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Added support for 128 bit xmodem send and more than 256 blocks. #10

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Added support for 128 bit xmodem send and more than 256 blocks. #10

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38 changes: 25 additions & 13 deletions xmodem/xmodem.go
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Original file line number Diff line number Diff line change
Expand Up @@ -65,22 +65,26 @@ func CRC16Constant(data []byte, length int) uint16 {
return u16CRC
}

func sendBlock(c io.ReadWriter, block uint8, data []byte) error {
//send STX
if _, err := c.Write([]byte{STX}); err != nil {
func sendBlock(c io.ReadWriter, block int, data []byte, packetPayloadLen int) error {
startByte := SOH
if packetPayloadLen == LONG_PACKET_PAYLOAD_LEN {
startByte = STX
}
// send start byte
if _, err := c.Write([]byte{startByte}); err != nil {
return err
}
if _, err := c.Write([]byte{block}); err != nil {
if _, err := c.Write([]byte{uint8(block % 256)}); err != nil {
return err
}
if _, err := c.Write([]byte{255 - block}); err != nil {
if _, err := c.Write([]byte{uint8(255 - (block % 256))}); err != nil {
return err
}

//send data
var toSend bytes.Buffer
toSend.Write(data)
for toSend.Len() < LONG_PACKET_PAYLOAD_LEN {
for toSend.Len() < packetPayloadLen {
toSend.Write([]byte{EOT})
}

Expand All @@ -94,7 +98,7 @@ func sendBlock(c io.ReadWriter, block uint8, data []byte) error {
}

//calc CRC
u16CRC := CRC16Constant(data, LONG_PACKET_PAYLOAD_LEN)
u16CRC := CRC16Constant(data, packetPayloadLen)

//send CRC
if _, err := c.Write([]byte{uint8(u16CRC >> 8)}); err != nil {
Expand All @@ -108,25 +112,33 @@ func sendBlock(c io.ReadWriter, block uint8, data []byte) error {
}

func ModemSend(c io.ReadWriter, data []byte) error {
return modemSend(c, data, SHORT_PACKET_PAYLOAD_LEN)
}

func ModemSend1K(c io.ReadWriter, data []byte) error {
return modemSend(c, data, LONG_PACKET_PAYLOAD_LEN)
}

func modemSend(c io.ReadWriter, data []byte, packetPayloadLen int) error {
oBuffer := make([]byte, 1)

if _, err := c.Read(oBuffer); err != nil {
return err
}

if oBuffer[0] == POLL {
var blocks uint8 = uint8(len(data) / LONG_PACKET_PAYLOAD_LEN)
if len(data) > int(int(blocks)*int(LONG_PACKET_PAYLOAD_LEN)) {
var blocks int = len(data) / packetPayloadLen
if len(data) > blocks*packetPayloadLen {
blocks++
}

failed := 0
var currentBlock uint8 = 0
var currentBlock = 0
for currentBlock < blocks && failed < 10 {
if int(int(currentBlock+1)*int(LONG_PACKET_PAYLOAD_LEN)) > len(data) {
sendBlock(c, currentBlock+1, data[int(currentBlock)*int(LONG_PACKET_PAYLOAD_LEN):])
if int(int(currentBlock+1)*int(packetPayloadLen)) > len(data) {
sendBlock(c, currentBlock+1, data[currentBlock*packetPayloadLen:], packetPayloadLen)
} else {
sendBlock(c, currentBlock+1, data[int(currentBlock)*int(LONG_PACKET_PAYLOAD_LEN):(int(currentBlock)+1)*int(LONG_PACKET_PAYLOAD_LEN)])
sendBlock(c, currentBlock+1, data[currentBlock*packetPayloadLen:(currentBlock+1)*packetPayloadLen], packetPayloadLen)
}

if _, err := c.Read(oBuffer); err != nil {
Expand Down