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math.unsigned: fix rsh() for uint256 too, add tests (#24865)

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Mike 2025-07-08 17:22:45 +03:00 committed by GitHub
parent bb7f9f2562
commit 09e1edbd17
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2 changed files with 36 additions and 10 deletions
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35
vlib/math/unsigned/uint256.v
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@ -230,17 +230,32 @@ pub fn (u Uint256) quo_rem_64(v u64) (Uint256, u64) {
} }
// rsh returns a new Uint256 that has been right bit shifted // rsh returns a new Uint256 that has been right bit shifted
pub fn (u Uint256) rsh(n_ u32) Uint256 { pub fn (u Uint256) rsh(n u32) Uint256 {
mut n := n_ mut s := Uint256{}
if n > 128 { if n == 0 {
return Uint256{u.hi.rsh(n - 128), uint128_zero} s.lo = u.lo
s.hi = u.hi
} else if n >= 256 {
s.lo = uint128_zero
s.hi = uint128_zero
} else if n == 128 {
s.hi = uint128_zero
s.lo = u.hi
} else if n > 128 {
s.hi = uint128_zero
s.lo = u.hi.rsh(n - 128)
} else if n == 64 {
s.lo = Uint128{u.lo.hi, u.hi.lo}
s.hi = Uint128{u.hi.hi, 0}
} else if n > 64 {
shift := n - 64
s.lo = Uint128{u.lo.hi >> shift | u.hi.lo << (64 - shift), u.hi.lo >> shift | u.hi.hi << (64 - shift)}
s.hi = Uint128{u.hi.hi >> shift, 0}
} else {
s.lo = Uint128{u.lo.lo >> n | u.lo.hi << (64 - n), u.lo.hi >> n | u.hi.lo << (64 - n)}
s.hi = Uint128{u.hi.lo >> n | u.hi.hi << (64 - n), u.hi.hi >> n}
} }
return s
if n > 64 {
n -= 64
return Uint256{Uint128{u.lo.hi >> n | u.hi.lo << (64 - n), u.hi.lo >> n | u.hi.hi << (64 - n)}, Uint128{u.hi.hi >> n, 0}}
}
return Uint256{Uint128{u.lo.lo >> n | u.lo.hi << (64 - n), u.lo.hi >> n | u.hi.lo << (64 - n)}, Uint128{u.hi.lo >> n | u.hi.hi << (64 - n), u.hi.hi >> n}}
} }
// lsh returns a new Uint256 that has been left bit shifted // lsh returns a new Uint256 that has been left bit shifted

11
vlib/math/unsigned/uint256_test.v
View File

@ -280,3 +280,14 @@ fn test_separators() {
fn test_new() { fn test_new() {
assert unsigned.uint256_new(unsigned.uint128_max, unsigned.uint128_max) == unsigned.uint256_max assert unsigned.uint256_new(unsigned.uint128_max, unsigned.uint128_max) == unsigned.uint256_max
} }
fn test_rsh() {
a := unsigned.uint256_from_dec_str('115792089237316195423570985008687907853269984665640564039457584007913129639935')!
assert a.str() == a.rsh(0).str()
assert '57896044618658097711785492504343953926634992332820282019728792003956564819967' == a.rsh(1).str()
assert '6277101735386680763835789423207666416102355444464034512895' == a.rsh(64).str()
assert '91343852333181432387730302044767688728495783935' == a.rsh(100).str()
assert '340282366920938463463374607431768211455' == a.rsh(128).str()
assert '170141183460469231731687303715884105727' == a.rsh(129).str()
assert unsigned.uint256_zero == a.rsh(256)
}