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author | Matt Joiner <anacrolix@gmail.com> | 2019-11-04 15:14:33 +1100 |
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committer | Matt Joiner <anacrolix@gmail.com> | 2019-11-04 15:14:33 +1100 |
commit | 80ec29f423aeb8f7de75c057b12b2e5cd8cb35ba (patch) | |
tree | 65b7923b152f9695a0a87dbc26a58bef1d10e29c /var.go | |
parent | Transfer project stewardship to anacrolix (diff) | |
download | stm-80ec29f423aeb8f7de75c057b12b2e5cd8cb35ba.tar.gz stm-80ec29f423aeb8f7de75c057b12b2e5cd8cb35ba.tar.xz |
Use atomic pointers for Var data
Diffstat (limited to 'var.go')
-rw-r--r-- | var.go | 30 |
1 files changed, 25 insertions, 5 deletions
@@ -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{}), } } |