Win32MessageFormatter.h

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/*  Win32Exception.h - Handy exception object that is capable
    of calling FormatMessage for sensible API error reporting.

    Copyright (C) 2001-2004 Mark Weaver
    Written by Mark Weaver <mark@npsl.co.uk>

    Part of the Open-Win32 library.
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
    License as published by the Free Software Foundation; either
    version 2 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Library General Public License for more details.

    You should have received a copy of the GNU Library General Public
    License along with this library; if not, write to the
    Free Software Foundation, Inc., 59 Temple Place - Suite 330,
    Boston, MA  02111-1307, USA.
*/

#ifndef OW32_Win32MessageFormatter_h
#define OW32_Win32MessageFormatter_h

#include <OW32/OW32Libs.h>
#include <stdio.h>

namespace OW32
{

class OW32_LIB_EXPORT CWin32MessageFormatterA
{
public:
    CWin32MessageFormatterA() /* throw() */ : 
        m_buffer(NULL),
        m_formatted("")
    {
        DWORD error = ::GetLastError();
        formatMessage(error);
    }

    CWin32MessageFormatterA(DWORD error) /* throw() */ :
        m_buffer(NULL),
        m_formatted("")
    {
        formatMessage(error);
    }

    ~CWin32MessageFormatterA() /* throw() */ 
    {
        if (m_buffer)
            ::LocalFree(m_buffer);
    }

    operator const char *() const /* throw() */ 
    {
        return m_formatted;
    }

private:
    void formatMessage(DWORD error) /* throw() */ 
    {
        if (::FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM, 
                0, error, 0, (LPSTR)&m_buffer, 0, NULL) != 0)
        {
            // Remove \n, \r\n from the string
            bool    prevCR = false;
            size_t  len = strlen(m_buffer);

            for (size_t i = 0; i < len; )
            {
                if (m_buffer[i] == '\n')
                {
                    memmove(m_buffer + i - prevCR, m_buffer + i + 1, sizeof(char) * (len - i));
                    len -= prevCR + 1;
                    i -= prevCR;
                    prevCR = false;
                }
                else
                {
                    if (m_buffer[i] == '\r')
                        prevCR = true;
                    ++i;
                }
            }

            m_formatted = m_buffer;
        }
        else
        {
            _snprintf(m_fixedBuffer, sizeof(m_fixedBuffer)/sizeof(m_fixedBuffer[0]),
                "API error code %lu", error);
            m_fixedBuffer[sizeof(m_fixedBuffer)/sizeof(m_fixedBuffer[0]) - 1] = '\0';
            m_formatted = m_fixedBuffer;
        }
    }

    char    *m_formatted;
    char    m_fixedBuffer[64];
    char    *m_buffer;
};

class OW32_LIB_EXPORT CWin32MessageFormatterW
{
public:
    CWin32MessageFormatterW() /* throw() */ : 
        m_buffer(NULL),
        m_formatted(L"")
    {
        DWORD error = ::GetLastError();
        formatMessage(error);
    }

    CWin32MessageFormatterW(DWORD error) /* throw() */ :
        m_buffer(NULL),
        m_formatted(L"")
    {
        formatMessage(error);
    }

    ~CWin32MessageFormatterW() /* throw() */ 
    {
        if (m_buffer)
            ::LocalFree(m_buffer);
    }

    operator const wchar_t *() const /* throw() */ 
    {
        return m_formatted;
    }

private:
    void formatMessage(DWORD error) /* throw() */ 
    {
        if (::FormatMessageW(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM, 
                0, error, 0, (LPWSTR)&m_buffer, 0, NULL) != 0)
        {
            // Remove \n, \r\n from the string
            bool    prevCR = false;
            size_t  len = wcslen(m_buffer);

            for (size_t i = 0; i < len; )
            {
                if (m_buffer[i] == L'\n')
                {
                    memmove(m_buffer + i - prevCR, m_buffer + i + 1, sizeof(wchar_t) * (len - i));
                    len -= prevCR + 1;
                    i -= prevCR;
                    prevCR = false;
                }
                else
                {
                    if (m_buffer[i] == L'\r')
                        prevCR = true;
                    ++i;
                }
            }

            m_formatted = m_buffer;
        }
        else
        {
            _snwprintf(m_fixedBuffer, sizeof(m_fixedBuffer)/sizeof(m_fixedBuffer[0]),
                L"API error code %lu", error);
            m_fixedBuffer[sizeof(m_fixedBuffer)/sizeof(m_fixedBuffer[0]) - 1] = L'\0';
            m_formatted = m_fixedBuffer;
        }
    }

    wchar_t *m_formatted;
    wchar_t m_fixedBuffer[64];
    wchar_t *m_buffer;
};

#ifdef _UNICODE
typedef CWin32MessageFormatterW CWin32MessageFormatter;
#else
typedef CWin32MessageFormatterA CWin32MessageFormatter;
#endif

} // namespace OW32

#endif // OW32_Win32MessageFormatter_h

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