9base

strtod.c (8562B)

---

 /* Copyright (c) 2002-2006 Lucent Technologies; see LICENSE */
 #include <stdlib.h>
 #include <math.h>
 #include <ctype.h>
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
 #include "plan9.h"
 #include "fmt.h"
 #include "fmtdef.h"
 
 static ulong
 umuldiv(ulong a, ulong b, ulong c)
 {
 	double d;
 
 	d = ((double)a * (double)b) / (double)c;
 	if(d >= 4294967295.)
 		d = 4294967295.;
 	return (ulong)d;
 }
 
 /*
  * This routine will convert to arbitrary precision
  * floating point entirely in multi-precision fixed.
  * The answer is the closest floating point number to
  * the given decimal number. Exactly half way are
  * rounded ala ieee rules.
  * Method is to scale input decimal between .500 and .999...
  * with external power of 2, then binary search for the
  * closest mantissa to this decimal number.
  * Nmant is is the required precision. (53 for ieee dp)
  * Nbits is the max number of bits/word. (must be <= 28)
  * Prec is calculated - the number of words of fixed mantissa.
  */
 enum
 {
 	Nbits	= 28,				/* bits safely represented in a ulong */
 	Nmant	= 53,				/* bits of precision required */
 	Prec	= (Nmant+Nbits+1)/Nbits,	/* words of Nbits each to represent mantissa */
 	Sigbit	= 1<<(Prec*Nbits-Nmant),	/* first significant bit of Prec-th word */
 	Ndig	= 1500,
 	One	= (ulong)(1<<Nbits),
 	Half	= (ulong)(One>>1),
 	Maxe	= 310,
 
 	Fsign	= 1<<0,		/* found - */
 	Fesign	= 1<<1,		/* found e- */
 	Fdpoint	= 1<<2,		/* found . */
 
 	S0	= 0,		/* _		_S0	+S1	#S2	.S3 */
 	S1,			/* _+		#S2	.S3 */
 	S2,			/* _+#		#S2	.S4	eS5 */
 	S3,			/* _+.		#S4 */
 	S4,			/* _+#.#	#S4	eS5 */
 	S5,			/* _+#.#e	+S6	#S7 */
 	S6,			/* _+#.#e+	#S7 */
 	S7			/* _+#.#e+#	#S7 */
 };
 
 static	int	xcmp(char*, char*);
 static	int	fpcmp(char*, ulong*);
 static	void	frnorm(ulong*);
 static	void	divascii(char*, int*, int*, int*);
 static	void	mulascii(char*, int*, int*, int*);
 
 typedef	struct	Tab	Tab;
 struct	Tab
 {
 	int	bp;
 	int	siz;
 	char*	cmp;
 };
 
 double
 fmtstrtod(const char *as, char **aas)
 {
 	int na, ex, dp, bp, c, i, flag, state;
 	ulong low[Prec], hig[Prec], mid[Prec];
 	double d;
 	char *s, a[Ndig];
 
 	flag = 0;	/* Fsign, Fesign, Fdpoint */
 	na = 0;		/* number of digits of a[] */
 	dp = 0;		/* na of decimal point */
 	ex = 0;		/* exonent */
 
 	state = S0;
 	for(s=(char*)as;; s++) {
 		c = *s;
 		if(c >= '0' && c <= '9') {
 			switch(state) {
 			case S0:
 			case S1:
 			case S2:
 				state = S2;
 				break;
 			case S3:
 			case S4:
 				state = S4;
 				break;
 
 			case S5:
 			case S6:
 			case S7:
 				state = S7;
 				ex = ex*10 + (c-'0');
 				continue;
 			}
 			if(na == 0 && c == '0') {
 				dp--;
 				continue;
 			}
 			if(na < Ndig-50)
 				a[na++] = c;
 			continue;
 		}
 		switch(c) {
 		case '\t':
 		case '\n':
 		case '\v':
 		case '\f':
 		case '\r':
 		case ' ':
 			if(state == S0)
 				continue;
 			break;
 		case '-':
 			if(state == S0)
 				flag |= Fsign;
 			else
 				flag |= Fesign;
 		case '+':
 			if(state == S0)
 				state = S1;
 			else
 			if(state == S5)
 				state = S6;
 			else
 				break;	/* syntax */
 			continue;
 		case '.':
 			flag |= Fdpoint;
 			dp = na;
 			if(state == S0 || state == S1) {
 				state = S3;
 				continue;
 			}
 			if(state == S2) {
 				state = S4;
 				continue;
 			}
 			break;
 		case 'e':
 		case 'E':
 			if(state == S2 || state == S4) {
 				state = S5;
 				continue;
 			}
 			break;
 		}
 		break;
 	}
 
