dskdrv.cpp

一个嵌入式系统的C代码

//*************************************************************************
//  MODULE : SimDsk - Conceptual Disk Driver for all types of drives.     *
//  AUTHOR : Ron Chernich                                                 *
//  PURPOSE: This object Provides the Intermediate level IO routines      *
//           (select, seek, etc) to interface between the File System and *
//           multiple instances of all types of physical disk units.      *
//  HISTORY:                                                              *
//    13-AUG-94 First version                                             *
//    17-AUG-94 Animation features added                                  *
//*************************************************************************

#include "cpmfs.hpp"

  #include <fcntl.h>
#ifdef _DOS_ENV
  #include <sys\types.h>
  #include <sys\stat.h>
  #include <io.h>

#endif

#ifdef UNIX
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <unistd.h>
#endif
#include <string.h>


///////////////////////////////////////////////////////////////////////////
// First we have the im plemenation of a FIFO queue that holds pending
// disk transfer requests..
//
XfReq* TreqstQ::Get (UINT16 n)
{
  XfReq *p = Peek(n);
  if (p) {
    DblDelete();
    --nInq;
  }
  return p;
}

XfReq* TreqstQ::Peek (UINT16 n)
{
  XfReq *p = (XfReq*)DblGetHead();
  if (n)
    while (--n)
      if (NULL == (p = (XfReq*)DblGetNext()))
        break;
  return p;
}

void TreqstQ::Purge (UINT16 n)
{
  XfReq *p = Get(n);
}

void TreqstQ::PurgeAll (void)
{
  while (nInq)
    Purge();
}


///////////////////////////////////////////////////////////////////////////
// The disk device is simulated through a host OS sequential file of the
// passed mount name.  If the file (created if necessary) length does not
// match the "disk" parameters, it is "initialized" by writing all "0xE5"
// records out to the required length. Info conveyed in the DPB are stored.
//
DskModel::DskModel (UINT16 id, UINT16 cls, Knl *pK, char *pSt, DPB& dsk, BYTE n) :
  port(id, cls, pK), nCurTrk(0), nCurAngle(0), nOpCnt(0), lHoldTime(0),
  nLid(n), bOk(FALSE), stage(DD_IDLE)
{
  char stName[128], *cp;

  strcpy(stName, pSt);
  cp = strrchr(stName, '.');
  if ((NULL == cp) || (strlen(stName) - (cp - stName) > 4))
    strcat(stName, ".dsk");

  #ifdef UNIX
	  fd = open(stName, O_CREAT | O_RDWR, S_IREAD | S_IWRITE );
  #endif
  #if defined(BC20) || defined(BC31)
	  fd = open(stName, O_CREAT | O_BINARY | O_RDWR, S_IREAD | S_IWRITE);
  #endif
  #if !defined(BC31) && !defined(BC20) && !defined(UNIX)
	  fd = open(stName, _O_CREAT | _O_BINARY | _O_RDWR, _S_IREAD | _S_IWRITE);
  #endif

  if (fd > 0) {
    struct stat info;
    message Msg(uID, ANI_DCREAT, nLid, (void*)&dsk.nTrks);
    stat(stName, &info);    
    long nBlks = dsk.nSecs * dsk.nTrks * dsk.nSides;
    if (info.st_size != (long)(nBlks * dsk.nSecSize)) {
      char *pBuf = new char[dsk.nSecSize];
      if (NULL == pBuf)
        return;
      memset(pBuf, 0xe5, dsk.nSecSize);
      for (int i = 0; i < nBlks; i++)
        if ((int)dsk.nSecSize != write(fd, pBuf, dsk.nSecSize))
          return;
      //_commit(fd);
      DELETE_ARRAY pBuf;
    } 
    nBps = dsk.nSecSize;
    nBpt = nBps * dsk.nSecs * dsk.nSides;
    nBpd = nBpt * dsk.nTrks;
    nSecAngle = (BYTE)(360 / (dsk.nSecs + 1));
    nAngleInc = dsk.nAngleInc;
    nTrkInc   = dsk.nTrkInc;
    nSettle   = dsk.nSettle;
    nErrRate  = dsk.nErrRate;
    lLastTime = Clock.GetTicks();
    pTx->SendMsg(ID_ANIM, &Msg);
    bOk = TRUE;
  }
}

