block.c

来自「winNT技术操作系统,国外开放的原代码和LIUX一样」· C语言 代码 · 共 110 行

/*
 * COPYRIGHT:        See COPYING in the top level directory
 * PROJECT:          ReactOS kernel
 * FILE:             services/fs/minix/minix.c
 * PURPOSE:          Minix FSD
 * PROGRAMMER:       David Welch ([e-mail])
 * UPDATE HISTORY:
 */

/* INCLUDES *****************************************************************/

#include <ntddk.h>

//#define NDEBUG
#include <debug.h>

#include "minix.h"

/* FUNCTIONS ****************************************************************/

static unsigned int MinixGetBlock(PDEVICE_OBJECT DeviceObject,
				  PMINIX_DEVICE_EXTENSION DeviceExt,
				  struct minix_inode* inode,
				  ULONG FileOffset)
{
   int block;
   PVOID BaseAddress;
   ULONG blk;

   blk = FileOffset / BLOCKSIZE;

   DPRINT("MinixGetBlock(inode %x, blk %d)\n",inode,blk);

   /*
    * The first few blocks are available in the inode
    */
   if (blk < 7)
     {
	block = inode->i_zone[blk];
	return(block);
     }
   blk = blk - 7;

   /*
    * Retrieve a single-indirect block
    */
   if (blk < 512)
     {
	block = inode->i_zone[7];

	BaseAddress = ExAllocatePool(NonPagedPool, 512);

	MinixReadSector(DeviceObject,
			block,
			BaseAddress);

	block = ((PUSHORT)(BaseAddress))[blk];

	ExFreePool(BaseAddress);

	return(block);
     }

   /*
    * Get a double indirect block
    */
   blk = blk - 512;
   block = inode->i_zone[8];

   BaseAddress = ExAllocatePool(NonPagedPool, 512);

   MinixReadSector(DeviceObject,
		   block,
		   BaseAddress);

   block = ((PUSHORT)BaseAddress)[(blk>>9)&511];

   ExFreePool(BaseAddress);


   BaseAddress = ExAllocatePool(NonPagedPool, 512);

   MinixReadSector(DeviceObject,
		   block,
		   BaseAddress);

   block = ((PUSHORT)BaseAddress)[blk&512];

   ExFreePool(BaseAddress);

   return(block);
}

NTSTATUS MinixReadBlock(PDEVICE_OBJECT DeviceObject,
			PMINIX_DEVICE_EXTENSION DeviceExt,
			struct minix_inode* inode,
			ULONG FileOffset,
			PULONG DiskOffset)
{
   unsigned int block;

   DPRINT("MinixReadBlock()\n");

   block = MinixGetBlock(DeviceObject, DeviceExt,inode, FileOffset);

   (*DiskOffset) = block * BLOCKSIZE;

   return(STATUS_SUCCESS);
}