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use crate::ids::Id;
pub const NUM_BITS: usize = 256;
const BITS_PER_BYTES: usize = 8;
pub fn equal_subset(start: usize, end: usize, id1: &Id, id2: &Id) -> bool {
if end == 0 {
return true;
}
let end = end - 1;
if start > end {
return true;
}
if end >= NUM_BITS {
return false;
}
let start_index = (start / BITS_PER_BYTES) as usize;
let end_index = (end / BITS_PER_BYTES) as usize;
if start_index + 1 < end_index
&& id1.0[(start_index + 1)..end_index] != id2.0[(start_index + 1)..end_index]
{
return false;
}
let start_bit = (start % BITS_PER_BYTES) as usize;
let end_bit = (end % BITS_PER_BYTES) as usize;
let start_mask: i32 = -1 << start_bit;
let end_mask: i32 = (1 << (end_bit + 1)) - 1;
if start_index == end_index {
let mask = start_mask & end_mask;
let b1 = mask & id1.0[start_index] as i32;
let b2 = mask & id2.0[start_index] as i32;
return b1 == b2;
}
let start1 = start_mask & id1.0[start_index] as i32;
let start2 = start_mask & id2.0[start_index] as i32;
let end1 = end_mask & id1.0[end_index] as i32;
let end2 = end_mask & id2.0[end_index] as i32;
start1 == start2 && end1 == end2
}
#[test]
fn test_equal_subset() {
let id1 = Id::from_slice(&vec![0xf0, 0x0f]);
let id2 = Id::from_slice(&vec![0xf0, 0x1f]);
assert!(equal_subset(0, 12, &id1, &id2));
assert!(!equal_subset(0, 13, &id1, &id2));
let id1 = Id::from_slice(&vec![0x1f, 0xf8]);
let id2 = Id::from_slice(&vec![0x10, 0x08]);
assert!(equal_subset(4, 12, &id1, &id2));
}
pub fn first_difference_subset(start: usize, end: usize, id1: &Id, id2: &Id) -> (usize, bool) {
if end == 0 {
return (0, false);
}
let end = end - 1;
if start > end {
return (0, false);
}
if end >= NUM_BITS {
return (0, false);
}
let start_index = (start / BITS_PER_BYTES) as usize;
let end_index = (end / BITS_PER_BYTES) as usize;
let start_bit = (start % BITS_PER_BYTES) as usize;
let end_bit = (end % BITS_PER_BYTES) as usize;
let start_mask: i32 = -1 << start_bit;
let end_mask: i32 = (1 << (end_bit + 1)) - 1;
if start_index == end_index {
let mask = start_mask & end_mask;
let b1 = mask & id1.0[start_index] as i32;
let b2 = mask & id2.0[start_index] as i32;
if b1 == b2 {
return (0, false);
}
let bd = b1 ^ b2;
return (
bd.trailing_zeros() as usize + start_index * BITS_PER_BYTES,
true,
);
}
let start1 = start_mask & id1.0[start_index] as i32;
let start2 = start_mask & id2.0[start_index] as i32;
if start1 != start2 {
let bd = start1 ^ start2;
return (
bd.trailing_zeros() as usize + start_index * BITS_PER_BYTES,
true,
);
}
for idx in (start_index + 1)..end_index {
let b1 = id1.0[idx];
let b2 = id2.0[idx];
if b1 != b2 {
let bd = b1 ^ b2;
return (bd.trailing_zeros() as usize + idx * BITS_PER_BYTES, true);
}
}
let end1 = end_mask & id1.0[end_index] as i32;
let end2 = end_mask & id2.0[end_index] as i32;
if end1 != end2 {
let bd = end1 ^ end2;
return (
bd.trailing_zeros() as usize + end_index * BITS_PER_BYTES,
true,
);
}
(0, false)
}
#[test]
fn test_first_difference_subset() {
let id1 = Id::from_slice(&vec![0xf0, 0x0f]);
let id2 = Id::from_slice(&vec![0xf0, 0x1f]);
assert_eq!(first_difference_subset(0, 12, &id1, &id2), (0, false));
assert_eq!(first_difference_subset(0, 13, &id1, &id2), (12, true));
let id1 = Id::from_slice(&vec![0x10]);
let id2 = Id::from_slice(&vec![0x00]);
assert_eq!(first_difference_subset(0, 4, &id1, &id2), (0, false));
assert_eq!(first_difference_subset(0, 5, &id1, &id2), (4, true));
}
#[derive(
std::clone::Clone,
std::cmp::Eq,
std::cmp::Ord,
std::cmp::PartialEq,
std::cmp::PartialOrd,
std::fmt::Debug,
std::hash::Hash,
)]
pub enum Bit {
Zero,
One,
}
impl std::convert::From<usize> for Bit {
fn from(v: usize) -> Self {
assert!(v <= 1);
match v {
0 => Bit::Zero,
1 => Bit::One,
_ => panic!("unexpected bit value {}", v),
}
}
}
impl Bit {
pub fn as_usize(&self) -> usize {
match self {
Bit::Zero => 0,
Bit::One => 1,
}
}
}