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in some cases, device sent package by some garbage bytes be attached … #39

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d420f8a
in some cases, device sent package by some garbage bytes be attached …
bezita Dec 3, 2018
b1be105
bug fixed, crc verify
bezita May 9, 2019
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16 changes: 16 additions & 0 deletions rtuclient.go
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Original file line number Diff line number Diff line change
Expand Up @@ -90,6 +90,22 @@ func (mb *rtuPackager) Verify(aduRequest []byte, aduResponse []byte) (err error)
// Decode extracts PDU from RTU frame and verify CRC.
func (mb *rtuPackager) Decode(adu []byte) (pdu *ProtocolDataUnit, err error) {
length := len(adu)

if length > 1 && adu[1] < 5 {
// adjust real length
if length < 3 {
err = fmt.Errorf("modbus: response length less than min '%v'", length)
return
} else {
real_len := int(adu[2]) + 5
if real_len > length {
err = fmt.Errorf("modbus: response length '%v' less than real length '%v'", length, real_len)
return
} else {
length = real_len
}
}
}
// Calculate checksum
var crc crc
crc.reset().pushBytes(adu[0 : length-2])
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11 changes: 6 additions & 5 deletions rtuclient_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -29,17 +29,17 @@ func TestRTUEncoding(t *testing.T) {

func TestRTUDecoding(t *testing.T) {
decoder := rtuPackager{}
adu := []byte{0x01, 0x10, 0x8A, 0x00, 0x00, 0x03, 0xAA, 0x10}
adu := []byte{0x05, 0x03, 0x02, 0x00, 0xAA, 0xC9, 0xFB, 0xFF, 0xFF, 0xFF, 0xFF}

pdu, err := decoder.Decode(adu)
if err != nil {
t.Fatal(err)
}

if 16 != pdu.FunctionCode {
t.Fatalf("Function code: expected %v, actual %v", 16, pdu.FunctionCode)
if 3 != pdu.FunctionCode {
t.Fatalf("Function code: expected %v, actual %v", 3, pdu.FunctionCode)
}
expected := []byte{0x8A, 0x00, 0x00, 0x03}
expected := []byte{0x02, 0x00, 0xAA}
if !bytes.Equal(expected, pdu.Data) {
t.Fatalf("Data: expected %v, actual %v", expected, pdu.Data)
}
Expand Down Expand Up @@ -88,7 +88,8 @@ func BenchmarkRTUDecoder(b *testing.B) {
decoder := rtuPackager{
SlaveId: 10,
}
adu := []byte{0x01, 0x10, 0x8A, 0x00, 0x00, 0x03, 0xAA, 0x10}
// adu := []byte{0x01, 0x10, 0x8A, 0x00, 0x00, 0x03, 0xAA, 0x10}
adu := []byte{0x05, 0x03, 0x02, 0x00, 0xAA, 0xC9, 0xFB, 0xFF, 0xFF, 0xFF}
for i := 0; i < b.N; i++ {
_, err := decoder.Decode(adu)
if err != nil {
Expand Down