//////////////
// Close our associated disk file.
//
DskModel::~DskModel (void)
{
  if (fd > 0)
    close(fd);
}

/////////////
// Calculate offset for a transfer, doing rudimentary validation
// RETURNS -1 .. record out of range, else record number.
//
long DskModel::CalcOffset (void)
{
  XfReq *p = ChanQ.Peek();
  long nOfs = (p->nTrk * p->nSid * nBpt) + ((p->nSec - 1) * nBps);
  return (nOfs <= (long)(nBpd - nBps)) ? nOfs : -1L;
}

/////////////////////
// Internal read simulates a "soft" (recoverable) error every <nErrRate>
// operations. On others, it calcs the location of the sector sized
// file sector to transfer and does so the address at the head of Q.
// RETURNS: TRUE  .. transfer Ok
//          FALSE .. bad params or soft (or even a host hard) error
//
BOOL DskModel::Read (void)
{
  if (++nOpCnt >= nErrRate)
    nOpCnt = 0;
  else {
    XfReq *p = ChanQ.Peek();
    long nOfs = CalcOffset();
    if ((nOfs > 0L) &&
        (nOfs == lseek(fd, nOfs, SEEK_SET)) &&
        ((int)nBps == read(fd, p->pDma, nBps)))
      return TRUE;
  }
  return FALSE;
}

/////////////////////
// Same sort of thing as for read operation..
// RETURNS: TRUE  .. transfer Ok
//          FALSE .. bad params or soft (or even a host hard) error
//
BOOL DskModel::Write (void)
{
  if (++nOpCnt >= nErrRate)
    nOpCnt = 0;
  else {
    XfReq *p = ChanQ.Peek();
    long nOfs = CalcOffset();
    if ((nOfs > 0L) &&
        (nOfs == lseek(fd, nOfs, SEEK_SET)) &&
        ((int)nBps == write(fd, p->pDma, nBps)))
      return TRUE;
  }
  return FALSE;
}

///////////////
// Port receive member simply adds passed Transfer Request to the queue
// of transfer rwquests (FIFO). A message is sent to the animator in case
// the disk model is being displayed, which will update the queue contents.
//
void DskModel::RxPort (PMSG pMsg)
{
  if (pMsg->pBody) {
    ChanQ.Put((XfReq*)pMsg->pBody);
    TransQ Tq(&ChanQ);
    message msg(uID, ANI_CHAN_ENQ, nLid, &Tq);
    pTx->SendMsg(ID_ANIM, &msg);
  }
}

