159 lines
3.8 KiB
C
159 lines
3.8 KiB
C
/*_ ecvt.c Sat May 20 1989 Modified by: Walter Bright */
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/* Copyright (C) 1986-1989 by Walter Bright */
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/* All Rights Reserved */
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#include <stdlib.h>
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#include <float.h>
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#define DIGMAX (DBL_DIG*2) /* max # of digits in string */
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/* (*2 is a good fudge factor) */
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#define DIGPREC (DBL_DIG+2) /* max # of significant digits */
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/* (+2 for fractional part after min */
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/* significant digits) */
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#define ECVT 0
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#define FCVT 1
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extern int _8087; /* 8087 flag */
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static char digstr[DIGMAX + 1 + 1]; /* +1 for end of string */
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/* +1 in case rounding adds */
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/* another digit */
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static double negtab[] =
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{1e-256,1e-128,1e-64,1e-32,1e-16,1e-8,1e-4,1e-2,1e-1,1.0};
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static double postab[] =
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{1e+256,1e+128,1e+64,1e+32,1e+16,1e+8,1e+4,1e+2,1e+1};
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static char * near pascal
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_floatcvt(int cnvflag,double val,int ndig,int *pdecpt,int *psign);
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/*************************
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* Convert double val to a string of
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* decimal digits.
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* ndig = # of digits in resulting string
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* Returns:
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* *pdecpt = position of decimal point from left of first digit
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* *psign = nonzero if value was negative
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*/
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char *ecvt(double val,int ndig,int *pdecpt,int *psign)
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{
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return _floatcvt(ECVT,val,ndig,pdecpt,psign);
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}
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/*************************
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* Convert double val to a string of
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* decimal digits.
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* nfrac = # of digits in resulting string past the decimal point
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* Returns:
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* *pdecpt = position of decimal point from left of first digit
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* *psign = nonzero if value was negative
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*/
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char *fcvt(double val,int nfrac,int *pdecpt,int *psign)
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{
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return _floatcvt(FCVT,val,nfrac,pdecpt,psign);
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}
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/*************************
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* Convert double val to a string of
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* decimal digits.
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* if (cnvflag == ECVT)
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* ndig = # of digits in resulting string past the decimal point
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* else
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* ndig = # of digits in resulting string
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* Returns:
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* *pdecpt = position of decimal point from left of first digit
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* *psign = nonzero if value was negative
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*/
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static char * near pascal
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_floatcvt(int cnvflag,double val,int ndig,int *pdecpt,int *psign)
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{ int decpt,pow,i,_8087save;
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char *p;
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*psign = (val < 0) ? ((val = -val),1) : 0;
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ndig = (ndig < 0) ? 0
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: (ndig < DIGMAX) ? ndig
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: DIGMAX;
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if (val == 0)
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{ for (p = &digstr[0]; p < &digstr[ndig]; p++)
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*p = '0';
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decpt = 0;
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}
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else
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{ /* Adjust things so that 1 <= val < 10 */
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_8087save = _8087;
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_8087 = 0; /* turn off 8087 (because it will hang */
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/* in these loops if val == DBL_MAX) */
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decpt = 1;
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pow = 256;
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i = 0;
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while (val < 1)
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{ while (val < negtab[i + 1])
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{ val *= postab[i];
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decpt -= pow;
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}
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pow >>= 1;
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i++;
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}
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pow = 256;
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i = 0;
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while (val >= 10)
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{ while (val >= postab[i])
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{ val *= negtab[i];
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decpt += pow;
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}
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pow >>= 1;
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i++;
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}
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_8087 = _8087save; /* restore flag */
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if (cnvflag == FCVT)
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{ ndig += decpt;
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ndig = (ndig < 0) ? 0
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: (ndig < DIGMAX) ? ndig
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: DIGMAX;
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}
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/* Pick off digits 1 by 1 and stuff into digstr[] */
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/* Do 1 extra digit for rounding purposes */
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for (p = &digstr[0]; p <= &digstr[ndig]; p++)
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{ int n;
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/* 'twould be silly to have zillions of digits */
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/* when only DIGPREC are significant */
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if (p >= &digstr[DIGPREC])
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*p = '0';
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else
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{ n = val;
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*p = n + '0';
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val = (val - n) * 10; /* get next digit */
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}
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}
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if (*--p >= '5') /* if we need to round */
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{
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while (1)
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{
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if (p == &digstr[0]) /* if at start */
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{ ndig += cnvflag;
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decpt++; /* shift dec pnt */
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digstr[0] = '1'; /* "100000..." */
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break;
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}
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*p = '0';
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--p;
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if (*p != '9')
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{ (*p)++;
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break;
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}
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} /* while */
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} /* if */
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} /* else */
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*pdecpt = decpt;
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digstr[ndig] = 0; /* terminate string */
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return &digstr[0];
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}
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