itoa函数的实现

因为ANSI标准库里面并没有包含itoa函数，所以自己专门写了一个:

//------------------------------------------------------------------------------

//Modified on: 12/29, 2008

//Change return type of itoa. No meaningful to return copy address "s"

//------------------------------------------------------------------------------

＃i nclude

static void reverse (char *);

//------------------------------------------------------------------------------
/// itoa: convert n to characters in s
///
//------------------------------------------------------------------------------
void itoa(int n, char *s)
{
  int sign;
  char *t = s;
 
  if ((sign = n) < 0)
    n = -n;
 
  do
  {
    *s++ = n % 10 + '0';
  }
  while ((n /= 10) >0);
 
  if (sign < 0)
    *s++ = '-';
 
  *s = '\0';
 
  reverse(t);
}

//------------------------------------------------------------------------------
/// reverse: reverse sting s in place
///
//------------------------------------------------------------------------------
void reverse(char *s)
{
  int c;
  char *t;
 
  for (t = s + (strlen(s) - 1); s < t; s++, t-- )
  {
    c = *s;
    *s = *t;
    *t = c;
  }
}