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gap.go
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gap.go
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package bluetooth
import (
"errors"
"time"
)
var (
errScanning = errors.New("bluetooth: a scan is already in progress")
errNotScanning = errors.New("bluetooth: there is no scan in progress")
errAdvertisementPacketTooBig = errors.New("bluetooth: advertisement packet overflows")
)
// MACAddress contains a Bluetooth address which is a MAC address.
type MACAddress struct {
// MAC address of the Bluetooth device.
MAC
isRandom bool
}
// IsRandom if the address is randomly created.
func (mac MACAddress) IsRandom() bool {
return mac.isRandom
}
// SetRandom if is a random address.
func (mac *MACAddress) SetRandom(val bool) {
mac.isRandom = val
}
// Set the address
func (mac *MACAddress) Set(val string) {
m, err := ParseMAC(val)
if err != nil {
return
}
mac.MAC = m
}
// AdvertisementOptions configures an advertisement instance. More options may
// be added over time.
type AdvertisementOptions struct {
// The (complete) local name that will be advertised. Optional, omitted if
// this is a zero-length string.
LocalName string
// ServiceUUIDs are the services (16-bit or 128-bit) that are broadcast as
// part of the advertisement packet, in data types such as "complete list of
// 128-bit UUIDs".
ServiceUUIDs []UUID
// Interval in BLE-specific units. Create an interval by using NewDuration.
Interval Duration
// ManufacturerData stores Advertising Data.
// Keys are the Manufacturer ID to associate with the data.
ManufacturerData map[uint16]interface{}
}
// Duration is the unit of time used in BLE, in 0.625µs units. This unit of time
// is used throughout the BLE stack.
type Duration uint16
// NewDuration returns a new Duration, in units of 0.625µs. It is used both for
// advertisement intervals and for connection parameters.
func NewDuration(interval time.Duration) Duration {
// Convert an interval to units of 0.625µs.
return Duration(uint64(interval / (625 * time.Microsecond)))
}
// Connection is a numeric identifier that indicates a connection handle.
type Connection uint16
// ScanResult contains information from when an advertisement packet was
// received. It is passed as a parameter to the callback of the Scan method.
type ScanResult struct {
// Bluetooth address of the scanned device.
Address Address
// RSSI the last time a packet from this device has been received.
RSSI int16
// The data obtained from the advertisement data, which may contain many
// different properties.
// Warning: this data may only stay valid until the next event arrives. If
// you need any of the fields to stay alive until after the callback
// returns, copy them.
AdvertisementPayload
}
// AdvertisementPayload contains information obtained during a scan (see
// ScanResult). It is provided as an interface as there are two possible
// implementations: an implementation that works with raw data (usually on
// low-level BLE stacks) and an implementation that works with structured data.
type AdvertisementPayload interface {
// LocalName is the (complete or shortened) local name of the device.
// Please note that many devices do not broadcast a local name, but may
// broadcast other data (e.g. manufacturer data or service UUIDs) with which
// they may be identified.
LocalName() string
// HasServiceUUID returns true whether the given UUID is present in the
// advertisement payload as a Service Class UUID. It checks both 16-bit
// UUIDs and 128-bit UUIDs.
HasServiceUUID(UUID) bool
// Bytes returns the raw advertisement packet, if available. It returns nil
// if this data is not available.
Bytes() []byte
// ManufacturerData returns a map with all the manufacturer data present in the
//advertising. IT may be empty.
ManufacturerData() map[uint16][]byte
}
// AdvertisementFields contains advertisement fields in structured form.
type AdvertisementFields struct {
// The LocalName part of the advertisement (either the complete local name
// or the shortened local name).
LocalName string
// ServiceUUIDs are the services (16-bit or 128-bit) that are broadcast as
// part of the advertisement packet, in data types such as "complete list of
// 128-bit UUIDs".
ServiceUUIDs []UUID
// ManufacturerData is the manufacturer data of the advertisement.
