/*=================================================================
 * mexatexit.c 
 * 
 * This example demonstrates how to use mexAtExit.  It allows you to
 * write strings to a data file, matlab.data.  The MEX-file
 * mexatexit.c registers an exit function that closes the datafile.
 * The input to the MEX-file mexatexit is a string.  You may continue
 * calling the function with new strings to add to the file
 * matlab.data. The data file will not be closed until the MEX-file is
 * cleared or MATLAB is exited, which cause the exit function to be
 * executed.

 * This is a MEX-file for MATLAB.  
 * Copyright 1984-2011 The MathWorks, Inc.
 * All rights reserved.
 *=================================================================*/


#include <stdio.h>
#include <string.h> /* strlen */
#include "mex.h"

static FILE  *fp=NULL;

/* Here is the exit function, which gets run when the MEX-file is
   cleared and when the user exits MATLAB. The mexAtExit function
   should always be declared as static. */
static void CloseStream(void)
{
  mexPrintf("Closing file matlab.data.\n");
  fclose(fp);
}

void 
mexFunction(int nlhs,mxArray *plhs[],int nrhs,const mxArray *prhs[])
{
    char *str;
    (void) plhs;      /* unused parameter */

    /* Check for proper number of input and output arguments */    
    if (nrhs != 1) {
        mexErrMsgIdAndTxt( "MATLAB:mexatexit:invalidNumInputs",
                "One input argument required.");
    } 
    if(nlhs > 1){
        mexErrMsgIdAndTxt( "MATLAB:mexatexit:maxrhs",
                "Too many output arguments.");
    }
    if (!(mxIsChar(prhs[0]))){
        mexErrMsgIdAndTxt( "MATLAB:mexatexit:invalidInput",
                "Input must be of type string.\n.");
    }
    
    if (fp==NULL){
	fp = fopen("matlab.data", "w");
	if (fp == NULL){
	    mexErrMsgIdAndTxt( "MATLAB:mexatexit:errorOpeningFile",
                "Could not open file matlab.data."); 
	}
	mexPrintf("Opening file matlab.data.\n");
	
	/* Register an exit function. You should only register the
	   exit function after the file has been opened successfully*/
	mexAtExit(CloseStream);
    }
    /* The user passes a string in prhs[0]; write the string
       to the data file. NOTE: you must free str after it is used */ 
    str=mxArrayToString(prhs[0]);
    if ((size_t)fprintf(fp,"%s\n", str) != strlen(str) +1){
        mxFree(str);
        mexErrMsgIdAndTxt( "MATLAB:mexatexit:errorWritingFile",
                "Could not write data to file.\n");
    }
    mexPrintf("Writing data to file.\n");
    mxFree(str);
}