src/Utils/FormatMessageWrapper.h

   1 // TortoiseGit - a Windows shell extension for easy version control
   2
   3 // Copyright (C) 2009-2010 - TortoiseSVN
   4
   5 // This program is free software; you can redistribute it and/or
   6 // modify it under the terms of the GNU General Public License
   7 // as published by the Free Software Foundation; either version 2
   8 // of the License, or (at your option) any later version.
   9
  10 // This program is distributed in the hope that it will be useful,
  11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 // GNU General Public License for more details.
  14
  15 // You should have received a copy of the GNU General Public License
  16 // along with this program; if not, write to the Free Software Foundation,
  17 // 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18 //
  19 #pragma once
  20
  21 /**
  22  * A wrapper class for calling the FormatMessage() Win32 function and controlling
  23  * the lifetime of the allocated error message buffer.
  24  */
  25
  26 class CFormatMessageWrapper
  27 {
  28 private:
  29     LPTSTR buffer;
  30     DWORD result;
  31     void release();
  32     void obtainMessage() { obtainMessage(::GetLastError()); }
  33     void obtainMessage(DWORD errorCode);
  34
  35 public:
  36     CFormatMessageWrapper() : buffer(0), result(0) {obtainMessage();}
  37     CFormatMessageWrapper(DWORD lastError) : buffer(0), result(0) {obtainMessage(lastError);}
  38     ~CFormatMessageWrapper() { release(); }
  39     operator LPCTSTR() { return buffer; }
  40     operator bool() { return result != 0; }
  41     bool operator!() { return result == 0; }
  42 };
  43
  44 inline void CFormatMessageWrapper::obtainMessage(DWORD errorCode)
  45 {
  46     // First of all release the buffer to make it possible to call this
  47     // method more than once on the same object.
  48     release();
  49     result = FormatMessage (FORMAT_MESSAGE_ALLOCATE_BUFFER |
  50                             FORMAT_MESSAGE_FROM_SYSTEM |
  51                             FORMAT_MESSAGE_IGNORE_INSERTS,
  52                             NULL,
  53                             errorCode,
  54                             MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
  55                             (LPTSTR) &buffer,
  56                             0,
  57                             NULL
  58                             );
  59 }
  60
  61 inline void CFormatMessageWrapper::release()
  62 {
  63     if(buffer != 0)
  64     {
  65         LocalFree(buffer);
  66         buffer = 0;
  67     }
  68
  69     result = 0;
  70 }