// Copyright 2015 The Crashpad Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef CRASHPAD_UTIL_WIN_GET_FUNCTION_H_
#define CRASHPAD_UTIL_WIN_GET_FUNCTION_H_
#include <windows.h>
//! \file
namespace crashpad {
namespace internal {
//! \brief Returns a function pointer to a named function in a library.
//!
//! Do not call this directly, use the GET_FUNCTION() or GET_FUNCTION_REQUIRED()
//! macros instead.
//!
//! This accesses \a library by calling `LoadLibrary()` and is subject to the
//! same restrictions as that function. Notably, it can’t be used from a
//! `DllMain()` entry point.
//!
//! \param[in] library The library to search in.
//! \param[in] function The function to search for. If a leading `::` is
//! present, it will be stripped.
//! \param[in] required If `true`, require the function to resolve by `DCHECK`.
//!
//! \return A pointer to the requested function on success. If \a required is
//! `true`, triggers a `DCHECK` assertion on failure, otherwise, `nullptr`
//! on failure.
FARPROC GetFunctionInternal(
const wchar_t* library, const char* function, bool required);
//! \copydoc GetFunctionInternal
template <typename FunctionType>
FunctionType* GetFunction(
const wchar_t* library, const char* function, bool required) {
return reinterpret_cast<FunctionType*>(
internal::GetFunctionInternal(library, function, required));
}
} // namespace internal
} // namespace crashpad
//! \brief Returns a function pointer to a named function in a library without
//! requiring that it be found.
//!
//! If the library or function cannot be found, this will return `nullptr`. This
//! macro is intended to be used to access functions that may not be available
//! at runtime.
//!
//! This macro returns a properly-typed function pointer. It is expected to be
//! used in this way:
//! \code
//! static const auto get_named_pipe_client_process_id =
//! GET_FUNCTION(L"kernel32.dll", ::GetNamedPipeClientProcessId);
//! if (get_named_pipe_client_process_id) {
//! BOOL rv = get_named_pipe_client_process_id(pipe, &client_process_id);
//! }
//! \endcode
//!
//! This accesses \a library by calling `LoadLibrary()` and is subject to the
//! same restrictions as that function. Notably, it can’t be used from a
//! `DllMain()` entry point.
//!
//! \param[in] library The library to search in.
//! \param[in] function The function to search for. A leading `::` is
//! recommended when a wrapper function of the same name is present.
//!
//! \return A pointer to the requested function on success, or `nullptr` on
//! failure.
//!
//! \sa GET_FUNCTION_REQUIRED
#define GET_FUNCTION(library, function) \
crashpad::internal::GetFunction<decltype(function)>( \
library, #function, false)
//! \brief Returns a function pointer to a named function in a library,
//! requiring that it be found.
//!
//! If the library or function cannot be found, this will trigger a `DCHECK`
//! assertion. This macro is intended to be used to access functions that are
//! always expected to be available at runtime but which are not present in any
//! import library.
//!
//! This macro returns a properly-typed function pointer. It is expected to be
//! used in this way:
//! \code
//! static const auto nt_query_object =
//! GET_FUNCTION_REQUIRED(L"ntdll.dll", ::NtQueryObject);
//! NTSTATUS status =
//! nt_query_object(handle, type, &info, info_length, &return_length);
//! \endcode
//!
//! This accesses \a library by calling `LoadLibrary()` and is subject to the
//! same restrictions as that function. Notably, it can’t be used from a
//! `DllMain()` entry point.
//!
//! \param[in] library The library to search in.
//! \param[in] function The function to search for. A leading `::` is
//! recommended when a wrapper function of the same name is present.
//!
//! \return A pointer to the requested function.
//!
//! \sa GET_FUNCTION
#define GET_FUNCTION_REQUIRED(library, function) \
crashpad::internal::GetFunction<decltype(function)>( \
library, #function, true)
#endif // CRASHPAD_UTIL_WIN_GET_FUNCTION_H_
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