/**********************************************************************/
/*  burst.c - this program computes the burstiness parameters a and   */
/*  b for an HTTP log, according to Chap. 10 of the book "Capacity    */
/*  Planning for Web Services: metrics, models, and methods"          */
/*  Prentice Hall, Upper Saddle River, NJ, 2002.                      */
/*                                                                    */
/*  This program has three parameters: -f <name>, that specifies      */
/*  the name of the file containing an HTTP typical log;              */ 
/*  -e <epochs> that specifies the number of epochs of the            */
/*  interval, according to definitions in Chap.  10;                  */
/*  -r <number> that specifies  the number of requests in the log     */
/*  to be processed. If this parameter is not specified, its          */
/*  value is assumed to be equal to the variable maxreq (10000)       */
/*                                                                    */
/**********************************************************************/

/* (c) 1998-2002 by Virgilio Almeida and Daniel A. Menasce

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <sys/types.h>
#include <time.h>

#define  MAXLINE 256
#define  MAXLOG 16281

time_t timevet[MAXLOG];
int numtime = 0;
double drand48();
char * cname = 0;
int epochs = 17;
#define MAXEPOCH 100
int maxreq = 10000; /* number of requests processed by default */
                    /* if the parameter r is omitted           */

int getMonth(char * month){
	if(!strcmp("Jan",month))
		return 0;
	if(month[0] == 'F')
		return 1;
	if(!strcmp("Mar",month))
		return 2;
	if(!strcmp("Apr",month))
		return 3;
	if(!strcmp("May",month))
		return 4;
	if(!strcmp("Jun",month))
		return 5;
	if(!strcmp("Jul",month))
		return 6;
	if(!strcmp("Aug",month))
		return 7;
	if(month[0] == 'S')
		return 8;
	if(month[0] == 'O')
		return 9;
	if(month[0] == 'N')
		return 10;
	if(month[0] == 'D')
		return 11;
	return(-1);
}


//format of pstr: "day/month/year:hour:min:sec"
void strptime2(char * pstr, struct tm* tm){
	char * aux = (char *) malloc (sizeof(char) * strlen(pstr));
	
	strncpy(aux,pstr,2);
	aux[2] ='\0';
	sscanf(aux,"%d",&(tm->tm_mday));
	strncpy(aux,&(pstr[3]),3);
	aux[3] ='\0';
	tm->tm_mon = getMonth(aux);
	strncpy(aux,&(pstr[7]),4);
	aux[4] ='\0';
	sscanf(aux,"%d",&(tm->tm_year));
	tm->tm_year = tm->tm_year - 1900;
	strncpy(aux,&(pstr[12]),2);
	aux[2] ='\0';
	sscanf(aux,"%d",&(tm->tm_hour));
	strncpy(aux,&(pstr[15]),2);
	aux[2] ='\0';
	sscanf(aux,"%d",&(tm->tm_min));
	strncpy(aux,&(pstr[18]),2);
	aux[2] ='\0';
	sscanf(aux,"%d",&(tm->tm_sec));
	tm->tm_yday = tm->tm_mday;
	switch(tm->tm_mon){
		case 0 : tm->tm_yday += 0;
				 break;
		case 1 : tm->tm_yday += 31;
				 break;
		case 2 : tm->tm_yday += 59;
				 break;
		case 3 : tm->tm_yday += 90;
				 break;
		case 4 : tm->tm_yday += 120;
				 break;
		case 5 : tm->tm_yday += 151;
				 break;
		case 6 : tm->tm_yday += 181;
				 break;
		case 7 : tm->tm_yday += 212;
				 break;
		case 8 : tm->tm_yday += 243;
				 break;
		case 9 : tm->tm_yday += 273;
				 break;
		case 10 : tm->tm_yday += 304;
				 break;
		case 11 : tm->tm_yday += 334;
				 break;
		default : tm->tm_yday = 0;
	}

