Reading in a binary file

**Bri Rock** · 07-07-2004

Hey guys,

I'm having a problem reading in a binary file.

Here's my snippet of code I'm trying to work with

Code:

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

static unsigned short read_array[25198325];

int main()
{
	//Tag directory of file
	const char *file1 = "/home/my_name/programs/InputFile.ima";

	//Set input file reading
	fstream reader(file1, ios::in | ios::binary);

	if (!reader)
	{
		cout << "\nFile doesn't exist\n" << endl;
		return 0;
	}

	//char ch;
	
	istream &read(read_array, 25198320);  
	//reader.read(read_array, 25198320);  

	return 0;

}

I'm trying to get help out of some books and some online help sites, but haven't gotten anywhere with those.
(i.e. I have no idea what I'm doing

)

So, I'm trying to just read in data from a 50 MB binary file, and to store all the data in the array before I do anything else.

I get this with the code above
error: invalid initialization of non-const reference of
type 'std::istream&' from a temporary of type 'int'

I've tried to change the array to type char, but that hasn't worked either. It really doesn't like that istream &read line. Other than that, the file initialization part seems fine.

Anyone have any ideas? That would help alot

Thanks,
Bri Rock

**skorman00** · 07-07-2004

Code:

istream &read(read_array, 25198320);

I don't like the looks of that! You already have a fstream object right? Well use that to read.

**swoopy** · 07-08-2004

> //reader.read(read_array, 25198320);

Try this:
reader.read(reinterpret_cast<char *> (read_array), 25198320);

Or:
reader.read(reinterpret_cast<char *> (read_array), sizeof(read_array));

Also, you can use gcount() to find out how many bytes were read:

cout << "bytes read: " << reader.gcount() << endl;

EDIT: Changed static_cast to reinterpret_cast. I have no idea what the differences are between static_cast, reinterpret_cast, and dynamic_cast. Except dynamic_cast occurs at runtime perhaps?

**Hammer** · 07-08-2004

>>50 MB binary file,
>>and to store all the data in the array
That's a fair sized amount of data to read in one go. You'd do better by reading chunks at a time, imho.

Code:

#include <iostream>
#include <fstream>
#include <string>

using namespace std;

static unsigned char     read_array[25198325];

int main(void)
{
  const char  *file1 = "junk1.cpp";

  fstream     reader(file1, ios::in | ios::binary);

  if (!reader)
  {
    cout << "\nFile doesn't exist\n" << endl;
    return(0);
  }

  reader.read(read_array, 25198320);
  cout << read_array;
  reader.close();

  return(0);
}

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