// PrepareWrite requests the server to prepare to write the value of an attribute.
// The server will respond to this request with a Prepare Write Response, so that
// the Client can verify that the value was received correctly.
// [Vol 3, Part F, 3.4.6.1 & 3.4.6.2]
func (c *Client) PrepareWrite(handle uint16, offset uint16, value []byte) (uint16, uint16, []byte, error) {
if len(value) > c.l2c.TxMTU()-5 {
return 0, 0, nil, ErrInvalidArgument
}
// Acquire and reuse the txBuf, and release it after usage.
txBuf := <-c.chTxBuf
defer func() { c.chTxBuf <- txBuf }()
req := PrepareWriteRequest(txBuf[:5+len(value)])
req.SetAttributeOpcode()
req.SetAttributeHandle(handle)
req.SetValueOffset(offset)
b, err := c.sendReq(req)
if err != nil {
return 0, 0, nil, err
}
// Convert and validate the response.
rsp := PrepareWriteResponse(b)
switch {
case rsp[0] == ErrorResponseCode && len(rsp) == 5:
return 0, 0, nil, ble.ATTError(rsp[4])
case rsp[0] == ErrorResponseCode && len(rsp) != 5:
fallthrough
case rsp[0] != rsp.AttributeOpcode():
fallthrough
case len(rsp) < 5:
return 0, 0, nil, ErrInvalidResponse
}
return rsp.AttributeHandle(), rsp.ValueOffset(), rsp.PartAttributeValue(), nil
}
// ExecuteWrite requests the server to write or cancel the write of all the prepared
// values currently held in the prepare queue from this Client. This request shall be
// handled by the server as an atomic operation. [Vol 3, Part F, 3.4.6.3 & 3.4.6.4]
func (c *Client) ExecuteWrite(flags uint8) error {
// Acquire and reuse the txBuf, and release it after usage.
txBuf := <-c.chTxBuf
defer func() { c.chTxBuf <- txBuf }()
req := ExecuteWriteRequest(txBuf[:1])
req.SetAttributeOpcode()
req.SetFlags(flags)
b, err := c.sendReq(req)
if err != nil {
return err
}
// Convert and validate the response.
rsp := ExecuteWriteResponse(b)
switch {
case rsp[0] == ErrorResponseCode && len(rsp) == 5:
return ble.ATTError(rsp[4])
case rsp[0] == ErrorResponseCode && len(rsp) == 5:
fallthrough
case rsp[0] != rsp.AttributeOpcode():
return ErrInvalidResponse
}
return nil
}
// Write requests the server to write the value of an attribute and acknowledge that
// this has been achieved in a Write Response. [Vol 3, Part F, 3.4.5.1 & 3.4.5.2]
func (c *Client) Write(handle uint16, value []byte) error {
if len(value) > c.l2c.TxMTU()-3 {
return ErrInvalidArgument
}
// Acquire and reuse the txBuf, and release it after usage.
txBuf := <-c.chTxBuf
defer func() { c.chTxBuf <- txBuf }()
req := WriteRequest(txBuf[:3+len(value)])
req.SetAttributeOpcode()
req.SetAttributeHandle(handle)
req.SetAttributeValue(value)
b, err := c.sendReq(req)
if err != nil {
return err
}
// Convert and validate the response.
rsp := WriteResponse(b)
switch {
case rsp[0] == ErrorResponseCode && len(rsp) == 5:
return ble.ATTError(rsp[4])
case rsp[0] == ErrorResponseCode && len(rsp) != 5:
fallthrough
case rsp[0] != rsp.AttributeOpcode():
return ErrInvalidResponse
}
return nil
}
// ReadBlob requests the server to read part of the value of an attribute at a
// given offset and return a specific part of the value in a Read Blob Response.
// [Vol 3, Part F, 3.4.4.5 & 3.4.4.6]
func (c *Client) ReadBlob(handle, offset uint16) ([]byte, error) {
// Acquire and reuse the txBuf, and release it after usage.
txBuf := <-c.chTxBuf
defer func() { c.chTxBuf <- txBuf }()
req := ReadBlobRequest(txBuf[:5])
req.SetAttributeOpcode()
req.SetAttributeHandle(handle)
req.SetValueOffset(offset)
b, err := c.sendReq(req)
if err != nil {
return nil, err
}
// Convert and validate the response.
rsp := ReadBlobResponse(b)
switch {
case rsp[0] == ErrorResponseCode && len(rsp) == 5:
return nil, ble.ATTError(rsp[4])
case rsp[0] == ErrorResponseCode && len(rsp) != 5:
fallthrough
case rsp[0] != rsp.AttributeOpcode():
fallthrough
case len(rsp) < 1:
return nil, ErrInvalidResponse
}
return rsp.PartAttributeValue(), nil
}
// ReadByType obtains the values of attributes where the attribute type is known
// but the handle is not known. [Vol 3, Part F, 3.4.4.1 & 3.4.4.2]
func (c *Client) ReadByType(starth, endh uint16, uuid ble.UUID) (int, []byte, error) {
if starth > endh || (len(uuid) != 2 && len(uuid) != 16) {
return 0, nil, ErrInvalidArgument
}
// Acquire and reuse the txBuf, and release it after usage.
txBuf := <-c.chTxBuf
defer func() { c.chTxBuf <- txBuf }()
req := ReadByTypeRequest(txBuf[:5+len(uuid)])
req.SetAttributeOpcode()
req.SetStartingHandle(starth)
req.SetEndingHandle(endh)
req.SetAttributeType(uuid)
b, err := c.sendReq(req)
if err != nil {
return 0, nil, err
}
// Convert and validate the response.
