diskio-windows.cc

//
// C++ Interface: diskio (Windows-specific components)
//
// Description: Class to handle low-level disk I/O for GPT fdisk
//
//
// Author: Rod Smith <rodsmith@rodsbooks.com>, (C) 2009
//
// Copyright: See COPYING file that comes with this distribution
//
//
// This program is copyright (c) 2009, 2010 by Roderick W. Smith. It is distributed
// under the terms of the GNU GPL version 2, as detailed in the COPYING file.

#define __STDC_LIMIT_MACROS
#define __STDC_CONSTANT_MACROS

#include <windows.h>
#include <winioctl.h>
#define fstat64 fstat
#define stat64 stat
#define S_IRGRP 0
#define S_IROTH 0
#include <stdio.h>
#include <string>
#include <stdint.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <iostream>

#include "support.h"
#include "diskio.h"

using namespace std;

// Returns the official Windows name for a shortened version of same.
void DiskIO::MakeRealName(void) {
   size_t colonPos;

   colonPos = userFilename.find(':', 0);
   if ((colonPos != string::npos) && (colonPos <= 3)) {
      realFilename = "\\\\.\\physicaldrive";
      realFilename += userFilename.substr(0, colonPos);
   } else {
      realFilename = userFilename;
   } // if/else
} // DiskIO::MakeRealName()

// Open the currently on-record file for reading
int DiskIO::OpenForRead(void) {
   int shouldOpen = 1;

   if (isOpen) { // file is already open
      if (openForWrite) {
         Close();
      } else {
         shouldOpen = 0;
      } // if/else
   } // if

   if (shouldOpen) {
      fd = CreateFile(realFilename.c_str(),GENERIC_READ, FILE_SHARE_READ | FILE_SHARE_WRITE,
                      NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
      if (fd == INVALID_HANDLE_VALUE) {
         CloseHandle(fd);
         cerr << "Problem opening " << realFilename << " for reading!\n";
         realFilename = "";
         userFilename = "";
         isOpen = 0;
         openForWrite = 0;
      } else {
         isOpen = 1;
         openForWrite = 0;
      } // if/else
   } // if

   return isOpen;
} // DiskIO::OpenForRead(void)

// An extended file-open function. This includes some system-specific checks.
// Returns 1 if the file is open, 0 otherwise....
int DiskIO::OpenForWrite(void) {
   if ((isOpen) && (openForWrite))
      return 1;

   // Close the disk, in case it's already open for reading only....
   Close();

   // try to open the device; may fail....
   fd = CreateFile(realFilename.c_str(), GENERIC_READ | GENERIC_WRITE,
                   FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_EXISTING,
                   FILE_ATTRIBUTE_NORMAL, NULL);
   // Preceding call can fail when creating backup files; if so, try
   // again with different option...
   if (fd == INVALID_HANDLE_VALUE) {
      CloseHandle(fd);
      fd = CreateFile(realFilename.c_str(), GENERIC_READ | GENERIC_WRITE,
                      FILE_SHARE_READ | FILE_SHARE_WRITE, NULL, OPEN_ALWAYS,
                      FILE_ATTRIBUTE_NORMAL, NULL);
   } // if
   if (fd == INVALID_HANDLE_VALUE) {
      CloseHandle(fd);
      isOpen = 0;
      openForWrite = 0;
      errno = GetLastError();
   } else {
      isOpen = 1;
      openForWrite = 1;
   } // if/else
   return isOpen;
} // DiskIO::OpenForWrite(void)

// Close the disk device. Note that this does NOT erase the stored filenames,
// so the file can be re-opened without specifying the filename.
void DiskIO::Close(void) {
   if (isOpen)
      CloseHandle(fd);
   isOpen = 0;
   openForWrite = 0;
} // DiskIO::Close()

// Returns block size of device pointed to by fd file descriptor. If the ioctl
// returns an error condition, assume it's a disk file and return a value of
// SECTOR_SIZE (512). If the disk can't be opened at all, return a value of 0.
int DiskIO::GetBlockSize(void) {
   DWORD blockSize = 0, retBytes;
   DISK_GEOMETRY_EX geom;

