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vm: implement reference counter

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It is convenient to have all reference-counting logic
in a separate struct.
This commit is contained in:
Evgenii Stratonikov 2020-05-12 16:05:10 +03:00
parent 81cbf183af
commit af2abedd86
5 changed files with 116 additions and 75 deletions
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58
pkg/vm/stack.go
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@ -125,9 +125,7 @@ type Stack struct {
top Element
name string
len int
itemCount map[StackItem]int
size *int
refs *refCounter
}
// NewStack returns a new stack name by the given name.
@ -138,8 +136,7 @@ func NewStack(n string) *Stack {
s.top.next = &s.top
s.top.prev = &s.top
s.len = 0
s.itemCount = make(map[StackItem]int)
s.size = new(int)
s.refs = newRefCounter()
return s
}
@ -171,58 +168,11 @@ func (s *Stack) insert(e, at *Element) *Element {
e.stack = s
s.len++
s.updateSizeAdd(e.value)
s.refs.Add(e.value)
return e
}
func (s *Stack) updateSizeAdd(item StackItem) {
*s.size++
switch item.(type) {
case *ArrayItem, *StructItem, *MapItem:
if s.itemCount[item]++; s.itemCount[item] > 1 {
return
}
switch t := item.(type) {
case *ArrayItem, *StructItem:
for _, it := range item.Value().([]StackItem) {
s.updateSizeAdd(it)
}
case *MapItem:
for i := range t.value {
s.updateSizeAdd(t.value[i].Value)
}
}
}
}
func (s *Stack) updateSizeRemove(item StackItem) {
*s.size--
switch item.(type) {
case *ArrayItem, *StructItem, *MapItem:
if s.itemCount[item] > 1 {
s.itemCount[item]--
return
}
delete(s.itemCount, item)
switch t := item.(type) {
case *ArrayItem, *StructItem:
for _, it := range item.Value().([]StackItem) {
s.updateSizeRemove(it)
}
case *MapItem:
for i := range t.value {
s.updateSizeRemove(t.value[i].Value)
}
}
}
}
// InsertAt inserts the given item (n) deep on the stack.
// Be very careful using it and _always_ check both e and n before invocation
// as it will silently do wrong things otherwise.
@ -300,7 +250,7 @@ func (s *Stack) Remove(e *Element) *Element {
e.stack = nil
s.len--
s.updateSizeRemove(e.value)
s.refs.Remove(e.value)
return e
}