ramdisk.c

ramdisk,著名的内存虚拟磁盘的源代码

//=============================================================================
//
// Compuware Corporation
// NuMega Lab
// 9 Townsend West
// Nashua, NH 03060  USA
//
// Copyright (c) 1998 Compuware Corporation. All Rights Reserved.
// Unpublished - rights reserved under the Copyright laws of the
// United States.
//
//=============================================================================

// RAMDISK.C - main module for VxD RAMDISK
// Copyright (c) 1996, Compuware Corporation

// This is the main module for the Registry File System Driver (RFSD). 
// RFSD presents the system Registry as file volume mounted on a hard
// drive under Windows 95. It does this by first creating a virtual 
// drive, and then installing a file system on that virtual drive. The
// file system maps file i/o calls to the system Registry. Specifically,
// directories are mapped to keys, files to values, and file contents
// to value data.
//
// RFSD is both a file system driver and a layered block device driver.
// As a file system driver, it translates file i/o requests into 
// calls to services that access the Registry. As a port driver, it
// simulates the existence of a hard drive, and provides routines to
// handle i/o requests to that drive.

// The driver may be built with either Microsoft Visual C++ 2.0 (or 
// later) or Borland C++ 4.02 (or later). 

#define   DEVICE_MAIN
#include  "ramdisk.h"
#undef    DEVICE_MAIN

// Here we declare key data structures for the driver. This macro
// invocation defines the Device Data Block for the VxD, the Device
// Registration Packet (DRP), and the IOS Linkage Block (ILB). 
// The macro is defined in vtoolsc.h. 
Declare_Port_Driver(RAMDISK,DRP_ESDI_PD,RAMDISK_NAME,\
	RAMDISK_REV,RAMDISK_FEATURE,RAMDISK_IFR,DRP_BT_ESDI,0)

// Set prototype for control message handler
DefineControlHandler(SYS_DYNAMIC_DEVICE_INIT, OnSysDynamicDeviceInit);
DefineControlHandler(SYS_DYNAMIC_DEVICE_EXIT, OnSysDynamicDeviceExit);

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
// Function
//	ControlDispatcher
//
// Purpose
//	Handles control messages sent by the system
//
// Parameters
//	dwControlMessage	message identifier
//	register parameters
//
// Return Value
//	The meaning of the return value varies depending on the
//	message, but in general, TRUE means success.
//
// Remarks
//	Like most all layered block device drivers, this driver
//	processes only SYS_DYNAMIC_DEVICE_INIT.
//
BOOL __cdecl ControlDispatcher(
	DWORD dwControlMessage,
	DWORD EBX,
	DWORD EDX,
	DWORD ESI,
	DWORD EDI,
	DWORD ECX)
{
	START_CONTROL_DISPATCH
		ON_SYS_DYNAMIC_DEVICE_INIT(OnSysDynamicDeviceInit);
		ON_SYS_DYNAMIC_DEVICE_EXIT(OnSysDynamicDeviceExit);
	END_CONTROL_DISPATCH

	return TRUE;
}

// - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 
// Function
//	OnSysDynamicDeviceInit
//
// Purpose
//	First level initialization of the RFSD
//
// Parameters
//	None
//
// Return Value
//	Returns TRUE if successful.
//
// Remarks
//	There are two tasks to accomplish. First, the driver must
//	register with the IFSMgr. If this is successful, the driver
//	registers with the I/O Supervisor.
//
	char base[DISKSIZE];

BOOL OnSysDynamicDeviceInit()
{	
	int add_i, nsec;	
	USHORT fatEntries;
	USHORT   fatSectorCnt;
	PUCHAR firstFatSector;
	PBOOTSECT bsp;
	PWORD  fat;

	for(add_i=0;add_i<DISKSIZE;add_i++)
		base[add_i]=0;
		
	bsp = (PBOOTSECT) base;
	fat = (PWORD) (base + 512);
	nsec = DISKSIZE/512;

	// Fill in dummy boot sector so we look like a disk
	bsp->jmpinst[0] = 0xEB;
	bsp->jmpinst[1] = 0x3C;
	bsp->jmpinst[2] = 0x90;
	memcpy(bsp->vendid, "WALTONEY", 8);
	bsp->secsize = 512;					// each sector is 512 bytes long
	bsp->clustsize = 1;					// one sector per cluster
	bsp->numrsv = 1;					// no reserved sectors besides this one
	bsp->numfat = 1;					// one FAT should be enough
	bsp->numfiles = 128;				// more than enough to prove the point!
	bsp->numsectors = 0;				// fill in totsectors instead
	bsp->media = 0xF8;					// claim we're a fixed disk
	bsp->fatsectors = (WORD) ((nsec + nsec + 511) / 512);
	bsp->tracksectors = (WORD) nsec;	// only 1 track, so all sectors are on it
	bsp->numtracks = 1;					// 1 track
	bsp->numhidden = 0;					// no hidden sectors
	bsp->totsectors = nsec;				// this many sectors
	bsp->drive = 0x80;					// flag for a hard drive
	bsp->xboot = 0x29;					// flag as extended boot sector
	bsp->volid = (DWORD) base;					// use base address as volume ID
	memcpy(bsp->label, "NO NAME    ", 11);
	memcpy(bsp->fattype, "FAT16   ", 8);
	
	bsp->part[0].indicator = 0x80;
	bsp->part[0].parttype = 4;			// DOS 16-bit FAT
	bsp->part[0].bias = 0;
	bsp->part[0].partsize = nsec;
	
	bsp->signature = 0xAA55;					// boot sector signature

	// Initialize the start of the FAT at sector 1

	fat[0] = 0xFFF8;			// reserved bytes
	fat[1] = 0xFFFF;
		
		
	// Now register with the IOS, passing a pointer to the Device 
	// Registration Packet that is declared above using macro
	// Declare_Port_Driver. No error returns are defined for this call.

	IOS_Register(&RAMDISK_Drp);

	// Return TRUE to indicate a successful initialization.

	return TRUE;
}




OnSysDynamicDeviceExit()
{
	return TRUE;
}