fwrite not writing property (or fread not reading properly)

I am trying to write to a dat file that contains a header on how many entries there are as well as the entries themselves. Below is the file writing code:

Code:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <malloc.h>

int main()
{
	float slavepos[] = {.083, .21, .072, 0, 0, 0};
	float delta = -0.001;
	int numslavepos = 100;

	float *slaveposwrite = (float*) malloc(100*6*sizeof(float));

	char *FileName = "NeedleBasePos.dat";
	FILE *fid;

	fid = fopen(FileName, "w");

	fwrite(&numslavepos, sizeof(int), 1, fid);

	for (int i = 0; i < 100; i++)
	{
		memcpy(&slaveposwrite[6*i], &slavepos[0], 6*sizeof(float));
		slavepos[1] += delta;
	}

	fwrite(slaveposwrite, sizeof(float), 6*100, fid);
	
	fclose(fid);
	free((void*) slaveposwrite);
	return 0;
}

As I read from the debugger, I'm getting something like the following that I'm assuming gets written to the file attached as arraywritten.txt

However, when I try to read the file in another code, while I'm reading the header properly in terms of the amount of entries, I am having trouble reading the entries properly. Below is my code for reading the file, and I have attached the garbage that I have read in arrayread.txt:

Code:

void SPHandleError(int i)
{
	char errormsg[200];
	switch(i) {
	case 1: sprintf(errormsg, "Error opening file NeedleBasePos.dat !"); break;
	case 2: sprintf(errormsg, "Input file has an incompatible data structure\n"); break;
	default: sprintf(errormsg, "An unhandled error has occured !!");
	}
	//if (MessageBox(NULL, errormsg, "Unrecoverable Error - Closing application", MB_ICONERROR))  exit(-1);
}

// Reading the needle trajectory from a text file
// STATUS UPDATED: SlavePos
void SlavePosFromFile( char *fname, slavepos_struct *needletippos )
{
#define SPHEADERSIZE		1

	FILE	*spfile;
	int		Sizes[SPHEADERSIZE], *Sizesptr = Sizes, pos;

	if( (spfile = fopen(fname, "rb")) == NULL)
	{
		SPHandleError(1);
	}
	else
	{
		printf("Bytes read for Needle Position trajectory from file '%s':\n", fname);
	}
	printf("NeedleBasePos.dat size = %d\n", fread(Sizes, sizeof(int), SPHEADERSIZE, spfile));
		needletippos->entries = *(Sizesptr++);

	needletippos->SlavePos = (float*) calloc(SLAVEPOSELEMENTS*needletippos->entries, sizeof(float));
	printf("SlavePos = %d\n",
		   fread(needletippos->SlavePos, sizeof(float), SLAVEPOSELEMENTS*needletippos->entries, spfile));

	// Check to see if more data is left in the file
	pos = ftell(spfile);
	fseek(spfile, 0, SEEK_END);
	if (ftell(spfile) != pos) SPHandleError(2);
	fclose(spfile);
	printf("Parameter file '%s' is read successfully.\n", fname);
}

I don't know what possibly could cause me not being able to read (or write) the values properly. Any suggestions would be much appreciated.

Nvm my question. Opened and read the file inconsistently in terms of the fopen flags.

Code:

	free((void*) slaveposwrite);

If you are actually using C rather than C++, then perhaps you should change the name of your source file to .c instead of .cpp, that way you do can convert any pointer to or from void * without a cast.

Although this is the C++ forum, so perhaps you wanted to use new [] and delete [] to create your local array. In which case you probably should use a ofstream/ifstream to write/read the data through, and using the write() and read() member functions of the streams.

--
Mats

I'm using C++ object-oriented functionalities in some parts of the code. However, I haven't changed it that this structure is also object-oriented. That's why I left the casting in there along with using free() function. Also, I had been using this file as a mex file to be run in the Matlab environment. Therefore, I kept using free in order to remain compatible with allocating memory in the right memory space in Matlab. Thanks for your inputs though.