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Return data of too large responses #81

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merged 4 commits into from
May 2, 2024
Merged

Return data of too large responses #81

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79d3fae
Introduce custom error for invalid data-sizes
srebhan Feb 1, 2024
0a13a3d
Return data if response is too large, fixes #52
srebhan Feb 1, 2024
f14741f
Comment new error type
srebhan Feb 1, 2024
828f9ad
Make clear expected and actual are in bytes
srebhan Feb 12, 2024
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75 changes: 50 additions & 25 deletions client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,17 @@ import (
"fmt"
)

// DataSizeError represents an error for invalid data-sizes i.e. for cases
// where the data-size does not match the expectation.
type DataSizeError struct {
ExpectedBytes int
ActualBytes int
}

func (e *DataSizeError) Error() string {
return fmt.Sprintf("modbus: response data size '%d' does not match count '%d'", e.ActualBytes, e.ExpectedBytes)
}

// ClientHandler is the interface that groups the Packager and Transporter methods.
type ClientHandler interface {
Packager
Expand Down Expand Up @@ -58,10 +69,12 @@ func (mb *client) ReadCoils(address, quantity uint16) (results []byte, err error
count := int(response.Data[0])
length := len(response.Data) - 1
if count != length {
err = fmt.Errorf("modbus: response data size '%v' does not match count '%v'", length, count)
return
err = &DataSizeError{ExpectedBytes: count, ActualBytes: length}
if length < count {
return
}
}
results = response.Data[1:]
results = response.Data[1 : count+1]
return
}

Expand Down Expand Up @@ -92,10 +105,12 @@ func (mb *client) ReadDiscreteInputs(address, quantity uint16) (results []byte,
count := int(response.Data[0])
length := len(response.Data) - 1
if count != length {
err = fmt.Errorf("modbus: response data size '%v' does not match count '%v'", length, count)
return
err = &DataSizeError{ExpectedBytes: count, ActualBytes: length}
if length < count {
return
}
}
results = response.Data[1:]
results = response.Data[1 : count+1]
return
}

Expand Down Expand Up @@ -126,14 +141,16 @@ func (mb *client) ReadHoldingRegisters(address, quantity uint16) (results []byte
count := int(response.Data[0])
length := len(response.Data) - 1
if count != length {
err = fmt.Errorf("modbus: response data size '%v' does not match count '%v'", length, count)
return
err = &DataSizeError{ExpectedBytes: count, ActualBytes: length}
if length < count {
return
}
}
if count != 2*int(quantity) {
err = fmt.Errorf("modbus: response data size '%v' does not match request quantity '%v'", length, quantity)
return
}
results = response.Data[1:]
results = response.Data[1 : count+1]
return
}

Expand Down Expand Up @@ -164,14 +181,16 @@ func (mb *client) ReadInputRegisters(address, quantity uint16) (results []byte,
count := int(response.Data[0])
length := len(response.Data) - 1
if count != length {
err = fmt.Errorf("modbus: response data size '%v' does not match count '%v'", length, count)
return
err = &DataSizeError{ExpectedBytes: count, ActualBytes: length}
if length < count {
return
}
}
if count != 2*int(quantity) {
err = fmt.Errorf("modbus: response data size '%v' does not match request quantity '%v'", length, quantity)
return
}
results = response.Data[1:]
results = response.Data[1 : count+1]
return
}

Expand Down Expand Up @@ -202,7 +221,7 @@ func (mb *client) WriteSingleCoil(address, value uint16) (results []byte, err er
}
// Fixed response length
if len(response.Data) != 4 {
err = fmt.Errorf("modbus: response data size '%v' does not match expected '%v'", len(response.Data), 4)
err = &DataSizeError{ExpectedBytes: 4, ActualBytes: len(response.Data)}
return
}
respValue := binary.BigEndian.Uint16(response.Data)
Expand Down Expand Up @@ -241,7 +260,7 @@ func (mb *client) WriteSingleRegister(address, value uint16) (results []byte, er
}
// Fixed response length
if len(response.Data) != 4 {
err = fmt.Errorf("modbus: response data size '%v' does not match expected '%v'", len(response.Data), 4)
err = &DataSizeError{ExpectedBytes: 4, ActualBytes: len(response.Data)}
return
}
respValue := binary.BigEndian.Uint16(response.Data)
Expand Down Expand Up @@ -286,7 +305,7 @@ func (mb *client) WriteMultipleCoils(address, quantity uint16, value []byte) (re
}
// Fixed response length
if len(response.Data) != 4 {
err = fmt.Errorf("modbus: response data size '%v' does not match expected '%v'", len(response.Data), 4)
err = &DataSizeError{ExpectedBytes: 4, ActualBytes: len(response.Data)}
return
}
respValue := binary.BigEndian.Uint16(response.Data)
Expand Down Expand Up @@ -331,7 +350,7 @@ func (mb *client) WriteMultipleRegisters(address, quantity uint16, value []byte)
}
// Fixed response length
if len(response.Data) != 4 {
err = fmt.Errorf("modbus: response data size '%v' does not match expected '%v'", len(response.Data), 4)
err = &DataSizeError{ExpectedBytes: 4, ActualBytes: len(response.Data)}
return
}
respValue := binary.BigEndian.Uint16(response.Data)
Expand Down Expand Up @@ -372,7 +391,7 @@ func (mb *client) MaskWriteRegister(address, andMask, orMask uint16) (results []
}
// Fixed response length
if len(response.Data) != 6 {
err = fmt.Errorf("modbus: response data size '%v' does not match expected '%v'", len(response.Data), 6)
err = &DataSizeError{ExpectedBytes: 6, ActualBytes: len(response.Data)}
return
}
respValue := binary.BigEndian.Uint16(response.Data)
Expand Down Expand Up @@ -427,11 +446,14 @@ func (mb *client) ReadWriteMultipleRegisters(readAddress, readQuantity, writeAdd
return
}
count := int(response.Data[0])
if count != (len(response.Data) - 1) {
err = fmt.Errorf("modbus: response data size '%v' does not match count '%v'", len(response.Data)-1, count)
return
length := len(response.Data) - 1
if count != length {
err = &DataSizeError{ExpectedBytes: count, ActualBytes: length}
if length < count {
return
}
}
results = response.Data[1:]
results = response.Data[1 : count+1]
return
}

Expand Down Expand Up @@ -461,11 +483,14 @@ func (mb *client) ReadFIFOQueue(address uint16) (results []byte, err error) {
return
}
count := int(binary.BigEndian.Uint16(response.Data))
if count != (len(response.Data) - 1) {
err = fmt.Errorf("modbus: response data size '%v' does not match count '%v'", len(response.Data)-1, count)
return
length := len(response.Data) - 1
if count != length {
err = &DataSizeError{ExpectedBytes: count, ActualBytes: length}
if length < count {
return
}
}
count = int(binary.BigEndian.Uint16(response.Data[2:]))
count = int(binary.BigEndian.Uint16(response.Data[2 : count+2]))
if count > 31 {
err = fmt.Errorf("modbus: fifo count '%v' is greater than expected '%v'", count, 31)
return
Expand Down