85 lines
1.8 KiB
Go
85 lines
1.8 KiB
Go
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// Copyright © 2016 Abcum Ltd
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package db
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import (
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"context"
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"fmt"
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"sync"
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"sync/atomic"
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)
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type mutex struct {
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m sync.Map
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l sync.Mutex
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}
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type value struct {
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v int
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r int64
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w int64
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l sync.RWMutex
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}
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func (m *mutex) Lock(ctx context.Context, key fmt.Stringer) {
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m.l.Lock()
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_, v := m.item(ctx, key)
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if v.v < vers(ctx) {
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m.l.Unlock()
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panic(errRaceCondition)
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}
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atomic.AddInt64(&v.w, 1)
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m.l.Unlock()
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v.l.Lock()
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}
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func (m *mutex) RLock(ctx context.Context, key fmt.Stringer) {
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m.l.Lock()
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_, v := m.item(ctx, key)
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atomic.AddInt64(&v.r, 1)
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m.l.Unlock()
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v.l.RLock()
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}
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func (m *mutex) Unlock(ctx context.Context, key fmt.Stringer) {
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m.l.Lock()
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defer m.l.Unlock()
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k, v := m.item(ctx, key)
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if w := atomic.LoadInt64(&v.w); w > 0 {
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if w := atomic.AddInt64(&v.w, -1); w <= 0 {
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m.m.Delete(k)
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}
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v.l.Unlock()
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}
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}
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func (m *mutex) RUnlock(ctx context.Context, key fmt.Stringer) {
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m.l.Lock()
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defer m.l.Unlock()
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k, v := m.item(ctx, key)
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if r := atomic.LoadInt64(&v.r); r > 0 {
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if r := atomic.AddInt64(&v.r, -1); r <= 0 {
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m.m.Delete(k)
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}
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v.l.RUnlock()
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}
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}
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func (m *mutex) item(ctx context.Context, key fmt.Stringer) (string, *value) {
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k := key.String()
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v, _ := m.m.LoadOrStore(k, &value{v: vers(ctx)})
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return k, v.(*value)
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}
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