100 lines
4.1 KiB
C++
100 lines
4.1 KiB
C++
#ifndef FRAMEWORK_GLOBALFUNCTIONS_DLEENCODER_H_
|
|
#define FRAMEWORK_GLOBALFUNCTIONS_DLEENCODER_H_
|
|
|
|
#include "fsfw/returnvalues/HasReturnvaluesIF.h"
|
|
#include <cstddef>
|
|
|
|
/**
|
|
* @brief This DLE Encoder (Data Link Encoder) can be used to encode and
|
|
* decode arbitrary data with ASCII control characters
|
|
* @details
|
|
* List of control codes:
|
|
* https://en.wikipedia.org/wiki/C0_and_C1_control_codes
|
|
*
|
|
* This encoder can be used to achieve a basic transport layer when using
|
|
* char based transmission systems.
|
|
* The passed source stream is converted into a encoded stream by adding
|
|
* a STX marker at the start of the stream and an ETX marker at the end of
|
|
* the stream. Any STX, ETX, DLE and CR occurrences in the source stream can be
|
|
* escaped by a DLE character. The encoder also replaces escaped control chars
|
|
* by another char, so STX, ETX and CR should not appear anywhere in the actual
|
|
* encoded data stream.
|
|
*
|
|
* When using a strictly char based reception of packets encoded with DLE,
|
|
* STX can be used to notify a reader that actual data will start to arrive
|
|
* while ETX can be used to notify the reader that the data has ended.
|
|
*/
|
|
class DleEncoder: public HasReturnvaluesIF {
|
|
public:
|
|
/**
|
|
* Create an encoder instance with the given configuration.
|
|
* @param escapeStxEtx
|
|
* @param escapeCr
|
|
*/
|
|
DleEncoder(bool escapeStxEtx = true, bool escapeCr = false);
|
|
virtual ~DleEncoder();
|
|
|
|
static constexpr uint8_t INTERFACE_ID = CLASS_ID::DLE_ENCODER;
|
|
static constexpr ReturnValue_t STREAM_TOO_SHORT = MAKE_RETURN_CODE(0x01);
|
|
static constexpr ReturnValue_t DECODING_ERROR = MAKE_RETURN_CODE(0x02);
|
|
|
|
//! Start Of Text character. First character is encoded stream
|
|
static constexpr uint8_t STX_CHAR = 0x02;
|
|
//! End Of Text character. Last character in encoded stream
|
|
static constexpr uint8_t ETX_CHAR = 0x03;
|
|
//! Data Link Escape character. Used to escape STX, ETX and DLE occurrences
|
|
//! in the source stream.
|
|
static constexpr uint8_t DLE_CHAR = 0x10;
|
|
static constexpr uint8_t CARRIAGE_RETURN = 0x0D;
|
|
|
|
/**
|
|
* Encodes the give data stream by preceding it with the STX marker
|
|
* and ending it with an ETX marker. DLE characters inside
|
|
* the stream are escaped by DLE characters. STX, ETX and CR characters can be escaped with a
|
|
* DLE character as well. The escaped characters are also encoded by adding
|
|
* 0x40 (which is reverted in the decoding process). This is performed so the source stream
|
|
* does not have STX/ETX/CR occurrences anymore, so the receiving side can simply parse for
|
|
* start and end markers
|
|
* @param sourceStream
|
|
* @param sourceLen
|
|
* @param destStream
|
|
* @param maxDestLen
|
|
* @param encodedLen
|
|
* @param addStxEtx Adding STX start marker and ETX end marker can be omitted,
|
|
* if they are added manually
|
|
* @param escapeStxEtx STX and ETX occurrences in the given source stream will be escaped and
|
|
* encoded by adding 0x40
|
|
* @param escapeCr CR characters in the given source stream will be escaped and encoded
|
|
* by adding 0x40
|
|
* @return
|
|
*/
|
|
ReturnValue_t encode(const uint8_t *sourceStream, size_t sourceLen,
|
|
uint8_t *destStream, size_t maxDestLen, size_t *encodedLen,
|
|
bool addStxEtx = true);
|
|
|
|
/**
|
|
* Converts an encoded stream back.
|
|
* @param sourceStream
|
|
* @param sourceStreamLen
|
|
* @param readLen
|
|
* @param destStream
|
|
* @param maxDestStreamlen
|
|
* @param decodedLen
|
|
* @param escapeStxEtx STX and ETX characters were escaped in the encoded stream and need to
|
|
* be decoded back as well
|
|
* @param escapeCr CR characters were escaped in the encoded stream and need to
|
|
* be decoded back as well by subtracting 0x40
|
|
* @return
|
|
*/
|
|
ReturnValue_t decode(const uint8_t *sourceStream,
|
|
size_t sourceStreamLen, size_t *readLen, uint8_t *destStream,
|
|
size_t maxDestStreamlen, size_t *decodedLen);
|
|
|
|
private:
|
|
|
|
bool escapeStxEtx;
|
|
bool escapeCr;
|
|
};
|
|
|
|
#endif /* FRAMEWORK_GLOBALFUNCTIONS_DLEENCODER_H_ */
|