 	/*
 	 * clean up return char-pointer
 	 */
 	switch(state) {
 	case S0:
 		if(xcmp(s, "nan") == 0) {
 			if(aas != nil)
 				*aas = s+3;
 			goto retnan;
 		}
 	case S1:
 		if(xcmp(s, "infinity") == 0) {
 			if(aas != nil)
 				*aas = s+8;
 			goto retinf;
 		}
 		if(xcmp(s, "inf") == 0) {
 			if(aas != nil)
 				*aas = s+3;
 			goto retinf;
 		}
 	case S3:
 		if(aas != nil)
 			*aas = (char*)as;
 		goto ret0;	/* no digits found */
 	case S6:
 		s--;		/* back over +- */
 	case S5:
 		s--;		/* back over e */
 		break;
 	}
 	if(aas != nil)
 		*aas = s;
 
 	if(flag & Fdpoint)
 	while(na > 0 && a[na-1] == '0')
 		na--;
 	if(na == 0)
 		goto ret0;	/* zero */
 	a[na] = 0;
 	if(!(flag & Fdpoint))
 		dp = na;
 	if(flag & Fesign)
 		ex = -ex;
 	dp += ex;
 	if(dp < -Maxe){
 		errno = ERANGE;
 		goto ret0;	/* underflow by exp */
 	} else
 	if(dp > +Maxe)
 		goto retinf;	/* overflow by exp */
 
 	/*
 	 * normalize the decimal ascii number
 	 * to range .[5-9][0-9]* e0
 	 */
 	bp = 0;		/* binary exponent */
 	while(dp > 0)
 		divascii(a, &na, &dp, &bp);
 	while(dp < 0 || a[0] < '5')
 		mulascii(a, &na, &dp, &bp);
 
 	/* close approx by naive conversion */
 	mid[0] = 0;
 	mid[1] = 1;
 	for(i=0; (c=a[i]) != '\0'; i++) {
 		mid[0] = mid[0]*10 + (c-'0');
 		mid[1] = mid[1]*10;
 		if(i >= 8)
 			break;
 	}
 	low[0] = umuldiv(mid[0], One, mid[1]);
 	hig[0] = umuldiv(mid[0]+1, One, mid[1]);
 	for(i=1; i<Prec; i++) {
 		low[i] = 0;
 		hig[i] = One-1;
 	}
 
 	/* binary search for closest mantissa */
 	for(;;) {
 		/* mid = (hig + low) / 2 */
 		c = 0;
 		for(i=0; i<Prec; i++) {
 			mid[i] = hig[i] + low[i];
 			if(c)
 				mid[i] += One;
 			c = mid[i] & 1;
 			mid[i] >>= 1;
 		}
 		frnorm(mid);
 
 		/* compare */
 		c = fpcmp(a, mid);
 		if(c > 0) {
 			c = 1;
 			for(i=0; i<Prec; i++)
 				if(low[i] != mid[i]) {
 					c = 0;
 					low[i] = mid[i];
 				}
 			if(c)
 				break;	/* between mid and hig */
 			continue;
 		}
 		if(c < 0) {
 			for(i=0; i<Prec; i++)
 				hig[i] = mid[i];
 			continue;
 		}
 
 		/* only hard part is if even/odd roundings wants to go up */
 		c = mid[Prec-1] & (Sigbit-1);
 		if(c == Sigbit/2 && (mid[Prec-1]&Sigbit) == 0)
 			mid[Prec-1] -= c;
 		break;	/* exactly mid */
 	}
 
 	/* normal rounding applies */
 	c = mid[Prec-1] & (Sigbit-1);
 	mid[Prec-1] -= c;
 	if(c >= Sigbit/2) {
 		mid[Prec-1] += Sigbit;
 		frnorm(mid);
 	}
 	goto out;
 
 ret0:
 	return 0;
 
 retnan:
 	return __NaN();
 
 retinf:
 	/*
 	 * Unix strtod requires these.  Plan 9 would return Inf(0) or Inf(-1). */
 	errno = ERANGE;
 	if(flag & Fsign)
 		return -HUGE_VAL;
 	return HUGE_VAL;
 
 out:
 	d = 0;
 	for(i=0; i<Prec; i++)
 		d = d*One + mid[i];
 	if(flag & Fsign)
 		d = -d;
 	d = ldexp(d, bp - Prec*Nbits);
 	if(d == 0){	/* underflow */
 		errno = ERANGE;
 	}
 	return d;
 }
 
 static void
 frnorm(ulong *f)
 {
 	int i, c;
 
 	c = 0;
 	for(i=Prec-1; i>0; i--) {
 		f[i] += c;
 		c = f[i] >> Nbits;
 		f[i] &= One-1;
 	}
 	f[0] += c;
 }
 
 static int
 fpcmp(char *a, ulong* f)
 {
 	ulong tf[Prec];
 	int i, d, c;
 
 	for(i=0; i<Prec; i++)
 		tf[i] = f[i];
 
 	for(;;) {
 		/* tf *= 10 */
 		for(i=0; i<Prec; i++)
 			tf[i] = tf[i]*10;
 		frnorm(tf);
 		d = (tf[0] >> Nbits) + '0';
 		tf[0] &= One-1;
 
