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68 lines
1.7 KiB
Go
68 lines
1.7 KiB
Go
package sds
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import (
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"context"
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"fmt"
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"regexp"
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"strconv"
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"strings"
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"github.com/ftl/tetra-pei/tetra"
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)
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type Encoder interface {
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Encode([]byte, int) ([]byte, int)
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}
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type EncoderFunc func() ([]byte, int)
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func (f EncoderFunc) Encode() ([]byte, int) {
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return f()
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}
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const (
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// CRLF line ending for AT commands
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CRLF = "\x0d\x0a"
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// CtrlZ line ending for PDUs
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CtrlZ = "\x1a"
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// SwitchToSDSTL is a short-cut for selecting the SDS-TL AI service with ISSI addressing and E2EE according to [PEI] 6.14.6
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SwitchToSDSTL = "AT+CTSDS=12,0,0,0,1"
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// SwitchToStatus is a short-cut for selecting the status AI service with ISSI addresssing according to [PEI] 6.14.6
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SwitchToStatus = "AT+CTSDS=13,0"
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)
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// SendMessage according to [PEI] 6.13.2
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func SendMessage(destination tetra.Identity, message Encoder) string {
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pdu := make([]byte, 0, 256)
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pduBits := 0
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pdu, pduBits = message.Encode(pdu, pduBits)
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return fmt.Sprintf("AT+CMGS=%s,%d"+CRLF+"%s"+CtrlZ, destination, pduBits, tetra.BinaryToHex(pdu))
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}
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var sendMessageDescription = regexp.MustCompile(`^\+CMGS: .+\(\d*-(\d*)\)$`)
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// RequestMaxMessagePDUBits uses the given RequesterFunc to find out how many bits a message PDU may have (see [PEI] 6.13.2).
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func RequestMaxMessagePDUBits(ctx context.Context, requester tetra.Requester) (int, error) {
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responses, err := requester.Request(ctx, "AT+CMGS=?")
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if err != nil {
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return 0, err
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}
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if len(responses) < 1 {
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return 0, fmt.Errorf("no response received")
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}
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response := strings.ToUpper(strings.TrimSpace(responses[0]))
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parts := sendMessageDescription.FindStringSubmatch(response)
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if len(parts) != 2 {
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return 0, fmt.Errorf("unexpected response: %s", responses[0])
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}
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result, err := strconv.Atoi(parts[1])
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if err != nil {
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return 0, err
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}
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return result, nil
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}
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