From: Rich Felker <dalias@aerifal.cx>
To: musl@lists.openwall.com
Subject: Re: float scanner status, upcoming release
Date: Mon, 9 Apr 2012 20:48:19 -0400 [thread overview]
Message-ID: <20120410004819.GB7281@brightrain.aerifal.cx> (raw)
In-Reply-To: <20120409191712.GA5269@brightrain.aerifal.cx>
[-- Attachment #1: Type: text/plain, Size: 170 bytes --]
Revised version of the code, in preparation to integrate with musl.
Still needs hex float support, and I want to eliminate the fscanf
dependency. Comments welcome.
Rich
[-- Attachment #2: floatscan.c --]
[-- Type: text/plain, Size: 5691 bytes --]
#define _XOPEN_SOURCE 700
#include <stdint.h>
#include <stdio.h>
#include <math.h>
#include <fenv.h>
#include <float.h>
#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
#define LD_B1B_DIG 2
#define LD_B1B_MAX 9007199, 254740991
#define KMAX 128
#else /* LDBL_MANT_DIG == 64 && LDBL_MAX_EXP == 16384 */
#define LD_B1B_DIG 3
#define LD_B1B_MAX 18, 446744073, 709551615
#define KMAX 2048
#endif
#define MASK (KMAX-1)
#if 0
static inline fast_unget(int c, FILE *f)
{
if (f->rpos) f->rpos--;
}
#undef ungetc
#define ungetc fast_unget
#endif
#undef getc
#define getc getc_unlocked
static long double decfloat(FILE *f, int c, int prec, int sign, int pok, off_t *pcnt)
{
uint32_t x[KMAX];
static const uint32_t th[] = { LD_B1B_MAX };
int i, j, k, a, z;
int rp=-1, dc=0;
int e10=0;
int e2;
long double y;
long double frac=0;
long double bias=0;
int bits=64;
int emin;
switch (prec) {
case 0:
bits = 24;
emin = -149;
break;
case 1:
bits = 53;
emin = -1074;
break;
case 2:
bits = LDBL_MANT_DIG;
emin = -16445;
break;
default:
return 0;
}
j=0;
k=0;
if (c<0) *pcnt += (c=getc(f))>=0;
/* Don't let leading zeros consume buffer space */
for (; c=='0'; *pcnt += (c=getc(f))>=0);
x[0] = 0;
for (; c-'0'<10U || c=='.'; *pcnt += (c=getc(f))>=0) {
if (c == '.') {
if (rp!=-1) break;
rp = dc;
} else if (k < KMAX) {
dc++;
if (j) x[k] = x[k]*10 + c-'0';
else x[k] = c-'0';
if (++j==9) {
k++;
j=0;
}
} else {
dc++;
x[KMAX-1] |= c-'0';
}
}
if (rp==-1) rp=dc;
if ((c|32)=='e') {
c = getc(f);
ungetc(c, f);
if (c!='+' && c!='-' && c-'0'>=10U) {
if (!pok) {
*pcnt = 0;
return 0;
} else {
--*pcnt;
}
} else {
int tmp = 0;
fscanf(f, "%d%n", &e10, &tmp);
*pcnt += tmp;
rp += e10;
/* FIXME: overflow */
}
} else if (c>=0) {
ungetc(c, f);
--*pcnt;
}
if (rp==dc && (!k || (k==1 && !j)) && (bits>30 || x[0]>>bits==0)) {
y = sign * (long double)x[0];
return y;
}
if (k<KMAX && j) {
for (; j<9; j++) x[k]*=10;
k++;
j=0;
}
a = 0;
z = k;
e2 = 0;
while (rp < 18+9*LD_B1B_DIG) {
uint32_t carry = 0;
e2 -= 29;
for (k=(z-1 & MASK); ; k=(k-1 & MASK)) {
uint64_t tmp = ((uint64_t)x[k] << 29) + carry;
if (tmp > 1000000000) {
carry = tmp / 1000000000;
x[k] = tmp % 1000000000;
} else {
carry = 0;
x[k] = tmp;
}
if (k==(z-1 & MASK) && k!=a && !x[k]) z = k;
if (k==a) break;
}
if (carry) {
rp += 9;
if (a == z) {
z = (z-1 & MASK);
x[z-1 & MASK] |= x[z];
}
a = (a-1 & MASK);
x[a] = carry;
}
}
if (rp % 9) {
static const int p10s[] = {
100000000, 10000000, 1000000, 100000,
10000, 1000, 100, 10
};
int rpm9 = rp % 9;
int p10 = p10s[rpm9-1];
