#include <stdio.h>
#include <math.h>
#include <string.h>
#include "mex.h"

/*  Gateway Routine */

void mexFunction(
		 int	nlhs,
		 mxArray	*plhs[],
		 int	nrhs,
		 const mxArray	*prhs[]
		 )
{
   double  *ecg; 
   short low,high,nleads;
   long   Nc,Nb,i,sp,p;
   FILE   *fp;
   char   *nombre;
   unsigned char  *buf;

   
   /* Compruebo el numero OK de los argumentos */

   if (nrhs != 2){
      mexErrMsgTxt("Ponme 2 argumentos de entrada.");
      return;
   } else if (nlhs > 1){
      mexErrMsgTxt("Ponme 1 argumento de salida.");
      return;
   }

   /* Debo crear un matriz para el argumento de salida */
  
   i        = (long) mxGetN(prhs[0])+1;
   nombre   = mxCalloc((int)i, sizeof(char));  
   mxGetString(prhs[0], nombre, i);
   Nc = mxGetM(prhs[1]);
   nleads = mxGetN(prhs[1]);
   ecg=mxGetPr(prhs[1]);  
   Nb = 3*Nc;                       /* Number of bytes to write */

   buf = (char *) malloc(Nb*sizeof(char));
   if (buf == NULL) {
      printf("Error: insufficient memory\n");
      return;
   }

/* Computational Routine */ 
  
   if((fp=fopen(nombre, "a")) == NULL){
      	printf("Error: Unable to open file %s.\n", nombre);
      	return(1);
     }
   else { 

	for (i=0,sp=0; i<Nc; i++){
	   buf[sp]=(0XFF & (int) ecg[i]);
           low=(0X0F00 & (int) ecg[i])>>8;
           high=(0X0F00 & (int) ecg[i+Nc])>>8;
	   buf[sp+1]=0XFF & (low + high*16);
  	   buf[sp+2]=(0XFF & (int) ecg[i+Nc]);
   	   sp  += 3 ;
        } 

	p=fwrite(buf, sizeof(char), Nb, fp);  
	fclose(fp);          
        plhs[0]=&p;
   }    
   mxFree(nombre);
   free(buf);
}