   // If disk isn't open, try to open it....
   if (!isOpen) {
      OpenForRead();
   } // if

   if (isOpen) {
      if (DeviceIoControl(fd, IOCTL_DISK_GET_DRIVE_GEOMETRY_EX, NULL, 0,
                          &geom, sizeof(geom), &retBytes, NULL)) {
         blockSize = geom.Geometry.BytesPerSector;
      } else { // was probably an ordinary file; set default value....
         blockSize = SECTOR_SIZE;
      } // if/else
   } // if (isOpen)

   return (blockSize);
} // DiskIO::GetBlockSize()

// In theory, returns the physical block size. In practice, this is only
// supported in Linux, as of yet.
// TODO: Get this working in Windows.
int DiskIO::GetPhysBlockSize(void) {
   return 0;
} // DiskIO::GetPhysBlockSize()

// Returns the number of heads, according to the kernel, or 255 if the
// correct value can't be determined.
uint32_t DiskIO::GetNumHeads(void) {
   return UINT32_C(255);
} // DiskIO::GetNumHeads();

// Returns the number of sectors per track, according to the kernel, or 63
// if the correct value can't be determined.
uint32_t DiskIO::GetNumSecsPerTrack(void) {
   return UINT32_C(63);
} // DiskIO::GetNumSecsPerTrack()

// Resync disk caches so the OS uses the new partition table. This code varies
// a lot from one OS to another.
// Returns 1 on success, 0 if the kernel continues to use the old partition table.
int DiskIO::DiskSync(void) {
   DWORD i;
   GET_LENGTH_INFORMATION buf;
   int retval = 0;

   // If disk isn't open, try to open it....
   if (!openForWrite) {
      OpenForWrite();
   } // if

   if (isOpen) {
      if (DeviceIoControl(fd, IOCTL_DISK_UPDATE_PROPERTIES, NULL, 0, &buf, sizeof(buf), &i, NULL) == 0) {
         cout << "Disk synchronization failed! The computer may use the old partition table\n"
              << "until you reboot or remove and re-insert the disk!\n";
      } else {
         cout << "Disk synchronization succeeded! The computer should now use the new\n"
              << "partition table.\n";
         retval = 1;
      } // if/else
   } else {
      cout << "Unable to open the disk for synchronization operation! The computer will\n"
           << "continue to use the old partition table until you reboot or remove and\n"
           << "re-insert the disk!\n";
   } // if (isOpen)
   return retval;
} // DiskIO::DiskSync()

// Seek to the specified sector. Returns 1 on success, 0 on failure.
int DiskIO::Seek(uint64_t sector) {
   int retval = 1;
   LARGE_INTEGER seekTo;

   // If disk isn't open, try to open it....
   if (!isOpen) {
      retval = OpenForRead();
   } // if

   if (isOpen) {
      seekTo.QuadPart = sector * (uint64_t) GetBlockSize();
      retval = SetFilePointerEx(fd, seekTo, NULL, FILE_BEGIN);
      if (retval == 0) {
         errno = GetLastError();
         cerr << "Error when seeking to " << seekTo.QuadPart << "! Error is " << errno << "\n";
         retval = 0;
      } // if
   } // if
   return retval;
} // DiskIO::Seek()

// A variant on the standard read() function. Done to work around
// limitations in FreeBSD concerning the matching of the sector
// size with the number of bytes read.
// Returns the number of bytes read into buffer.
int DiskIO::Read(void* buffer, int numBytes) {
   int blockSize = 512, i, numBlocks;
   char* tempSpace;
   DWORD retval = 0;

