disks.c

#include <windows.h>
#include <stdio.h>

typedef unsigned __int64 u64;
typedef unsigned u32;

static int isDiskAvailable(char upperLetter)
{
    if(!('A' <= upperLetter && upperLetter <= 'Z'))
        return 0;

    const DWORD d = GetLogicalDrives();
    return (d >> (upperLetter - 'A')) & 1;
}

static HANDLE openDiskHandle(char disk)
{
    char buff[10];
    buff[0] = '\\';
    buff[1] = '\\';
    buff[2] = '.';
    buff[3] = '\\';
    buff[4] = disk;
    buff[5] = ':';
    buff[6] = '\0';
    return CreateFileA(buff, GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING, 0x0, NULL);
}

static u64 getBytesPerSector(HANDLE disk)
{
    DISK_GEOMETRY geo;
    DWORD bytesgiven;
    BOOL ok;

    if(disk == INVALID_HANDLE_VALUE)
        return 0u;

    ok = DeviceIoControl(disk, IOCTL_DISK_GET_DRIVE_GEOMETRY, NULL, 0, &geo, sizeof(geo), &bytesgiven, NULL);
    if(ok)
        return (u64)geo.BytesPerSector;

    return 0u;
}

static u64 littleu64(const char * buff)
{
    const unsigned char * b = (const unsigned char*)buff;
    u64 ret = 0u;
    int i;

    for(i = 7; i >= 0; --i)
        ret = (ret << 8) + (u64)b[i];

    return ret;
}

static u32 littleu32(const char * buff)
{
    const unsigned char * b = (const unsigned char*)buff;
    u32 ret = 0u;
    int i;

    for(i = 3; i >= 0; --i)
        ret = (ret << 8) + (u32)b[i];

    return ret;
}

static void askEnterToContinue(void)
{
    char dummy[5];

    printf("Press enter to continue\n");
    fgets(dummy, 2, stdin);
}

static int readBuffer(HANDLE handle, void * buff, u64 size)
{
    DWORD dummyreadsize;
    return ReadFile(handle, buff, size, &dummyreadsize, NULL) != 0;
}

static int hasNtfsHeader(const char * buff)
{
    const unsigned char * b = (const unsigned char*)buff;
    if(b[0] != 0xeb) return 0;
    if(b[1] != 0x52) return 0;
    if(b[2] != 0x90) return 0;
    if(b[3] != 'N') return 0;
    if(b[4] != 'T') return 0;
    if(b[5] != 'F') return 0;
    if(b[6] != 'S') return 0;
    if(b[7] != ' ') return 0;
    if(b[8] != ' ') return 0;
    if(b[9] != ' ') return 0;
    if(b[10] != ' ') return 0;
    return 1;
}

int main(int argc, char ** argv)
{
    int i;
#define MYBUFF_SIZE 8192
    char mybuff[MYBUFF_SIZE];
    HANDLE diskhandle;
    u64 bytespersector;

    for(i = 'A'; i <= 'Z'; ++i)
    {
        if(!isDiskAvailable(i))
            continue;

        diskhandle = openDiskHandle(i);
        if(diskhandle == INVALID_HANDLE_VALUE)
        {
            printf("Disk %c: INVALID_HANDLE_VALUE, GetLastError() == %u\n", i, (unsigned)GetLastError());
            continue;
        } /* if */

        bytespersector = getBytesPerSector(diskhandle);

        if(bytespersector <= MYBUFF_SIZE)
        {
            if(readBuffer(diskhandle, mybuff, bytespersector))
            {
                if(hasNtfsHeader(mybuff))
                {
                    const u64 totalsectors = littleu64(mybuff + 0x28);
                    const u64 totalbytes = totalsectors * bytespersector;
                    const double gib = (totalbytes / (1024 * 1024)) / 1024.0;
                    const char * fmt = "Disk %c: %llu bytes per sector, %.4f GiB total\n";
                    printf(fmt, i, bytespersector, gib);
                }
                else
                {
                    printf("Disk %c: no NTFS header\n", i);
                }
            }
            else
            {
                printf("Disk %c: ReadFile() == 0, GetLastError() == %u\n", i, (unsigned)GetLastError());
            }
        }
        else
        {
            const char * fmt = "Disk %c: %llu bytes per sector, MYBUFF_SIZE too small (%u) to read into\n";
            printf(fmt, i, bytespersector, (unsigned)MYBUFF_SIZE);
        }

        if(!CloseHandle(diskhandle))
            printf("CloseHandle failed, GetLastError() = %u\n", (unsigned)GetLastError());
    } /* for */

    askEnterToContinue();
    return 0;
}