_fs_setfpos.c

keil arm flash fs 最新版 在Ｋｅｉｌ ａｒｍ下使用

/*----------------------------------------------------------------------------
 *      R T L  -  F l a s h   F i l e   S y s t e m
 *----------------------------------------------------------------------------
 *      Name:    _FS_SETFPOS.C 
 *      Purpose: Low level Set File Position Indicator Function
 *      Rev.:    V3.22
 *----------------------------------------------------------------------------
 *      This code is part of the RealView Run-Time Library.
 *      Copyright (c) 2004-2008 KEIL - An ARM Company. All rights reserved.
 *---------------------------------------------------------------------------*/

#include "File_Config.h"

/*--------------------------- __setfpos -------------------------------------*/

int __setfpos (int handle, U32 pos) {
   /* Low level Set file position pointer function. */
   FALLOC fa;
   IOB *fcb;
   U32 bl,adr,fidx,prev;
   U32 i,fpos;

   fcb  = &_iob[handle];
   if (fcb->drive == DRV_MCARD) {
      if (fat_set_fpos (fcb, pos) == __TRUE) {
         /* File Position indicator changed. */
         return (0);
      }
      return (-1);
   }
   if (fcb->flags & _IOWRT) {
      if ((fcb->flags & _IOAPPEND) && (fcb->fsize == pos)) {
         if (fs_AllocBlock (fcb) == __TRUE) {
            return (0);
         }
      }
      return (-1);
   }

   fidx = 0;
   fpos = 0;
   bl = fcb->_fblock;
nextbl:
   for (i = 0; i < fcb->NumSect; i++) {
      /* Search for file blocks identified with identification 'fileID' */
      adr = fs_adr_sig (bl, fcb);
      adr = fs_rd_sig (adr, &fa.end);
      if (fa.end != fcb->InitVal) {
         for (prev = 0; ; prev = fa.end) {
            adr = fs_rd_alloc (adr, &fa);
            if (fa.fileID == fcb->fileID  &&  fa.index == fidx) {
               /* All file blocks are 4-byte aligned. */
               prev = (prev + 3) & ~3;
               fidx++; 
               if (fpos + (fa.end - prev) < pos) {
                  /* Go and try next File Block */
                  fpos += (fa.end - prev);
                  goto nextbl; 
               }

               /* OK, the right File Block Index is found */
               fcb->_fblock = bl;
               fcb->_fidx = fidx;
               /* File opened for read. */
               fcb->_fbot = prev + pos - fpos;
               fcb->_ftop = fa.end;
               return (0);
            }
            if (fa.end == fcb->InitVal) break;
         }
      }
      if (++bl == fcb->NumSect) {
         bl = 0;
      }
   }
   return (-1);
}

/*----------------------------------------------------------------------------
 * end of file
 *---------------------------------------------------------------------------*/