle.
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*
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* To prevent accidental use of a freed Handle whose slot has already been reused, a global counter
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* is kept and incremented every time a Handle is created. This is the Handle's "generation". The
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* value of the counter is stored into the Handle as well as in the handle table (in the
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* "generations" array). When looking up a handle, the Handle's generation must match with the
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* value stored on the class, otherwise the Handle is considered invalid.
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*
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* To find free slots when allocating a Handle without needing to scan the entire object array, the
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* generations field of unallocated slots is re-purposed as a linked list of indices to free slots.
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* When a Handle is created, an index is popped off the list and used for the new Handle. When it
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* is destroyed, it is again pushed onto the list to be re-used by the next allocation. It is
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* likely that this allocation strategy differs from the one used in CTR-OS, but this hasn't been
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* verified and isn't likely to cause any problems.
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*/
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class HandleTable final : NonCopyable {
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public:
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HandleTable();
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~HandleTable();
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/**
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* Allocates a handle for the given object.
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* @return The created Handle or one of the following errors:
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* - `ERR_HANDLE_TABLE_FULL`: the maximum number of handles has been exceeded.
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*/
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ResultVal<Handle> Create(SharedPtr<Object> obj);
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/**
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* Returns a new handle that points to the same object as the passed in handle.
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* @return The duplicated Handle or one of the following errors:
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* - `ERR_INVALID_HANDLE`: an invalid handle was passed in.
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* - Any errors returned by `Create()`.
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*/
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ResultVal<Handle> Duplicate(Handle handle);
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/**
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* Closes a handle, removing it from the table and decreasing the object's ref-count.
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* @return `RESULT_SUCCESS` or one of the following errors:
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* - `ERR_INVALID_HANDLE`: an invalid handle was passed in.
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*/
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ResultCode Close(Handle handle);
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/// Checks if a handle is valid and points to an existing object.
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bool IsValid(Handle handle) const;
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/**
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* Looks up a handle.
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* @return Pointer to the looked-up object, or `nullptr` if the handle is not valid.
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*/
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SharedPtr<Object> GetGeneric(Handle handle) const;
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/**
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* Looks up a handle while verifying its type.
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* @return Pointer to the looked-up object, or `nullptr` if the handle is not valid or its
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* type differs from the requested one.
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*/
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template <class T>
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SharedPtr<T> Get(Handle handle) const {
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return DynamicObjectCast<T>(GetGeneric(handle));
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}
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/// Closes all handles held in this table.
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void Clear();
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private:
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/// This is the maximum limit of handles allowed per process in Horizon
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static constexpr std::size_t MAX_COUNT = 1024;
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/// Stores the Object referenced by the handle or null if the slot is empty.
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std::array<SharedPtr<Object>, MAX_COUNT> objects;
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/**
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* The value of `next_generation` when the handle was created, used to check for validity. For
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* empty slots, contains the index of the next free slot in the list.
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*/
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std::array<u16, MAX_COUNT> generations;
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/**
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* Global counter of the number of created handles. Stored in `generations` when a handle is
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* created, and wraps around to 1 when it hits 0x8000.
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*/
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u16 next_generation;
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/// Head of the free slots linked list.
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u16 next_free_slot;
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};
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} // namespace Kernel
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