source/ps/DllLoader.h

   1 /* Copyright (C) 2014 Wildfire Games.
   2  * This file is part of 0 A.D.
   3  *
   4  * 0 A.D. is free software: you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation, either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * 0 A.D. is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with 0 A.D.  If not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 #ifndef INCLUDED_DLLLOADER
  19 #define INCLUDED_DLLLOADER
  20
  21 #include "ps/Errors.h"
  22 #include "ps/CLogger.h"
  23
  24 ERROR_GROUP(DllLoader);
  25 ERROR_TYPE(DllLoader, DllNotLoaded);
  26 ERROR_TYPE(DllLoader, SymbolNotFound);
  27
  28 class DllLoader
  29 {
  30 public:
  31         /**
  32          * Prepare the DLL loader. Does no actual work.
  33          *
  34          * @param name base name of the library (from which we'll derive
  35          *  "name.dll", "libname_dbg.so", etc). Pointer must remain valid for
  36          *  this object's lifetime (which is fine if you just use a string literal).
  37          * @param loadErrorLogMethod Allows to set the CLogger log level that is
  38          *  used when the DllLoader reports loading errors.
  39          */
  40         DllLoader(const char* name, CLogger::ELogMethod loadErrorLogMethod = CLogger::Error);
  41
  42         ~DllLoader();
  43
  44         /**
  45          * Attempt to load and initialise the library, if not already. Can be harmlessly
  46          * called multiple times. Returns false if unsuccessful.
  47          */
  48         bool LoadDLL();
  49
  50         /**
  51          * Check whether the library has been loaded successfully. Returns false
  52          * before {@link #LoadDLL} has been called; otherwise returns the same as
  53          * LoadDLL did.
  54          */
  55         bool IsLoaded() const;
  56
  57         /**
  58          * Unload the library, if it has been loaded already. (Usually not needed,
  59          * since the destructor will unload it.)
  60          */
  61         void Unload();
  62
  63         /**
  64          * Attempt to load a named symbol from the library. If {@link #IsLoaded} is
  65          * false, throws PSERROR_DllLoader_DllNotLoaded. If it cannot load the
  66          * symbol, throws PSERROR_DllLoader_SymbolNotFound. In both cases, sets fptr
  67          * to NULL. Otherwise, fptr is set to point to the loaded function.
  68          *
  69          * @throws PSERROR_DllLoader
  70          */
  71         template <typename T>
  72         void LoadSymbol(const char* name, T& fptr) const;
  73
  74         /**
  75          * Override the build-time setting of the directory to search for libraries.
  76          */
  77         static void OverrideLibdir(const char* libdir);
  78
  79 private:
  80         // Typeless version - the public LoadSymbol hides the slightly ugly
  81         // casting from users.
  82         void LoadSymbolInternal(const char* name, void** fptr) const;
  83
  84         void LogLoadError(const char* errors);
  85
  86         const char* m_Name;
  87         void* m_Handle;
  88         CLogger::ELogMethod m_LoadErrorLogMethod;
  89 };
  90
  91 template <typename T>
  92 void DllLoader::LoadSymbol(const char* name, T& fptr) const
  93 {
  94         LoadSymbolInternal(name, (void**)&fptr);
  95 }
  96
  97 #endif // INCLUDED_DLLLOADER