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memo.go
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memo.go
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package mgutil
import (
"sync"
)
type memo struct {
sync.Mutex
k, v interface{}
}
func (m *memo) value() interface{} {
m.Lock()
defer m.Unlock()
return m.v
}
func (m *memo) read(new func() interface{}) interface{} {
m.Lock()
defer m.Unlock()
if m.v != nil {
return m.v
}
m.v = new()
return m.v
}
type Memo struct {
mu sync.Mutex
ml []*memo
}
func (m *Memo) index(k interface{}) (int, *memo) {
for i, p := range m.ml {
if p.k == k {
return i, p
}
}
return -1, nil
}
func (m *Memo) memo(k interface{}) *memo {
m.mu.Lock()
defer m.mu.Unlock()
_, p := m.index(k)
if p == nil {
p = &memo{k: k}
m.ml = append(m.ml, p)
}
return p
}
func (m *Memo) Read(k interface{}, new func() interface{}) interface{} {
if m == nil {
return new()
}
return m.memo(k).read(new)
}
func (m *Memo) Del(k interface{}) {
if m == nil {
return
}
m.mu.Lock()
defer m.mu.Unlock()
i, _ := m.index(k)
if i < 0 {
return
}
m.ml[i] = m.ml[len(m.ml)-1]
m.ml[len(m.ml)-1] = nil
m.ml = m.ml[:len(m.ml)-1]
}
func (m *Memo) Clear() {
if m == nil {
return
}
m.mu.Lock()
defer m.mu.Unlock()
m.ml = nil
}
func (m *Memo) Values() map[interface{}]interface{} {
if m == nil {
return nil
}
m.mu.Lock()
defer m.mu.Unlock()
vals := make(map[interface{}]interface{}, len(m.ml))
for k, p := range m.ml {
if v := p.value(); v != nil {
vals[k] = v
}
}
return vals
}