logmsg.cpp

伯克利做的SFTP安全文件传输协议

// logmsg.cc
// code for logmsg.h
// copyright SafeTP Development Group, Inc., 2000  Terms of use are as specified in license.txt

#include "logmsg.h"     // this module
#include "xassert.h"    // xfailure
#include "str.h"        // stringb

#include <fstream.h>    // ofstream

// define a sleep function
#if defined(__WIN32__)

#include <windows.h>     // Sleep

#define SHARING_MODE , filebuf::sh_read

static void waitABit()
{
  Sleep(500);   // 1/2 sec
}

static void failure(char const *filename)
{
  MessageBox((HWND)NULL,
             stringb("Failure writing to logfile " << filename),
             "Log Failure",
             MB_OK);
}


#elif defined(__UNIX__)

#include <unistd.h>      // sleep

// g++2.8.1 doesn't define filebuf::sh_read
#define SHARING_MODE

static void waitABit()
{
  sleep(1);     // 1 sec
}

static void failure(char const *filename)
{
  xfailure(stringb("Failure writing to logfile %s" << filename));
}

#else
#  error Must define a system type, e.g. __WIN32__ or __UNIX__
#endif


void LogMessage(char const* msg, char const *filename) {
  ofstream logfile;
  int retry=0;
  int success=0;
  // get a lock
  while (!success && retry < 10) {
    logfile.clear();
    logfile.open(filename, ios::app SHARING_MODE);
    if (logfile.fail()) {
      waitABit();
      retry++;
      }
    else success = 1;
    }
  if (!success) {
    failure(filename);
    return;   // used only if 'failure' returns
  }

  // SM: wanted to see log contention approximation
  if (retry > 0) {
    logfile << "(after " << retry << " retries) ";
  }

  logfile << msg << endl;
  logfile.close();
  }


// ---------- test code --------------------------
#ifdef TEST_LOGMSG

#include <stdio.h>    // printf
#include "exc.h"      // xBase

int main()
{
  printf("writing to tlog.log\n");

  try {
    LogMessage("This is a sample log entry.", "tlog.log");
  }
  catch (xBase &x) {
    return printf("exception caught: %s\n", x.why());
  }

  return 0;
}

#endif // TEST_LOGGING