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read_ctf_shm.c
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Sun, May 25, 15:07

read_ctf_shm.c
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/*
* READ_CTF_SHM reads metainformation or selected blocks of data from
* shared memory. This function can be used for real-time processing of
* data while it is being acquired.
*
* Use as
* [msgType msgId sampleNumber numSamples numChannels] = read_ctf_shm;
* or
* [data] = read_ctf_shm(msgNumber);
* [data] = read_ctf_shm(msgNumber, numValues);
*
* 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 *msgType, *msgId, *sampleNumber, *numSamples, *numChannels;
int shmid, shmsize, i;
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==0) {
/* read the meta information from all packets */
plhs[0] = mxCreateNumericMatrix(1, ACQ_MSGQ_SIZE, mxINT32_CLASS, mxREAL);
plhs[1] = mxCreateNumericMatrix(1, ACQ_MSGQ_SIZE, mxINT32_CLASS, mxREAL);
plhs[2] = mxCreateNumericMatrix(1, ACQ_MSGQ_SIZE, mxINT32_CLASS, mxREAL);
plhs[3] = mxCreateNumericMatrix(1, ACQ_MSGQ_SIZE, mxINT32_CLASS, mxREAL);
plhs[4] = mxCreateNumericMatrix(1, ACQ_MSGQ_SIZE, mxINT32_CLASS, mxREAL);
msgType = mxGetData(plhs[0]);
msgId = mxGetData(plhs[1]);
sampleNumber = mxGetData(plhs[2]);
numSamples = mxGetData(plhs[3]);
numChannels = mxGetData(plhs[4]);
for (i=0; i<ACQ_MSGQ_SIZE; i++) {
msgType[i] = (int)(packet[i].message_type);
msgId[i] = packet[i].messageId;
sampleNumber[i] = packet[i].sampleNumber;
numSamples[i] = packet[i].numSamples;
numChannels[i] = packet[i].numChannels;
}
}
else {
if (nrhs==2) {
numValues = (int)mxGetScalar(prhs[1]);
numValues = ( numValues>28160 ? 28160 : numValues ); /* check boundary */
numValues = ( numValues<0 ? 0 : numValues ); /* check boundary */
}
/* read the data from the selected packet */
/* one-offset in Matlab, zero-offset in C */
i = mxGetScalar(prhs[0]) - 1;
if (i<0)
mexErrMsgTxt("Cannot read before the first packet");
if (i>=ACQ_MSGQ_SIZE)
mexErrMsgTxt("Cannot read after the last packet");
plhs[0] = mxCreateNumericMatrix(1, numValues, mxINT32_CLASS, mxREAL);
memcpy(mxGetData(plhs[0]), packet[i].data, numValues*sizeof(int));
}
/* detach from the segment */
if (shmdt(packet) == -1)
mexErrMsgTxt("shmdt");
} /* end of mexFunction */

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