 		/* compare next digit */
 		c = *a;
 		if(c == 0) {
 			if('0' < d)
 				return -1;
 			if(tf[0] != 0)
 				goto cont;
 			for(i=1; i<Prec; i++)
 				if(tf[i] != 0)
 					goto cont;
 			return 0;
 		}
 		if(c > d)
 			return +1;
 		if(c < d)
 			return -1;
 		a++;
 	cont:;
 	}
 }
 
 static void
 divby(char *a, int *na, int b)
 {
 	int n, c;
 	char *p;
 
 	p = a;
 	n = 0;
 	while(n>>b == 0) {
 		c = *a++;
 		if(c == 0) {
 			while(n) {
 				c = n*10;
 				if(c>>b)
 					break;
 				n = c;
 			}
 			goto xx;
 		}
 		n = n*10 + c-'0';
 		(*na)--;
 	}
 	for(;;) {
 		c = n>>b;
 		n -= c<<b;
 		*p++ = c + '0';
 		c = *a++;
 		if(c == 0)
 			break;
 		n = n*10 + c-'0';
 	}
 	(*na)++;
 xx:
 	while(n) {
 		n = n*10;
 		c = n>>b;
 		n -= c<<b;
 		*p++ = c + '0';
 		(*na)++;
 	}
 	*p = 0;
 }
 
 static	Tab	tab1[] =
 {
 	 1,  0, "",
 	 3,  1, "7",
 	 6,  2, "63",
 	 9,  3, "511",
 	13,  4, "8191",
 	16,  5, "65535",
 	19,  6, "524287",
 	23,  7, "8388607",
 	26,  8, "67108863",
 	27,  9, "134217727",
 };
 
 static void
 divascii(char *a, int *na, int *dp, int *bp)
 {
 	int b, d;
 	Tab *t;
 
 	d = *dp;
 	if(d >= (int)(nelem(tab1)))
 		d = (int)(nelem(tab1))-1;
 	t = tab1 + d;
 	b = t->bp;
 	if(memcmp(a, t->cmp, t->siz) > 0)
 		d--;
 	*dp -= d;
 	*bp += b;
 	divby(a, na, b);
 }
 
 static void
 mulby(char *a, char *p, char *q, int b)
 {
 	int n, c;
 
 	n = 0;
 	*p = 0;
 	for(;;) {
 		q--;
 		if(q < a)
 			break;
 		c = *q - '0';
 		c = (c<<b) + n;
 		n = c/10;
 		c -= n*10;
 		p--;
 		*p = c + '0';
 	}
 	while(n) {
 		c = n;
 		n = c/10;
 		c -= n*10;
 		p--;
 		*p = c + '0';
 	}
 }
 
 static	Tab	tab2[] =
 {
 	 1,  1, "",				/* dp = 0-0 */
 	 3,  3, "125",
 	 6,  5, "15625",
 	 9,  7, "1953125",
 	13, 10, "1220703125",
 	16, 12, "152587890625",
 	19, 14, "19073486328125",
 	23, 17, "11920928955078125",
 	26, 19, "1490116119384765625",
 	27, 19, "7450580596923828125",		/* dp 8-9 */
 };
 
 static void
 mulascii(char *a, int *na, int *dp, int *bp)
 {
 	char *p;
 	int d, b;
 	Tab *t;
 
 	d = -*dp;
 	if(d >= (int)(nelem(tab2)))
 		d = (int)(nelem(tab2))-1;
 	t = tab2 + d;
 	b = t->bp;
 	if(memcmp(a, t->cmp, t->siz) < 0)
 		d--;
 	p = a + *na;
 	*bp -= b;
 	*dp += d;
 	*na += d;
 	mulby(a, p+d, p, b);
 }
 
 static int
 xcmp(char *a, char *b)
 {
 	int c1, c2;
 
 	while((c1 = *b++) != '\0') {
 		c2 = *a++;
 		if(isupper(c2))
 			c2 = tolower(c2);
 		if(c1 != c2)
 			return 1;
 	}
 	return 0;
 }