cpmfs.cpp

一个嵌入式系统的C代码

//*************************************************************************
//  MODULE : CpmFs - A file system based on the old CP/M design           *
//  AUTHOR : Ron Chernich                                                 *
//  PURPOSE: Provides reudimentary (nonheirarachial) file system for RCOS *
//  HISTORY:                                                              *
//    13-AUG-94 First version                                             *
//    21-AUG-94 Unit tests on open/create/read/write completed Ok.        *
//*************************************************************************

#include "cpmfs.hpp"


            
//////////////////////////////////////////////////////////////////////////
//              A CP/M-like file system (RIP, Garry Kildal).
//------------------------------------------------------------------------
// C::tor regesters us with the Kernel for e-mail and null's out
// the BDOS array, awaiting mounting of the drives..
//
CpmFs::CpmFs (UINT16 id, UINT16 cls, Knl *pK) : port(id, cls, pK)
{
  for (int idx = 0; idx < MAX_DRIVES; idx++)
    pUnit[idx] = NULL;
}

/////////////////
// close off simulated disks
//
CpmFs::~CpmFs (void)
{
  for (int idx = 0; idx < MAX_DRIVES; idx++)
    if (NULL != pUnit[idx])
      delete pUnit[idx];
}

/////////////
// This member called when disk has started up ok.  We create a new BDOS
// object in our private array, passing it the supplied structs which
// are used to define the disk layout - for example:
// 
//   a CP/M IBM 3740 format 8" diskette reserved the first two tracks
//   as system tracks (unused) and used 1024 byte allocation blocks.
//   With 26 x 128 byte sectors and 77 tracks, this results in total
//   user capacity = ((26 * 128 * 77) - (64 * 32)) / 1024 = 243 K.
//   By convention, 64 directory entries were specified.  The directory
//   immediatly follows the system tracks, so 64 x 32 bytes = 2K, ie
//   the first two allocation blocks are reserved for the directory,
//   leaving 241K for user file space.
//
// The BDOS also needed to know the actual value used for the first
// sector of each track (0 or 1) and what sector "skew" would be used
// for track access.  This allows the BDOS to convert the logical
// sector which it calculates from the record within block numbers into
// an actual physical disk sector.
//
// Finally, since 8" drives did not support any knid of "door opened"
// interrupt, removable media needed to be checked to make sure the
// disk had not been changed in order to prevent trashing the disk
// structure by writing one disks data to another.  This was accomplished
// by specifying the number of "checked" directory entries.  A vector
// of checksums was built for each "checked" directory entry which was
// checked before all write operations.  Slow?  You bet!
//
void CpmFs::MountDrive (UINT16 nDrv, char cUnit, DPB& mac, DPARAM& dprm)
{
  UINT16 idx = UINT16(cUnit - 'A');
  if ((idx >= 0) && (idx < MAX_DRIVES) && (NULL == pUnit[idx])) {
    pUnit[idx] = new CpmBdos(mac, dprm, nDrv);
    pUnit[idx]->pTx = pTx;
    pUnit[idx]->nId = uID;
    pUnit[idx]->LogDisk();
  }
}

///////////////
// All File System requests arrive here.  We just create an XfReq instance,
// fill in what we can, then call the appropriate member func of the BDOS
// instance corresponding to the drive unit specified in the FCB.
//
void CpmFs::RxPort (PMSG pM)
{ 
  PFCBREF pRef = (PFCBREF)pM->pBody;
  PFCB pFcb = pRef->pFcbRef;
  if (pFcb == NULL)
    return;
  UINT16 idx = pFcb->de.nUsrNmbr;
  if ((idx >= MAX_DRIVES) || (NULL == pUnit[idx]))
    DevError(ET_FileSysErr, FALSE);
  else {
    XfReq *pX = new XfReq(pM->wSender, pFcb);
    pX->pFnCb = pUnit[idx];
    switch (pM->wMsgType & ~MM_Sync) {
      case FS_Open     : pUnit[idx]->Open(pX);     break;
      case FS_Creat    : pUnit[idx]->Creat(pX);    break;
      case FS_Close    : pUnit[idx]->Close(pX);    break;
      case FS_ReadSeq  : pUnit[idx]->Read(pX, 0);  break;
      case FS_ReadRan  : pUnit[idx]->Read(pX, 1);  break;
      case FS_WriteSeq : pUnit[idx]->Write(pX, 0); break;
      case FS_WriteRan : pUnit[idx]->Write(pX, 1); break;
      case FS_Delete   : pUnit[idx]->Remov(pX);    break;
      case FS_Rename   : break;
      case FS_Stat     : break;
      case FS_FindFirst: break;
      case FS_FindNext : break;
    default:
      DevError(ET_FileSysErr, FALSE);
    }
  }
}


//////////////////////////////////////////////////////////////////////////
// Default Transfer request C::tor - just preset simple stuff.
//
XfReq::XfReq (UINT16 uOwner) :
 nSid(1), pNxt(NULL), nRetry(3), bRes(FALSE), uProc(uOwner)
{ }

//////////////
// Transfer request C::tor has a user (or BDOS) FCB to work with..
//
XfReq::XfReq (UINT16 uOwner, PFCB pUfcb) :
 nSid(1), pNxt(NULL), nRetry(3), bRes(FALSE), uProc(uOwner)
{
  pFcb  = pUfcb;
  pDma  = pUfcb->pBuf;
}


/////////////////////////////////// eof ////////////////////////////////////