/* ** i_module.h ** **--------------------------------------------------------------------------- ** Copyright 2016 Braden Obrzut ** All rights reserved. ** ** Redistribution and use in source and binary forms, with or without ** modification, are permitted provided that the following conditions ** are met: ** ** 1. Redistributions of source code must retain the above copyright ** notice, this list of conditions and the following disclaimer. ** 2. Redistributions in binary form must reproduce the above copyright ** notice, this list of conditions and the following disclaimer in the ** documentation and/or other materials provided with the distribution. ** 3. The name of the author may not be used to endorse or promote products ** derived from this software without specific prior written permission. ** ** THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR ** IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES ** OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. ** IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, ** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT ** NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF ** THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. **--------------------------------------------------------------------------- ** */ #pragma once #include <assert.h> #include <string> #include <initializer_list> /* FModule Run Time Library Loader * * This provides an interface for loading optional dependencies or detecting * version specific symbols at run time. These classes largely provide an * interface for statically declaring the symbols that are going to be used * ahead of time, thus should not be used on the stack or as part of a * dynamically allocated object. The procedure templates take the FModule * as a template argument largely to make such use of FModule awkward. * * Declared procedures register themselves with FModule and the module will not * be considered loaded unless all required procedures can be resolved. In * order to remove the need for boilerplate code, optional procedures do not * enforce the requirement that the value is null checked before use. As a * debugging aid debug builds will check that operator bool was called at some * point, but this is just a first order sanity check. */ class FModule; class FStaticModule; template<FModule &Module, typename Proto> class TOptProc; template<FModule &Module, typename Proto> class TReqProc; template<FStaticModule &Module, typename Proto, Proto Sym> class TStaticProc; class FModule { template<FModule &Module, typename Proto> friend class TOptProc; template<FModule &Module, typename Proto> friend class TReqProc; struct StaticProc { void *Call; const char* Name; StaticProc *Next; bool Optional; }; void RegisterStatic(StaticProc &proc) { proc.Next = reqSymbols; reqSymbols = &proc; } void *handle = nullptr; // Debugging aid const char *name; // Since FModule is supposed to be statically allocated it is assumed that // reqSymbols will be initialized to nullptr avoiding initialization order // problems with declaring procedures. StaticProc *reqSymbols; bool Open(const char* lib); void *GetSym(const char* name); public: template<FModule &Module, typename Proto, Proto Sym> using Opt = TOptProc<Module, Proto>; template<FModule &Module, typename Proto, Proto Sym> using Req = TReqProc<Module, Proto>; FModule(const char* name) : name(name) {}; ~FModule() { Unload(); } // Load a shared library using the first library name which satisfies all // of the required symbols. bool Load(std::initializer_list<const char*> libnames); void Unload(); bool IsLoaded() const { return handle != nullptr; } }; // Null version of FModule which satisfies the API so the same code can be used // for run time and compile time linking. class FStaticModule { template<FStaticModule &Module, typename Proto, Proto Sym> friend class TStaticProc; const char *name; public: template<FStaticModule &Module, typename Proto, Proto Sym> using Opt = TStaticProc<Module, Proto, Sym>; template<FStaticModule &Module, typename Proto, Proto Sym> using Req = TStaticProc<Module, Proto, Sym>; FStaticModule(const char* name) : name(name) {}; bool Load(std::initializer_list<const char*> libnames) { return true; } void Unload() {} bool IsLoaded() const { return true; } }; // Allow FModuleMaybe<DYN_XYZ> to switch based on preprocessor flag. // Use FModuleMaybe<DYN_XYZ>::Opt and FModuleMaybe<DYN_XYZ>::Req for procs. template<bool Dynamic> struct TModuleType { using Type = FModule; }; template<> struct TModuleType<false> { using Type = FStaticModule; }; template<bool Dynamic> using FModuleMaybe = typename TModuleType<Dynamic>::Type; // ------------------------------------------------------------------------ template<FModule &Module, typename Proto> class TOptProc { FModule::StaticProc proc; #ifndef NDEBUG mutable bool checked = false; #endif // I am not a pointer bool operator==(void*) const; bool operator!=(void*) const; public: TOptProc(const char* function) { proc.Name = function; proc.Optional = true; Module.RegisterStatic(proc); } operator Proto() const { #ifndef NDEBUG assert(checked); #endif return (Proto)proc.Call; } explicit operator bool() const { #ifndef NDEBUG assert(Module.IsLoaded()); checked = true; #endif return proc.Call != nullptr; } }; template<FModule &Module, typename Proto> class TReqProc { FModule::StaticProc proc; // I am not a pointer bool operator==(void*) const; bool operator!=(void*) const; public: TReqProc(const char* function) { proc.Name = function; proc.Optional = false; Module.RegisterStatic(proc); } operator Proto() const { #ifndef NDEBUG assert(Module.IsLoaded()); #endif return (Proto)proc.Call; } explicit operator bool() const { return true; } }; template<FStaticModule &Module, typename Proto, Proto Sym> class TStaticProc { // I am not a pointer bool operator==(void*) const; bool operator!=(void*) const; public: TStaticProc(const char* function) {} operator Proto() const { return Sym; } explicit operator bool() const { return Sym != nullptr; } }; void FModule_SetProgDir(const char* progdir); extern std::string module_progdir;