dataframe/src/dataframe.cpp

/*
 * @file dataframe.cpp
 * @brief Simple Data Frame
 *
 * @date: 31. 12. 2022
 * @author: juraj
 */

/**
 * @mainpage DataFrame library
 *
Create formatted frame from basic types:
 - uint8_t, int8_t => 1Byte
 - uint16_t, int16_t => 2Bytes
 - uint32_t, int32_t => 4Bytes
 - float => 4Bytes

 Data are stared in Little Endian format.

Structure of data frame:
  - starting byte (0xCC)
  - length of frame: count of bytes in payload. The first 2 bytes is not included to overal length. Maximum length: 254 (0xFE)
  - payload
  - CRC8

 The library contans universal function:
 - `uint8_t crc8(uint8_t crc, uint8_t Size, uint8_t *Buffer);`
  - crc - inital value for CRC computig. For new frame, use 0x0
  - Size - size of data Buffer

   \code{.c}
    void main(){
		uint8_t data[128];

	    packet_create(data, 128);
		packet_add_uint8(0xAB);
		packet_add_uint16(0xABCD);
		packet_add_uint32(0x12345678);
		packet_add_float(0.265);

		int data_length = packet_commit();
    }
  \endcode

 */

#include "dataframe.h"

/**
 * @brief Helper function to compute CRC.
 * @param crc - initial CRC, use 0 if dont know about it.
 * @param Size - size of input buffer
 * @param Buffer - input array with bytes
 */
uint8_t crc8(uint8_t crc, uint8_t Size, uint8_t *Buffer)
{
    // https://community.st.com/s/question/0D50X0000CDmAkpSQF/calculate-crc8
    static const unsigned char CrcTable[] = { // 0x97 Polynomial Table, 8-bit,
            0x00,0x97,0xB9,0x2E,0xE5,0x72,0x5C,0xCB,
            0x5D,0xCA,0xE4,0x73,0xB8,0x2F,0x01,0x96,
            0xBA,0x2D,0x03,0x94,0x5F,0xC8,0xE6,0x71,
            0xE7,0x70,0x5E,0xC9,0x02,0x95,0xBB,0x2C,
            0xE3,0x74,0x5A,0xCD,0x06,0x91,0xBF,0x28,
            0xBE,0x29,0x07,0x90,0x5B,0xCC,0xE2,0x75,
            0x59,0xCE,0xE0,0x77,0xBC,0x2B,0x05,0x92,
            0x04,0x93,0xBD,0x2A,0xE1,0x76,0x58,0xCF,
            0x51,0xC6,0xE8,0x7F,0xB4,0x23,0x0D,0x9A,
            0x0C,0x9B,0xB5,0x22,0xE9,0x7E,0x50,0xC7,
            0xEB,0x7C,0x52,0xC5,0x0E,0x99,0xB7,0x20,
            0xB6,0x21,0x0F,0x98,0x53,0xC4,0xEA,0x7D,
            0xB2,0x25,0x0B,0x9C,0x57,0xC0,0xEE,0x79,
            0xEF,0x78,0x56,0xC1,0x0A,0x9D,0xB3,0x24,
            0x08,0x9F,0xB1,0x26,0xED,0x7A,0x54,0xC3,
            0x55,0xC2,0xEC,0x7B,0xB0,0x27,0x09,0x9E,
            0xA2,0x35,0x1B,0x8C,0x47,0xD0,0xFE,0x69,
            0xFF,0x68,0x46,0xD1,0x1A,0x8D,0xA3,0x34,
            0x18,0x8F,0xA1,0x36,0xFD,0x6A,0x44,0xD3,
            0x45,0xD2,0xFC,0x6B,0xA0,0x37,0x19,0x8E,
            0x41,0xD6,0xF8,0x6F,0xA4,0x33,0x1D,0x8A,
            0x1C,0x8B,0xA5,0x32,0xF9,0x6E,0x40,0xD7,
            0xFB,0x6C,0x42,0xD5,0x1E,0x89,0xA7,0x30,
            0xA6,0x31,0x1F,0x88,0x43,0xD4,0xFA,0x6D,
            0xF3,0x64,0x4A,0xDD,0x16,0x81,0xAF,0x38,
            0xAE,0x39,0x17,0x80,0x4B,0xDC,0xF2,0x65,
            0x49,0xDE,0xF0,0x67,0xAC,0x3B,0x15,0x82,
            0x14,0x83,0xAD,0x3A,0xF1,0x66,0x48,0xDF,
            0x10,0x87,0xA9,0x3E,0xF5,0x62,0x4C,0xDB,
            0x4D,0xDA,0xF4,0x63,0xA8,0x3F,0x11,0x86,
            0xAA,0x3D,0x13,0x84,0x4F,0xD8,0xF6,0x61,
            0xF7,0x60,0x4E,0xD9,0x12,0x85,0xAB,0x3C };

    while(Size--)
    {
        crc = crc ^ *Buffer++; // Apply Byte
        crc = CrcTable[crc & 0xFF]; // One round of 8-bits
    }

    if (crc == 0){
    	crc = 1;
    }

    return(crc);
}



DataFrame::DataFrame(uint8_t *frame, uint8_t size, DataframeType_t type)
{
	_frame = frame;
	_capacity = size;
	_type = type;
	this->Init();
}

void DataFrame::Init(void)
{
	if(_type == TYPE_HEADER_CRC){
		_frame[0] = HEADER_CHAR;
		_frame[1] = 0;	//length of packet
		_length = 2;
	}

	if(_type == TYPE_PLAIN){
		_frame[1] = 0;	//length of packet
		_length = 1;
	}
}

bool DataFrame::AddUint8(uint8_t d)
{
    if((_length+1) >= _capacity){
        return false;
    }

	_frame[_length] = d;
	_length++;
    return true;
}

bool DataFrame::AddUint16(uint16_t d)
{
    if((_length+2) >= _capacity){
        return false;
    }

    _frame[_length++] =  d & 0xFF;
    _frame[_length++] =  (d >> 8) & 0xFF;

    return true;
}

bool DataFrame::AddUint32(uint32_t d)
{
    if((_length+4) >= _capacity){
        return false;
    }

    _frame[_length++] =  d & 0xFF;
    _frame[_length++] = (d >> 8) & 0xFF;
    _frame[_length++] = (d >> 16) & 0xFF;
	_frame[_length++] = (d >> 24) & 0xFF;

    return true;

}

bool DataFrame::AddInt8(int8_t d)
{
	return this->AddUint8((uint8_t)d);
}

bool DataFrame::AddInt16(int16_t d)
{
	return this->AddUint16((uint16_t)d);
}

bool DataFrame::AddInt32(int32_t d)
{
	return this->AddUint32((uint32_t)d);
}

bool DataFrame::AddFloat(float f)
{
    if((_length+4) >= _capacity){
        return false;
    }

	 uint8_t *ptr;
	 ptr = (unsigned char *)&f;

	 _frame[_length++] = *(ptr);
	 _frame[_length++] = *(ptr+1);
	 _frame[_length++] = *(ptr+2);
	 _frame[_length++] = *(ptr+3);

	 return true;
}

uint8_t DataFrame::Commit(void)
{
	if(_type == TYPE_HEADER_CRC){
		// compute _length
		_length++;
		_frame[1] = _length - 2;
		_frame[_length - 1] = crc8(0, _length-1, _frame);
		// length of payload: from byte 2 to CRC byte (the last)
	}
	if(_type == TYPE_PLAIN){
		_frame[0] = _length;
	}
	return _length;

}

uint8_t* DataFrame::GetFrame(void){
	return _frame;
}