ManufacturerData map[uint16][]byte
}
// advertisementFields wraps AdvertisementFields to implement the
// AdvertisementPayload interface. The methods to implement the interface (such
// as LocalName) cannot be implemented on AdvertisementFields because they would
// conflict with field names.
type advertisementFields struct {
AdvertisementFields
}
// LocalName returns the underlying LocalName field.
func (p *advertisementFields) LocalName() string {
return p.AdvertisementFields.LocalName
}
// HasServiceUUID returns true whether the given UUID is present in the
// advertisement payload as a Service Class UUID.
func (p *advertisementFields) HasServiceUUID(uuid UUID) bool {
for _, u := range p.AdvertisementFields.ServiceUUIDs {
if u == uuid {
return true
}
}
return false
}
// Bytes returns nil, as structured advertisement data does not have the
// original raw advertisement data available.
func (p *advertisementFields) Bytes() []byte {
return nil
}
// ManufacturerData returns the underlying ManufacturerData field.
func (p *advertisementFields) ManufacturerData() map[uint16][]byte {
return p.AdvertisementFields.ManufacturerData
}
// rawAdvertisementPayload encapsulates a raw advertisement packet. Methods to
// get the data (such as LocalName()) will parse just the needed field. Scanning
// the data should be fast as most advertisement packets only have a very small
// (3 or so) amount of fields.
type rawAdvertisementPayload struct {
data [31]byte
len uint8
}
// Bytes returns the raw advertisement packet as a byte slice.
func (buf *rawAdvertisementPayload) Bytes() []byte {
return buf.data[:buf.len]
}
// findField returns the data of a specific field in the advertisement packet.
//
// See this list of field types:
// https://www.bluetooth.com/specifications/assigned-numbers/generic-access-profile/
func (buf *rawAdvertisementPayload) findField(fieldType byte) []byte {
data := buf.Bytes()
for len(data) >= 2 {
fieldLength := data[0]
if int(fieldLength)+1 > len(data) {
// Invalid field length.
return nil
}
if fieldType == data[1] {
return data[2 : fieldLength+1]
}
data = data[fieldLength+1:]
}
return nil
}
// LocalName returns the local name (complete or shortened) in the advertisement
// payload.
func (buf *rawAdvertisementPayload) LocalName() string {
b := buf.findField(9) // Complete Local Name
if len(b) != 0 {
return string(b)
}
b = buf.findField(8) // Shortened Local Name
if len(b) != 0 {
return string(b)
}
return ""
}
// HasServiceUUID returns true whether the given UUID is present in the
// advertisement payload as a Service Class UUID. It checks both 16-bit UUIDs
// and 128-bit UUIDs.
func (buf *rawAdvertisementPayload) HasServiceUUID(uuid UUID) bool {
if uuid.Is16Bit() {
b := buf.findField(0x03) // Complete List of 16-bit Service Class UUIDs
if len(b) == 0 {
b = buf.findField(0x02) // Incomplete List of 16-bit Service Class UUIDs
}
uuid := uuid.Get16Bit()
for i := 0; i < len(b)/2; i++ {
foundUUID := uint16(b[i*2]) | (uint16(b[i*2+1]) << 8)
if uuid == foundUUID {
return true
}
}
return false
} else {
b := buf.findField(0x07) // Complete List of 128-bit Service Class UUIDs
if len(b) == 0 {
b = buf.findField(0x06) // Incomplete List of 128-bit Service Class UUIDs
}
uuidBuf1 := uuid.Bytes()
for i := 0; i < len(b)/16; i++ {
uuidBuf2 := b[i*16 : i*16+16]
match := true
for i, c := range uuidBuf1 {
if c != uuidBuf2[i] {
match = false
break
}
}
if match {
return true
}
}
return false
}
}
// ManufacturerData returns the manufacturer data in the advertisement payload.
func (buf *rawAdvertisementPayload) ManufacturerData() map[uint16][]byte {
mData := make(map[uint16][]byte)
data := buf.Bytes()
for len(data) >= 2 {
fieldLength := data[0]
if int(fieldLength)+1 > len(data) {
// Invalid field length.
return nil
}
// If this is the manufacturer data
if byte(0xFF) == data[1] {
mData[uint16(data[2])+(uint16(data[3])<<8)] = data[4 : fieldLength+1]
}
data = data[fieldLength+1:]
}
return mData
}
// reset restores this buffer to the original state.
func (buf *rawAdvertisementPayload) reset() {
// The data is not reset (only the length), because with a zero length the
// data is undefined.
buf.len = 0
}
// addFromOptions constructs a new advertisement payload (assumed to be empty
// before the call) from the advertisement options. It returns true if it fits,
// false otherwise.
func (buf *rawAdvertisementPayload) addFromOptions(options AdvertisementOptions) (ok bool) {
buf.addFlags(0x06)
if options.LocalName != "" {
if !buf.addCompleteLocalName(options.LocalName) {
return false
}
}
// TODO: if there are multiple 16-bit UUIDs, they should be listed in
// one field.
