81 lines
1.2 KiB
Go
81 lines
1.2 KiB
Go
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package alloclim
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import "sync"
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// Manages reservations sharing a common allocation limit.
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type Limiter struct {
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// Maximum outstanding allocation space.
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Max int64
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initOnce sync.Once
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mu sync.Mutex
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// Current unallocated space.
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value int64
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// Reservations waiting to in the order they arrived.
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waiting []*Reservation
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}
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func (me *Limiter) initValue() {
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me.value = me.Max
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}
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func (me *Limiter) init() {
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me.initOnce.Do(func() {
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me.initValue()
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})
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}
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func (me *Limiter) Reserve(n int64) *Reservation {
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r := &Reservation{
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l: me,
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n: n,
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}
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me.init()
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me.mu.Lock()
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if n <= me.value {
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me.value -= n
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r.granted.Set()
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} else {
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me.waiting = append(me.waiting, r)
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}
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me.mu.Unlock()
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return r
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}
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func (me *Limiter) doWakesLocked() {
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for {
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if len(me.waiting) == 0 {
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break
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}
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r := me.waiting[0]
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switch {
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case r.cancelled.IsSet():
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case r.n <= me.value:
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if r.wake() {
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me.value -= r.n
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}
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default:
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return
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}
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me.waiting = me.waiting[1:]
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}
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}
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func (me *Limiter) doWakes() {
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me.mu.Lock()
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me.doWakesLocked()
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me.mu.Unlock()
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}
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func (me *Limiter) addValue(n int64) {
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me.mu.Lock()
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me.value += n
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me.doWakesLocked()
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me.mu.Unlock()
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}
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func (me *Limiter) Value() int64 {
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me.mu.Lock()
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defer me.mu.Unlock()
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return me.value
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}
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