stddbg.c

#include <stdio.h>
#include <io.h>
#include <fcntl.h>
#include <windows.h>

FILE* stddbg = NULL;
FILE* wstddbg = NULL;

static DWORD WINAPI OutputDebugStringAProc(_In_ LPVOID lpParameter)
{
    HANDLE hFile = (HANDLE) lpParameter;
    CHAR buf[1024];
    DWORD read = 0;
    while (ReadFile(hFile, buf, (ARRAYSIZE(buf) - 1) * sizeof(buf[0]), &read, NULL))
    {
        buf[read / sizeof(buf[0])] = '\0';
        OutputDebugStringA(buf);
    }
    CloseHandle(hFile);
    return 0;
}

static DWORD WINAPI OutputDebugStringWProc(_In_ LPVOID lpParameter)
{
    HANDLE hFile = (HANDLE) lpParameter;
    WCHAR buf[1024];
    DWORD read = 0;
    while (ReadFile(hFile, buf, (ARRAYSIZE(buf) - 1) * sizeof(buf[0]), &read, NULL))
    {
        buf[read / sizeof(buf[0])] = L'\0';
        OutputDebugStringW(buf);
    }
    CloseHandle(hFile);
    return 0;
}

FILE* fhopen(_In_ HANDLE FileHandle, _In_z_ char const* Mode)
{
    int Flags = 0;

    for (char const* ModeIt = Mode; *ModeIt != '\0'; ++ModeIt)
    {
        switch (*ModeIt)
        {
        case 'a': Flags |= _O_WRONLY | _O_APPEND; break;
        case 'r': Flags |= _O_RDONLY; break;
        case 'w': Flags |= _O_WRONLY; break;
        case '+': Flags &= ~(_O_RDONLY | _O_WRONLY); Flags |= _O_RDWR; break;
        case 'b': Flags |= _O_BINARY; break;
        case 't': Flags |= _O_TEXT; break;
        }
    }

    int d = _open_osfhandle((intptr_t) FileHandle, Flags);
    return _fdopen(d, Mode);
}

FILE* opendbg(LPTHREAD_START_ROUTINE lpOutputProc)
{
    HANDLE hRead = INVALID_HANDLE_VALUE;
    HANDLE hWrite = INVALID_HANDLE_VALUE;
    CreatePipe(&hRead, &hWrite, NULL, 0);

    HANDLE hThread = CreateThread(NULL, 0, lpOutputProc, hRead, 0, NULL);

    FILE* f = fhopen(hWrite, "w");
    setvbuf(f, NULL, _IONBF, 0);

    return f;
}

int initstddbg(void)
{
    if (stddbg == NULL)
        stddbg = opendbg(OutputDebugStringAProc);
    if (wstddbg == NULL)
        wstddbg = opendbg(OutputDebugStringWProc);
    return 0;
}

#ifdef STDDBG_TEST
int main()
{
    initstddbg();

    fprintf(stddbg, "stddbg\n");
    fwprintf(wstddbg, L"wstddbg\n");

    Sleep(10000);

    return 0;
}
#endif