spacepacketutils.hpp

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/*
Space packet utils header file
 
Author: Ryan Hughes
 
CRC calculation functionality is adapted from cFS under the Apache 2.0 license
https://github.com/nasa/cFE/blob/5dc12a7d2ac296ba59a3c3862936697587e67652/modules/es/fsw/src/cfe_es_api.c#L1575
*/
 
#ifndef COMMUNICATION_SPACEPACKETUTILS_HPP
#define COMMUNICATION_SPACEPACKETUTILS_HPP
 
#include <cstddef>
#include <stdint.h>
#include <algorithm>
#include <cstdio>
#include "architecture/Time.h"
 
#include "types.h"
 
namespace warpos {
// CCSDS packet version number is 0 for standard telemetry and telecommand applications
// Maximum length of the packet version number is 3 bits
static const uint8 CCSDS_PACKET_VERSION_NUM = 0;

static const uint32 CCSDS_PRI_HDR_LEN_BYTES = 6;

static const uint32 CCSDS_SEC_HDR_LEN_BYTES = 8;

static const uint32 CCSDS_FULL_HDR_LEN_BYTES = CCSDS_PRI_HDR_LEN_BYTES + CCSDS_SEC_HDR_LEN_BYTES;

static const uint32 CRC16_LEN_BYTES = 2;

int16 computeCRC16(uint32 &crc, const uint8 *packet_ptr, size_t length,
                     uint32 input_crc = 0);

int16 validateCRC16(const uint32 &crc, const uint8 *packet_ptr, size_t length,
                      uint32 input_crc = 0);

int16 computeFletcher8Checksum(const uint8* packet_ptr, uint8 length, uint16 &checksum);

int16 validateFletcher8Checksum(const uint8* packet_ptr, uint8 length, const uint16 &checksum);

int16 writeCCSDSHeader(uint8 *header, bool is_tlm, uint16 apid, uint8 seq_flag,
                       uint16 seq_count, uint16 data_len, clockwerk::Time timestamp, uint8 instance);

int16 readCCSDSHeader(uint8 *header, bool &is_tlm, uint16 &apid,
                      uint8 &seq_flag, uint16 &seq_count, uint16 &data_len,
                      clockwerk::Time &timestamp, uint8 &instance);

template <class T>
T changeEndian(T in)
{
    char* const p = reinterpret_cast<char*>(&in);
    for (size_t i = 0; i < sizeof(T) / 2; ++i)
        std::swap(p[i], p[sizeof(T) - i - 1]);
 
    return in;
}

template <class T, std::size_t N>
std::array<T, N> changeEndian(const std::array<T, N>& in) {
    std::array<T, N> out;
    for (std::size_t i = 0; i < N; ++i)
        out[i] = changeEndian(in[i]);
    return out;
}
 
} // namespace clockwerk
 
#endif