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[ruby/bigdecimal] Fix uint64 conversion

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Stop using logarithm to compute the number of components.
Instead, use the theoretical maximum number of components for buffer,
and count up the actual number of components during conversion.

https://github.com/ruby/bigdecimal/commit/9067b353ac
This commit is contained in:
Kenta Murata 2021-01-30 13:00:03 +09:00
parent 868d66e0b5
commit 4e2e1d6093
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GPG Key ID: CEFE8AFB6081B062
2 changed files with 27 additions and 12 deletions
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23
ext/bigdecimal/bigdecimal.c
View File

@ -2727,23 +2727,22 @@ rb_uint64_convert_to_BigDecimal(uint64_t uval, RB_UNUSED_VAR(size_t digs), int r
vp->frac[0] = (DECDIG)uval;
}
else {
const size_t len = (size_t)ceil(log10((double)uval) / BASE_FIG);
vp = VpAllocReal(len);
vp->MaxPrec = len;
vp->Prec = len;
vp->exponent = len;
VpSetSign(vp, 1);
size_t i, ntz = 0;
for (i = 0; i < len; ++i) {
DECDIG buf[BIGDECIMAL_INT64_MAX_LENGTH] = {0,};
size_t exp = 0, ntz = 0;
for (; uval > 0; ++exp) {
DECDIG r = uval % BASE;
vp->frac[len - i - 1] = r;
if (r == 0) ++ntz;
buf[BIGDECIMAL_INT64_MAX_LENGTH - exp - 1] = r;
uval /= BASE;
}
vp->Prec -= ntz;
const size_t len = exp - ntz;
vp = VpAllocReal(len);
vp->MaxPrec = len;
vp->Prec = len;
vp->exponent = exp;
VpSetSign(vp, 1);
MEMCPY(vp->frac, buf + BIGDECIMAL_INT64_MAX_LENGTH - exp, DECDIG, len);
}
return BigDecimal_wrap_struct(obj, vp);

16
ext/bigdecimal/bigdecimal.h
View File

@ -54,9 +54,25 @@
#if SIZEOF_DECDIG == 4
# define BIGDECIMAL_BASE ((DECDIG)1000000000U)
# define BIGDECIMAL_COMPONENT_FIGURES 9
/*
* The number of components required for a 64-bit integer.
*
* INT64_MAX: 9_223372036_854775807
* UINT64_MAX: 18_446744073_709551615
*/
# define BIGDECIMAL_INT64_MAX_LENGTH 3
#elif SIZEOF_DECDIG == 2
# define BIGDECIMAL_BASE ((DECDIG)10000U)
# define BIGDECIMAL_COMPONENT_FIGURES 4
/*
* The number of components required for a 64-bit integer.
*
* INT64_MAX: 922_3372_0368_5477_5807
* UINT64_MAX: 1844_6744_0737_0955_1615
*/
# define BIGDECIMAL_INT64_MAX_LENGTH 5
#else
# error Unknown size of DECDIG
#endif