findvsb.c

intel的一个高效率FLASH文件系统。思路很好

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/*--------------------------------------------------------------------------
-
-     findvsb.c -- Find specified VSB
-
---------------------------------------------------------------------------*/

#include "datatype.h"
#include "flashdef.h"
#include "vsb.h"
#include "vsbdata.h"


////////////////////////////////////////////////////////////////////////////
/*
  2002-07-23 modify by wangfei
  replace Memory_Copy by memcpy
*/
////////////////////////////////////////////////////////////////////////////


/***************External globals defined in writevat.c*********************/

extern MEMORY_STATUS status[];   /* GlobalMediaStatistics: */
extern MEMORY_STATUS * status_ptr;  /* GlobalMediaStatistics: */


//void memcpy(void *, void *, DWORD);

/**************************************************************************
*
*     FindVSB -- Search for specified VSB starting at last find block
*
*     ENTRY -
*     BYTE -   Component number to search in
*     WORD -   VSB number to search for
*
*     EXIT -
*     WORD -   ERR_NONE if VSB found
*              CurrentVSB = offset within block of VSB location
*              CurrentBlock = Block number VSB found in
*              CurrentIndex = VSB index in the VAT within block
*
*    ERR_NOT_FOUND    ERR_VSB_INVALID
*
***************************************************************************/
WORD FindVSB( BYTE ComponentID,  /* Component number to search */
              WORD VSBToFind )   /* VSB ID to search for */
{
   WORD     vi = 1;              /* VSB counter */
   WORD     *VATEntry;           /* current VAT buffer */
   DWORD    FlashAddr;           /* Physical flash address */
   BYTE     BlockNumber = 0;     /* Block number being searched */
   BYTE     BlockCount;          /* Number of blocks searched */
   WORD     BytesToRead;         /* bytes of VAT to read for each loop */
   WORD     cnt;                 /* loop index for reading vat */
   WORD     VatBufferSize;       /* max amount to buffer for type of find */
   LAST_VSB *pLastLogicalVSB;
   WORD     tempVAT = 0;
   WORD     RetVal;

   status_ptr = &status[ComponentID];
   VSBFound = FALSE;

   /* Looking for a free one? */
   if( VSBToFind != VSB_FREE )
   {
      if (ReclaimThresholdOverride == FALSE)
      {
         /* return error if an invalid vsb number*/
         if( VSBToFind == 0 ||
             ((VSBToFind > MAXIMUM_VSB-RECLAIM_THRESHOLD) &&
             (VSBToFind != MAXIMUM_VSB+1)) )
            return( ERR_VSB_INVALID );
      }
      else
      {
         if( VSBToFind == 0 || ((VSBToFind > MAXIMUM_VSB) &&
             (VSBToFind != MAXIMUM_VSB+1)) )
         {
            /* return error */
            ReclaimThresholdOverride = FALSE;
            return( ERR_VSB_INVALID );
         }
      }
   }


   VSBToFind |= VSB_DISCARD_MASK;


   if(VSBToFind == VSB_FREE)
   {

      /* set up search start block for finding freeVSB*/
      BlockNumber = WriteBlock[ComponentID];
      vi = FreeVSB[ComponentID];
      VatBufferSize = FREE_VSB_BUFFER_SIZE;

   }