dle encoder doc added
This commit is contained in:
parent
a8f2cf910b
commit
df850116ff
@ -1,95 +1,124 @@
|
||||
#include "DleEncoder.h"
|
||||
#include "../globalfunctions/DleEncoder.h"
|
||||
|
||||
DleEncoder::DleEncoder() {
|
||||
DleEncoder::DleEncoder() {}
|
||||
|
||||
DleEncoder::~DleEncoder() {}
|
||||
|
||||
ReturnValue_t DleEncoder::encode(const uint8_t* sourceStream,
|
||||
size_t sourceLen, uint8_t* destStream, size_t maxDestLen,
|
||||
size_t* encodedLen, bool addStxEtx) {
|
||||
if (maxDestLen < 2) {
|
||||
return STREAM_TOO_SHORT;
|
||||
}
|
||||
size_t encodedIndex = 0, sourceIndex = 0;
|
||||
uint8_t nextByte;
|
||||
if (addStxEtx) {
|
||||
destStream[0] = STX_CHAR;
|
||||
++encodedIndex;
|
||||
}
|
||||
|
||||
DleEncoder::~DleEncoder() {
|
||||
while (encodedIndex < maxDestLen and sourceIndex < sourceLen)
|
||||
{
|
||||
nextByte = sourceStream[sourceIndex];
|
||||
// STX, ETX and CR characters in the stream need to be escaped with DLE
|
||||
if (nextByte == STX_CHAR or nextByte == ETX_CHAR or nextByte == CARRIAGE_RETURN) {
|
||||
if (encodedIndex + 1 >= maxDestLen) {
|
||||
return STREAM_TOO_SHORT;
|
||||
}
|
||||
else {
|
||||
destStream[encodedIndex] = DLE_CHAR;
|
||||
++encodedIndex;
|
||||
/* Escaped byte will be actual byte + 0x40. This prevents
|
||||
* STX, ETX, and carriage return characters from appearing
|
||||
* in the encoded data stream at all, so when polling an
|
||||
* encoded stream, the transmission can be stopped at ETX.
|
||||
* 0x40 was chosen at random with special requirements:
|
||||
* - Prevent going from one control char to another
|
||||
* - Prevent overflow for common characters */
|
||||
destStream[encodedIndex] = nextByte + 0x40;
|
||||
}
|
||||
}
|
||||
// DLE characters are simply escaped with DLE.
|
||||
else if (nextByte == DLE_CHAR) {
|
||||
if (encodedIndex + 1 >= maxDestLen) {
|
||||
return STREAM_TOO_SHORT;
|
||||
}
|
||||
else {
|
||||
destStream[encodedIndex] = DLE_CHAR;
|
||||
++encodedIndex;
|
||||
destStream[encodedIndex] = DLE_CHAR;
|
||||
}
|
||||
}
|
||||
else {
|
||||
destStream[encodedIndex] = nextByte;
|
||||
}
|
||||
++encodedIndex;
|
||||
++sourceIndex;
|
||||
}
|
||||
|
||||
if (sourceIndex == sourceLen and encodedIndex < maxDestLen) {
|
||||
if (addStxEtx) {
|
||||
destStream[encodedIndex] = ETX_CHAR;
|
||||
++encodedIndex;
|
||||
}
|
||||
*encodedLen = encodedIndex;
|
||||
return RETURN_OK;
|
||||
}
|
||||
else {
|
||||
return STREAM_TOO_SHORT;
|
||||
}
|
||||
}
|
||||
|
||||
ReturnValue_t DleEncoder::decode(const uint8_t *sourceStream,
|
||||
uint32_t sourceStreamLen, uint32_t *readLen, uint8_t *destStream,
|
||||
uint32_t maxDestStreamlen, uint32_t *decodedLen) {
|
||||
uint32_t encodedIndex = 0, decodedIndex = 0;
|
||||
size_t sourceStreamLen, size_t *readLen, uint8_t *destStream,
|
||||
size_t maxDestStreamlen, size_t *decodedLen) {
|
||||
size_t encodedIndex = 0, decodedIndex = 0;
|
||||
uint8_t nextByte;
