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big: Split up int_mod_bits (res = val % (1 << bits))

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Jeroen van Rijn
2021-08-11 20:59:53 +02:00
parent c3db24f834
commit d4a03acbc3
2 changed files with 47 additions and 37 deletions
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core/math/big/basic.odin
+4 -32
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@@ -321,39 +321,11 @@ lcm :: proc { int_lcm, };
remainder = numerator % (1 << bits)
*/
int_mod_bits :: proc(remainder, numerator: ^Int, bits: int) -> (err: Error) {
if err = clear_if_uninitialized(remainder); err != nil { return err; }
if err = clear_if_uninitialized(numerator); err != nil { return err; }
if remainder == nil || numerator == nil { return .Invalid_Pointer; }
if err = clear_if_uninitialized(remainder, numerator); err != nil { return err; }
if bits < 0 { return .Invalid_Argument; }
if bits == 0 { return zero(remainder); }
/*
If the modulus is larger than the value, return the value.
*/
err = copy(remainder, numerator);
if bits >= (numerator.used * _DIGIT_BITS) || err != nil {
return;
}
/*
Zero digits above the last digit of the modulus.
*/
zero_count := (bits / _DIGIT_BITS);
zero_count += 0 if (bits % _DIGIT_BITS == 0) else 1;
/*
Zero remainder. Special case, can't use `zero_unused`.
*/
if zero_count > 0 {
mem.zero_slice(remainder.digit[zero_count:]);
}
/*
Clear the digit that is not completely outside/inside the modulus.
*/
remainder.digit[bits / _DIGIT_BITS] &= DIGIT(1 << DIGIT(bits % _DIGIT_BITS)) - DIGIT(1);
return clamp(remainder);
return #force_inline internal_int_mod_bits(remainder, numerator, bits);
}
mod_bits :: proc { int_mod_bits, };
mod_bits :: proc { int_mod_bits, };