21100ebc19
Support both 16-bit and 128-bit UUIDs on both Linux and Nordic chips.
227 lines
7.7 KiB
Go
227 lines
7.7 KiB
Go
package bluetooth
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import "errors"
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var (
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errScanning = errors.New("bluetooth: a scan is already in progress")
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errNotScanning = errors.New("bluetooth: there is no scan in progress")
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errAdvertisementPacketTooBig = errors.New("bluetooth: advertisement packet overflows")
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)
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// AdvertisementOptions configures an advertisement instance. More options may
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// be added over time.
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type AdvertisementOptions struct {
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// The (complete) local name that will be advertised. Optional, omitted if
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// this is a zero-length string.
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LocalName string
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// ServiceUUIDs are the services (16-bit or 128-bit) that are broadcast as
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// part of the advertisement packet, in data types such as "complete list of
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// 128-bit UUIDs".
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ServiceUUIDs []UUID
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// Interval in BLE-specific units. Create an interval by using
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// NewAdvertiseInterval.
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Interval AdvertisementInterval
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}
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// AdvertisementInterval is the advertisement interval in 0.625µs units.
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type AdvertisementInterval uint32
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// NewAdvertisementInterval returns a new advertisement interval, based on an
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// interval in milliseconds.
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func NewAdvertisementInterval(intervalMillis uint32) AdvertisementInterval {
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// Convert an interval to units of
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return AdvertisementInterval(intervalMillis * 8 / 5)
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}
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// Connection is a numeric identifier that indicates a connection handle.
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type Connection uint16
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// ScanResult contains information from when an advertisement packet was
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// received. It is passed as a parameter to the callback of the Scan method.
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type ScanResult struct {
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// MAC address of the scanned device.
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Address MAC
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// RSSI the last time a packet from this device has been received.
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RSSI int16
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// The data obtained from the advertisement data, which may contain many
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// different properties.
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// Warning: this data may only stay valid until the next event arrives. If
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// you need any of the fields to stay alive until after the callback
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// returns, copy them.
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AdvertisementPayload
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}
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// AdvertisementPayload contains information obtained during a scan (see
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// ScanResult). It is provided as an interface as there are two possible
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// implementations: an implementation that works with raw data (usually on
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// low-level BLE stacks) and an implementation that works with structured data.
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type AdvertisementPayload interface {
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// LocalName is the (complete or shortened) local name of the device.
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// Please note that many devices do not broadcast a local name, but may
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// broadcast other data (e.g. manufacturer data or service UUIDs) with which
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// they may be identified.
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LocalName() string
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// Bytes returns the raw advertisement packet, if available. It returns nil
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// if this data is not available.
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Bytes() []byte
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}
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// AdvertisementFields contains advertisement fields in structured form.
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type AdvertisementFields struct {
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// The LocalName part of the advertisement (either the complete local name
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// or the shortened local name).
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LocalName string
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}
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// advertisementFields wraps AdvertisementFields to implement the
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// AdvertisementPayload interface. The methods to implement the interface (such
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// as LocalName) cannot be implemented on AdvertisementFields because they would
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// conflict with field names.
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type advertisementFields struct {
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AdvertisementFields
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}
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// LocalName returns the underlying LocalName field.
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func (p *advertisementFields) LocalName() string {
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return p.AdvertisementFields.LocalName
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}
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// Bytes returns nil, as structured advertisement data does not have the
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// original raw advertisement data available.
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func (p *advertisementFields) Bytes() []byte {
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return nil
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}
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// rawAdvertisementPayload encapsulates a raw advertisement packet. Methods to
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// get the data (such as LocalName()) will parse just the needed field. Scanning
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// the data should be fast as most advertisement packets only have a very small
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// (3 or so) amount of fields.
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type rawAdvertisementPayload struct {
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data [31]byte
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len uint8
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}
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// Bytes returns the raw advertisement packet as a byte slice.
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func (buf *rawAdvertisementPayload) Bytes() []byte {
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return buf.data[:buf.len]
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}
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// findField returns the data of a specific field in the advertisement packet.
