multiply.c

计算阶乘的程序 在红旗linux桌面6.0（linux内核版本2.6.23.1-4）

#include <stdio.h>
#include <stdlib.h>
#define M 1.0e+256
#define N 33554432L

unsigned int multiply(unsigned int n, double *result, unsigned int highest);
void print(double *outdata, unsigned int highest);
int main(int argc, char *argv[])
{
	  unsigned int i = 0, n =0, highest = 0;
	  double *data;
	  data = malloc(N);
	  *data = 1.0;
	  if(argc != 2)
	   {
			printf("The Parameter is wrong\n");
			exit(1);
	  }
	  else
	  {
			while(*(argv[1] + i) != '\0')
			{
				  if((*(argv[1] + i) <= 0x39) && (*(argv[1] + i) >= 0x30))
						i++;
				  else
				  {
						printf("The Parameter is wrong\n");
						exit(1);
				   }
			}
	  }
	  n = atoi(argv[1]);
	  printf("The %d! = ", n);
	  for(i = 2; i <= n; i++)
			highest = multiply(i, data, highest);
	  print(data, highest);
	  free(data);
	  exit(0);
}
unsigned int multiply(unsigned int n, double *result, unsigned int highest)
{
	  double tmp;
	  double carrier = 0.0;
	  int i;
	  for(i = 0; i <= highest; i++)
	  {
			tmp = n;
			tmp *= *(result + i);
			tmp += carrier;
			if(tmp > 1.0e+256)
			{	  carrier = tmp / M;
				  *(result + i) = tmp - carrier*M;
			}
			else
			{
			      carrier = 0.0;
				  *(result + i) = tmp;
			}
	  }
	  if(carrier)
			*(result + (++highest)) = carrier;
	  return highest;
}
void print(double *outdata, unsigned int highest)
{
	  FILE *Buff;
	  unsigned  char data[32];
	  unsigned char *index;
	  unsigned int index1;
	  if(highest == 0)
			printf("%.18e", *(outdata + highest));
	  else
	  {
	  Buff = fopen("./out", "w+");
	  fprintf(Buff,"%.18e", *(outdata + highest));
	  fclose(Buff);
	  Buff = fopen("./out", "r");
	  fread(data, sizeof(unsigned char), 32, Buff);
	  printf("%.22s",data);
	  index = data + 22;
	  index1 = atoi(index);
	  printf("%u",  index1 + highest*256);
	  fclose(Buff);
	  remove("./out");
	  }
	  printf("\n");
}