Logger.h

#ifndef LOGGER_H_
  #define LOGGER_H_
 
  #include <stdio.h>
  #include <stdexcept>
 
  using namespace std;
 
  class Logger {
    public:
      Logger(const char* filename) throw(runtime_error);
      void log_packet(const unsigned char* data, const int len) throw(runtime_error);
      virtual ~Logger();
 
    private:
      void write(const void* buffer, const size_t len) throw(runtime_error);
      FILE* file;
};
 
#endif /*LOGGER_H_*/

Logger.cpp

#include <stdlib.h>
 
#ifdef WIN32
  #include <sys/types.h> 
  #include <sys/timeb.h>
#else
  #include <time.h>
  #include <sys/time.h>
#endif
 
#include "Logger.h"
 
/* Global Header Data */
#define MAGIC_NUMBER		0xa1b2c3d4
#define CURRENT_PCAP_MAJOR	2
#define CURRENT_PCAP_MINOR	4
#define	ZONE_GMT		0
#define WTAP_ENCAP_USER0	147
typedef struct pcap_hdr_s {
  unsigned int magic_number;  	/* magic number */
  unsigned short version_major; /* major version number */
  unsigned short version_minor; /* minor version number */
  int  thiszone;       		/* GMT to local correction */
  unsigned int sigfigs;        	/* accuracy of timestamps */
  unsigned int snaplen;        	/* max length of captured packets, in octets */
  unsigned int network;        	/* data link type */
} pcap_hdr_t;
 
/* Record Header Data */
typedef struct pcaprec_hdr_s {
  unsigned int ts_sec;         /* timestamp seconds */
  unsigned int ts_usec;        /* timestamp microseconds */
  unsigned int incl_len;       /* number of octets of packet saved in file */
  unsigned int orig_len;       /* actual length of packet */
} pcaprec_hdr_t;
 
Logger::Logger(const char* filename) throw(runtime_error){
  file = fopen(filename, "w");
  if (file == NULL)
    throw runtime_error("[ERROR] opening file");
 
  /* Write Global Header */
  pcap_hdr_t header;
  header.magic_number = MAGIC_NUMBER;
  header.version_major = CURRENT_PCAP_MAJOR;
  header.version_minor = CURRENT_PCAP_MINOR;
  header.thiszone = ZONE_GMT;
  header.sigfigs = 0;
  header.snaplen = 0xFFFF;
  header.network = WTAP_ENCAP_USER0; /*See: http://anonsvn.wireshark.org/wireshark/trunk/wiretap/libpcap.c */
  write(&header, sizeof(pcap_hdr_t));
}
 
void Logger::write(const void* buffer, const size_t len) throw(runtime_error) {
  if (fwrite(buffer, len, 1, file) != 1) 
    throw runtime_error("[ERROR] writing to file");
}
 
void Logger::log_packet(const unsigned char* data, const int len) throw(runtime_error) {
  unsigned int sec, sec;
 
#ifdef WIN32
  struct _timeb timebuffer;
  _ftime(&timebuffer);
  sec = (unsigned int)timebuffer.time;
  usec = ((unsigned int)timebuffer.millitm) * 1000;
#else
  struct timeval time;
  gettimeofday(&time, NULL);
  sec = time.tv_sec;
  usec = time.tv_usec;
#endif
 
  pcaprec_hdr_t recHeader;
  recHeader.ts_sec  = sec;
  recHeader.ts_usec = usec;
  recHeader.incl_len = len;
  recHeader.orig_len = len;
  write(&recHeader, sizeof(pcaprec_hdr_t));
  write(data, len);
}
 
Logger::~Logger() {	
  if (file != NULL)
    fclose(file);
}