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add support for jumbo messages with len > 255 #60

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add support for jumbo messages with len > 255 #60

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226bf6f
add support for jump messages with len > 255
catkira Feb 26, 2024
ef3b510
apply clang-format
catkira Feb 26, 2024
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8 changes: 8 additions & 0 deletions inc/msp/Client.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -309,6 +309,14 @@ class Client {
*/
uint8_t crcV1(const uint8_t id, const ByteVector& data) const;

/**
* @brief crcV1_2 Computes a checksum for MSPv1 messages
* @param start_val uint8_t start value for crc
* @param data Bytes which are part of the checksum
* @return uint8_t checksum
*/
uint8_t crcV1_2(const uint8_t start_val, const ByteVector& data) const;

/**
* @brief packMessageV2 Packs data ID and data payload into a MSPv2
* formatted buffer ready for sending to the serial device
Expand Down
44 changes: 39 additions & 5 deletions src/Client.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -243,6 +243,14 @@ uint8_t Client::crcV1(const uint8_t id, const ByteVector& data) const {
return crc;
}

uint8_t Client::crcV1_2(const uint8_t start_val, const ByteVector& data) const {
uint8_t crc = start_val;
for(const uint8_t d : data) {
crc = crc ^ d;
}
return crc;
}

ByteVector Client::packMessageV2(const msp::ID id,
const ByteVector& data) const {
ByteVector msg;
Expand Down Expand Up @@ -363,12 +371,25 @@ std::pair<iterator, bool> Client::messageReady(iterator begin,
// not even enough data for a header
if(available < 6) return std::make_pair(begin, false);

const uint8_t payload_size = uint8_t(*(i + 3));
uint16_t payload_size = uint8_t(*(i + 3));
uint8_t extra_idx = 0;
if(payload_size == 0xFF) {
if(available < 8) return std::make_pair(begin, false);

payload_size = *(i + 5);
payload_size += static_cast<uint16_t>(*(i + 6)) << 8;
extra_idx = 2;
if(log_level_ >= DEBUG)
std::cout << "received jumbo message with payload_size "
<< payload_size << " available bytes " << available
<< std::endl;
}

// incomplete xfer
if(available < size_t(5 + payload_size + 1))
if(available < size_t(5 + extra_idx + payload_size + 1))
return std::make_pair(begin, false);

std::advance(i, 5 + payload_size + 1);
std::advance(i, 5 + extra_idx + payload_size + 1);
}
else if(*i == '$' && *(i + 1) == 'X') {
// not even enough data for a header
Expand Down Expand Up @@ -403,12 +424,25 @@ ReceivedMessage Client::processOneMessageV1() {
const bool ok_id = (dir != '!');

// payload length
const uint8_t len = extractChar();
uint16_t len = extractChar();

// message ID
uint8_t id = extractChar();
ret.id = msp::ID(id);

uint8_t crc_start_val = len ^ id;

if(len == 0xFF) {
len = extractChar();
crc_start_val ^= len;
uint8_t temp = extractChar();
len += temp << 8;
crc_start_val ^= temp;
if(log_level_ >= DEBUG)
std::cout << "received jumbo message with length " << len
<< std::endl;
}

if(log_level_ >= WARNING && !ok_id) {
std::cerr << "Message v1 with ID " << size_t(ret.id)
<< " is not recognised!" << std::endl;
Expand All @@ -421,7 +455,7 @@ ReceivedMessage Client::processOneMessageV1() {

// CRC
const uint8_t rcv_crc = extractChar();
const uint8_t exp_crc = crcV1(id, ret.payload);
const uint8_t exp_crc = crcV1_2(crc_start_val, ret.payload);
const bool ok_crc = (rcv_crc == exp_crc);

if(log_level_ >= WARNING && !ok_crc) {
Expand Down