rsp := ReadByTypeResponse(b)
switch {
case rsp[0] == ErrorResponseCode && len(rsp) == 5:
return 0, nil, ble.ATTError(rsp[4])
case rsp[0] == ErrorResponseCode && len(rsp) != 5:
fallthrough
case rsp[0] != rsp.AttributeOpcode():
fallthrough
case len(rsp) < 4 || len(rsp.AttributeDataList())%int(rsp.Length()) != 0:
return 0, nil, ErrInvalidResponse
}
return int(rsp.Length()), rsp.AttributeDataList(), nil
}
// ExchangeMTU informs the server of the client’s maximum receive MTU size and
// request the server to respond with its maximum receive MTU size. [Vol 3, Part F, 3.4.2.1]
func (c *Client) ExchangeMTU(clientRxMTU int) (serverRxMTU int, err error) {
if clientRxMTU < ble.DefaultMTU || clientRxMTU > ble.MaxMTU {
return 0, ErrInvalidArgument
}
// Acquire and reuse the txBuf, and release it after usage.
// The same txBuf, or a newly allocate one, if the txMTU is changed,
// will be released back to the channel.
txBuf := <-c.chTxBuf
defer func() { c.chTxBuf <- txBuf }()
// Let L2CAP know the MTU we can handle.
c.l2c.SetRxMTU(clientRxMTU)
req := ExchangeMTURequest(txBuf[:3])
req.SetAttributeOpcode()
req.SetClientRxMTU(uint16(clientRxMTU))
b, err := c.sendReq(req)
if err != nil {
return 0, err
}
// Convert and validate the response.
rsp := ExchangeMTUResponse(b)
switch {
case rsp[0] == ErrorResponseCode && len(rsp) == 5:
return 0, ble.ATTError(rsp[4])
case rsp[0] == ErrorResponseCode && len(rsp) != 5:
fallthrough
case rsp[0] != rsp.AttributeOpcode():
fallthrough
case len(rsp) != 3:
return 0, ErrInvalidResponse
}
txMTU := int(rsp.ServerRxMTU())
if len(txBuf) != txMTU {
// Let L2CAP know the MTU that the remote device can handle.
c.l2c.SetTxMTU(txMTU)
// Put a re-allocated txBuf back to the channel.
// The txBuf has been captured in deferred function.
txBuf = make([]byte, txMTU, txMTU)
}
return txMTU, nil
}
// FindInformation obtains the mapping of attribute handles with their associated types.
// This allows a Client to discover the list of attributes and their types on a server.
// [Vol 3, Part F, 3.4.3.1 & 3.4.3.2]
func (c *Client) FindInformation(starth, endh uint16) (fmt int, data []byte, err error) {
if starth == 0 || starth > endh {
return 0x00, nil, ErrInvalidArgument
}
// Acquire and reuse the txBuf, and release it after usage.
txBuf := <-c.chTxBuf
defer func() { c.chTxBuf <- txBuf }()
req := FindInformationRequest(txBuf[:5])
req.SetAttributeOpcode()
req.SetStartingHandle(starth)
req.SetEndingHandle(endh)
b, err := c.sendReq(req)
if err != nil {
return 0x00, nil, err
}
// Convert and validate the response.
rsp := FindInformationResponse(b)
switch {
case rsp[0] == ErrorResponseCode && len(rsp) == 5:
return 0x00, nil, ble.ATTError(rsp[4])
case rsp[0] == ErrorResponseCode && len(rsp) != 5:
fallthrough
case rsp[0] != rsp.AttributeOpcode():
fallthrough
case len(rsp) < 6:
fallthrough
case rsp.Format() == 0x01 && ((len(rsp)-2)%4) != 0:
fallthrough
case rsp.Format() == 0x02 && ((len(rsp)-2)%18) != 0:
return 0x00, nil, ErrInvalidResponse
}
return int(rsp.Format()), rsp.InformationData(), nil
}
// ReadMultiple requests the server to read two or more values of a set of
// attributes and return their values in a Read Multiple Response.
// Only values that have a known fixed size can be read, with the exception of
// the last value that can have a variable length. The knowledge of whether
// attributes have a known fixed size is defined in a higher layer specification.
// [Vol 3, Part F, 3.4.4.7 & 3.4.4.8]
func (c *Client) ReadMultiple(handles []uint16) ([]byte, error) {
// Should request to read two or more values.
if len(handles) < 2 || len(handles)*2 > c.l2c.TxMTU()-1 {
return nil, ErrInvalidArgument
}
// Acquire and reuse the txBuf, and release it after usage.
txBuf := <-c.chTxBuf
defer func() { c.chTxBuf <- txBuf }()
req := ReadMultipleRequest(txBuf[:1+len(handles)*2])
req.SetAttributeOpcode()
p := req.SetOfHandles()
for _, h := range handles {
binary.LittleEndian.PutUint16(p, h)
p = p[2:]
}
b, err := c.sendReq(req)
if err != nil {
return nil, err
}
// Convert and validate the response.
rsp := ReadMultipleResponse(b)
switch {
case rsp[0] == ErrorResponseCode && len(rsp) == 5:
return nil, ble.ATTError(rsp[4])
case rsp[0] == ErrorResponseCode && len(rsp) != 5:
fallthrough
case rsp[0] != rsp.AttributeOpcode():
fallthrough
case len(rsp) < 1:
return nil, ErrInvalidResponse
}
return rsp.SetOfValues(), nil
}
func (m msg) err() error {
if code := m.result(); code != 0 {
return ble.ATTError(code)
}
return nil
}