syncthing/lib/connections/registry/registry.go

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// Copyright (C) 2019 The Syncthing Authors.
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.
// Registry tracks connections/addresses on which we are listening on, to allow us to pick a connection/address that
// has a NAT port mapping. This also makes our outgoing port stable and same as incoming port which should allow
// better probability of punching through.
package registry
import (
"sort"
"strings"
"github.com/syncthing/syncthing/lib/sync"
)
var (
Default = New()
)
type Registry struct {
mut sync.Mutex
available map[string][]interface{}
}
func New() *Registry {
return &Registry{
mut: sync.NewMutex(),
available: make(map[string][]interface{}),
}
}
func (r *Registry) Register(scheme string, item interface{}) {
r.mut.Lock()
defer r.mut.Unlock()
r.available[scheme] = append(r.available[scheme], item)
}
func (r *Registry) Unregister(scheme string, item interface{}) {
r.mut.Lock()
defer r.mut.Unlock()
candidates := r.available[scheme]
for i, existingItem := range candidates {
if existingItem == item {
copy(candidates[i:], candidates[i+1:])
candidates[len(candidates)-1] = nil
r.available[scheme] = candidates[:len(candidates)-1]
break
}
}
}
func (r *Registry) Get(scheme string, less func(i, j interface{}) bool) interface{} {
r.mut.Lock()
defer r.mut.Unlock()
candidates := make([]interface{}, 0)
for availableScheme, items := range r.available {
// quic:// should be considered ok for both quic4:// and quic6://
if strings.HasPrefix(scheme, availableScheme) {
candidates = append(candidates, items...)
}
}
if len(candidates) == 0 {
return nil
}
sort.Slice(candidates, func(i, j int) bool {
return less(candidates[i], candidates[j])
})
return candidates[0]
}
func Register(scheme string, item interface{}) {
Default.Register(scheme, item)
}
func Unregister(scheme string, item interface{}) {
Default.Unregister(scheme, item)
}
func Get(scheme string, less func(i, j interface{}) bool) interface{} {
return Default.Get(scheme, less)
}