www.pudn.com > system.rar > ecvt.c

/****************************************************************************/ 
/*  ecvt v2.54                                                              */ 
/*  Copyright (c) 1995-2004 Texas Instruments Incorporated                  */ 
/****************************************************************************/ 
#include  
 
int ltoa(long val, char *buffer); 
 
char *ecvt(long double value, int ndigit, int *decpt, int *sign) 
 
{ 
    static char out[100];  
 
    int   digits = 0;         /* NUMBER OF DIGITS BEFORE .       */ 
    char *pos    = out + 1;      
    int   temp; 
 
    out[0] = '0';                      /* JUST IN CASE WE ROUND.          */ 
    ndigit++;                          /* DO ONE EXTRA DIGIT FOR ROUNDING */ 
 
    /*--------------------------------------------------------------------*/ 
    /* IF TRYING TO CONVERT INFINITY, RETURN HUGE_VALL OF PROPER SIGN     */ 
    /*--------------------------------------------------------------------*/ 
    {  
       int *ptr = (int *)&value; 
 
       if (((*ptr >> 20) & 0x7ff) == 0x7ff)  
	  value = (*ptr & 0x80000000) ? -HUGE_VALL : HUGE_VALL; 
    } 
 
    /*--------------------------------------------------------------------*/ 
    /* PERFORM PRESCALING - MAKE SURE NUMBER HAS INTEGRAL WHOLE PART      */ 
    /*--------------------------------------------------------------------*/ 
    if (*sign = (value < 0)) value = -value; 
    while (value > 0x7FFFFFFF) { value /= 10; digits++; } 
    while (value && value < 1) { value *= 10; digits--; } 
 
    /*--------------------------------------------------------------------*/ 
    /* WRITE OUT INTEGRAL PART OF NUMBER.                                 */ 
    /*--------------------------------------------------------------------*/ 
    pos    += temp    = ltoa((long)value, pos); 
    *decpt  = digits + temp; 
 
    /*--------------------------------------------------------------------*/ 
    /* WRITE OUT FRACTIONAL PART OF NUMBER                                */ 
    /*--------------------------------------------------------------------*/ 
    if (temp >= ndigit)  
	 pos = out + ndigit + 1; 
    else if ((ndigit -= temp) > 0) do 
    { 
         value -= (int) value; 
	 *pos++ = (int)(value *= 10.0) + '0'; 
    } 
    while (--ndigit); 
 
    /*--------------------------------------------------------------------*/ 
    /* PERFORM ROUNDING.  NOTE THAT pos IS CURRENTLY POINTING AT AN EXTRA */ 
    /* DIGIT WHICH WAS CONVERTED FOR THIS PURPOSE.                        */ 
    /*--------------------------------------------------------------------*/ 
    if (*--pos >= '5') 
    { 
	char *ptr = pos; 
	while ((*--ptr += 1) > '9') *ptr = '0'; 
	if (ptr == out) { *--pos = 0; *decpt += 1; return(out); } 
    } 
	 
    *pos = 0; 
    return out + 1; 
}