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mruby-rational: refactor float to rational conversion

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- the function `float_decode_internal` was removed
- simplified `rational_new_f()`
- do not need to call `ldexp`
- allocate less bigint objects
This commit is contained in:
Yukihiro "Matz" Matsumoto
2024-10-14 08:29:52 +09:00
parent 51b11a6919
commit 7b5608e78a
1 changed files with 32 additions and 38 deletions
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mrbgems/mruby-rational/src/rational.c
+32 -38
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@@ -306,61 +306,55 @@ mrb_rational_new(mrb_state *mrb, mrb_int nume, mrb_int deno)
#define mrb_int_fit_p(x,t) ((t)MRB_INT_MIN <= (x) && (x) <= (t)MRB_INT_MAX)
static mrb_value
float_decode_internal(mrb_state *mrb, mrb_float f, mrb_value *v, int *n)
{
f = (mrb_float)frexp_rat(f, n);
if (isinf(f)) rat_overflow(mrb);
f = (mrb_float)ldexp_rat(f, RAT_MANT_DIG);
*n -= RAT_MANT_DIG;
#ifdef RAT_BIGINT
if (mrb_int_fit_p(f, mrb_float)) return mrb_int_value(mrb, (mrb_int)f);
return mrb_bint_new_float(mrb, f);
#else
if (!mrb_int_fit_p(f, mrb_float)) rat_overflow(mrb);
return mrb_int_value(mrb, (mrb_int)f);
#endif
}
static mrb_value
int_lshift(mrb_state *mrb, mrb_value v, mrb_int n)
{
if (mrb_integer_p(v)) {
uint64_t u = (uint64_t)mrb_integer(v);
if (mrb_int_fit_p(u << n, uint64_t))
return mrb_int_value(mrb, (mrb_int)(u << n));
mrb_float f = (mrb_float)mrb_integer(v);
f *= 1<<n;
if (mrb_int_fit_p(f, mrb_float))
return mrb_int_value(mrb, (mrb_int)f);
}
#ifndef RAT_BIGINT
rat_overflow(mrb);
#else
if (!mrb_bigint_p(v)) {
v = mrb_as_bint(mrb, v);
}
return mrb_bint_lshift(mrb, v, n);
return mrb_bint_lshift(mrb, mrb_as_bint(mrb, v), n);
#endif
}
static mrb_value
rational_new_f(mrb_state *mrb, mrb_float f)
{
int n;
mrb_check_num_exact(mrb, f);
mrb_value v = float_decode_internal(mrb, f, &v, &n);
if (f == 0.0) {
return rational_new_i(mrb, 0, 1);
}
int exp;
// Extract mantissa and exponent
double mantissa = frexp_rat(f, &exp);
const mrb_int precision = ((mrb_int)1) << RAT_MANT_DIG;
if (n == 0) {
return rational_new_b(mrb, v, ONE);
}
if (n > 0)
return mrb_as_rational(mrb, int_lshift(mrb, v, n));
n = -n;
mrb_value d = int_lshift(mrb, ONE, n);
#ifdef RAT_BIGINT
if (!mrb_integer_p(v) || !mrb_integer_p(d)) {
return rational_new_b(mrb, mrb_as_bint(mrb, v), mrb_as_bint(mrb, d));
}
mrb_int nume = (mrb_int)(mantissa * precision);
mrb_int deno = precision;
if (exp > 0) {
mrb_int temp;
if (mrb_int_mul_overflow(nume, ((mrb_int)1)<<exp, &temp)) {
#ifndef RAT_BIGINT
rat_overflow(mrb);
#else
mrb_value n = int_lshift(mrb, mrb_int_value(mrb, nume), exp);
if (mrb_bigint_p(n)) {
return rational_new_b(mrb, n, mrb_int_value(mrb, deno));
}
#endif
return rational_new_i(mrb, mrb_integer(v), mrb_integer(d));
}
nume = temp;
}
else {
deno >>= exp;
}
return rational_new_i(mrb, nume, deno);
}
static mrb_float