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doc and improvements for DLE encoder

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This commit is contained in:
Robin Müller 2020-07-07 16:36:41 +02:00
parent cb691db807
commit 4f1f610ae0
3 changed files with 78 additions and 28 deletions
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39
globalfunctions/DleEncoder.cpp
View File

@ -1,18 +1,16 @@
#include <framework/globalfunctions/DleEncoder.h>
DleEncoder::DleEncoder() {
}
DleEncoder::DleEncoder() {}
DleEncoder::~DleEncoder() {
}
DleEncoder::~DleEncoder() {}
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;
return DECODING_ERROR;
}
++encodedIndex;
while ((encodedIndex < sourceStreamLen) && (decodedIndex < maxDestStreamlen)
@ -20,14 +18,18 @@ ReturnValue_t DleEncoder::decode(const uint8_t *sourceStream,
&& (sourceStream[encodedIndex] != STX)) {
if (sourceStream[encodedIndex] == DLE) {
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) {
destStream[decodedIndex] = nextByte;
} else {
// The next byte is a STX, DTX or 0x0D character which
// was escaped by a DLE character
if ((nextByte == 0x42) || (nextByte == 0x43)
|| (nextByte == 0x4D)) {
destStream[decodedIndex] = nextByte - 0x40;
} else {
return RETURN_FAILED;
return DECODING_ERROR;
}
}
++encodedIndex;
@ -38,7 +40,7 @@ ReturnValue_t DleEncoder::decode(const uint8_t *sourceStream,
++decodedIndex;
}
if (sourceStream[encodedIndex] != ETX) {
return RETURN_FAILED;
return DECODING_ERROR;
} else {
*readLen = ++encodedIndex;
*decodedLen = decodedIndex;
@ -47,12 +49,12 @@ ReturnValue_t DleEncoder::decode(const uint8_t *sourceStream,
}
ReturnValue_t DleEncoder::encode(const uint8_t* sourceStream,
uint32_t sourceLen, uint8_t* destStream, uint32_t maxDestLen,
uint32_t* encodedLen, bool addStxEtx) {
size_t sourceLen, uint8_t* destStream, size_t maxDestLen,
size_t* encodedLen, bool addStxEtx) {
if (maxDestLen < 2) {
return RETURN_FAILED;
return STREAM_TOO_SHORT;
}
uint32_t encodedIndex = 0, sourceIndex = 0;
size_t encodedIndex = 0, sourceIndex = 0;
uint8_t nextByte;
if (addStxEtx) {
destStream[0] = STX;
@ -62,15 +64,16 @@ ReturnValue_t DleEncoder::encode(const uint8_t* sourceStream,
nextByte = sourceStream[sourceIndex];
if ((nextByte == STX) || (nextByte == ETX) || (nextByte == 0x0D)) {
if (encodedIndex + 1 >= maxDestLen) {
return RETURN_FAILED;
return STREAM_TOO_SHORT;
} else {
destStream[encodedIndex] = DLE;
++encodedIndex;
// Escaped byte will be actual byte + 0x40.
destStream[encodedIndex] = nextByte + 0x40;
}
} else if (nextByte == DLE) {
if (encodedIndex + 1 >= maxDestLen) {
return RETURN_FAILED;
return STREAM_TOO_SHORT;
} else {
destStream[encodedIndex] = DLE;
++encodedIndex;
@ -90,6 +93,6 @@ ReturnValue_t DleEncoder::encode(const uint8_t* sourceStream,
*encodedLen = encodedIndex;
return RETURN_OK;
} else {
return RETURN_FAILED;
return STREAM_TOO_SHORT;
}
}

64
globalfunctions/DleEncoder.h
View File

@ -1,25 +1,71 @@
#ifndef DLEENCODER_H_
#define DLEENCODER_H_
#ifndef FRAMEWORK_GLOBALFUNCTIONS_DLEENCODER_H_
#define FRAMEWORK_GLOBALFUNCTIONS_DLEENCODER_H_
#include <framework/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 startr of the stream and an ETX marker at the end of
* the stream. Any STX, ETX and DLE occurences in the source stream are escaped
* by a DLE character.
*/
class DleEncoder: public HasReturnvaluesIF {
private:
DleEncoder();
virtual ~DleEncoder();
public:
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 const uint8_t STX = 0x02;
//! End Of Text character. Last character in encoded stream
static const uint8_t ETX = 0x03;
//! Data Link Escape character. Used to escape STX, ETX and DLE occurences
//! in the source stream.
static const uint8_t DLE = 0x10;
static ReturnValue_t decode(const uint8_t *sourceStream,
uint32_t sourceStreamLen, uint32_t *readLen, uint8_t *destStream,
uint32_t maxDestStreamlen, uint32_t *decodedLen);
/**
* 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.
* @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);
static ReturnValue_t encode(const uint8_t *sourceStream, uint32_t sourceLen,
uint8_t *destStream, uint32_t maxDestLen, uint32_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_ */

3
returnvalues/FwClassIds.h
View File

@ -64,7 +64,8 @@ enum {
LOCAL_POOL_OWNER_IF, //LPIF 58
POOL_VARIABLE_IF, //PVA 59
HOUSEKEEPING_MANAGER, //HKM 60
PUS_PARSER, //PUSP 61
DLE_ENCODER, //DLEE 61
PUS_PARSER, //PUSP 62
FW_CLASS_ID_COUNT //is actually count + 1 !
};