uint32_t carry = 0;
for (k=a; k!=z; k=(k+1 & MASK)) {
uint32_t tmp = x[k] % p10;
x[k] = x[k]/p10 + carry;
carry = 1000000000/p10 * tmp;
if (k==a && !x[k]) {
a = (a+1 & MASK);
rp -= 9;
}
}
if (carry) {
if ((z+1 & MASK) != a) {
x[z] = carry;
z = (z+1 & MASK);
} else x[z-1 & MASK] |= 1;
}
rp += 9-rpm9;
}
for (;;) {
uint32_t carry = 0;
int sh = 1;
for (i=0; i<LD_B1B_DIG; i++) {
k = (a+i & MASK);
if (k == z || x[k] < th[i]) {
i=LD_B1B_DIG;
break;
}
if (x[a+i & MASK] > th[i]) break;
}
if (i==LD_B1B_DIG && rp==9*LD_B1B_DIG) break;
/* FIXME: find a way to compute optimal sh */
if (rp > 9+9*LD_B1B_DIG) sh = 9;
e2 += sh;
for (k=a; k!=z; k=(k+1 & MASK)) {
uint32_t tmp = x[k] & (1<<sh)-1;
x[k] = (x[k]>>sh) + carry;
carry = (1000000000>>sh) * tmp;
if (k==a && !x[k]) {
a = (a+1 & MASK);
rp -= 9;
}
}
if (carry) {
if ((z+1 & MASK) != a) {
x[z] = carry;
z = (z+1 & MASK);
} else x[z-1 & MASK] |= 1;
}
}
for (y=i=0; i<LD_B1B_DIG && (a+i & MASK)!=z; i++)
y = 1000000000.0L * y + x[a+i & MASK];
y *= sign;
if (bits > LDBL_MANT_DIG+e2-emin) {
bits = LDBL_MANT_DIG+e2-emin;
if (bits<0) bits=0;
}
if (bits < LDBL_MANT_DIG) {
bias = copysignl(scalbn(1, 2*LDBL_MANT_DIG-bits-1), y);
frac = fmodl(y, scalbn(1, LDBL_MANT_DIG-bits));
y -= frac;
y += bias;
}
if ((a+i & MASK) != z) {
uint32_t t = x[a+i & MASK];
if (t < 500000000 && (t || (a+i+1 & MASK) != z))
frac += 0.25*sign;
else if (t > 500000000)
frac += 0.75*sign;
else if (t == 500000000) {
if ((a+i+1 & MASK) == z)
frac += 0.5*sign;
else
frac += 0.75*sign;
}
}
y += frac;
y -= bias;
y = scalbnl(y, e2);
return y;
}
static long double hexfloat(FILE *f, int c, int prec, int sign, int pok, off_t *pcnt)
{
return 0;
}
long double __floatscan(FILE *f, int c, int prec, int pok, off_t *pcnt)
{
int sign = 1;
int i;
if (c<0) *pcnt += (c=getc(f))>=0;
if (c=='+' || c=='-') {
sign -= 2*(c=='-');
*pcnt += (c=getc(f))>=0;
}
for (i=0; i<8 && (c|32)=="infinity"[i]; i++)
if (i<7) c = getc(f);
if (i==3 || i==8 || (i>3 && pok)) {
if (i==3 && c>=0) ungetc(c, f);
if (i==8) *pcnt += 7;
else *pcnt += 2;
return sign * INFINITY;
}
if (!i) for (i=0; i<3 && (c|32)=="nan"[i]; i++)
if (i<3) c = getc(f);
if (i==3) {
*pcnt += 2;
return sign>0 ? NAN : -NAN;
}
if (i || c-'0'>10U) {
ungetc(c, f);
*pcnt = 0;
return -1;
}
if (c=='0') {
*pcnt += (c=getc(f))>=0;
if ((c|32) == 'x')
return hexfloat(f, -1, prec, sign, pok, pcnt);
}
return decfloat(f, c, prec, sign, pok, pcnt);
}
#include <string.h>
int main(int argc, char **argv)
{
FILE *f = 0;
if (argc>1) f = fmemopen(argv[1], strlen(argv[1]), "r");
if (!f) f = stdin;
off_t pos = 0;
long double y = __floatscan(f, -1, 0, 1, &pos);
printf("%.21Lg (read %lld)\n", y, (long long)pos);
return 0;
}
next prev parent reply other threads:[~2012-04-10 0:48 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-09 19:17 Rich Felker
2012-04-09 19:21 ` Rich Felker
2012-04-10 0:09 ` Pascal Cuoq
2012-04-10 0:36 ` Rich Felker
2012-04-10 0:48 ` Rich Felker [this message]
2012-04-10 12:15 ` Szabolcs Nagy
2012-04-10 13:02 ` Rich Felker
2012-04-10 15:24 ` Rich Felker
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