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group.go
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group.go
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package peerstream
import (
"errors"
"sync"
"unsafe"
)
// ErrGroupNotFound signals no such group exists
var ErrGroupNotFound = errors.New("group not found")
// Group is an object used to associate a group of
// Streams, Connections, and Listeners. It can be anything,
// it is meant to work like a KeyType in maps
type Group interface{}
// Groupable is an interface for a set of objects that can
// be assigned groups: Streams, Connections, and Listeners.
// Objects inherit groups (e.g. a Stream inherits the groups
// of its parent Connection, and in turn that of its Listener).
type Groupable interface {
// Groups returns the groups this object belongs to
Groups() []Group
// InGroup returns whether this object belongs to a Group
InGroup(g Group) bool
// AddGroup adds this object to a group
AddGroup(g Group)
}
// groupSet is a struct designed to be embedded and
// give things group memebership
type groupSet struct {
m map[Group]struct{}
sync.RWMutex
}
func (gs *groupSet) Add(g Group) {
gs.Lock()
defer gs.Unlock()
gs.m[g] = struct{}{}
}
func (gs *groupSet) Remove(g Group) {
gs.Lock()
defer gs.Unlock()
delete(gs.m, g)
}
func (gs *groupSet) Has(g Group) bool {
gs.RLock()
defer gs.RUnlock()
_, ok := gs.m[g]
return ok
}
func (gs *groupSet) Groups() []Group {
gs.RLock()
defer gs.RUnlock()
out := make([]Group, 0, len(gs.m))
for k := range gs.m {
out = append(out, k)
}
return out
}
// AddSet adds all elements in another set.
func (gs *groupSet) AddSet(gs2 *groupSet) {
// acquire locks in order
p1 := uintptr(unsafe.Pointer(gs))
p2 := uintptr(unsafe.Pointer(gs2))
switch {
case p1 < p2:
gs.Lock()
gs2.RLock()
defer gs.Unlock()
defer gs2.RUnlock()
case p1 > p2:
gs2.Lock()
gs.Lock()
defer gs2.Unlock()
defer gs.Unlock()
default:
return // they're the same!
}
for g := range gs2.m {
gs.m[g] = struct{}{}
}
}