71 lines
1.4 KiB
Go
71 lines
1.4 KiB
Go
// Package command provides communication patterns for Goodwe inverters using
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// the Modbus protocol.
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package command
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import (
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"bufio"
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"fmt"
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"io"
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"log"
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"time"
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)
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type Command interface {
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String() string
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ValidateResponse([]byte) ([]byte, error)
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}
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type Conn interface {
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io.ReadWriter
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SetDeadline(time.Time) error
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}
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const (
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maxAttempts = 4
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timeout = time.Second * 10
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readBufferSizeBytes = 8_192
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)
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// Send writes the command to the provided Writer, and reads and validates the
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// response.
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func Send(cmd Command, conn Conn) ([]byte, error) {
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var (
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resp []byte
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err error
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attempts int
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)
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for {
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if resp, err = tryRequest(cmd, conn); err != nil {
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attempts++
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log.Printf("error executing command (attempt %d): %s", attempts, err)
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if attempts <= 3 {
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continue
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}
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return nil, fmt.Errorf("error executing command: %s", err)
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}
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return resp, nil
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}
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}
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func tryRequest(cmd Command, conn Conn) ([]byte, error) {
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if err := conn.SetDeadline(time.Now().Add(timeout)); err != nil {
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return nil, fmt.Errorf("error setting deadline: %s", err)
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}
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p := make([]byte, readBufferSizeBytes)
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_, err := fmt.Fprint(conn, cmd.String())
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if err != nil {
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return nil, fmt.Errorf("error writing to socket: %s", err)
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}
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r := bufio.NewReader(conn)
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n, err := r.Read(p)
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if err != nil {
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return nil, fmt.Errorf("error reading from socket: %s", err)
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}
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return cmd.ValidateResponse(p[:n])
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}
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