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0ef4b55d8d
Add RWMutex to protect concurrent map access in Set, Unset, and ForEach methods. Change New() to return *U pointer type for proper synchronization. Signed-off-by: Cangming H <cangmingh@gmail.com>
69 lines
1.2 KiB
Go
69 lines
1.2 KiB
Go
// Package uniq keeps track of "thing" that are either "todo" or "done". Multiple
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// identical events will only be processed once.
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package uniq
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import "sync"
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// U keeps track of item to be done.
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type U struct {
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mu sync.RWMutex
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u map[string]item
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}
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type item struct {
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state int // either todo or done
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f func() error // function to be executed.
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}
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// New returns a new initialized U.
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func New() *U { return &U{u: make(map[string]item)} }
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// Set sets function f in U under key. If the key already exists it is not overwritten.
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func (u *U) Set(key string, f func() error) {
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// Read lock for check
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u.mu.RLock()
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_, exists := u.u[key]
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u.mu.RUnlock()
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if exists {
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return
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}
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// Write lock for modification
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u.mu.Lock()
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defer u.mu.Unlock()
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// Double-check to avoid TOCTOU
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if _, ok := u.u[key]; ok {
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return
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}
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u.u[key] = item{todo, f}
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}
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// Unset removes the key.
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func (u *U) Unset(key string) {
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u.mu.Lock()
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defer u.mu.Unlock()
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delete(u.u, key)
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}
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// ForEach iterates over u and executes f for each element that is 'todo' and sets it to 'done'.
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func (u *U) ForEach() error {
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u.mu.Lock()
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defer u.mu.Unlock()
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for k, v := range u.u {
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if v.state == todo {
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v.f()
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}
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v.state = done
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u.u[k] = v
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}
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return nil
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}
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const (
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todo = 1
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done = 2
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)
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