Read specific sector on hard drive using C language on windows - c

Question

i have tried this code it works when i read a sector from an USB flash drive but it does'nt work with any partiton on hard drive , so i want to know if it's the same thing when you try to read from usb or from hard drive
int ReadSector(int numSector,BYTE* buf){
int retCode = 0;
BYTE sector[512];
DWORD bytesRead;
HANDLE device = NULL;
device = CreateFile("\\\\.\\H:", // Drive to open
GENERIC_READ, // Access mode
FILE_SHARE_READ, // Share Mode
NULL, // Security Descriptor
OPEN_EXISTING, // How to create
0, // File attributes
NULL); // Handle to template
if(device != NULL)
{
SetFilePointer (device, numSector*512, NULL, FILE_BEGIN) ;
if (!ReadFile(device, sector, 512, &bytesRead, NULL))
{
printf("Error in reading disk\n");
}
else
{
// Copy boot sector into buffer and set retCode
memcpy(buf,sector, 512);
retCode=1;
}
CloseHandle(device);
// Close the handle
}
return retCode;}

Answer 1

The problem is the sharing mode. You have specified FILE_SHARE_READ which means that nobody else is allowed to write to the device, but the partition is already mounted read/write so it isn't possible to give you that sharing mode. If you use FILE_SHARE_READ|FILE_SHARE_WRITE it will work. (Well, provided the disk sector size is 512 bytes, and provided the process is running with administrator privilege.)
You're also checking for failure incorrectly; CreateFile returns INVALID_HANDLE_VALUE on failure rather than NULL.
I tested this code successfully:
#include <windows.h>
#include <stdio.h>
int main(int argc, char ** argv)
{
int retCode = 0;
BYTE sector[512];
DWORD bytesRead;
HANDLE device = NULL;
int numSector = 5;
device = CreateFile(L"\\\\.\\C:", // Drive to open
GENERIC_READ, // Access mode
FILE_SHARE_READ|FILE_SHARE_WRITE, // Share Mode
NULL, // Security Descriptor
OPEN_EXISTING, // How to create
0, // File attributes
NULL); // Handle to template
if(device == INVALID_HANDLE_VALUE)
{
printf("CreateFile: %u\n", GetLastError());
return 1;
}
SetFilePointer (device, numSector*512, NULL, FILE_BEGIN) ;
if (!ReadFile(device, sector, 512, &bytesRead, NULL))
{
printf("ReadFile: %u\n", GetLastError());
}
else
{
printf("Success!\n");
}
return 0;
}