libradhook/include/radhook/api.h

#ifndef __LIBRADHOOK_API_H__
#define __LIBRADHOOK_API_H__

#include <cstdint>
#include <cstddef>

#include <type_traits>

#ifndef RADHOOK_API
# define RADHOOK_API
#endif // RADHOOK_API

// versioning
#define RADHOOK_VERSION_MAJOR 1
#define RADHOOK_VERSION_MINOR 1
#define RADHOOK_VERSION_PATCH 0

#if _MSC_VER
# include <sal.h> // for source code annotations
#else
# define _In_
# define _In_opt_
# define _Out_
# define _Out_opt_
# define _Outptr_
# define _Ret_z_
# define _Success_(expr)
# define _Out_writes_to_(size, count)
#endif

enum class RadHookResult : int {
    Success = 0,
    AlreadyInstalled,
    NotInstalled,
    AlreadyEnabled,
    AlreadyDisabled,
    MemoryAllocFailed,
    MemoryProtectFailed,
    DisassemblyFailed,
    InvalidTarget,
    InvalidDetour,
    InvalidHandle,
    TrampolineTooFar,
    TargetTooSmall,
    Unknown,
};

_Ret_z_
/**
 * @brief Creates a human readable name for a status code.
 *
 * @param result Status code returned by a RadHook API function.
 * @return Null-terminated string describing the status code.
 */
RADHOOK_API
const char*
RadHookResultToString(
    RadHookResult result
    );

struct RadHookOpaque;
using RadHookHandle = RadHookOpaque*;

_Success_(return == RadHookResult::Success)
/**
 * @brief Creates and installs a hook.
 *
 * Redirects execution from @p target to @p detour and enables the hook
 * immediately upon successful creation.
 *
 * @param target Function or address to hook.
 * @param detour Replacement function to execute.
 * @param outHandle Receives the created hook handle on success. Set to
 * nullptr on failure.
 *
 * @return Operation result.
 */
RADHOOK_API
RadHookResult
RadHookCreate(
    _In_ void* target,
    _In_ void* detour,
    _Out_ RadHookHandle* outHandle
    );

_Success_(return == RadHookResult::Success)
/**
 * @brief Creates and installs a hook from a function pointer.
 *
 * Convenience overload that accepts a typed function pointer for the target.
 *
 * @tparam TargetFn Target function pointer type.
 * @param target Target function to hook.
 * @param detour Replacement function.
 * @param outHandle Receives the created hook handle on success.
 *
 * @return Operation result.
 */
template <typename TargetFn>
requires std::is_function_v<std::remove_pointer_t<TargetFn>>
RadHookResult
RadHookCreate(
    TargetFn target,
    _In_ void* detour,
    _Out_ RadHookHandle* outHandle
    ) 
{
    return RadHookCreate(
        reinterpret_cast<void*>(target),
        detour,
        outHandle
    );
}

/**
 * @brief Enables an installed hook.
 *
 * Re-applies the jump from the target function to its detour.
 *
 * @param handle Hook handle.
 *
 * @return RadHookResult::AlreadyEnabled if the hook is already enabled;
 * otherwise the result of the operation.
 */
RADHOOK_API
RadHookResult
RadHookEnable(
    _In_ RadHookHandle handle
    );

/**
 * @brief Disables an installed hook.
 *
 * Restores the original bytes at the target function.
 *
 * @param handle Hook handle.
 *
 * @return RadHookResult::AlreadyDisabled if the hook is already disabled;
 * otherwise the result of the operation.
 */
RADHOOK_API
RadHookResult
RadHookDisable(
    _In_ RadHookHandle handle
    );

/**
 * @brief Destroys a hook.
 *
 * Disables the hook if necessary, releases any allocated resources,
 * and invalidates the handle.
 *
 * @param handle Hook handle.
 *
 * @return Operation result.
 */
RADHOOK_API
RadHookResult
RadHookDestroy(
    _In_ RadHookHandle handle
    );

/**
 * @brief Enables every registered hook.
 *
 * Hooks that are already enabled are left unchanged.
 *
 * @return Operation result.
 */
RADHOOK_API
RadHookResult
RadHookEnableAll();

/**
 * @brief Disables every registered hook.
 *
 * Hooks that are already disabled are left unchanged.
 *
 * @return Operation result.
 */
RADHOOK_API
RadHookResult
RadHookDisableAll();

/**
 * @brief Returns the number of currently registered hooks.
 *
 * Destroyed hooks are not included.
 *
 * @return Number of registered hooks.
 */
RADHOOK_API
size_t
RadHookGetCount();

_Out_writes_to_(maxCount, return)
/**
 * @brief Retrieves registered hook handles.
 *
 * Copies up to @p maxCount currently registered hook handles into
 * @p outHandles.
 *
 * @param outHandles Destination buffer.
 * @param maxCount Maximum number of handles to copy.
 *
 * @return Number of handles copied.
 */
RADHOOK_API
size_t
RadHookGetHandles(
    _Out_ RadHookHandle* outHandles,
    _In_ size_t maxCount
    );

/**
 * @brief Checks whether a hook handle is valid.
 *
 * @param handle Hook handle.
 *
 * @return true if the handle refers to a registered hook; otherwise false.
 */
RADHOOK_API
bool
RadHookIsValid(
    _In_ RadHookHandle handle
    );

