#include <string.h>
#include <stdio.h>

char hexa2char(char *s) 
{ char x;
  x=0;
  if (s[0]>='A') x+=s[0]+10-'A'; else x+=s[0]-'0';
  x*=16;
  if (s[1]>='A') x+=s[1]+10-'A'; else x+=s[1]-'0';
  return(x);
}

char *textval(char *s) 
{ int i,j,n;
  char *r;
/* n : nombre de caracteres a allouer */
  i=0; j=0;
  while (s[i] != '\0' && s[i] != '&')
  { if (s[i] == '%') j++;
    i++;
  }
  n = i - (2*j);
  r = (char*) malloc (n * sizeof(char));
/* r : chaine renvoyee */
  i = 0; j = 0;
  while (s[i] != '\0' && s[i] != '&')
    {switch (s[i])
       {case '%' : 
	  r[j] = hexa2char(&s[i+1]);
	  i+=2; break;
	case '+' :
	  r[j] = ' '; break;
	default :
	  r[j] = s[i];
	}
     i++; j++;
   }
  r[j] = '\0';
  return(r);
}

int varsuiv(char *s, int i)
{ while (s[i] != '\0' && s[i] != '&') i++;
  if (s[i] == '\0') return(-1); else return(i+1);
}

int idval(char *s , char *v, int n)
{ int i, o, l;
  l = strlen(v);
  i = o = 0;
  while (i != -1)
    {if (strncmp(&s[i],v,l) == 0) o++;
     if (o == n) return(i+l+1); 
     i = varsuiv(s,i);
   }
}

int nbocc(char *s , char *v)
{ int i, o, l;
  if (s==NULL) return(0);
  l = strlen(v);
  i = o = 0;
  while (i != -1)
    {if (strncmp(&s[i],v,l) == 0) o++;
     i = varsuiv(s,i);
   }
  return(o);
}

char *getval(char *s , char *v, int n)
{ int i;  
  if (s==NULL) return(NULL);
  i = idval(s,v,n);
  if (s[i] == '\0' || s[i] == '&') return(NULL);
  return(textval(&s[i]));
}