jamulus/src/protocol.cpp

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/******************************************************************************\
* Copyright (c) 2004-2006
*
* Author(s):
* Volker Fischer
*
Protocol message definition
+-----------+------------+-----------------+--------------+-------------+
| 2 byte ID | 1 byte cnt | 2 byte length n | n bytes data | 2 bytes CRC |
+-----------+------------+-----------------+--------------+-------------+
- message ID defined by the defines PROTMESSID_x
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- cnt: counter which is increment for each message and wraps around at 255
- length n in bytes of the data
- actual data, dependent on message type
- 16 bits CRC, calculating over the entire message, is transmitted inverted
Generator polynom: G_16(x) = x^16 + x^12 + x^5 + 1, initial state: all ones
*
******************************************************************************
*
* This program is free software; you can redistribute it and/or modify it under
* the terms of the GNU General Public License as published by the Free Software
* Foundation; either version 2 of the License, or (at your option) any later
* version.
*
* This program is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License along with
* this program; if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
\******************************************************************************/
#include "protocol.h"
/* Implementation *************************************************************/
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bool CProtocol::ParseMessage ( const CVector<uint8_t>& vecIn,
int& iCnt,
int& iID,
CVector<uint8_t>& vecData )
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{
/*
return code: true -> ok; false -> error
*/
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int iLenBy, i;
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unsigned int iCurPos;
// query length of input vector
const int iVecInLenByte = vecIn.Size();
// vector must be at least "MESS_LEN_WITHOUT_DATA_BYTE" bytes long
if ( iVecInLenByte < MESS_LEN_WITHOUT_DATA_BYTE )
{
return false; // return error code
}
// decode header -----
iCurPos = 0; // start from beginning
/* 2 bytes ID */
iID = static_cast<int> ( GetValFromStream ( vecIn, iCurPos, 2 ) );
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/* 1 byte cnt */
iCnt = static_cast<int> ( GetValFromStream ( vecIn, iCurPos, 1 ) );
/* 2 bytes length */
iLenBy = static_cast<int> ( GetValFromStream ( vecIn, iCurPos, 2 ) );
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// make sure the length is correct
if ( iLenBy != iVecInLenByte - MESS_LEN_WITHOUT_DATA_BYTE )
{
return false; // return error code
}
// now check CRC -----
CCRC CRCObj;
const int iLenCRCCalc = MESS_HEADER_LENGTH_BYTE + iLenBy;
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iCurPos = 0; // start from beginning
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for ( i = 0; i < iLenCRCCalc; i++ )
{
CRCObj.AddByte ( static_cast<uint8_t> (
GetValFromStream ( vecIn, iCurPos, 1 ) ) );
}
if ( CRCObj.GetCRC () != GetValFromStream ( vecIn, iCurPos, 2 ) )
{
return false; // return error code
}
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// decode data -----
iCurPos = MESS_HEADER_LENGTH_BYTE; // start from beginning of data
for ( i = 0; i < iLenBy; i++ )
{
vecData[i] = static_cast<uint8_t> (
GetValFromStream ( vecIn, iCurPos, 1 ) );
}
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return true; // everything was ok
}
uint32_t CProtocol::GetValFromStream ( const CVector<uint8_t>& vecIn,
unsigned int& iPos,
const unsigned int iNumOfBytes )
{
/*
note: iPos is automatically incremented in this function
*/
// 4 bytes maximum since we return uint32
ASSERT ( ( iNumOfBytes > 0 ) && ( iNumOfBytes <= 4 ) );
ASSERT ( vecIn.Size() >= iPos + iNumOfBytes );
uint32_t iRet = 0;
for ( int i = 0; i < iNumOfBytes; i++ )
{
iRet |= vecIn[iPos] << ( i * 8 /* size of byte */ );
iPos++;
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}
return iRet;
}
void CProtocol::GenMessage ( CVector<uint8_t>& vecOut,
const int iCnt,
const int iID,
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const CVector<uint8_t>& vecData )
{
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int i;
// query length of data vector
const int iDataLenByte = vecData.Size();
// total length of message = 7 + "iDataLenByte"
// 2 byte ID + 1 byte cnt + 2 byte length + n bytes data + 2 bytes CRC
const int iTotLenByte = 7 + iDataLenByte;
// init message vector
vecOut.Init( iTotLenByte );
// encode header -----
unsigned int iCurPos = 0; // init position pointer
/* 2 bytes ID */
PutValOnStream ( vecOut, iCurPos,
static_cast<uint32_t> ( iID ), 2 );
/* 1 byte cnt */
PutValOnStream ( vecOut, iCurPos,
static_cast<uint32_t> ( iCnt ), 1 );
/* 2 bytes length */
PutValOnStream ( vecOut, iCurPos,
static_cast<uint32_t> ( iDataLenByte ), 2 );
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// encode data -----
for ( i = 0; i < iDataLenByte; i++ )
{
PutValOnStream ( vecOut, iCurPos,
static_cast<uint32_t> ( vecData[i] ), 1 );
}
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// encode CRC -----
CCRC CRCObj;
iCurPos = 0; // start from beginning
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const int iLenCRCCalc = MESS_HEADER_LENGTH_BYTE + iDataLenByte;
for ( i = 0; i < iLenCRCCalc; i++ )
{
CRCObj.AddByte ( static_cast<uint8_t> (
GetValFromStream ( vecOut, iCurPos, 1 ) ) );
}
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PutValOnStream ( vecOut, iCurPos,
static_cast<uint32_t> ( CRCObj.GetCRC () ), 2 );
}
void CProtocol::PutValOnStream ( CVector<uint8_t>& vecIn,
unsigned int& iPos,
const uint32_t iVal,
const unsigned int iNumOfBytes )
{
/*
note: iPos is automatically incremented in this function
*/
// 4 bytes maximum since we use uint32
ASSERT ( ( iNumOfBytes > 0 ) && ( iNumOfBytes <= 4 ) );
ASSERT ( vecIn.Size() >= iPos + iNumOfBytes );
for ( int i = 0; i < iNumOfBytes; i++ )
{
vecIn[iPos] =
( iVal >> ( i * 8 /* size of byte */ ) ) & 255 /* 11111111 */;
iPos++;
}
}