[perl #67034] reuse buffer on read increases size of buffer

# New Ticket Created by  guenter weber 
# Please include the string:  [perl #67034]
# in the subject line of all future correspondence about this issue. 
# <URL: http://rt.perl.org/rt3/Ticket/Display.html?id=67034 >


To: perlbug@perl.org
Subject: reuse buffer on read increases size of buffer
Cc: root@localhost
Reply-To: docc@webersheim.de
Message-Id: <5.10.0_5617_1246189723@kopernikus.search.b.superkabel.de>

This is a bug report for perl from docc@webersheim.de,
generated with the help of perlbug 1.36 running under perl 5.10.0.


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[Please enter your report here]

hy, i am iterating through a file by 9728000 bytes, file is size >100mb


use Devel::Size;

my $filename = "100mb.txt";
open(HF,"<",$filename);
binmode HF;

my $filesize= -s $filename
my $ed2k_block_size = 9728000;
my $readsize = ($filesize>=$ed2k_block_size ? $ed2k_block_size :
$filesize);

while ( ( $n = read ( HF, $data, $readsize,$offset) ) != 0){
		 print "$n bytes read\n";
	         print Devel::Size::size($data) . " of data\n";

		$data="";
               $readsize = ( ( $filesize-$readsize ) >=
$ed2k_block_size ? $ed2k_block_size : $filesize-$readsize);
		$offset += $ed2k_block_size;

}

i get:

9728000 bytes read
9728056 of data
9728000 bytes read
19456056 of data
9728000 bytes read
29184056 of data
9728000 bytes read
38912056 of data
9728000 bytes read
48640056 of data
9728000 bytes read
58368056 of data
9728000 bytes read
68096056 of data
9728000 bytes read
77824056 of data
9728000 bytes read
87552056 of data
9728000 bytes read
97280056 of data
7577600 bytes read
107008056 of data


as i am parsing the data to the md4 routine, this is not good :)

same problem on 5.10 on debian x64 as on 9.04 ubuntu x64 perl 5.10


[Please do not change anything below this line]
-----------------------------------------------------------------
---
Flags:
    category=core
    severity=high
---
Site configuration information for perl 5.10.0:

Configured by Debian Project at Mon Jan  5 22:36:05 UTC 2009.

Summary of my perl5 (revision 5 version 10 subversion 0) configuration:
  Platform:
    osname=linux, osvers=2.6.24-16-server,
archname=x86_64-linux-gnu-thread-multi
    uname='linux yellow 2.6.24-16-server #1 smp thu apr 10 13:15:38 utc
2008 x86_64 gnulinux '
    config_args='-Dusethreads -Duselargefiles -Dccflags=-DDEBIAN
-Dcccdlflags=-fPIC -Darchname=x86_64-linux-gnu -Dprefix=/usr
-Dprivlib=/usr/share/perl/5.10 -Darchlib=/usr/lib/perl/5.10
-Dvendorprefix=/usr -Dvendorlib=/usr/share/perl5
-Dvendorarch=/usr/lib/perl5 -Dsiteprefix=/usr/local
-Dsitelib=/usr/local/share/perl/5.10.0
-Dsitearch=/usr/local/lib/perl/5.10.0 -Dman1dir=/usr/share/man/man1
-Dman3dir=/usr/share/man/man3 -Dsiteman1dir=/usr/local/man/man1
-Dsiteman3dir=/usr/local/man/man3 -Dman1ext=1 -Dman3ext=3perl
-Dpager=/usr/bin/sensible-pager -Uafs -Ud_csh -Ud_ualarm -Uusesfio
-Uusenm -DDEBUGGING=-g -Doptimize=-O2 -Duseshrplib
-Dlibperl=libperl.so.5.10.0 -Dd_dosuid -des'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=define, usemultiplicity=define
    useperlio=define, d_sfio=undef, uselargefiles=define, usesocks=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN
-fno-strict-aliasing -pipe -I/usr/local/include -D_LARGEFILE_SOURCE
-D_FILE_OFFSET_BITS=64',
    optimize='-O2 -g',
    cppflags='-D_REENTRANT -D_GNU_SOURCE -DDEBIAN -fno-strict-aliasing
-pipe -I/usr/local/include'
    ccversion='', gccversion='4.3.3 20081217 (prerelease)',
gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16
    ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t',
lseeksize=8
    alignbytes=8, prototype=define
  Linker and Libraries:
    ld='cc', ldflags =' -L/usr/local/lib'
    libpth=/usr/local/lib /lib /usr/lib /lib64 /usr/lib64
    libs=-lgdbm -lgdbm_compat -ldb -ldl -lm -lpthread -lc -lcrypt
    perllibs=-ldl -lm -lpthread -lc -lcrypt
    libc=/lib/libc-2.9.so, so=so, useshrplib=true,
libperl=libperl.so.5.10.0
    gnulibc_version='2.9'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -g -L/usr/local/lib'

Locally applied patches:
    

---
@INC for perl 5.10.0:
    /etc/perl
    /usr/local/lib/perl/5.10.0
    /usr/local/share/perl/5.10.0
    /usr/lib/perl5
    /usr/share/perl5
    /usr/lib/perl/5.10
    /usr/share/perl/5.10
    /usr/local/lib/site_perl
    .

---
Environment for perl 5.10.0:
    HOME=/root
    LANG=de_DE.UTF-8
    LANGUAGE (unset)
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

• [perl #67034] reuse buffer on read increases size of buffer by guenter weber
• Re: [perl #67034] reuse buffer on read increases size of buffer by Tony Cook
• Re: [perl #67034] reuse buffer on read increases size of buffer by Günter Weber