Writing to specific disk areas.

Okay, here's the deal. I want to know how to write to specific area's on the hard disk in C++. Such as:

writing zeros to a specified sector
writing the MBR
formatting the disk w/out 'system("format c:");'
formatting a disk in a specific format, or a new one
writing to FAT tables
writing partitions

I know other languages can do this better, but I'd prefer C++, or the syntax for BAT files.
I'm quite interested in making one of those disk wiping programs, and creating a partitioning utility. A defragment utility, or a FAT table/MBR backup utility is also on the list.

So if you have specific information, or specific pages to view, that would be helpful as I can't seem to find too much via google.

AxessTerminated

Umm, maybe start by checking out the source code for something like mkfs.fat32? That should give you a general idea of how its done.

I googled 'mkfs.fat32 "source code" ' and got nothing useful, i tried without the quotes as well. Where can I obtain the source? From what I did see, it seems to be a Linux app, is this so?

My bad, I have mkfs.fat32 set to alias a particular "mkfs.msdos" command.
Yes, it is a linux app, but it should at least give you a starting point on how to approach the design of the application.

You have not specified what OS you are using, such operations are likely highly OS specific - there is no standard API to do it.

Under Linux you would have to determine what device file the device was (for example /dev/hda), and open the file, seek to the appropriate place and read/write as necessary.

On NT, it would be similar, you could use CreateFile with the raw disc device name (I believe they are called something like \\.\c or something). These NT device names are rather weird, you should look them up.

Of course in either case you'll need root or administrator privileges to open the raw device.

By the way, those backslashes above may get trashed by AO.

Slarty

You have not specified what OS you are using, such operations are likely highly OS specific - there is no standard API to do it.

Under Linux you would have to determine what device file the device was (for example /dev/hda), and open the file, seek to the appropriate place and read/write as necessary.

On NT, it would be similar, you could use CreateFile with the raw disc device name (I believe they are called something like \\.\c or something). These NT device names are rather weird, you should look them up.

Of course in either case you'll need root or administrator privileges to open the raw device.

By the way, those backslashes above may get trashed by AO.

Slarty

I always thought you'd do raw disk writing using BIOS, at least that's how I've seen it done before. Perhaps a good book on assembler would be what you need to learn some basics of it. I learned a bit of that kind of thing from "The revolutionary guide to assembly language". It's a little out of date, but if you like doing hardcore BIOS and DOS level programming, it's a good read. As for doing it in C++, I'd say familarize yourself with working with BIOS (I'm not a C++ programmer, so i don't know anything about it).

I always thought you'd do raw disk writing using BIOS, at least that's how I've seen it done before. Perhaps a good book on assembler would be what you need to learn some basics of it. I learned a bit of that kind of thing from "The revolutionary guide to assembly language". It's a little out of date, but if you like doing hardcore BIOS and DOS level programming, it's a good read. As for doing it in C++, I'd say familarize yourself with working with BIOS (I'm not a C++ programmer, so i don't know anything about it).

Flaming Rain, I believe you are a bit confused on what BIOS are...I'm very familiar with them, and they have nothing to do with writing to disk.

Anyways, This would be done on a Windows box, though could be used for a Linux box as well. I know there is no API, that's why I'm looking for sample code. For instance, I want to write all zeros to sector 5, how could I go about doing that? Also, I'd like to access the MBR via C++; editing, deleting, creating new ones...etc etc.


[edit]
P.S. I'm aware that learning assembly would make this easier in the long run and all that good stuff, but I'm looking for a way to do this in C++, without the asm() backdoor, or any assembly for that matter. I'm too lazy to learn that on my own.
[/edit]

Flaming Rain, I believe you are a bit confused on what BIOS are...I'm very familiar with them, and they have nothing to do with writing to disk.

Anyways, This would be done on a Windows box, though could be used for a Linux box as well. I know there is no API, that's why I'm looking for sample code. For instance, I want to write all zeros to sector 5, how could I go about doing that? Also, I'd like to access the MBR via C++; editing, deleting, creating new ones...etc etc.


[edit]
P.S. I'm aware that learning assembly would make this easier in the long run and all that good stuff, but I'm looking for a way to do this in C++, without the asm() backdoor, or any assembly for that matter. I'm too lazy to learn that on my own.
[/edit]

/me gets out book.

int 13h is the BIOS disk reading, writing, and controlling interrupt. Here are some functions:

00h: Reset Disk System
01h: Read Disk System Status
02h: Read Sector
03h: Write Sector
04h: Verify Sector
05h: Format Track
06h: Format Bad Track
07h: Format Drive, Starting at Given Track
08h: Get Drive Parameters
09h: Initialize Fixed Disk Tables
0Ah: Read Sector Long
0Bh: Write Sector Long
0Ch: Seek Cylinder
0Dh: Reset Fixed Disk System
10h: Test Drive Status
11h: Recalibrate Drive
19h: Park Heads

Now, I know this book is a bit old, but, that's what it has to say about everything. If you'd like, I could post the entries for each function. That's all I really know about the topic though, as I haven't tried to do much else. I have a tutorial somewhere on my other machine about boot-sector structure and doing coding for it.

Other than this, I would guess that an OS would have support for such a thing, and there should be documentation around about doing something like that.

[edit]

Forgot to mention that this book doesn't talk about protected-mode programming.

[/edit]

Found a little something

http://www.codeguru.com/Cpp/W-P/syst...cle.php/c5765/

I would think you may have problems with your app getting
permission, under a modern OS, to write to absolute (physical)
sectors. It probably would have been easy in DOS, but normally
the OS manages the low level physical interface to disk
and user apps have to ask the OS to create, open or write to
files.

thanks rcgreen, that's been the most helpful thus far. but what about doing this without windows intervention? as in, a bootable floppy disk that runs an EXE with a menu giving the choice of different format types and such.

Bear in mind that BIOS interrupts are only effective when running under a DOS or pre-boot environment, and certainly won't be avaible while running (for example) Windows.

In a Windows DOS BOX, you will be able to execute the safer BIOS functions, but it's extremely unlikely that dos boxes allow and app to do direct hard disc IO.

Also, discs that the BIOS doesn't know about can never be accessed this way, for example, non-bootable SCSI, non-bootable USB etc.

If you really really want to do this in win32 (which seems highly unlikely but I'll humour you), You need to use CreateFile() with a raw device name (Works with NT NOT win9x (but who cares, win9x should be just a bad memory these days)). This needs administrator rights, may need some other rights that you have to turn on (on a per-process basis), and is very likely to wreck your machine if you don't know what you're doing.

Slarty