On Fri, Sep 23, 2005 at 10:40:27PM -0700, Ilya Zakharevich wrote:
> Let me repeat it yet again: it should be easier to rewrite PerlIO
> stuff from scratch than try to fix bugs in it.
>
> Example (on unix):
>
> unix2dos .tcshrc | perl -we 'binmode STDIN, ":crlf" or die; print while read
> STDIN, $_, 32000'
...
> (Yes, it makes a seek() in the process of conversion "\r\n" to "\n".
> This is why the call works - accidentally - with plain files.)
One can better understand how it works now by makeing a file (as in
perl -wle 'binmode STDOUT, ":crlf"; $c = shift;
print "0123456789" while $c--' 4e5 > /tmp/l
) and running
truss perl -we 'binmode STDIN, ":crlf" or die;
1 while read STDIN, $_, 32000' < /tmp/l
on it. It goes like this:
fstat64(0, 0xFFBFEB08) = 0
read(0, " 0 1 2 3 4 5 6 7 8 9\r\n".., 8192) = 8192
llseek(0, 12, SEEK_SET) = 12
llseek(0, 0, SEEK_CUR) = 12
read(0, " 0 1 2 3 4 5 6 7 8 9\r\n".., 8192) = 8192
llseek(0, 24, SEEK_SET) = 24
llseek(0, 0, SEEK_CUR) = 24
read(0, " 0 1 2 3 4 5 6 7 8 9\r\n".., 8192) = 8192
llseek(0, 36, SEEK_SET) = 36
llseek(0, 0, SEEK_CUR) = 36
read(0, " 0 1 2 3 4 5 6 7 8 9\r\n".., 8192) = 8192
llseek(0, 48, SEEK_SET) = 48
llseek(0, 0, SEEK_CUR) = 48
etc. 2 (sic!) seek()s and one read() (of 8K!) on each CR converted.
No wonder it goes as quick as 64KB/sec here...
Hope this helps,
Ilya