/**
 * @brief Checks whether a hook is currently enabled.
 *
 * @param handle Hook handle.
 *
 * @return true if the hook is enabled; otherwise false.
 */
RADHOOK_API
bool
RadHookIsEnabled(
    _In_ RadHookHandle handle
    );

/**
 * @brief Returns the hooked target function.
 *
 * @param handle Hook handle.
 *
 * @return Pointer to the original target function, or nullptr if the handle
 * is invalid.
 */
RADHOOK_API
void*
RadHookGetTarget(
    _In_ RadHookHandle handle
    );

/**
 * @brief Returns the detour function.
 *
 * @param handle Hook handle.
 *
 * @return Pointer to the detour function, or nullptr if the handle is
 * invalid.
 */
RADHOOK_API
void*
RadHookGetDetour(
    _In_ RadHookHandle handle
    );

/**
 * @brief Returns the trampoline containing the relocated original code.
 *
 * Calling the returned function executes the original implementation while
 * bypassing the installed hook.
 *
 * @param handle Hook handle.
 *
 * @return Pointer to the trampoline, or nullptr if unavailable.
 */
RADHOOK_API
void*
RadHookGetOriginal(
    _In_ RadHookHandle handle
    );

/**
 * @brief Returns the trampoline cast to a function pointer type.
 *
 * @tparam FnPtr Desired function pointer type.
 * @param handle Hook handle.
 *
 * @return Trampoline cast to @p FnPtr.
 */
template <typename FnPtr>
FnPtr
RadHookGetOriginalAs(
    _In_ RadHookHandle handle
    ) 
{
    return reinterpret_cast<FnPtr>(RadHookGetOriginal(handle));
}

_Out_writes_to_(maxCount, return)
/**
 * @brief Enumerates currently registered hooks.
 *
 * Copies up to @p maxCount active hook handles into @p out.
 * Handles are written in no particular order.
 *
 * This function only returns hooks that are currently registered
 * and not destroyed.
 *
 * @param out Destination buffer for hook handles.
 * @param maxCount Maximum number of handles to copy.
 *
 * @return Number of hook handles written into @p out.
 */
RADHOOK_API
size_t
RadHookEnumerate(
    _Out_ RadHookHandle* out,
    _In_ size_t maxCount
    );

/**
 * @brief Returns the library version.
 *
 * Any of the output parameters may be nullptr if that component is not
 * needed. Useful for verifying ABI compatibility when radhook is loaded
 * as a shared library independently of the consuming module.
 *
 * @param outMajor Receives the major version, or nullptr.
 * @param outMinor Receives the minor version, or nullptr.
 * @param outPatch Receives the patch version, or nullptr.
 */
RADHOOK_API
void
RadHookGetVersion(
    _Out_opt_ int* outMajor,
    _Out_opt_ int* outMinor,
    _Out_opt_ int* outPatch
    );

_Success_(return == RadHookResult::Success)
/**
 * @brief Creates and installs a hook on a vtable slot.
 *
 * @param vtable Pointer to the base of the vtable.
 * @param index Index of the slot to hook.
 * @param detour Replacement function.
 * @param outHandle Receives the created hook handle on success. Set to nullptr on failure.
 *
 * @return InvalidTarget if @p vtable is nullptr or the slot
 * at @p index is empty; otherwise the result of the operation.
 */
RADHOOK_API
RadHookResult
RadHookVTableCreate(
    _In_ void** vtable,
    _In_ size_t index,
    _In_ void* detour,
    _Out_ RadHookHandle* outHandle
    );

/**
 * @brief Queues a hook to be enabled on the next RadHookApplyQueued call.
 *
 * Does not modify the hook itself. If the same handle is queued for both
 * enable and disable before RadHookApplyQueued runs, the most recent call
 * wins.
 *
 * @param handle Hook handle.
 *
 * @return RadHookResult::InvalidHandle if the handle is not registered;
 * otherwise RadHookResult::Success.
 */
RADHOOK_API
RadHookResult
RadHookQueueEnable(
    _In_ RadHookHandle handle
    );

/**
 * @brief Queues a hook to be disabled on the next RadHookApplyQueued call.
 *
 * Does not modify the hook itself. If the same handle is queued for both
 * enable and disable before RadHookApplyQueued runs, the most recent call
 * wins.
 *
 * @param handle Hook handle.
 *
 * @return RadHookResult::InvalidHandle if the handle is not registered;
 * otherwise RadHookResult::Success.
 */
RADHOOK_API
RadHookResult
RadHookQueueDisable(
    _In_ RadHookHandle handle
    );

/**
 * @brief Applies all queued enable/disable operations.
 *
 * Every hook with a pending queued action has that action applied and its
 * queue cleared, regardless of individual outcomes. Hooks with no queued
 * action are left untouched.
 *
 * @return The result of the first queued operation that did not succeed
 * (ignoring RadHookResult::AlreadyEnabled / RadHookResult::AlreadyDisabled),
 * or RadHookResult::Success if all applied cleanly.
 */
RADHOOK_API
RadHookResult
RadHookApplyQueued();

#endif // __LIBRADHOOK_API_H__