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標題: gcvt函數源碼如果ccs的stdlib庫函數中沒有，可以看過來 [打印本頁]

作者: xt123~ 時間: 2023-5-25 16:40
標題: gcvt函數源碼如果ccs的stdlib庫函數中沒有，可以看過來
#define PSH(X) (*(buf++)=(X))
#define PSH1(X) (*(buf--)=(X))
#define PEEK() buf[-1]
#define POP() *(--buf) = '\0'
#define PLUS 1
#define SPACE 2

char *gcvt(float f, uint16_t ndigit, char *buf)
{
   int i;
   uint32_t z,k;
   //int exp = 0;
   char *c = buf;
   float f2,t,scal;
   int sign = 0;

   if((int)ndigit == -1)
   ndigit = 5;

   /* Unsigned long long only allows for 20 digits of precision
   * which is already more than double supports, so we limit the
   * digits to this.  long double might require an increase if it is ever
   * implemented.
   */
   if (ndigit > 20)
      ndigit = 20;

   if (f < 0.0) {
   sign = 1;
   f = -f;
      buf++;
   }

   scal = 1;
   for (i=ndigit; i>0; i--)
      scal *= 10;
   k = f + 0.1 / scal;
   f2 = f - k;
   if (!f) {
   PSH('0');
   if(ndigit > 0)
      PSH('.');
   for (i=0;i<ndigit;i++)
      PSH('0');
      PSH(0);
      return c;
   }

   i = 1;
   while (f >= 10.0) {
   f /= 10.0;
   i++;
   }

   buf += i + ndigit + 1;

   PSH1(0);

   if(ndigit > 0) {
      t = f2 * scal;
      z = t + 0.5;
   for (i = 0;i < ndigit;i++)
   {
      PSH1('0'+ (z % 10));
      z /= 10;
   }
   PSH1('.');
   }
   else
   PSH1(0);

   do {
   PSH1('0'+ (k % 10));
   k /= 10;
   }while (k);

   if (sign)
   PSH1('-');
   return c;
}

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