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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/object.h"
#include "core/hle/result.h"
namespace Kernel {
enum KernelHandle : Handle {
InvalidHandle = 0,
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:
/// This is the maximum limit of handles allowed per process in Horizon
static constexpr std::size_t MAX_COUNT = 1024;
HandleTable();
~HandleTable();
/**
* Allocates a handle for the given object.
* @return The created Handle or one of the following errors:
* - `ERR_HANDLE_TABLE_FULL`: 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:
/// 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;
};
} // namespace Kernel
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