Re: Help with binary files, read, and eof
From: Ulrich Schöbel (usus_at_tclers.tk)
Date: 02/03/04
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Date: Tue, 03 Feb 2004 14:50:25 +0100
Hi Mark,
the changes below should help.
Best regards
Ulrich
Mark Curry wrote:
>
> I'm attemping to read binary files, and am running into issue with
> respect to EOF. Been through the FAQ and the wiki for info on using
> binary files, but can't seem to find the problem.
>
> Short description: I'm reading in a binary file, 255 bytes at a time.
> For each 255 byte "packet", I prepend 5 bytes, and send the whole thing
> out a filehandle configured for the serial port.
>
> My problem is with EOF handling. My files that I'm processing are
> always an integer multiple off 255 bytes in length. The current file
> I'm using is 9945 bytes = 255 bytes * 39 "packets".
>
> When running my script, however, it always outputs the first 39
> packets, without a problem, but then one additional packet
> of garbage data. I've stared at my EOF handling for hours, and
> cannot pick out the problem.
>
> Here's the main code, snipped to as short as I can manage.
>
> set count 0
> if [ catch { open $filename r } fh1 ] {
> puts stderr "Cannot open $filename : $fh1"
> } else {
> fconfigure $fh1 -translation binary -encoding binary
> set noquit 1
> while { $noquit } {
> set read_bytes [ read $fh1 255 ]
Insert your 'check for EOF' here
> set read_bytes_length [ expr [ string length $read_bytes ] ]
>
> # Send out Header to serial port ($fh)
> puts -nonewline $fh \xa0
> puts -nonewline $fh \x1e
> puts -nonewline $fh \x56
> puts -nonewline $fh \x05
> puts -nonewline $fh \x00
> flush $fh
>
> # Send out data to serial port
> if { $read_bytes_length != 0 } {
> puts -nonewline $fh $read_bytes
> puts stderr "Packet $count. read_bytes_length=$read_bytes_length"
> incr count
> }
> flush $fh
>
> # Check for EOF
> if [ eof $fh1 ] {
> for { set i $read_bytes_length } { $i < 255 } { incr i } {
> puts $fh \x00 # If, for some reason filesize is not an
> # integer number of packets, then pad zeros
> }
> set noquit 0
continue
> } elseif { $read_bytes_length != 255 } {
> puts stderr "ERROR read_bytes_length!=255, and EOF NOT detected."
> }
> }
> close $fh1
> }
>
> The script shows "Packet 39. read_bytes_length=255" being sent out. Only
> packets 0 - 38 should be sent. (I keep thinking it some basic problem
> with counting from 0 / counting from 1, but I can't see it).
>
> Any help appreciated.
> Using Tcl v8.4.4
>
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