How to Find the Size of an .FPT File with Different Blocksizes

Last reviewed: September 10, 1995
Article ID: Q136284
The information in this article applies to:
  • Microsoft Visual FoxPro for Windows, version 3.0
  • Microsoft Foxpro for MS-DOS, versions 2.0, 2.5, 2.5a, 2.6, 2.6a
  • Microsoft Foxpro for Windows, versions 2.5, 2.5a, 2.5b, 2.6, 2.6a

SUMMARY

Sometimes changing the blocksize of a memo field can result in significant savings in disk space. The BLOCKTEST() function listed in this article can determine exactly how much disk space can be gained or lost with different blocksizes.

MORE INFORMATION

  1. Open a program file called LowLevel.prg and add this code:

    FUNCTION BLOCKTEST PARAMETER lnTempsize CLEAR IF lnTempsize>0

         IF lnTempsize<=32
           lnTempsize=lnTempsize*512
         ENDIF
         lnTempblk=0
         lcFilename=LEFT(DBF(),LEN(DBF())-4)
         lnBlksize=VAL(SYS(2012))
         USE
         lnHandle=FOPEN(lcFilename+".FPT")
         IF lnHandle>0
    
            lnFilesize=FSEEK(lnHandle,0,2)
            =FSEEK(lnHandle,0)
            lcByte=FREAD(lnHandle,8)
            lnBlknum=ASC(SUBSTR(lcByte,4,1))+(ASC(SUBSTR(lcByte,3,1))*256)+;
               (ASC(SUBSTR(lcByte,2,1))*256*256)+;
               (ASC(SUBSTR(lcByte,1,1))*256*256*256)
            ?  "Current Memo Stats"
            ?  "    Blocksize    "+ALLTRIM(STR(lnBlksize))
            ?  "    # of blocks  "+ALLTRIM(STR(lnBlknum))
            ?  "    Filesize     "+ALLTRIM(STR(lnFilesize))+" Bytes"
            lnBlkend=0
            lni=1
            DO WHILE lnBlkend<512
               lnBlkend=lni*lnBlksize
               lni=lni+1
            ENDDO
            =FSEEK(lnHandle,lnBlkend+4)
            lnRec=0
            FOR lni=lni TO lnBlknum
               lcByte=FREAD(lnHandle,4)
               =FSEEK(lnHandle,lnBlksize-4,1)
               IF (lnBlksize*lni)>lnBlkend
                  lnx=ASC(SUBSTR(lcByte,4,1))+:
                     (ASC(SUBSTR(lcByte,3,1))*256)+;
                     (ASC(SUBSTR(lcByte,2,1))*256*256)+;
                     (ASC(SUBSTR(lcByte,1,1))*256*256*256)+8
                  lnRec=lnRec+1
                  lnk=INT((lnx-1)/lnBlksize)
                  lni=lni+lnk
                  lnTempblk=lnTempblk+INT(lnx/lnTempsize)+;
                     IIF(MOD(lnx,lnTempsize)=0,0,1)
                  =FSEEK(lnHandle,(lnBlksize*lnk),1)
               ENDIF
            ENDFOR
            =FCLOSE(lnHandle)
            lnTempblk=lnTempblk+INT(512/lnTempsize)+;
               IIF(MOD(512,lnTempsize)=0,0,1)
            lnTempfile=lnTempsize*lnTempblk
            ?
            ?  "Requested Memo Stats"
            ?  "    Blocksize    "+ALLTRIM(STR(lnTempsize))
            ?  "    # of blocks  "+ALLTRIM(STR(lnTempblk))
            ?  "    Filesize     "+ALLTRIM(STR(lnTempfile))+" Bytes"
            ?
            ? "Savings: "+ALLTRIM(STR(lnFilesize-lnTempfile))+" Bytes"
            USE &lcFilename
            IF lnRec>RECCOUNT()
              ?
              ? ALLTRIM(str(lnrec-reccount()))+;
                 " disconneted records in memo file."
              ? "Please PACK MEMO and run this command again"
            ENDIF
            RETURN lnTempfile
         ENDIF
       ENDIF
    
    

  2. Save and close LowLevel.prg.

  3. Test the function by opening a table with a memo field. For this example, the table is Restaurs.dbf. A blocksize of 64 will be tested. In the Command window, type:

    SET PROCEDURE TO LOWLEVEL.PRG USE C:\FPW26\SAMPLE\ORGANIZE\DBFS\RESTAURS =BLOCKTEST(64)

    Note that if the current blocksize is 64, there will be no savings in creating a new file with the same blocksize.

  4. Test it again using the following different block sizes:

    =BLOCKTEST(32) =BLOCKTEST(35) =BLOCKTEST(40)

  5. To change the blocksize of Restaurs.dbf TO 40, use these commands:

    SET BLOCKSIZE TO 40 COPY TO TEMP USE

    ERASE RESTAURS.DBF ERASE RESTAURS.FPT

    RENAME TEMP.DBF TO RESTAURS.DBF RENAME TEMP.FPT TO RESTAURS.FPT


Additional reference words: 3.00 VFoxWin FoxWin FoxDos 2.00 2.50 2.50a
2.50b 2.60 2.60a 3.00
KBCategory: kbprg kbcode
KBSubcategory: FxprgTable


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Last reviewed: September 10, 1995
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