|
||||
if (*sourceStream != STX) {
|
||||
return RETURN_FAILED;
|
||||
if (*sourceStream != STX_CHAR) {
|
||||
return DECODING_ERROR;
|
||||
}
|
||||
++encodedIndex;
|
||||
|
||||
while ((encodedIndex < sourceStreamLen) && (decodedIndex < maxDestStreamlen)
|
||||
&& (sourceStream[encodedIndex] != ETX)
|
||||
&& (sourceStream[encodedIndex] != STX)) {
|
||||
if (sourceStream[encodedIndex] == DLE) {
|
||||
&& (sourceStream[encodedIndex] != ETX_CHAR)
|
||||
&& (sourceStream[encodedIndex] != STX_CHAR)) {
|
||||
if (sourceStream[encodedIndex] == DLE_CHAR) {
|
||||
nextByte = sourceStream[encodedIndex + 1];
|
||||
if (nextByte == 0x10) {
|
||||
// The next byte is a DLE character that was escaped by another
|
||||
// DLE character, so we can write it to the destination stream.
|
||||
if (nextByte == DLE_CHAR) {
|
||||
destStream[decodedIndex] = nextByte;
|
||||
} else {
|
||||
if ((nextByte == 0x42) || (nextByte == 0x43)
|
||||
|| (nextByte == 0x4D)) {
|
||||
}
|
||||
else {
|
||||
/* The next byte is a STX, DTX or 0x0D character which
|
||||
* was escaped by a DLE character. The actual byte was
|
||||
* also encoded by adding + 0x40 to preven having control chars,
|
||||
* in the stream at all, so we convert it back. */
|
||||
if (nextByte == 0x42 or nextByte == 0x43 or nextByte == 0x4D) {
|
||||
destStream[decodedIndex] = nextByte - 0x40;
|
||||
} else {
|
||||
return RETURN_FAILED;
|
||||
}
|
||||
else {
|
||||
return DECODING_ERROR;
|
||||
}
|
||||
}
|
||||
++encodedIndex;
|
||||
} else {
|
||||
}
|
||||
else {
|
||||
destStream[decodedIndex] = sourceStream[encodedIndex];
|
||||
}
|
||||
|
||||
++encodedIndex;
|
||||
++decodedIndex;
|
||||
}
|
||||
if (sourceStream[encodedIndex] != ETX) {
|
||||
return RETURN_FAILED;
|
||||
} else {
|
||||
|
||||
if (sourceStream[encodedIndex] != ETX_CHAR) {
|
||||
*readLen = ++encodedIndex;
|
||||
return DECODING_ERROR;
|
||||
}
|
||||
else {
|
||||
*readLen = ++encodedIndex;
|
||||
*decodedLen = decodedIndex;
|
||||
return RETURN_OK;
|
||||
}
|
||||
}
|
||||
|
||||
ReturnValue_t DleEncoder::encode(const uint8_t* sourceStream,
|
||||
uint32_t sourceLen, uint8_t* destStream, uint32_t maxDestLen,
|
||||
uint32_t* encodedLen, bool addStxEtx) {
|
||||
if (maxDestLen < 2) {
|
||||
return RETURN_FAILED;
|
||||
}
|
||||
uint32_t encodedIndex = 0, sourceIndex = 0;
|
||||
uint8_t nextByte;
|
||||
if (addStxEtx) {
|
||||
destStream[0] = STX;
|
||||
++encodedIndex;
|
||||
}
|
||||
while ((encodedIndex < maxDestLen) && (sourceIndex < sourceLen)) {
|
||||
nextByte = sourceStream[sourceIndex];
|
||||
if ((nextByte == STX) || (nextByte == ETX) || (nextByte == 0x0D)) {
|
||||
if (encodedIndex + 1 >= maxDestLen) {
|
||||
return RETURN_FAILED;
|
||||
} else {
|
||||
destStream[encodedIndex] = DLE;
|
||||
++encodedIndex;
|
||||
destStream[encodedIndex] = nextByte + 0x40;
|
||||
}
|
||||
} else if (nextByte == DLE) {
|
||||
if (encodedIndex + 1 >= maxDestLen) {