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func (buf *rawAdvertisementPayload) findField(fieldType byte) []byte {
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data := buf.Bytes()
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for len(data) >= 2 {
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fieldLength := data[0]
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if int(fieldLength)+1 > len(data) {
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// Invalid field length.
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return nil
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}
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if fieldType == data[1] {
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return data[2 : fieldLength+1]
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}
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data = data[fieldLength+1:]
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}
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return nil
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}
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// LocalName returns the local name (complete or shortened) in the advertisement
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// payload.
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func (buf *rawAdvertisementPayload) LocalName() string {
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b := buf.findField(9) // Complete Local Name
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if len(b) != 0 {
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println("complete")
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return string(b)
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}
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b = buf.findField(8) // Shortened Local Name
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if len(b) != 0 {
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println("shortened")
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return string(b)
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}
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return ""
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}
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// addFromOptions constructs a new advertisement payload (assumed to be empty
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// before the call) from the advertisement options. It returns true if it fits,
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// false otherwise.
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func (buf *rawAdvertisementPayload) addFromOptions(options AdvertisementOptions) (ok bool) {
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buf.addFlags(0x06)
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if options.LocalName != "" {
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if !buf.addCompleteLocalName(options.LocalName) {
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return false
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}
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}
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// TODO: if there are multiple 16-bit UUIDs, they should be listed in
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// one field.
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// This is not possible for 128-bit service UUIDs (at least not in
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// legacy advertising) because of the 31-byte advertisement packet
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// limit.
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for _, uuid := range options.ServiceUUIDs {
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if !buf.addServiceUUID(uuid) {
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return false
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}
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}
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return true
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}
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// addFlags adds a flags field to the advertisement buffer. It returns true on
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// success (the flags can be added) and false on failure.
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func (buf *rawAdvertisementPayload) addFlags(flags byte) (ok bool) {
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if int(buf.len)+3 > len(buf.data) {
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return false // flags don't fit
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}
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buf.data[buf.len] = 2 // length of field (including type)
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buf.data[buf.len+1] = 0x01 // type, 0x01 means Flags
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buf.data[buf.len+2] = flags // the flags
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buf.len += 3
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return true
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}
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// addCompleteLocalName adds the Complete Local Name field to the advertisement
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// buffer. It returns true on success (the name fits) and false on failure.
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func (buf *rawAdvertisementPayload) addCompleteLocalName(name string) (ok bool) {
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if int(buf.len)+len(name)+2 > len(buf.data) {
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return false // name doesn't fit
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}
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buf.data[buf.len] = byte(len(name) + 1) // length of field (including type)
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buf.data[buf.len+1] = 9 // type, 0x09 means Complete Local name
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copy(buf.data[buf.len+2:], name) // copy the name into the buffer
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buf.len += byte(len(name) + 2)
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return true
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}
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// addServiceUUID adds a Service Class UUID (16-bit or 128-bit). It has
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// currently only been designed for adding single UUIDs: multiple UUIDs are
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// stored in separate fields without joining them together in one field.
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func (buf *rawAdvertisementPayload) addServiceUUID(uuid UUID) (ok bool) {
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// Don't bother with 32-bit UUID support, it doesn't seem to be used in
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// practice.
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if uuid.Is16Bit() {
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if int(buf.len)+4 > len(buf.data) {
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return false // UUID doesn't fit.
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}
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shortUUID := uuid.Get16Bit()
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buf.data[buf.len+0] = 3 // length of field, including type
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buf.data[buf.len+1] = 0x03 // type, 0x03 means "Complete List of 16-bit Service Class UUIDs"
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buf.data[buf.len+2] = byte(shortUUID)
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buf.data[buf.len+3] = byte(shortUUID >> 8)
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buf.len += 4
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return true
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} else {
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if int(buf.len)+18 > len(buf.data) {
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return false // UUID doesn't fit.
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}
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buf.data[buf.len+0] = 17 // length of field, including type
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buf.data[buf.len+1] = 0x07 // type, 0x07 means "Complete List of 128-bit Service Class UUIDs"
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rawUUID := uuid.Bytes()
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copy(buf.data[buf.len+2:], rawUUID[:])
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buf.len += 18
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return true
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}
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}
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