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From: mdavis@pro-sol.cts.com (Morgan Davis)
Newsgroups: comp.sys.apple2
Subject: Re: Applesoft problem: finding the end of a text file
Message-ID: <7127@crash.cts.com>
Date: 22 Jan 91 05:56:14 GMT
Sender: root@crash.cts.com
Lines: 43

In-Reply-To: message from dunadan@blake.u.washington.edu
 
Here's a trick for finding the end of file of a text file from
Applesoft under BASIC.SYSTEM.  It is pretty fast, and requires no
extensive error handling.
 
10 FILE$ = "your file name goes here"
20 D$ = CHR$(4) : EOF = 48840
30 PRINT D$ "APPEND" FILE$
40 PRINT D$ "CLOSE" FILE$
50 SIZE = PEEK (EOF) + PEEK (EOF + 1) * 256 + PEEK (EOF + 2) * 65536
50 PRINT FILE$ " contains " SIZE " bytes"
 
The magic here is that when you do an APPEND, BASIC.SYSTEM opens the
file and does a GET_EOF call in order to move the file pointer to
the end of the file.  After closing the file, the end of file value
is still intact at $BEC8 (48840).
 
You can make this a general purpose file-size-getter by inserting
and changing these lines:
 
25 PRINT D$ "VERIFY" FILE$
30 PRINT D$ "APPEND" FILE$ ",T" PEEK(48824)
 
After a VERIFY (which is a GET_FILE_INFO MLI call), the file's information
such as type, aux type, etc., is left intact in memory.  The only problem
with this code is that it might balk on locked files, as the APPEND
assumes a WRITE.  I haven't test it against a locked file, but you can.
 
BTW, in MD-BASIC this kind of tricky coding is amazingly simple and clean.
As an example for those of you with MD-BASIC, here is the equivalent code:
 
        File$ = "your file name goes here"
        fVerify File$
        fAppend File$ ",T" PEEK(_FIFILID)
        Size = peek24(_SEOF)
        PRINT File$ " contains " Size " bytes"
 
--Morgan Davis

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