// This is not possible for 128-bit service UUIDs (at least not in
// legacy advertising) because of the 31-byte advertisement packet
// limit.
for _, uuid := range options.ServiceUUIDs {
if !buf.addServiceUUID(uuid) {
return false
}
}
if len(options.ManufacturerData) > 0 {
buf.addManufacturerData(options.ManufacturerData)
}
return true
}
// addManufacturerData adds manufacturer data ([]byte) entries to the advertisement payload.
func (buf *rawAdvertisementPayload) addManufacturerData(manufacturerData map[uint16]interface{}) (ok bool) {
payloadData := buf.Bytes()
for manufacturerID, rawData := range manufacturerData {
data := rawData.([]byte)
// Check if the manufacturer ID is within the range of 16 bits (0-65535).
if manufacturerID > 0xFFFF {
// Invalid manufacturer ID.
return false
}
fieldLength := len(data) + 3
// Build manufacturer ID parts
manufacturerDataBit := byte(0xFF)
manufacturerIDPart1 := byte(manufacturerID & 0xFF)
manufacturerIDPart2 := byte((manufacturerID >> 8) & 0xFF)
payloadData = append(payloadData, byte(fieldLength), manufacturerDataBit, manufacturerIDPart1, manufacturerIDPart2)
payloadData = append(payloadData, data...)
}
buf.len = uint8(len(payloadData))
copy(buf.data[:], payloadData)
return true
}
// addFlags adds a flags field to the advertisement buffer. It returns true on
// success (the flags can be added) and false on failure.
func (buf *rawAdvertisementPayload) addFlags(flags byte) (ok bool) {
if int(buf.len)+3 > len(buf.data) {
return false // flags don't fit
}
buf.data[buf.len] = 2 // length of field (including type)
buf.data[buf.len+1] = 0x01 // type, 0x01 means Flags
buf.data[buf.len+2] = flags // the flags
buf.len += 3
return true
}
// addCompleteLocalName adds the Complete Local Name field to the advertisement
// buffer. It returns true on success (the name fits) and false on failure.
func (buf *rawAdvertisementPayload) addCompleteLocalName(name string) (ok bool) {
if int(buf.len)+len(name)+2 > len(buf.data) {
return false // name doesn't fit
}
buf.data[buf.len] = byte(len(name) + 1) // length of field (including type)
buf.data[buf.len+1] = 9 // type, 0x09 means Complete Local name
copy(buf.data[buf.len+2:], name) // copy the name into the buffer
buf.len += byte(len(name) + 2)
return true
}
// addServiceUUID adds a Service Class UUID (16-bit or 128-bit). It has
// currently only been designed for adding single UUIDs: multiple UUIDs are
// stored in separate fields without joining them together in one field.
func (buf *rawAdvertisementPayload) addServiceUUID(uuid UUID) (ok bool) {
// Don't bother with 32-bit UUID support, it doesn't seem to be used in
// practice.
if uuid.Is16Bit() {
if int(buf.len)+4 > len(buf.data) {
return false // UUID doesn't fit.
}
shortUUID := uuid.Get16Bit()
buf.data[buf.len+0] = 3 // length of field, including type
buf.data[buf.len+1] = 0x03 // type, 0x03 means "Complete List of 16-bit Service Class UUIDs"
buf.data[buf.len+2] = byte(shortUUID)
buf.data[buf.len+3] = byte(shortUUID >> 8)
buf.len += 4
return true
} else {
if int(buf.len)+18 > len(buf.data) {
return false // UUID doesn't fit.
}
buf.data[buf.len+0] = 17 // length of field, including type
buf.data[buf.len+1] = 0x07 // type, 0x07 means "Complete List of 128-bit Service Class UUIDs"
rawUUID := uuid.Bytes()
copy(buf.data[buf.len+2:], rawUUID[:])
buf.len += 18
return true
}
}
// ConnectionParams are used when connecting to a peripherals.
type ConnectionParams struct {
// The timeout for the connection attempt. Not used during the rest of the
// connection. If no duration is specified, a default timeout will be used.
ConnectionTimeout Duration
// Minimum and maximum connection interval. The shorter the interval, the
// faster data can travel between both devices but also the more power they
// will draw. If no intervals are specified, a default connection interval
// will be used.
MinInterval Duration
MaxInterval Duration
}