1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140

use std::ops::Range;
use crate::{Btrit, Utrit, RawEncoding, RawEncodingBuf, ShiftTernary};

const TPB: usize = 4;
const BAL: i8 = 40;

#[repr(transparent)]
pub struct T4B1([()]);

impl T4B1 {
    unsafe fn make(ptr: *const i8, offset: usize, len: usize) -> *const Self {
        let len = (len << 2) | (offset % TPB);
        std::mem::transmute((ptr.offset((offset / TPB) as isize), len))
    }

    unsafe fn ptr(&self, index: usize) -> *const i8 {
        let byte_offset = (self.len_offset().1 + index) / TPB;
        (self.0.as_ptr() as *const i8).offset(byte_offset as isize)
    }

    fn len_offset(&self) -> (usize, usize) {
        (self.0.len() >> 2, self.0.len() & 0b11)
    }
}

fn extract(x: i8, elem: usize) -> Btrit {
    if elem < TPB {
        Utrit::from_u8((((x + BAL) / 3i8.pow(elem as u32)) % 3) as u8).shift()
    } else {
        unreachable!("Attempted to extract invalid element {} from balanced T4B1", elem)
    }
}

fn insert(x: i8, elem: usize, trit: Btrit) -> i8 {
    if elem < TPB {
        let utrit = trit.shift();
        let ux = x + BAL;
        let ux = ux + (utrit.into_u8() as i8 - (ux / 3i8.pow(elem as u32)) % 3) * 3i8.pow(elem as u32);
        ux - BAL
    } else {
        unreachable!("Attempted to insert invalid element {} into balanced T4B1", elem)
    }
}

impl RawEncoding for T4B1 {
    type Trit = Btrit;
    type Buf = T4B1Buf;

    fn empty() -> &'static Self {
        unsafe { &*Self::make(&[] as *const _, 0, 0) }
    }

    fn len(&self) -> usize {
        self.len_offset().0
    }

    fn as_i8_slice(&self) -> &[i8] {
        assert!(self.len_offset().1 == 0);
        unsafe { &*(Self::make(self.ptr(0), 0, (self.len() as f32 / TPB as f32).ceil() as usize) as *const _) }
    }

    unsafe fn as_i8_slice_mut(&mut self) -> &mut [i8] {
        assert!(self.len_offset().1 == 0);
        &mut *(Self::make(self.ptr(0), 0, (self.len() as f32 / TPB as f32).ceil() as usize) as *mut _)
    }

    unsafe fn get_unchecked(&self, index: usize) -> Self::Trit {
        let b = self.ptr(index).read();
        extract(b, (self.len_offset().1 + index) % TPB)
    }

    unsafe fn set_unchecked(&mut self, index: usize, trit: Self::Trit) {
        let b = self.ptr(index).read();
        let b = insert(b, (self.len_offset().1 + index) % TPB, trit);
        (self.ptr(index) as *mut i8).write(b);
    }

    unsafe fn slice_unchecked(&self, range: Range<usize>) -> &Self {
        &*Self::make(self.ptr(range.start), (self.len_offset().1 + range.start) % TPB, range.end - range.start)
    }

    unsafe fn slice_unchecked_mut(&mut self, range: Range<usize>) -> &mut Self {
        &mut *(Self::make(self.ptr(range.start), (self.len_offset().1 + range.start) % TPB, range.end - range.start) as *mut Self)
    }

    fn is_valid(b: &i8) -> bool { *b >= -BAL && *b <= BAL }

    unsafe fn from_raw_unchecked(b: &[i8], num_trits: usize) -> &Self {
        debug_assert!(num_trits <= b.len()*TPB);
        &*Self::make(b.as_ptr() as *const _, 0, num_trits)
    }

    unsafe fn from_raw_unchecked_mut(b: &mut [i8], num_trits: usize) -> &mut Self {
        debug_assert!(num_trits <= b.len()*TPB);
        &mut *(Self::make(b.as_ptr() as *const _, 0, num_trits) as *mut _)
    }
}

#[derive(Clone)]
pub struct T4B1Buf(Vec<i8>, usize);

impl RawEncodingBuf for T4B1Buf {
    type Slice = T4B1;

    fn new() -> Self {
        Self(Vec::new(), 0)
    }

    fn push(&mut self, trit: <Self::Slice as RawEncoding>::Trit) {
        if self.1 % TPB == 0 {
            self.0.push(insert(0, 0, trit));
        } else {
            let last_index = self.0.len() - 1;
            let b = unsafe { self.0.get_unchecked_mut(last_index) };
            *b = insert(*b, self.1 % TPB, trit);
        }
        self.1 += 1;
    }

    fn pop(&mut self) -> Option<<Self::Slice as RawEncoding>::Trit> {
        let val = if self.1 == 0 {
            return None;
        } else if self.1 % TPB == 1 {
            self.0.pop().map(|b| extract(b, 0))
        } else {
            let last_index = self.0.len() - 1;
            unsafe { Some(extract(*self.0.get_unchecked(last_index), (self.1 + TPB - 1) % TPB)) }
        };
        self.1 -= 1;
        val
    }

    fn as_slice(&self) -> &Self::Slice {
        unsafe { &*Self::Slice::make(self.0.as_ptr() as _, 0, self.1) }
    }

    fn as_slice_mut(&mut self) -> &mut Self::Slice {
        unsafe { &mut *(Self::Slice::make(self.0.as_ptr() as _, 0, self.1) as *mut _) }
    }
}