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

• 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