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add copy_term/3 (#232)

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This commit is contained in:
Mark Thom
2019-11-29 00:44:23 -07:00
parent 335202b9d9
commit 9c9c484ee4
8 changed files with 81 additions and 23 deletions
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72
src/prolog/machine/copier.rs
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@@ -5,6 +5,12 @@ use std::ops::IndexMut;
type Trail = Vec<(Ref, HeapCellValue)>;
#[derive(Clone, Copy)]
pub enum AttrVarPolicy {
DeepCopy,
StripAttributes
}
pub(crate) trait CopierTarget: IndexMut<usize, Output = HeapCellValue> {
fn threshold(&self) -> usize;
fn push(&mut self, _: HeapCellValue);
@@ -13,9 +19,10 @@ pub(crate) trait CopierTarget: IndexMut<usize, Output = HeapCellValue> {
fn stack(&mut self) -> &mut AndStack;
}
pub(crate) fn copy_term<T: CopierTarget>(target: T, addr: Addr) {
let mut copy_term_state = CopyTermState::new(target);
copy_term_state.copy_term_impl(addr);
pub(crate)
fn copy_term<T: CopierTarget>(target: T, addr: Addr, attr_var_policy: AttrVarPolicy) {
let mut copy_term_state = CopyTermState::new(target, attr_var_policy);
copy_term_state.copy_term_impl(addr);
}
struct CopyTermState<T: CopierTarget> {
@@ -23,15 +30,17 @@ struct CopyTermState<T: CopierTarget> {
scan: usize,
old_h: usize,
target: T,
attr_var_policy: AttrVarPolicy
}
impl<T: CopierTarget> CopyTermState<T> {
fn new(target: T) -> Self {
fn new(target: T, attr_var_policy: AttrVarPolicy) -> Self {
CopyTermState {
trail: vec![],
scan: 0,
old_h: target.threshold(),
target,
attr_var_policy
}
}
@@ -41,6 +50,14 @@ impl<T: CopierTarget> CopyTermState<T> {
&mut self.target[scan]
}
fn attr_var_redirect_tag(&self) -> impl Fn(usize) -> Addr {
if let AttrVarPolicy::DeepCopy = self.attr_var_policy {
Addr::AttrVar
} else {
Addr::HeapCell
}
}
fn reinstantiate_var(&mut self, addr: Addr, threshold: usize) {
match addr {
Addr::HeapCell(h) => {
@@ -58,8 +75,10 @@ impl<T: CopierTarget> CopyTermState<T> {
));
}
Addr::AttrVar(h) => {
self.target[threshold] = HeapCellValue::Addr(Addr::AttrVar(threshold));
self.target[h] = HeapCellValue::Addr(Addr::AttrVar(threshold));
let redirect_tag = self.attr_var_redirect_tag();
self.target[threshold] = HeapCellValue::Addr(redirect_tag(threshold));
self.target[h] = HeapCellValue::Addr(redirect_tag(threshold));
self.trail
.push((Ref::AttrVar(h), HeapCellValue::Addr(Addr::AttrVar(h))));
}
@@ -94,10 +113,22 @@ impl<T: CopierTarget> CopyTermState<T> {
let rd = self.target.store(self.target.deref(ra));
match rd.clone() {
Addr::AttrVar(h) | Addr::HeapCell(h) if h >= self.old_h => {
Addr::AttrVar(h) if h >= self.old_h => {
let redirect_tag = self.attr_var_redirect_tag();
self.target[threshold] = HeapCellValue::Addr(redirect_tag(h));
}
Addr::HeapCell(h) if h >= self.old_h => {
self.target[threshold] = HeapCellValue::Addr(rd)
}
ra @ Addr::AttrVar(_) | ra @ Addr::HeapCell(..) | ra @ Addr::StackCell(..) => {
Addr::AttrVar(h) => {
if Addr::AttrVar(h) == rd {
self.reinstantiate_var(Addr::AttrVar(h), threshold);
} else {
let redirect_tag = self.attr_var_redirect_tag();
self.target[threshold] = HeapCellValue::Addr(redirect_tag(h));
}
}
ra @ Addr::HeapCell(..) | ra @ Addr::StackCell(..) => {
if ra == rd {
self.reinstantiate_var(ra, threshold);
} else {
@@ -121,20 +152,29 @@ impl<T: CopierTarget> CopyTermState<T> {
let rd = self.target.store(self.target.deref(addr.clone()));
match rd.clone() {
Addr::AttrVar(h) | Addr::HeapCell(h) if h >= self.old_h => {
Addr::AttrVar(h) if h >= self.old_h => {
let redirect_tag = self.attr_var_redirect_tag();
*self.value_at_scan() = HeapCellValue::Addr(redirect_tag(h));
self.scan += 1;
}
Addr::HeapCell(h) if h >= self.old_h => {
*self.value_at_scan() = HeapCellValue::Addr(rd);
self.scan += 1;
}
Addr::AttrVar(h) if addr == rd => {
let redirect_tag = self.attr_var_redirect_tag();
let threshold = self.target.threshold();
self.target
.push(HeapCellValue::Addr(Addr::AttrVar(threshold)));
let list_val = self.target[h + 1].clone();
self.target.push(list_val);
self.target
.push(HeapCellValue::Addr(redirect_tag(threshold)));
if let Addr::AttrVar(_) = redirect_tag(threshold) {
let list_val = self.target[h + 1].clone();
self.target.push(list_val);
}
self.reinstantiate_var(addr, threshold);
*self.value_at_scan() = HeapCellValue::Addr(Addr::AttrVar(threshold));
*self.value_at_scan() = HeapCellValue::Addr(redirect_tag(threshold));
}
_ if addr == rd => {
let scan = self.scan;
@@ -185,8 +225,8 @@ impl<T: CopierTarget> CopyTermState<T> {
HeapCellValue::Addr(addr) => match addr {
Addr::Lis(addr) => self.copy_list(addr),
addr @ Addr::AttrVar(_)
| addr @ Addr::HeapCell(_)
| addr @ Addr::StackCell(..) => self.copy_var(addr),
| addr @ Addr::HeapCell(_)
| addr @ Addr::StackCell(..) => self.copy_var(addr),
Addr::Str(addr) => self.copy_structure(addr),
Addr::Con(_) | Addr::DBRef(_) => self.scan += 1,
},