diff options
Diffstat (limited to 'src/internal/floatscan.c')
| -rw-r--r-- | src/internal/floatscan.c | 35 |
1 files changed, 27 insertions, 8 deletions
diff --git a/src/internal/floatscan.c b/src/internal/floatscan.c index 28a09c25..0e1f6d06 100644 --- a/src/internal/floatscan.c +++ b/src/internal/floatscan.c @@ -59,12 +59,15 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po int i, j, k, a, z; long long lrp=-1, dc=0; long long e10=0; + int lnz = 0; int gotdig = 0; int rp; int e2; long double y; long double frac=0; long double bias=0; + static const int p10s[] = { 10, 100, 1000, 10000, + 100000, 1000000, 10000000, 100000000 }; j=0; k=0; @@ -78,6 +81,7 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po if (lrp!=-1) break; lrp = dc; } else if (k < KMAX-2) { + if (c!='0') lnz = dc; dc++; if (j) x[k] = x[k]*10 + c-'0'; else x[k] = c-'0'; @@ -114,9 +118,11 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po return 0; } - if (!x[0]) - return sign * 0.0; - if (lrp==dc && (!k || (k==1 && !j)) && (bits>30 || x[0]>>bits==0)) + /* Handle zero specially to avoid nasty special cases later */ + if (!x[0]) return sign * 0.0; + + /* Optimize small integers (w/no exponent) and over/under-flow */ + if (lrp==dc && dc<10 && (bits>30 || x[0]>>bits==0)) return sign * (long double)x[0]; if (lrp > -emin/2) { errno = ERANGE; @@ -127,6 +133,7 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po return sign * LDBL_MIN * LDBL_MIN; } + /* Align incomplete final B1B digit */ if (k<KMAX && j) { for (; j<9; j++) x[k]*=10; k++; @@ -138,13 +145,19 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po e2 = 0; rp = lrp; + /* Optimize small to mid-size integers (even in exp. notation) */ + if (lnz<9 && lnz<=rp && rp < 18) { + if (rp == 9) return sign * (long double)x[0]; + if (rp < 9) return sign * (long double)x[0] / p10s[8-rp]; + int bitlim = bits-3*(int)(rp-9); + if (bitlim>30 || x[0]>>bitlim==0) + return sign * (long double)x[0] * p10s[rp-10]; + } + + /* Align radix point to B1B digit boundary */ if (rp % 9) { - static const int p10s[] = { - 100000000, 10000000, 1000000, 100000, - 10000, 1000, 100, 10 - }; int rpm9 = rp>=0 ? rp%9 : rp%9+9; - int p10 = p10s[rpm9-1]; + int p10 = p10s[8-rpm9]; uint32_t carry = 0; for (k=a; k!=z; k++) { uint32_t tmp = x[k] % p10; @@ -159,6 +172,7 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po rp += 9-rpm9; } + /* Upscale until desired number of bits are left of radix point */ while (rp < 9*LD_B1B_DIG || (rp == 9*LD_B1B_DIG && x[a]<th[0])) { uint32_t carry = 0; e2 -= 29; @@ -185,6 +199,7 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po } } + /* Downscale until exactly number of bits are left of radix point */ for (;;) { uint32_t carry = 0; int sh = 1; @@ -218,6 +233,7 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po } } + /* Assemble desired bits into floating point variable */ for (y=i=0; i<LD_B1B_DIG; i++) { if ((a+i & MASK)==z) x[z=(z+1 & MASK)] = 0; y = 1000000000.0L * y + x[a+i & MASK]; @@ -225,11 +241,13 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po y *= sign; + /* Limit precision for denormal results */ if (bits > LDBL_MANT_DIG+e2-emin) { bits = LDBL_MANT_DIG+e2-emin; if (bits<0) bits=0; } + /* Calculate bias term to force rounding, move out lower bits */ 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)); @@ -237,6 +255,7 @@ static long double decfloat(FILE *f, int c, int bits, int emin, int sign, int po y += bias; } + /* Process tail of decimal input so it can affect rounding */ if ((a+i & MASK) != z) { uint32_t t = x[a+i & MASK]; if (t < 500000000 && (t || (a+i+1 & MASK) != z)) |