//////////////////
// This member is called on every pass around the RCOS loop in <main>,
// effectively acting as the disk sub-system's time slice.  If there
// are no transfers in the queue, we just update the angular disk
// position and exit. If there is something at the head of queue, we:
//
//   1. Step the heads until nCurTrk = required track (with animation),
//   2. Delay for the head settle period,
//   3. After the settle, calculate the delay until the disk rotation
//      (based on the current angular position) will bring the required
//      sector "under" the heads,
//   4. Perform the read or write operation, then
//   5. Remove the head of queue <XfReq> object, call the animator, then
//      call the CpmDsk::NxtFunc function (using the pointer in the XfReq)
//      which is analogous to issuing a "disk operation" complete interrupt.
//
void DskModel::Scheduler (void)
{
  UINT32 lTm = Clock.GetTicks();
  UINT16 nMs = (UINT16)(lTm - lLastTime);
  UINT16 ndTheta = nMs / nAngleInc;
  if (ndTheta) {
    if (361 < (nCurAngle += ndTheta))
      nCurAngle %= 360;
    message msg(uID, ANI_SPIN, nLid, (void*)&nCurAngle);
    pTx->SendMsg(ID_ANIM, &msg);
  }
  lLastTime = lTm;
  //
  // If there is a transfer pending, do (in order):
  //  1. Seek to track
  //  2. Wait head settling time
  //  3. Wait out rotational latency
  //  4. Perform transfer.
  // if (by luck) we are already on track, skip steps 1 and 2
  //
  if (ChanQ.GetLen()) {
    XfReq *p = ChanQ.Peek();
    switch (stage) {
      //
      // The disk drive has nothing to do and a transfer is waiting. If we
      // are on-cylinder, we can immediatly begin scanning for the required
      // sector. Otherwise we'll have to go the whole hog - seek, settle etc..
      //
      case DD_IDLE:
        if (nCurTrk != p->nTrk) {
          UINT16 nTargTrk = p->nTrk;
          if (nCurTrk < nTargTrk)
            nTargTrk |= 0x8000;
          message msg(uID, ANI_BEGIN_SEEK, nLid, (void*)&nTargTrk);
          pTx->SendMsg(ID_ANIM, &msg);
          stage = DD_SEEK;
        }
        else {
          message msg(uID, ANI_ONTRACK, p->nSec);
          pTx->SendMsg(ID_ANIM, &msg);
          UINT16 nSecPos = (p->nSec - 1) * nSecAngle;
          if (nSecPos < nCurAngle)
            lHoldTime = lLastTime + ((nCurAngle - nSecPos) / nAngleInc);
          else
            lHoldTime = lLastTime + ((360 - nCurAngle + nSecPos) / nAngleInc);
          stage = DD_TRANSFER;
        }
        break;
      //
      // We are seeking.  Move the heads at the best rate the mechanics will
      // accomodate until we arrive on cylinder, then set in the anticipated
      // time after which the heads will be stable enough to start reading..
      //
      case DD_SEEK: {
          INT16 nInc = nMs / nTrkInc;
          if (nInc) {
            INT16 nGap = abs(nCurTrk - p->nTrk);
            if (nInc > nGap)
              nInc = nGap;
            if (nCurTrk > p->nTrk)
              nInc = -nInc;
            message msg(uID, ANI_SEEK, 0,(void*)&nInc);
            pTx->SendMsg(ID_ANIM, &msg);
            nCurTrk += nInc;
            if (nCurTrk == p->nTrk) {
              lHoldTime = lLastTime;
              stage = DD_SETTLE;
            }
          }       
        }
        break;
      //
      // We are on track and the head settling time has been set. If it has
      // expired, calculate rotational time delay until the desired sector
      // arrives..
      //
      case DD_SETTLE:
        if (nSettle <= lLastTime - lHoldTime) {
          UINT16 nSecPos = (p->nSec - 1) * nSecAngle;
          if (nSecPos < nCurAngle)
            lHoldTime = lLastTime + ((nCurAngle - nSecPos) / nAngleInc);
          else
            lHoldTime = lLastTime + ((360 - nCurAngle + nSecPos) / nAngleInc);
          message msg(uID, ANI_ONTRACK, p->nSec);
          pTx->SendMsg(ID_ANIM, &msg);
          stage = DD_WAIT;
        }
        break;
      //
      // When we reach here, we see if the rotational delay has expired
      //
      case DD_WAIT:
        if (lLastTime >= lHoldTime) {
          lHoldTime = 0L;
          stage = DD_TRANSFER;
        }
        break;
      //
      // Ready to perform the read/write operation, de-queue the transfer
      // request, run the display animation, then callback (interrupt) the
      // file system to do the next stage of the BDOS operation..
      //
      case DD_TRANSFER: {
          TransQ Tq(&ChanQ);
          message msg(uID, ANI_RWOP, nLid, &Tq);
          pTx->SendMsg(ID_ANIM, &msg);
          switch (p->cmnd) {
            case DD_READ : p->bRes = Read();  break;
            case DD_WRITE: p->bRes = Write(); break;
          }
          ChanQ.Purge();
          stage = DD_IDLE;
          p->pFnCb->NxtFunc(p);
        }
        break;
    }
  }
}


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