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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package sensor provides sensor events from various movement sensors.
package sensor // import "golang.org/x/mobile/exp/sensor"
import (
"errors"
"time"
)
// Type represents a sensor type.
type Type int
var sensorNames = map[Type]string{
Accelerometer: "Accelerometer",
Gyroscope: "Gyrsocope",
Magnetometer: "Magnetometer",
}
// String returns the string representation of the sensor type.
func (t Type) String() string {
if n, ok := sensorNames[t]; ok {
return n
}
return "Unknown sensor"
}
const (
Accelerometer = Type(0)
Gyroscope = Type(1)
Magnetometer = Type(2)
)
// Event represents a sensor event.
type Event struct {
// Sensor is the type of the sensor the event is coming from.
Sensor Type
// Timestamp is a device specific event time in nanoseconds.
// Timestamps are not Unix times, they represent a time that is
// only valid for the device's default sensor.
Timestamp int64
// Data is the event data.
//
// If the event source is Accelerometer,
// - Data[0]: acceleration force in x axis in m/s^2
// - Data[1]: acceleration force in y axis in m/s^2
// - Data[2]: acceleration force in z axis in m/s^2
//
// If the event source is Gyroscope,
// - Data[0]: rate of rotation around the x axis in rad/s
// - Data[1]: rate of rotation around the y axis in rad/s
// - Data[2]: rate of rotation around the z axis in rad/s
//
// If the event source is Magnetometer,
// - Data[0]: force of gravity along the x axis in m/s^2
// - Data[1]: force of gravity along the y axis in m/s^2
// - Data[2]: force of gravity along the z axis in m/s^2
//
Data []float64
}
// Manager multiplexes sensor event data from various sensor sources.
type Manager struct {
m *manager // platform-specific implementation of the underlying manager
}
// Enable enables a sensor with the specified delay rate.
// If there are multiple sensors of type t on the device, Enable uses
// the default one.
// If there is no default sensor of type t on the device, an error returned.
// Valid sensor types supported by this package are Accelerometer,
// Gyroscope, Magnetometer and Altimeter.
func (m *Manager) Enable(t Type, delay time.Duration) error {
if m.m == nil {
m.m = new(manager)
m.m.initialize()
}
if t < 0 || int(t) >= len(sensorNames) {
return errors.New("sensor: unknown sensor type")
}
return m.m.enable(t, delay)
}
// Disable disables to feed the manager with the specified sensor.
func (m *Manager) Disable(t Type) error {
if m.m == nil {
m.m = new(manager)
m.m.initialize()
}
if t < 0 || int(t) >= len(sensorNames) {
return errors.New("sensor: unknown sensor type")
}
return m.m.disable(t)
}
// Read reads a series of events from the manager.
// It may read up to len(e) number of events, but will return
// less events if timeout occurs.
func (m *Manager) Read(e []Event) (n int, err error) {
if m.m == nil {
m.m = new(manager)
m.m.initialize()
}
return m.m.read(e)
}
// Close stops the manager and frees the related resources.
// Once Close is called, Manager becomes invalid to use.
func (m *Manager) Close() error {
if m.m == nil {
return nil
}
return m.m.close()
}