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write_ctf_shm.c
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Sun, May 25, 14:49

write_ctf_shm.c
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/*
* WRITE_CTF_SHM writes a packet to shared memory. This function can be
* used for real-time processing of data while it is being acquired.
*
* Use as
* write_ctf_shm(msgNumber, msgType, msgId, sampleNumber, numSamples, numChannels, data);
*
* Copyright (C) 2007, Robert Oostenveld
*
* $Id$
*/
#include <string.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include "mex.h"
#include <limits.h>
#define ACQ_MSGQ_SIZE 600
#define ACQ_MSGQ_SHMKEY 0x39457f73
#define ACQ_MSGQ_SHMPROJID 12345
#define ACQ_MSGQ_SHMPATH "/opt/ctf/bin/Acq"
typedef enum
{
ACQ_MSGQ_SETUP_COLLECTION,
ACQ_MSGQ_DATA,
ACQ_MSGQ_CLOSE_CONNECTION,
ACQ_MSGQ_INVALID = INT_MAX
} ACQ_MessageType;
typedef struct
{
ACQ_MessageType message_type;
int messageId;
int sampleNumber;
int numSamples;
int numChannels;
int data[28160];
} ACQ_MessagePacketType;
void
mexFunction (int nlhs, mxArray * plhs[], int nrhs, const mxArray * prhs[])
{
key_t key;
ACQ_MessagePacketType *packet;
int msgNumber, msgType, msgId, sampleNumber, numSamples, numChannels, *data;
int shmid, shmsize;
int numValues = 28160;
shmsize = sizeof(ACQ_MessagePacketType) * ACQ_MSGQ_SIZE;
/* make the key
if ((key = ftok(ACQ_MSGQ_SHMPATH, ACQ_MSGQ_SHMPROJID)) == -1) {
perror("ftok");
exit(1);
}
*/
/* use the pre-defined key */
key = ACQ_MSGQ_SHMKEY;
/* connect to (and possibly create) the segment */
if ((shmid = shmget(key, shmsize, 0644 | IPC_CREAT )) == -1)
mexErrMsgTxt("shmget");
/* attach to the segment to get a pointer to it */
packet = shmat(shmid, (void *)0, 0);
if ((char *)packet == (char *)(-1))
mexErrMsgTxt("shmat");
if (nrhs<7)
mexErrMsgTxt("Not enough input arguments");
msgNumber = (int)mxGetScalar(prhs[0])-1; /* one offset in Matlab, zero offset in C */
/*
msgType = (int)mxGetScalar(prhs[1]);
msgId = (int)mxGetScalar(prhs[2]);
sampleNumber = (int)mxGetScalar(prhs[3]);
numSamples = (int)mxGetScalar(prhs[4]);
numChannels = (int)mxGetScalar(prhs[5]);
*/
if (mxGetClassID(prhs[6]) != mxINT32_CLASS)
mexErrMsgTxt("Invalid type of data, should be int32");
if (msgNumber<0)
mexErrMsgTxt("Cannot write before the first packet");
if (msgNumber>=ACQ_MSGQ_SIZE)
mexErrMsgTxt("Cannot write after the last packet");
numValues = mxGetNumberOfElements(prhs[6]);
numValues = ( numValues>28160 ? 28160 : numValues ); /* check boundary */
numValues = ( numValues<0 ? 0 : numValues ); /* check boundary */
/* write the meta-information to the packet */
packet[msgNumber].message_type = (int)mxGetScalar(prhs[1]);
packet[msgNumber].messageId = (int)mxGetScalar(prhs[2]);
packet[msgNumber].sampleNumber = (int)mxGetScalar(prhs[3]);
packet[msgNumber].numSamples = (int)mxGetScalar(prhs[4]);
packet[msgNumber].numChannels = (int)mxGetScalar(prhs[5]);
/* write the data to the packet */
memcpy(packet[msgNumber].data, mxGetData(prhs[6]), numValues*sizeof(int));
/* detach from the segment */
if (shmdt(packet) == -1)
mexErrMsgTxt("shmdt");
} /* end of mexFunction */

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