ramdisk.c

NUcleus plus 支持的文件系统。 是学习文件系统的很好参考资料。

/************************************************************************
*                                                                       
*       Copyright (c) 2002 by Accelerated Technology, Inc.              
*                                                                       
*  PROPRIETARY RIGHTS of Accelerated Technology are  involved in        
*  the subject matter of this material.  All manufacturing,             
*  reproduction, use, and sales rights pertaining to this subject       
*  matter are  governed by the license agreement.  The recipient of     
*     this software implicitly accepts the terms of the license.        
*                                                                       
*                                                                       
*************************************************************************

*************************************************************************
* FILE NAME                                     VERSION                 
*                                                                       
*       RAMDISK.C                               FILE  2.3.2              
*                                                                       
* COMPONENT                                                             
*                                                                       
*       Nucleus File                                                    
*                                                                       
* DESCRIPTION                                                           
*                                                                       
*       Provides a configurable ram drive capability.                   
*                                                                       
*       In an earlier version we allocated a linear array. We have      
*       changed this to a paged approach. This allows us to create      
*       larger ramdisks on segmented (INTEL) systems. It could even be  
*       modified to work with EMS or XMS pretty easily now.             
*                                                                       
*       To use this utility you must port two functions and provide two 
*       constants.                                                      
*                                                                       
* DATA STRUCTURES                                                       
*                                                                       
*       None.                                                           
*                                                                       
* FUNCTIONS                                                             
*                                                                       
*       These three driver entry points are plugged into the pc_bdevsw  
*       table in devtable.c                                             
*                                                                       
*       pc_rd_raw_open                      Always fails. No need for it.
*       pc_rd_open                          Open the ram disk. (called  
*                                            when a file system is      
*                                            mounted.)                  
*       pc_rd_io                            Ram disk block io routine.  
*       pc_rd_close                         Close the ramdisk. Called   
*                                            when a file system is      
*                                            unmounted.                 
*                                                                       
* DEPENDENCIES                                                          
*                                                                       
*       nucleus.h                           System definitions          
*       pcdisk.h                            File common definitions     
*                                                                       
* NOTE: This module is linked in with File.lib.  After you make   *
*       changes, you must rebuild File.lib.                       *
*******************************************************************/

#include        "plus\nucleus.h"

#if (0)  /* MNT port */
#include        <time.h>
#include        "hardware.h"
#endif

#include        "file\pcdisk.h"

#if (!RAMDISK_FROMPOOL)
/* We will use malloc */
#include        <stdio.h>
#include        <stdlib.h>
#endif  /* !RAMDISK_FROMPOOL */


#if (RAMDISK_FROMPOOL)
    NU_PARTITION_POOL   NUF_RAMDISK_PARTITION;
#endif


/*  Global data definitions.  */
UINT8           *rd_pages[NUM_RAMDISK_PAGES] = {0};
UINT16           rd_opencount = 0;


/************************************************************************
* FUNCTION                                                              
*                                                                       
*       rd_alloc_page                                                   
*                                                                       
* DESCRIPTION                                                           
*                                                                       
*       This function allocates one page of memory from a Nucleus       
*       fixed partition.                                                
*                                                                       
* AUTHOR                                                                
*                                                                       
*       Takahiro Takahashi
*                                                                       
* INPUTS                                                                
*                                                                       
*       None.                                                           
*                                                                       
* OUTPUTS                                                               
*                                                                       
*       Pointer to the page allocated.                                  
*                                                                       
*************************************************************************/
UINT8 *rd_alloc_page(VOID)
{
STATUS      status;

#if (RAMDISK_FROMPOOL)
UINT8       *mem_address;


    /*  Allocate a page.  */
    status = NU_Allocate_Partition(&NUF_RAMDISK_PARTITION, (VOID **)&mem_address,
                          NU_NO_SUSPEND);

    if (status == NU_SUCCESS)
        return(mem_address);
    else
        return((UINT8 *)0);

#else  /*  not RAMDISK_FROMPOOL  */

    /* Using MALLOC instead of Allocate_Partition */
UINT8       *mem_address;
OPTION      preempt_status;


    /*  Don't let anyone interfere with the malloc.  Anticpating DOS non-
        reentrancy.  */
    preempt_status = NU_Change_Preemption(NU_NO_PREEMPT);

    /*  Get the memory.  */
    mem_address = (UINT8 *)malloc(NUF_RAMDISK_PARTITION_SIZE);

    /*  Others can take over now since the malloc is complete. */
    NU_Change_Preemption(preempt_status);
    return(mem_address);

#endif /*  RAMDISK_FROMPOOL  */

}


/************************************************************************
* FUNCTION                                                              
*                                                                       
*       rd_freec_page                                                   
*                                                                       
* DESCRIPTION                                                           
*                                                                       
*       This function deallocates one page of memory from a Nucleus     
*       fixed partition.                                                
*                                                                       
* AUTHOR                                                                
*                                                                       
*       Takahiro Takahashi
*                                                                       
* INPUTS                                                                
*                                                                       
*       *page                               Pointer to memory to be     
*                                            deallocated.               
*                                                                       
* OUTPUTS                                                               
*                                                                       
*       Pointer to the page allocated.                                  
*                                                                       
*************************************************************************/
VOID   rd_free_page(UINT8 *page)
{

#if (RAMDISK_FROMPOOL)

    /*  If the input parameter is valid, deallocate.  */
    if (page)
        NU_Deallocate_Partition((VOID *)page);

#else

    /* Using free() instead of dealloc */
OPTION      preempt_status;


    /*  Don't let anyone interfere with the malloc.  Anticpating DOS non-
        reentrancy.  */
    preempt_status = NU_Change_Preemption(NU_NO_PREEMPT);

    /*  If the input is valid, deallocate the page.  */
    if (page)
        free(page);

    /*  Others can take over now since the malloc is complete. */
    NU_Change_Preemption(preempt_status);

#endif

}


/************************************************************************
* FUNCTION                                                              
*                                                                       
*       pc_rd_ioctl                                                     
*                                                                       
* DESCRIPTION                                                           
*                                                                       
*       This function doesn't do anything for the RAM Disk.  It is      
*       included for devtable consistency.                              
*                                                                       
* AUTHOR                                                                
*                                                                       
*       Takahiro Takahashi
*                                                                       
* INPUTS                                                                
*                                                                       
*       None.                                                           
*                                                                       
* OUTPUTS                                                               
*                                                                       
*       None.                                                           
*                                                                       
*************************************************************************/
INT pc_rd_ioctl(UINT16 driveno, UINT16 command, VOID *buffer)