DOCUMENT:Q136284  15-FEB-2000  [foxpro]
TITLE   :How to Find the Size of an .FPT File with Different Blocksizes
PRODUCT :Microsoft FoxPro
PROD/VER:MS-DOS:2.0,2.5,2.5a,2.6,2.6a; WINDOWS:2.5,2.5a,2.5b,2.6,2.6a,3.0
OPER/SYS:
KEYWORDS:

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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 
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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 query words: VFoxWin FoxWin FoxDos

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Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbFoxproSearch kbZNotKeyword3 kbFoxPro200DOS kbFoxPro250DOS kbFoxPro250aDOS kbFoxPro260DOS kbFoxPro260aDOS kbFoxPro260 kbFoxPro250 kbFoxPro250a kbFoxPro250b kbFoxPro260a kbVFP300
Version           : MS-DOS:2.0,2.5,2.5a,2.6,2.6a; WINDOWS:2.5,2.5a,2.5b,2.6,2.6a,3.0

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