Wii trace module

To debug better a Wii application / game i have created a trace C++ module with is logging trace event to file. Please checkout the following code. I hope it benefit someone!

trace.h

#ifndef TRACE_H
#define TRACE_H

class Trace
{
  private:
	FILE * fp;
	char * getDate();

  public:
  	// Constructor & Destructor
	Trace();
 	~Trace();
	
	// Methodes
	int open(const char *filename);
	int event( const char *functionName, int threadNr, const char *event, ...);
	int eventRaw( char character);
	int close();
};

#endif

trace.cpp

#include <stdio.h>
#include <gccore.h>
#include <ogcsys.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <ogcsys.h>
#include <stdarg.h>
#include <time.h>

#include "trace.h"

// Enable / Disable trace file functionality
bool traceOn = false;

// ------------------------------
// Constructor
// ------------------------------

Trace::Trace()
{
	fp=NULL;
}

// ------------------------------
// Destructor
// ------------------------------

Trace::~Trace()
{
  close();
}

// ------------------------------
// Methods
// ------------------------------

// Open trace file
int Trace::open(const char *filename)
{
   int returnValue=0;
   
   if (!traceOn) return -1;
         
   if((fp=fopen(filename, "wb"))==NULL) 
   {
      printf("Error: Cannot open trace file.\n");
      returnValue=-2;
   }   
   return returnValue;
}


// Close trace file
int Trace::close()
{
   int returnValue=0;
   
   if (fp!=NULL)
   {
       fclose(fp);
   }	
   return returnValue;
}


// Create trace timestamp
char * Trace::getDate()
{
  struct tm *now = NULL;
  time_t time_value = 0;
  static char buf[ 128 ] ;
  
  // Clear memory  
  memset(buf, sizeof(buf), 0x00);
  
  /* Get time value */
  time_value = time(NULL);          
  
  /* Get time and date structure */
  now = localtime(&time_value);     

  // Create time stamp
  sprintf(buf,"%02d-%02d-%04d %02d:%02d:%02d",
	now->tm_mday, now->tm_mon+1, now->tm_year+1900, 
	now->tm_hour,now->tm_min,now->tm_sec);
	
  return buf;
}

// Save trace event in trace file
int Trace::event( const char *functionName, int threadNr, const char *event, ...)
{
   int returnValue=0;
   char buf[ MAX_LEN ];
   
   // Clear memory  
   memset(buf, MAX_LEN, 0x00);
   
   if (!traceOn) return -1;
   
   // Expend event string
   va_list list;
   va_start(list, event );
   vsprintf(buf, event, list);
   
   if (fp!=NULL)
   {
      // Save string to file
	  fprintf(fp,"%s [thread%d-%s] %s\n",getDate(), threadNr, functionName, buf); 
	  fflush(fp); 
   }
   
   return returnValue;
}


// Save trace event in trace file
int Trace::eventRaw( char character)
{
   int returnValue=0;
   
   if (!traceOn) return -1;
     
   if (fp!=NULL)
   {
      // Save string to file
	  fprintf(fp,"%c",character); 
	  fflush(fp); 
   }
   
   return returnValue;
}