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authorMatt Joiner <anacrolix@gmail.com>2019-11-04 15:14:33 +1100
committerMatt Joiner <anacrolix@gmail.com>2019-11-04 15:14:33 +1100
commit80ec29f423aeb8f7de75c057b12b2e5cd8cb35ba (patch)
tree65b7923b152f9695a0a87dbc26a58bef1d10e29c /var.go
parentTransfer project stewardship to anacrolix (diff)
downloadstm-80ec29f423aeb8f7de75c057b12b2e5cd8cb35ba.tar.gz
stm-80ec29f423aeb8f7de75c057b12b2e5cd8cb35ba.tar.xz
Use atomic pointers for Var data
Diffstat (limited to 'var.go')
-rw-r--r--var.go30
1 files changed, 25 insertions, 5 deletions
diff --git a/var.go b/var.go
index bf48a41..2d0cb21 100644
--- a/var.go
+++ b/var.go
@@ -1,20 +1,40 @@
package stm
-import "sync"
+import (
+ "sync/atomic"
+ "unsafe"
+)
// Holds an STM variable.
type Var struct {
- mu sync.Mutex
+ state *varSnapshot
+ watchers map[*Tx]struct{}
+}
+
+func (v *Var) addr() *unsafe.Pointer {
+ return (*unsafe.Pointer)(unsafe.Pointer(&v.state))
+}
+
+func (v *Var) loadState() *varSnapshot {
+ return (*varSnapshot)(atomic.LoadPointer(v.addr()))
+}
+
+func (v *Var) changeValue(new interface{}) {
+ version := v.loadState().version
+ atomic.StorePointer(v.addr(), unsafe.Pointer(&varSnapshot{version: version + 1, val: new}))
+}
+
+type varSnapshot struct {
val interface{}
version uint64
-
- watchers map[*Tx]struct{}
}
// Returns a new STM variable.
func NewVar(val interface{}) *Var {
return &Var{
- val: val,
+ state: &varSnapshot{
+ val: val,
+ },
watchers: make(map[*Tx]struct{}),
}
}