Q136284: How to Find the Size of an .FPT File with Different Blocksizes

Article: Q136284
Product(s): Microsoft FoxPro
Version(s): 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
Operating System(s): 
Keyword(s): 
Last Modified: 15-FEB-2000

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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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