102 lines
3.6 KiB
Rust
102 lines
3.6 KiB
Rust
use prolog::and_stack::*;
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use prolog::ast::*;
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use std::ops::IndexMut;
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pub trait CopierTarget
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{
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fn source(&self) -> usize;
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fn threshold(&self) -> usize;
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fn push(&mut self, HeapCellValue);
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fn store(&self, Addr) -> Addr;
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fn deref(&self, Addr) -> Addr;
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fn stack(&mut self) -> &mut AndStack;
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// duplicate_term(L1, L2) uses Cheney's algorithm to copy the term at
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// L1 to L2. forwarding_terms is kept to restore the innards of L1
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// after it's been copied to L2.
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fn duplicate_term(&mut self, a: Addr) where Self: IndexMut<usize, Output=HeapCellValue>
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{
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let mut forward_trail: Vec<(Ref, HeapCellValue)>= Vec::new();
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let mut scan = self.source();
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let old_h = self.threshold();
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self.push(HeapCellValue::from(a));
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while scan < self.threshold() {
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match self[scan].clone() {
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HeapCellValue::Con(_) | HeapCellValue::NamedStr(_, _) =>
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scan += 1,
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HeapCellValue::Lis(a) => {
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self[scan] = HeapCellValue::Lis(self.threshold());
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let hcv = self[a].clone();
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self.push(hcv);
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let hcv = self[a+1].clone();
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self.push(hcv);
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scan += 1;
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},
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HeapCellValue::Ref(r) => {
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let ra = Addr::from(r);
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let rd = self.store(self.deref(ra.clone()));
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match rd {
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Addr::HeapCell(hc) if hc >= old_h => {
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self[scan] = HeapCellValue::Ref(Ref::HeapCell(hc));
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scan += 1;
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},
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_ if ra == rd => {
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self[scan] = HeapCellValue::Ref(Ref::HeapCell(scan));
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match r {
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Ref::HeapCell(hc) =>
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self[hc] = HeapCellValue::Ref(Ref::HeapCell(scan)),
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Ref::StackCell(fr, sc) =>
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self.stack()[fr][sc] = Addr::HeapCell(scan)
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};
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forward_trail.push((r, HeapCellValue::Ref(r)));
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scan += 1;
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},
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_ => self[scan] = HeapCellValue::from(rd)
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}
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},
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HeapCellValue::Str(s) => {
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match self[s].clone() {
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HeapCellValue::NamedStr(arity, name) => {
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let threshold = self.threshold();
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self[scan] = HeapCellValue::Str(threshold);
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self[s] = HeapCellValue::Str(threshold);
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forward_trail.push((Ref::HeapCell(s),
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HeapCellValue::NamedStr(arity, name.clone())));
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self.push(HeapCellValue::NamedStr(arity, name));
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for i in 0 .. arity {
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let hcv = self[s + 1 + i].clone();
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self.push(hcv);
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}
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},
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HeapCellValue::Str(o) =>
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self[scan] = HeapCellValue::Str(o),
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_ => {}
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};
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scan += 1;
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}
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};
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}
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for (r, hcv) in forward_trail {
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match r {
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Ref::HeapCell(hc) => self[hc] = hcv,
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Ref::StackCell(fr, sc) => self.stack()[fr][sc] = hcv.as_addr(0)
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}
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}
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}
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}
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