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Error with binary IO

killer13666 (7)
I am trying to make a program like a virtual machine, and therefore I need to have a virtual hard drive. I have it split across four files, each being exactly 67,108,864 bytes (at this point, the files consist of 0x00 throughout the entire file). When I try to write to the beginning of one of the files, I get a "EXC_BAD_ACCESS (code=1, address=0xff)" from Xcode. I have no idea what I am doing wrong. Here is my source code.

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#include <iostream>
#include <fstream>

using namespace std;

int main()
{
	fstream drive1("main1.vhd", ios::in | ios::out | ios::binary);
	fstream drive2("main2.vhd", ios::in | ios::out | ios::binary);
	fstream drive3("main3.vhd", ios::in | ios::out | ios::binary);
	fstream drive4("main4.vhd", ios::in | ios::out | ios::binary);
	
	drive1.seekg(0, ios::end);
	const long size1 = drive1.tellg();
	drive1.seekg(0, ios::beg);
	
	drive2.seekg(0, ios::end);
	const long size2 = drive2.tellg();
	drive2.seekg(0, ios::beg);
	
	drive3.seekg(0, ios::end);
	const long size3 = drive3.tellg();
	drive3.seekg(0, ios::beg);
	
	drive4.seekg(0, ios::end);
	const long size4 = drive4.tellg();
	drive2.seekg(0, ios::beg);
	
	if (size1!=67108864 && size2!=67108864 && size3!=67108864 && size4!=67108864)
	{
		cout << "The hard drive files are not the correct size and cannot be addressed properly\n";
		return 9;
	}
	
	drive1.seekp(0, ios::beg);
	drive2.seekp(0, ios::beg);
	drive3.seekp(0, ios::beg);
	drive4.seekp(0, ios::beg);
	
	unsigned char byte = 0xff;
	
	drive1.write(reinterpret_cast<char*>(byte), sizeof(byte));
	
	return 0;
}
LB (13399)
You are writing to disk, from memory at address 0xff - maybe you meant to write 0xff to disk instead of the memory at 0xff?

drive1.write(&byte, sizeof(byte));

Always remember: if you have to cast, something is wrong.
Last edited on
ne555 (10692)
> Always remember: if you have to cast, something is wrong.
foo.cpp:42:15: error: cannot initialize a parameter of type 'const char_type *' (aka 'const char *') with an rvalue of type 'unsigned char *'
        drive1.write(&byte, sizeof(byte));
                     ^~~~~
Last edited on
LB (13399)
I was wrong :)
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