char LogPath[100];
FILE *hLog;
int LogDirty;
DWORD LogTick;

void LogReOpen (void)
{
    hLog = fopen(LogPath, "ab");
    if (hLog == NULL) {
        fprintf(stderr, "Open failed: %s\n", LogPath);
        exit(1);
    }
    LogDirty = 0;
    LogTick = GetTickCount();

    return;
}

//
// Get next log sequence number. This is found
// in the file \seq.txt -- which is created if
// not present.
//

int NextSequence (void)
{
    FILE *f;
    char *Path = "\\seq.txt";
    long Value;

    f = fopen(Path, "r");
    if (f == NULL) {
        Value = 1;

    } else {
        fscanf(f, "%ld", &Value);
        fclose(f);
    }

    f = fopen(Path, "w");
    fprintf(f, "%ld", Value + 1);
    fclose(f);

    return Value;
}

BOOL WINAPI CtrlHandler (DWORD CtrlType);

void LogOpen (char *Path)
{
    long LogNumber;

    if (strstr(Path, "%d") != NULL) {
        LogNumber = NextSequence();
        sprintf(LogPath, Path, LogNumber);

    } else if (Path == NULL) {
        LogNumber = NextSequence();
        sprintf(LogPath, "log%d.txt", LogNumber);

    } else {
        strcpy(LogPath, Path);
    }
    fprintf(stderr, "** Opening file %s\n", LogPath);
    LogReOpen();
    SetConsoleCtrlHandler(CtrlHandler, TRUE);

    return;
}

void LogClose (void)
{
    fprintf(stderr, "** Closing %s\n", LogPath);
    fclose(hLog);

    return;
}

//
// Close and re-open the log file to guarantee
// the data has been flushed to disk.
//

#define SYNC_SECONDS 15

void LogSync (void)
{
    if (LogDirty) {
        if (GetTickCount() - LogTick > (SYNC_SECONDS * 1000)) {
            fclose(hLog);
            DEBUG printf("[checkpoint]\n");
            LogReOpen();
        }
    }

    return;
}

void LogWrite (char *Buffer, DWORD Size)
{
    if (Size != 0) {
        fwrite(Buffer, Size, 1, stdout);
        fflush(stdout);

        if (fwrite(Buffer, Size, 1, hLog) != 1) {
            fprintf(stderr, "Log file fwrite error - ignoring!\n");
            // exit(1);
        }
        fflush(hLog);
        LogDirty = 1;
    }

    LogSync();
    return;
}

//
// Return Modified Julian Day (MJD) given
// calendar year, month (1-12), and day (1-31).
// - Valid for Gregorian dates from 17-Nov-1858.
// - Adapted from sci.astro FAQ.
//

long _DateToMjd (long Year, long Month, long Day)
{
    return
        367 * Year
        - 7 * (Year + (Month + 9) / 12) / 4
        - 3 * ((Year + (Month - 9) / 7) / 100 + 1) / 4
        + 275 * Month / 9
        + Day
        + 1721028
        - 2400000;
}

//
// Generate sequence number, MJD, and/or UTC time stamp.
//

char *LogTimeStamp (int type)
{
    static char buf[100];  // STATIC
    static long Sequence = 0;
    char ms[10];
    char *p;
    SYSTEMTIME St;

    GetSystemTime(&St);
    buf[0] = '\0';
    p = buf;

    //
    // Display line sequence number.
    //

    if (type & TS_SEQ) {
        Sequence += 1;
        p += sprintf(p, "%ld ", Sequence);
    }

    //
    // Display Modified Julian Date.
    //

    if (type & TS_MJD) {
        long Mjd, Seconds;

        Mjd = _DateToMjd(St.wYear, St.wMonth, St.wDay);
        Seconds = (((St.wHour * 60) + St.wMinute) * 60) + St.wSecond;
        p += sprintf(p, "%.6lf ", Mjd + Seconds / 86400.0);
    }

    //
    // Display UTC date and time (and milliseconds).
    //

    ms[0] = '\0';
    if (type & TS_MS) {
        sprintf(ms, ".%.3ld", St.wMilliseconds);
    }

    if (type & (TS_UTC | TS_MS)) {
        p += sprintf(p, "%.4d-%.2d-%.2d %.2d:%.2d:%.2d%s ",
                     St.wYear, St.wMonth, St.wDay,
                     St.wHour, St.wMinute, St.wSecond,
                     ms);
    }

    return buf;  // STATIC
}

//
// Flush log file on ctrl-c exit.
//

BOOL WINAPI CtrlHandler (DWORD CtrlType)
{
    if (CtrlType == CTRL_C_EVENT) {
        LogClose();
#ifdef COMM_CLOSE
        CommClose();
#endif
        exit(0);
    }

    return TRUE;
}