How to read blocks of float[15] from a binary file???

[delic]

I thought the following would read in blocks of 15 floats from a binary file but after a bunch of correct reads all the output numbers are giberish, numbers like 1E-20 type stuff..

I have to use stdio routines like fread, I have written the same code with fstreams and it works fine. I am missing some stdio quirk or something.. It seems to get hosed when the _cnt variable in the FILE structure becomes < then the size of 15 floats (60).. I believe it has to do with the buffering of the file, which is the system 4096 size.

I have done more debugging.. _cnt gets to a value of 1 then the next fread reads data that is 1516 bytes downstream instead of 60 (note that this is not even a multiple of 60, my block size).. for no reason, I have no seeks or anything in the code..

float CPDATA[15];
do{
fread((char*)CPDATA,sizeof(float)*15, 1, thO->fd);
//outfile read info to a file
outfile<<ftell(thO->fd)<<" ";
for(int i=0;i<15;i++)
outfile<<CPDATA[i]<<" ";
outfile<<endl;

k++;
}while(k<j);

[dumah]

Ok, my C sucks as I have been using C++ for ages (much nicer IMO ), so any nasties here, please forgive me.

You shoulnd have to look at the members of the FILE struct for something as simple as this, my guess is a problem with your code

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

#define MY_MAX_FLOATS 15

int main(){

	FILE *out = 0,*in = 0;//File pointers
	float* ptrFloat = 0;//memory I will use to read file
	char *szFileName = "Hello.txt";//Name of file
	int i;//iterator
	float flArray[MY_MAX_FLOATS];//Array I will write to file
	
	for(i = 0;i < MY_MAX_FLOATS;i++)
		flArray[i] = i+1 * 1.1;//fill array wilth float info
	
	out = fopen(szFileName,"wb");//open output file
	if(!out){
		puts("Error opening file");
		return 1;
	}
	
	fwrite(flArray,sizeof(float)*MY_MAX_FLOATS,1,out);//Write info to file
	if(ferror(out)){
		puts("Error writting to file");
		fclose(out);
		return 1;
	}
	
	fclose(out);//close output file
	
	//*********************************************************************
	// We now have a file with 15 floats that we want to read
	//*********************************************************************
	
	in = fopen(szFileName,"rb");//open file to read
	if(!in){
		puts("Error opening file");
		return 1;
	}
	
	ptrFloat = malloc(MY_MAX_FLOATS * sizeof(float));//allocate memory for 15 floats
	if(!ptrFloat){
		puts("Error allocating memory");
		fclose(in);
		return 1;
	}
	
	fread(ptrFloat,sizeof(float)*MY_MAX_FLOATS,1,in);//read all that data
	if(ferror(in)){
		puts("Error reading file");
		fclose(in);
		return 1;
	}
	
	for(i = 0;i < MY_MAX_FLOATS; ++i){
		printf("%.2f\n",ptrFloat[i]);//write to screen
	}
	
	fclose(in);//free file
	free(flArray);//And memory
	return 0;
}

[delic]

Well thanks for the reply.. Yeah it has to do with the porting of the code to windows from unix..

Aggh, I agree c++ is much nicer and that is why this was one of those cases where it is easier to rewrite the code using fstreams. And I did and it worked great..

It had to have been some wierd stdio bug or something because I literally rewrote each line of code with an equivalent line of fstream code and it works great.. So in the end I still dont know the C code doesnt work but I went around the probelm..