diff options
Diffstat (limited to 'Python/dtoa.c')
| -rw-r--r-- | Python/dtoa.c | 109 |
1 files changed, 90 insertions, 19 deletions
diff --git a/Python/dtoa.c b/Python/dtoa.c index 44dc01f1d5..8996a7210c 100644 --- a/Python/dtoa.c +++ b/Python/dtoa.c @@ -204,7 +204,24 @@ typedef union { double d; ULong L[2]; } U; MAX_ABS_EXP in absolute value get truncated to +-MAX_ABS_EXP. MAX_ABS_EXP should fit into an int. */ #ifndef MAX_ABS_EXP -#define MAX_ABS_EXP 19999U +#define MAX_ABS_EXP 1100000000U +#endif +/* Bound on length of pieces of input strings in _Py_dg_strtod; specifically, + this is used to bound the total number of digits ignoring leading zeros and + the number of digits that follow the decimal point. Ideally, MAX_DIGITS + should satisfy MAX_DIGITS + 400 < MAX_ABS_EXP; that ensures that the + exponent clipping in _Py_dg_strtod can't affect the value of the output. */ +#ifndef MAX_DIGITS +#define MAX_DIGITS 1000000000U +#endif + +/* Guard against trying to use the above values on unusual platforms with ints + * of width less than 32 bits. */ +#if MAX_ABS_EXP > INT_MAX +#error "MAX_ABS_EXP should fit in an int" +#endif +#if MAX_DIGITS > INT_MAX +#error "MAX_DIGITS should fit in an int" #endif /* The following definition of Storeinc is appropriate for MIPS processors. @@ -265,6 +282,16 @@ 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 +1513,36 @@ 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) { @@ -1498,6 +1555,7 @@ _Py_dg_strtod(const char *s00, char **se) Long L; BCinfo bc; Bigint *bb, *bb1, *bd, *bd0, *bs, *delta; + size_t ndigits, fraclen; dval(&rv) = 0.; @@ -1520,39 +1578,52 @@ _Py_dg_strtod(const char *s00, char **se) c = *++s; lz = s != s1; - /* Point s0 at the first nonzero digit (if any). nd0 will be the position - of the point relative to s0. nd will be the total number of digits - ignoring leading zeros. */ + /* Point s0 at the first nonzero digit (if any). fraclen will be the + number of digits between the decimal point and the end of the + digit string. ndigits will be the total number of digits ignoring + leading zeros. */ s0 = s1 = s; while ('0' <= c && c <= '9') c = *++s; - nd0 = nd = s - s1; + ndigits = s - s1; + fraclen = 0; /* Parse decimal point and following digits. */ if (c == '.') { c = *++s; - if (!nd) { + if (!ndigits) { s1 = s; while (c == '0') c = *++s; lz = lz || s != s1; - nd0 -= s - s1; + fraclen += (s - s1); s0 = s; } s1 = s; while ('0' <= c && c <= '9') c = *++s; - nd += s - s1; + ndigits += s - s1; + fraclen += s - s1; + } + + /* Now lz is true if and only if there were leading zero digits, and + ndigits gives the total number of digits ignoring leading zeros. A + valid input must have at least one digit. */ + if (!ndigits && !lz) { + if (se) + *se = (char *)s00; + goto parse_error; } - /* Now lz is true if and only if there were leading zero digits, and nd - gives the total number of digits ignoring leading zeros. A valid input - must have at least one digit. */ - if (!nd && !lz) { + /* Range check ndigits and fraclen to make sure that they, and values + computed with them, can safely fit in an int. */ + if (ndigits > MAX_DIGITS || fraclen > MAX_DIGITS) { if (se) *se = (char *)s00; goto parse_error; } + nd = (int)ndigits; + nd0 = (int)ndigits - (int)fraclen; /* Parse exponent. */ e = 0; @@ -1886,20 +1957,20 @@ _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 +2126,7 @@ _Py_dg_strtod(const char *s00, char **se) + Exp_msk1 ; word1(&rv) = 0; - dsign = 0; + /* dsign = 0; */ break; } } @@ -2092,7 +2163,7 @@ _Py_dg_strtod(const char *s00, char **se) goto undfl; } } - dsign = 1 - dsign; + /* dsign = 1 - dsign; */ break; } if ((aadj = ratio(delta, bs)) <= 2.) { |