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

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

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.

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

   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