|
||||
return RETURN_FAILED;
|
||||
} else {
|
||||
destStream[encodedIndex] = DLE;
|
||||
++encodedIndex;
|
||||
destStream[encodedIndex] = DLE;
|
||||
}
|
||||
} else {
|
||||
destStream[encodedIndex] = nextByte;
|
||||
}
|
||||
++encodedIndex;
|
||||
++sourceIndex;
|
||||
}
|
||||
if ((sourceIndex == sourceLen) && (encodedIndex < maxDestLen)) {
|
||||
if (addStxEtx) {
|
||||
destStream[encodedIndex] = ETX;
|
||||
++encodedIndex;
|
||||
}
|
||||
*encodedLen = encodedIndex;
|
||||
return RETURN_OK;
|
||||
} else {
|
||||
return RETURN_FAILED;
|
||||
}
|
||||
}
|
||||
|
||||
@ -1,25 +1,79 @@
|
||||
#ifndef DLEENCODER_H_
|
||||
#define DLEENCODER_H_
|
||||
#ifndef FRAMEWORK_GLOBALFUNCTIONS_DLEENCODER_H_
|
||||
#define FRAMEWORK_GLOBALFUNCTIONS_DLEENCODER_H_
|
||||
|
||||
#include "../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 strean 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 occurences in the source stream are
|
||||
* 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 enoded 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 {
|
||||
private:
|
||||
DleEncoder();
|
||||
virtual ~DleEncoder();
|
||||
|
||||
public:
|
||||
static const uint8_t STX = 0x02;
|
||||
static const uint8_t ETX = 0x03;
|
||||
static const uint8_t DLE = 0x10;
|
||||
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);
|
||||
|
||||
static ReturnValue_t decode(const uint8_t *sourceStream,
|
||||
uint32_t sourceStreamLen, uint32_t *readLen, uint8_t *destStream,
|
||||
uint32_t maxDestStreamlen, uint32_t *decodedLen);
|
||||
//! 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 occurences
|
||||
//! in the source stream.
|
||||
static constexpr uint8_t DLE_CHAR = 0x10;
|
||||
static constexpr uint8_t CARRIAGE_RETURN = 0x0D;
|
||||
|
||||
static ReturnValue_t encode(const uint8_t *sourceStream, uint32_t sourceLen,
|
||||
uint8_t *destStream, uint32_t maxDestLen, uint32_t *encodedLen,
|
||||
/**
|
||||
* Encodes the give data stream by preceding it with the STX marker
|
||||
* and ending it with an ETX marker. STX, ETX and DLE characters inside
|
||||
* the stream are escaped by DLE characters and also replaced by adding
|
||||
* 0x40 (which is reverted in the decoing process).
|
||||
* @param sourceStream
|
||||
* @param sourceLen
|
||||
* @param destStream
|
||||
* @param maxDestLen
|
||||
* @param encodedLen
|
||||
* @param addStxEtx
|
||||
* Adding STX and ETX can be omitted, if they are added manually.
|
||||
* @return
|
||||
*/
|
||||
static 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
|
||||
* @return
|
||||
*/
|
||||
static ReturnValue_t decode(const uint8_t *sourceStream,
|
||||
size_t sourceStreamLen, size_t *readLen, uint8_t *destStream,
|
||||
size_t maxDestStreamlen, size_t *decodedLen);
|
||||
};
|
||||
|
||||
#endif /* DLEENCODER_H_ */
|
||||
#endif /* FRAMEWORK_GLOBALFUNCTIONS_DLEENCODER_H_ */
|
||||
|
||||
Loading…
Reference in New Issue
Block a user