diff options
Diffstat (limited to 'Python/dtoa.c')
| -rw-r--r-- | Python/dtoa.c | 54 |
1 files changed, 47 insertions, 7 deletions
diff --git a/Python/dtoa.c b/Python/dtoa.c index 44dc01f..83861ac 100644 --- a/Python/dtoa.c +++ b/Python/dtoa.c @@ -265,6 +265,16 @@ typedef union { double d; ULong L[2]; } U; #define Big0 (Frac_mask1 | Exp_msk1*(DBL_MAX_EXP+Bias-1)) #define Big1 0xffffffff +/* Standard NaN used by _Py_dg_stdnan. */ + +#define NAN_WORD0 0x7ff80000 +#define NAN_WORD1 0 + +/* Bits of the representation of positive infinity. */ + +#define POSINF_WORD0 0x7ff00000 +#define POSINF_WORD1 0 + /* struct BCinfo is used to pass information from _Py_dg_strtod to bigcomp */ typedef struct BCinfo BCinfo; @@ -1486,6 +1496,36 @@ bigcomp(U *rv, const char *s0, BCinfo *bc) return 0; } +/* Return a 'standard' NaN value. + + There are exactly two quiet NaNs that don't arise by 'quieting' signaling + NaNs (see IEEE 754-2008, section 6.2.1). If sign == 0, return the one whose + sign bit is cleared. Otherwise, return the one whose sign bit is set. +*/ + +double +_Py_dg_stdnan(int sign) +{ + U rv; + word0(&rv) = NAN_WORD0; + word1(&rv) = NAN_WORD1; + if (sign) + word0(&rv) |= Sign_bit; + return dval(&rv); +} + +/* Return positive or negative infinity, according to the given sign (0 for + * positive infinity, 1 for negative infinity). */ + +double +_Py_dg_infinity(int sign) +{ + U rv; + word0(&rv) = POSINF_WORD0; + word1(&rv) = POSINF_WORD1; + return sign ? -dval(&rv) : dval(&rv); +} + double _Py_dg_strtod(const char *s00, char **se) { @@ -1886,20 +1926,20 @@ _Py_dg_strtod(const char *s00, char **se) bd2++; /* At this stage bd5 - bb5 == e == bd2 - bb2 + bbe, bb2 - bs2 == 1, - and bs == 1, so: + and bs == 1, so: tdv == bd * 10**e = bd * 2**(bbe - bb2 + bd2) * 5**(bd5 - bb5) srv == bb * 2**bbe = bb * 2**(bbe - bb2 + bb2) - 0.5 ulp(srv) == 2**(bbe-1) = bs * 2**(bbe - bb2 + bs2) + 0.5 ulp(srv) == 2**(bbe-1) = bs * 2**(bbe - bb2 + bs2) - It follows that: + It follows that: M * tdv = bd * 2**bd2 * 5**bd5 M * srv = bb * 2**bb2 * 5**bb5 M * 0.5 ulp(srv) = bs * 2**bs2 * 5**bb5 - for some constant M. (Actually, M == 2**(bb2 - bbe) * 5**bb5, but - this fact is not needed below.) + for some constant M. (Actually, M == 2**(bb2 - bbe) * 5**bb5, but + this fact is not needed below.) */ /* Remove factor of 2**i, where i = min(bb2, bd2, bs2). */ @@ -2055,7 +2095,7 @@ _Py_dg_strtod(const char *s00, char **se) + Exp_msk1 ; word1(&rv) = 0; - dsign = 0; + /* dsign = 0; */ break; } } @@ -2092,7 +2132,7 @@ _Py_dg_strtod(const char *s00, char **se) goto undfl; } } - dsign = 1 - dsign; + /* dsign = 1 - dsign; */ break; } if ((aadj = ratio(delta, bs)) <= 2.) { |