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Merge pull request #6420 from mlgudi/fix-math-big-powmod-int-mul-high

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Fix two bugs in `core:math/big` modular exponentiation
This commit is contained in:
Jeroen van Rijn
2026-03-15 11:26:28 +01:00
committed by GitHub
parent 3e80523f7d f82fbc9405
commit fcac43e08f
2 changed files with 15 additions and 6 deletions
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2
core/math/big/prime.odin
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@@ -101,7 +101,7 @@ internal_int_power_modulo :: proc(res, G, X, P: ^Int, allocator := context.alloc
If the modulus is odd or dr != 0 use the montgomery method.
*/
if internal_int_is_odd(P) || dr != 0 {
return _private_int_exponent_mod(res, G, X, P, dr)
return _private_int_exponent_mod_fast(res, G, X, P, dr)
}
/*

19
core/math/big/private.odin
View File

@@ -439,8 +439,14 @@ _private_int_mul_high :: proc(dest, a, b: ^Int, digits: int, allocator := contex
return _private_int_mul_high_comba(dest, a, b, digits)
}
internal_grow(dest, a.used + b.used + 1) or_return
dest.used = a.used + b.used + 1
/*
Set up temporary output `Int`, which we'll swap for `dest` when done.
*/
t := &Int{}
internal_grow(t, a.used + b.used + 1) or_return
t.used = a.used + b.used + 1
pa := a.used
pb := b.used
@@ -451,20 +457,23 @@ _private_int_mul_high :: proc(dest, a, b: ^Int, digits: int, allocator := contex
/*
Calculate the double precision result.
*/
r := _WORD(dest.digit[ix + iy]) + _WORD(a.digit[ix]) * _WORD(b.digit[iy]) + _WORD(carry)
r := _WORD(t.digit[ix + iy]) + _WORD(a.digit[ix]) * _WORD(b.digit[iy]) + _WORD(carry)
/*
Get the lower part.
*/
dest.digit[ix + iy] = DIGIT(r & _WORD(_MASK))
t.digit[ix + iy] = DIGIT(r & _WORD(_MASK))
/*
Carry the carry.
*/
carry = DIGIT(r >> _WORD(_DIGIT_BITS))
}
dest.digit[ix + pb] = carry
t.digit[ix + pb] = carry
}
internal_swap(dest, t)
internal_destroy(t)
return internal_clamp(dest)
}