	/*leap year*/
	if (!tm->tm_year%4 && (tm->tm_year%100 || !tm->tm_year%400)){
		tm->tm_yday++;
	}
	
	tm->tm_isdst = 1;
	
	/*day of week set to Sunday.*/
	tm->tm_wday = 0;
	free(aux);
}

int getline(FILE *fp, char * line){

  int pos,ch;

  memset((void*)line,0,MAXLINE);
  pos = 0;
  while (((ch=fgetc(fp)) != '\n') && !feof(fp)){
    line[pos] = ch;
    pos++;
  }
  line[pos] = 0;
  return pos;
}

void usage(){
  printf("burst - Calculates the burstiness parameters\n");
  printf("Options: \n");
  printf("         -f <name>           (input file name) \n");
  printf("         -e <num>            (number of epochs) \n");
  printf("         -r <num>            (number of requests) \n");

}


void parse_args(argc,argv)
int argc;
char ** argv;
{
     int c=1;
     while (c < argc) {
	  /* data file name */
	  if (!strcmp("-f",argv[c])){
	       cname = strdup(argv[c+1]);
	  }
	  /* epochs */
	  if (!strcmp("-e",argv[c])){
	       epochs = atoi(argv[c+1]);
	       if (epochs > MAXEPOCH) {
		    epochs = MAXEPOCH;
		    fprintf(stderr,"Number of epochs must be less than %d\n",
			 MAXEPOCH);
	       }
	  }
	  /* requests */
	  if(!strcmp("-r",argv[c])){
	       maxreq = atoi(argv[c+1]);
	  }
	  if(!strcmp("-h",argv[c])){
	       usage();
	       exit(1);
	  }
	  c += 2;
     }
}


int main(int argc, char ** argv){
  int i,j;
  int cc;
  FILE * file_in;
  struct tm tm;
  char * pstr;
  char line[MAXLINE];
  int Arr[MAXEPOCH], ArrPlus, ArrPlusCount, ArrMinus, ArrMinusCount;
  double Lambda_k[MAXEPOCH];
  double Lambda, totalduration,epochduration, a, b;
  time_t limit;

  parse_args(argc,argv);

  file_in = fopen(cname, "r");
  if (file_in == (FILE *) 0) {
      fprintf (stderr, "fopen failed opening input file %s",cname);
      exit(-1);
  }

  while (numtime < maxreq && getline(file_in,line) != 0){
    pstr = strstr(line,"]");
    *pstr = 0;
    pstr = strstr(line,"[");
    pstr ++;
    /* original call: strptime(pstr,"%d/%b/%Y:%T%t",&tm);
	 * at DOS, strptime doesn't exists... Use strptime2 defined
	 * above.*/
	strptime2(pstr,&tm);
    timevet[numtime] = mktime(&tm);
    numtime ++;
  }
  fclose(file_in);

  Lambda = (double)(numtime)/(timevet[numtime-1]-timevet[0]);
  totalduration = (double)(timevet[numtime-1]-timevet[0]);
  epochduration = totalduration/epochs;
  ArrPlus = ArrPlusCount = ArrMinus = ArrMinusCount = cc = 0;
  j = 0;
  for (i=0; i<epochs; i++){
    limit = (time_t) (timevet[0] + epochduration*(i+1));
    for (Arr[i]=0; (j<numtime) && (timevet[j]<=limit); j++,Arr[i]++);
    Lambda_k[i] = (double)(epochs*Arr[i])/totalduration;
    if (Lambda_k[i] > Lambda){
       ArrPlus ++;
       ArrPlusCount += Arr[i];
    }
    if (Lambda_k[i] <= Lambda) {
       ArrMinus ++;
       ArrMinusCount += Arr[i];
    }
  }

  b = (double)(ArrPlus)/epochs;
  a = (double)(ArrPlusCount)/(b*numtime);
  printf("burstiness parameter a = %f\n",a);
  printf("burstiness parameter b = %f\n",b);

  return 0;
}