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use super::*;
use super::conj::*;
pub fn pop(prism: AnchoredLine) -> (Unit, Unit) {
let guide = Guide::hydrate(unaliased(prism));
if guide.count <= TAIL_CAP {
pop_untailed(guide)
} else {
pop_tailed(guide)
}
}
pub fn pop_untailed(guide: Guide) -> (Unit, Unit) {
if guide.count == 0 {
(guide.segment().unit(), Unit::from(0))
} else {
let popped = guide.root[(guide.count - 1) as i32];
(guide.dec_count().store().segment().unit(), popped)
}
}
pub fn pop_tailed(guide: Guide) -> (Unit, Unit) {
let tail_count = tail_count(guide.count);
if tail_count != 1 {
let tail = {
let tail = guide.root[-1].segment();
if tail.is_aliased() {
let s = Segment::new(TAIL_CAP);
let tails = tail.at(0..tail_count);
tails.to(s);
tails.split();
if tail.unalias() == 0 {
tails.retire();
Segment::free(tail);
}
guide.root.set(-1, s.unit());
s
} else {
tail
}
};
let popped = tail[tail_count - 1];
(guide.dec_count().store().segment().unit(), popped)
} else {
pop_tailed_drained(guide)
}
}
pub fn pop_tailed_drained(guide: Guide) -> (Unit, Unit) {
let tail = guide.root[-1].segment();
let popped = tail[0];
if tail.is_aliased() {
popped.handle().split();
if tail.unalias() == 0 {
popped.handle().retire();
Segment::free(tail);
}
} else {
tail.unalias();
Segment::free(tail);
}
let tailoff = tailoff(guide.count);
let tail_path = tailoff - TAIL_CAP;
if tail_path == 0 {
(guide.dec_count().store().segment().unit(), popped)
} else {
let last_index = tail_path - 1;
let path_diff = tail_path ^ last_index;
let ret = match digit_count(last_index).cmp(&digit_count(path_diff)) {
Ordering::Less => { shrink_height(guide, tailoff) },
Ordering::Equal => { shrink_root(guide, tailoff) },
Ordering::Greater => { shrink_child(guide, tailoff) },
};
(ret, popped)
}
}
pub fn unlink_tail(mut s: Segment, height: u32) -> Segment {
for i in 0..height {
if !s.is_aliased() {
let t = s[0].segment();
s.unalias();
Segment::free(s);
s = t;
} else {
return unlink_tail_aliased(s, height - i);
}
}
s
}
pub fn unlink_tail_aliased(mut s: Segment, height: u32) -> Segment {
let tail = {
let mut t = s;
for _ in 0..height {
t = t[0].segment();
}
t
};
tail.alias();
for _ in 0..(height + 1) {
if s.unalias() == 0 {
let t = s[0].segment();
Segment::free(s);
s = t;
} else {
break
}
}
tail
}
pub fn shrink_height(guide: Guide, tailoff: u32) -> Unit {
let last_index = tailoff - 1;
let tail_path_head = guide.root[1].segment();
let path_height = trailing_zero_digit_count(last_index >> BITS);
let tail = unlink_tail(tail_path_head, path_height);
guide.root.set(-1, tail.unit());
let g = if guide.root.has_index(TAIL_CAP as i32 - 1) {
guide
} else {
let s = Segment::new(guide.root.index + TAIL_CAP);
guide.segment().at(0..(guide.root.index + 1)).to(s);
let mut g = guide;
g.prism = guide.prism.with_seg(s);
guide.segment().unalias();
Segment::free(guide.segment());
g.reroot()
};
let c = g.root[0].segment();
c.at(0..TAIL_CAP).to_offset(g.segment(), g.root.index);
if c.is_aliased() {
let contents = c.at(0..TAIL_CAP);
contents.split();
if c.unalias() == 0 {
contents.retire();
Segment::free(c);
}
} else {
c.unalias();
Segment::free(c);
}
g.dec_count().store().segment().unit()
}
pub fn shrink_root(guide: Guide, tailoff: u32) -> Unit {
let last_index = tailoff - 1;
let root_count = root_content_count(tailoff);
let tail_path_head = guide.root[(root_count - 1) as i32].segment();
let path_height = trailing_zero_digit_count(last_index >> BITS);
let tail = unlink_tail(tail_path_head, path_height);
guide.root.set(-1, tail.unit());
guide.dec_count().store().segment().unit()
}
pub fn unalias_edge_path_pop(mut curr: AnchoredLine, d: &mut Digits) -> AnchoredLine {
let count = d.count as u32;
for _i in 0..count {
let s = curr[0].segment();
let digit = d.pop();
if !s.is_aliased() {
curr = s.line_at(digit);
} else {
let t = {
let t = Segment::new(size(digit + 1));
let range = s.at(0..(digit + 1));
range.to(t);
range.alias();
if s.unalias() == 0 {
range.unalias();
Segment::free(s);
}
t
};
curr.set(0, t.unit());
curr = t.line_at(digit);
}
}
curr
}
pub fn shrink_child(guide: Guide, tailoff: u32) -> Unit {
let last_index = tailoff - 1;
let zero_count = trailing_zero_digit_count(last_index >> BITS);
let digit_count = digit_count(last_index);
let c = {
let mut d = Digits::new(last_index, digit_count, digit_count - zero_count - 1);
unalias_edge_path_pop(guide.root.offset(d.pop() as i32), &mut d)
};
let tail = unlink_tail(c[0].segment(), zero_count);
guide.root.set(-1, tail.unit());
guide.dec_count().store().segment().unit()
}