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registry.go
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registry.go
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// Copyright (C) 2017 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package bind
import (
"context"
"sync"
"github.com/google/gapid/core/context/keys"
"github.com/google/gapid/core/data/id"
"github.com/google/gapid/core/log"
)
type (
registryKeyTy string
propertyKey struct {
d Device
k interface{}
}
)
const registryKey = registryKeyTy("registryKeyID")
// PutRegistry attaches a registry to a Context.
func PutRegistry(ctx context.Context, m *Registry) context.Context {
return keys.WithValue(ctx, registryKey, m)
}
// GetRegistry retrieves the registry from a context previously annotated by
// PutRegistry.
func GetRegistry(ctx context.Context) *Registry {
val := ctx.Value(registryKey)
if val == nil {
panic(string(registryKey + " not present"))
}
return val.(*Registry)
}
// Registry is holds a list of registered devices. It provides methods for
// listening for devices that are added to and removed from the device.
type Registry struct {
sync.Mutex
devices []Device
properties map[propertyKey]interface{}
listeners map[DeviceListener]struct{}
}
// NewRegistry returns a newly constructed Registry.
func NewRegistry() *Registry {
return &Registry{
listeners: make(map[DeviceListener]struct{}),
properties: make(map[propertyKey]interface{}),
}
}
// DeviceListener is the interface implemented by types that respond to devices
// being added to and removed from the registry.
type DeviceListener interface {
OnDeviceAdded(context.Context, Device)
OnDeviceRemoved(context.Context, Device)
}
// NewDeviceListener returns a DeviceListener that delegates calls on to
// onDeviceAdded and onDeviceRemoved.
func NewDeviceListener(onDeviceAdded, onDeviceRemoved func(context.Context, Device)) DeviceListener {
return &funcDeviceListener{onDeviceAdded, onDeviceRemoved}
}
// funcDeviceListener is an implementatation of DeviceListener that delegates
// calls on to the field functions.
type funcDeviceListener struct {
onAdded func(context.Context, Device)
onRemoved func(context.Context, Device)
}
func (l funcDeviceListener) OnDeviceAdded(ctx context.Context, d Device) {
if f := l.onAdded; f != nil {
f(ctx, d)
}
}
func (l funcDeviceListener) OnDeviceRemoved(ctx context.Context, d Device) {
if f := l.onRemoved; f != nil {
f(ctx, d)
}
}
// Listen registers l to be called whenever a device is added to or removed from
// the registry. l will be unregistered when the returned function is called.
func (r *Registry) Listen(l DeviceListener) (unregister func()) {
r.Lock()
r.listeners[l] = struct{}{}
r.Unlock()
return func() {
r.Lock()
delete(r.listeners, l)
r.Unlock()
}
}
// Device looks up the device with the specified identifier.
// If no device with the specified identifier was registered with the Registry
// then nil is returner.
func (r *Registry) Device(id id.ID) Device {
r.Lock()
defer r.Unlock()
for _, d := range r.devices {
if d.Instance().Id.ID() == id {
return d
}
}
return nil
}
// Devices returns the list of devices registered with the Registry.
func (r *Registry) Devices() []Device {
r.Lock()
defer r.Unlock()
out := make([]Device, len(r.devices))
copy(out, r.devices)
return out
}
// DefaultDevice returns the first device registered with the Registry.
func (r *Registry) DefaultDevice() Device {
r.Lock()
defer r.Unlock()
if len(r.devices) == 0 {
return nil
}
return r.devices[0]
}
// AddDevice registers the device dev with the Registry.
func (r *Registry) AddDevice(ctx context.Context, d Device) {
if d != nil {
r.Lock()
defer r.Unlock()
for _, t := range r.devices {
if t == d {
return // already added
}
}
ctx := log.V{"device": d}.Bind(ctx)
log.I(ctx, "Adding new device")
r.devices = append(r.devices, d)
for l := range r.listeners {
l.OnDeviceAdded(ctx, d)
}
}
}
// RemoveDevice unregisters the device d with the Registry.
func (r *Registry) RemoveDevice(ctx context.Context, d Device) {
if d != nil {
r.Lock()
defer r.Unlock()
for i, t := range r.devices {
if t == d {
ctx := log.V{"device": d}.Bind(ctx)
log.I(ctx, "Removing existing device")
copy(r.devices[i:], r.devices[i+1:])
r.devices = r.devices[:len(r.devices)-1]
for l := range r.listeners {
l.OnDeviceRemoved(ctx, d)
}
}
}
}
}
// DeviceProperty returns the property with the key k for the device d,
// previously set with SetDeviceProperty. If the property for the device does
// not exist then nil is returned.
func (r *Registry) DeviceProperty(ctx context.Context, d Device, k interface{}) interface{} {
r.Lock()
defer r.Unlock()
return r.properties[propertyKey{d, k}]
}
// SetDeviceProperty sets the property with the key k to the value v for the
// device d. This property can be retrieved with DeviceProperty.
// Properties will persist in the registry even when the device has not been
// added or has been removed.
func (r *Registry) SetDeviceProperty(ctx context.Context, d Device, k, v interface{}) {
r.Lock()
defer r.Unlock()
r.properties[propertyKey{d, k}] = v
}