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ape: bring strtod() in line with plan9's libc version

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This commit is contained in:
cinap_lenrek 2016-09-11 23:20:55 +02:00
parent 5b66b52623
commit a0150376df
1 changed files with 53 additions and 28 deletions
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81
sys/src/ape/lib/fmt/strtod.c
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@ -27,17 +27,6 @@
#define ulong _fmtulong
typedef unsigned long ulong;
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.
@ -55,6 +44,7 @@ enum
{
Nbits = 28, /* bits safely represented in a ulong */
Nmant = 53, /* bits of precision required */
Bias = 1022,
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,
@ -62,10 +52,6 @@ enum
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 */
@ -74,6 +60,10 @@ enum
S5, /* _+#.#e +S6 #S7 */
S6, /* _+#.#e+ #S7 */
S7, /* _+#.#e+# #S7 */
Fsign = 1<<0, /* found - */
Fesign = 1<<1, /* found e- */
Fdpoint = 1<<2, /* found . */
};
static int xcmp(char*, char*);
@ -81,6 +71,8 @@ static int fpcmp(char*, ulong*);
static void frnorm(ulong*);
static void divascii(char*, int*, int*, int*);
static void mulascii(char*, int*, int*, int*);
static void divby(char*, int*, int);
static ulong umuldiv(ulong, ulong, ulong);
typedef struct Tab Tab;
struct Tab
@ -93,8 +85,8 @@ struct Tab
double
fmtstrtod(const char *as, char **aas)
{
int na, ex, dp, bp, c, i, flag, state;
ulong low[Prec], hig[Prec], mid[Prec];
int na, ona, ex, dp, bp, c, i, flag, state;
ulong low[Prec], hig[Prec], mid[Prec], num, den;
double d;
char *s, a[Ndig];
@ -225,7 +217,7 @@ fmtstrtod(const char *as, char **aas)
if(flag & Fesign)
ex = -ex;
dp += ex;
if(dp < -Maxe){
if(dp < -Maxe-Nmant/3){ /* actually -Nmant*log(2)/log(10), but Nmant/3 close enough */
errno = ERANGE;
goto ret0; /* underflow by exp */
} else
@ -241,18 +233,33 @@ fmtstrtod(const char *as, char **aas)
divascii(a, &na, &dp, &bp);
while(dp < 0 || a[0] < '5')
mulascii(a, &na, &dp, &bp);
a[na] = 0;
/*
* very small numbers are represented using
* bp = -Bias+1. adjust accordingly.
*/
if(bp < -Bias+1){
ona = na;
divby(a, &na, -bp-Bias+1);
if(na < ona){
memmove(a+ona-na, a, na);
memset(a, '0', ona-na);
na = ona;
}
a[na] = 0;
bp = -Bias+1;
}
/* close approx by naive conversion */
mid[0] = 0;
mid[1] = 1;
for(i=0; c=a[i]; i++) {
mid[0] = mid[0]*10 + (c-'0');
mid[1] = mid[1]*10;
if(i >= 8)
break;
num = 0;
den = 1;
for(i=0; i<9 && (c=a[i]); i++) {
num = num*10 + (c-'0');
den *= 10;
}
low[0] = umuldiv(mid[0], One, mid[1]);
hig[0] = umuldiv(mid[0]+1, One, mid[1]);
low[0] = umuldiv(num, One, den);
hig[0] = umuldiv(num+1, One, den);
for(i=1; i<Prec; i++) {
low[i] = 0;
hig[i] = One-1;
@ -386,7 +393,7 @@ fpcmp(char *a, ulong* f)
}
static void
divby(char *a, int *na, int b)
_divby(char *a, int *na, int b)
{
int n, c;
char *p;
@ -428,6 +435,18 @@ xx:
*p = 0;
}
static void
divby(char *a, int *na, int b)
{
while(b > 9){
_divby(a, na, 9);
a[*na] = 0;
b -= 9;
}
if(b > 0)
_divby(a, na, b);
}
static Tab tab1[] =
{
1, 0, "",
@ -536,3 +555,9 @@ xcmp(char *a, char *b)
}
return 0;
}
static ulong
umuldiv(ulong a, ulong b, ulong c)
{
return ((uvlong)a * (uvlong)b) / c;
}