   // If disk isn't open, try to open it....
   if (!isOpen) {
      OpenForRead();
   } // if

   if (isOpen) {
      // Compute required space and allocate memory
      blockSize = GetBlockSize();
      if (numBytes <= blockSize) {
         numBlocks = 1;
         tempSpace = new char [blockSize];
      } else {
         numBlocks = numBytes / blockSize;
         if ((numBytes % blockSize) != 0)
            numBlocks++;
         tempSpace = new char [numBlocks * blockSize];
      } // if/else
      if (tempSpace == NULL) {
         cerr << "Unable to allocate memory in DiskIO::Read()! Terminating!\n";
         exit(1);
      } // if

      // Read the data into temporary space, then copy it to buffer
      ReadFile(fd, tempSpace, numBlocks * blockSize, &retval, NULL);
      for (i = 0; i < numBytes; i++) {
         ((char*) buffer)[i] = tempSpace[i];
      } // for

      // Adjust the return value, if necessary....
      if (((numBlocks * blockSize) != numBytes) && (retval > 0))
         retval = numBytes;

      delete[] tempSpace;
   } // if (isOpen)
   return retval;
} // DiskIO::Read()

// A variant on the standard write() function.
// Returns the number of bytes written.
int DiskIO::Write(void* buffer, int numBytes) {
   int blockSize = 512, i, numBlocks, retval = 0;
   char* tempSpace;
   DWORD numWritten;

   // If disk isn't open, try to open it....
   if ((!isOpen) || (!openForWrite)) {
      OpenForWrite();
   } // if

   if (isOpen) {
      // Compute required space and allocate memory
      blockSize = GetBlockSize();
      if (numBytes <= blockSize) {
         numBlocks = 1;
         tempSpace = new char [blockSize];
      } else {
         numBlocks = numBytes / blockSize;
         if ((numBytes % blockSize) != 0) numBlocks++;
         tempSpace = new char [numBlocks * blockSize];
      } // if/else
      if (tempSpace == NULL) {
         cerr << "Unable to allocate memory in DiskIO::Write()! Terminating!\n";
         exit(1);
      } // if

      // Copy the data to my own buffer, then write it
      for (i = 0; i < numBytes; i++) {
         tempSpace[i] = ((char*) buffer)[i];
      } // for
      for (i = numBytes; i < numBlocks * blockSize; i++) {
         tempSpace[i] = 0;
      } // for
      WriteFile(fd, tempSpace, numBlocks * blockSize, &numWritten, NULL);
      retval = (int) numWritten;

      // Adjust the return value, if necessary....
      if (((numBlocks * blockSize) != numBytes) && (retval > 0))
         retval = numBytes;

      delete[] tempSpace;
   } // if (isOpen)
   return retval;
} // DiskIO:Write()

// Returns the size of the disk in blocks.
uint64_t DiskIO::DiskSize(int *err) {
   uint64_t sectors = 0; // size in sectors
   DWORD bytes, moreBytes; // low- and high-order bytes of file size
   GET_LENGTH_INFORMATION buf;
   DWORD i;

   // If disk isn't open, try to open it....
   if (!isOpen) {
      OpenForRead();
   } // if

   if (isOpen) {
      // Note to self: I recall testing a simplified version of
      // this code, similar to what's in the __APPLE__ block,
      // on Linux, but I had some problems. IIRC, it ran OK on 32-bit
      // systems but not on 64-bit. Keep this in mind in case of
      // 32/64-bit issues on MacOS....
      if (DeviceIoControl(fd, IOCTL_DISK_GET_LENGTH_INFO, NULL, 0, &buf, sizeof(buf), &i, NULL)) {
         sectors = (uint64_t) buf.Length.QuadPart / GetBlockSize();
         *err = 0;
      } else { // doesn't seem to be a disk device; assume it's an image file....
         bytes = GetFileSize(fd, &moreBytes);
         sectors = ((uint64_t) bytes + ((uint64_t) moreBytes) * UINT32_MAX) / GetBlockSize();
         *err = 0;
      } // if
   } else {
      *err = -1;
      sectors = 0;
   } // if/else (isOpen)

   return sectors;
} // DiskIO::DiskSize()