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// Package prioritybitmap implements a set of integers ordered by attached
// priorities.
package prioritybitmap
import (
"sync"
"github.com/anacrolix/missinggo/bitmap"
"github.com/anacrolix/missinggo/iter"
"github.com/anacrolix/missinggo/orderedmap"
)
var (
bitSets = sync.Pool{
New: func() interface{} {
return make(map[int]struct{}, 1)
},
}
)
// Maintains set of ints ordered by priority.
type PriorityBitmap struct {
mu sync.Mutex
// From priority to singleton or set of bit indices.
om orderedmap.OrderedMap
// From bit index to priority
priorities map[int]int
}
var _ bitmap.Interface = (*PriorityBitmap)(nil)
func (me *PriorityBitmap) Contains(bit int) bool {
_, ok := me.priorities[bit]
return ok
}
func (me *PriorityBitmap) Len() int {
return len(me.priorities)
}
func (me *PriorityBitmap) Clear() {
me.om = nil
me.priorities = nil
}
func (me *PriorityBitmap) deleteBit(bit int) (priority int, ok bool) {
priority, ok = me.priorities[bit]
if !ok {
return
}
switch v := me.om.Get(priority).(type) {
case int:
if v != bit {
panic("invariant broken")
}
case map[int]struct{}:
if _, ok := v[bit]; !ok {
panic("invariant broken")
}
delete(v, bit)
if len(v) != 0 {
return
}
bitSets.Put(v)
}
me.om.Unset(priority)
if me.om.Len() == 0 {
me.om = nil
}
return
}
func bitLess(l, r interface{}) bool {
return l.(int) < r.(int)
}
func (me *PriorityBitmap) lazyInit() {
me.om = orderedmap.New(func(l, r interface{}) bool {
return l.(int) < r.(int)
})
me.priorities = make(map[int]int)
}
// Returns true if the priority is changed, or the bit wasn't present.
func (me *PriorityBitmap) Set(bit int, priority int) bool {
if p, ok := me.priorities[bit]; ok && p == priority {
return false
}
if oldPriority, deleted := me.deleteBit(bit); deleted && oldPriority == priority {
panic("should have already returned")
}
if me.priorities == nil {
me.priorities = make(map[int]int)
}
me.priorities[bit] = priority
if me.om == nil {
me.om = orderedmap.New(bitLess)
}
_v, ok := me.om.GetOk(priority)
if !ok {
// No other bits with this priority, set it to a lone int.
me.om.Set(priority, bit)
return true
}
switch v := _v.(type) {
case int:
newV := bitSets.Get().(map[int]struct{})
newV[v] = struct{}{}
newV[bit] = struct{}{}
me.om.Set(priority, newV)
case map[int]struct{}:
v[bit] = struct{}{}
default:
panic(v)
}
return true
}
func (me *PriorityBitmap) Remove(bit int) bool {
me.mu.Lock()
defer me.mu.Unlock()
if _, ok := me.deleteBit(bit); !ok {
return false
}
delete(me.priorities, bit)
if len(me.priorities) == 0 {
me.priorities = nil
}
if me.om != nil && me.om.Len() == 0 {
me.om = nil
}
return true
}
func (me *PriorityBitmap) Iter(f iter.Callback) {
me.IterTyped(func(i int) bool {
return f(i)
})
}
func (me *PriorityBitmap) IterTyped(_f func(i bitmap.BitIndex) bool) bool {
me.mu.Lock()
defer me.mu.Unlock()
if me == nil || me.om == nil {
return true
}
f := func(i int) bool {
me.mu.Unlock()
defer me.mu.Lock()
return _f(i)
}
return iter.All(func(key interface{}) bool {
value := me.om.Get(key)
switch v := value.(type) {
case int:
return f(v)
case map[int]struct{}:
for i := range v {
if !f(i) {
return false
}
}
}
return true
}, me.om.Iter)
}
func (me *PriorityBitmap) IsEmpty() bool {
if me.om == nil {
return true
}
return me.om.Len() == 0
}
// ok is false if the bit is not set.
func (me *PriorityBitmap) GetPriority(bit int) (prio int, ok bool) {
prio, ok = me.priorities[bit]
return
}
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