Re^3: Non-blocking Reads from Pipe Filehandle

Wrong! Win32::API does no defined check.

Hm, Maybe you're right, but it doesn't seem to be necessary. With your insight about buffering & EOF and a little wrapping, this seems to work quite nicely:

#! perl -slw
use strict;
use Win32API::File qw[ GetOsFHandle ];
use Win32::API::Prototype;

ApiLink(
    'Kernel32', q[
        BOOL PeekNamedPipe(
            HANDLE hNamedPipe,
            LPVOID lpBuffer,
            DWORD nBufferSize,
            LPDWORD lpBytesRead,
            DWORD *lpTotalBytesAvail,
            LPDWORD lpBytesLeftThisMessage
        )
    ]
) or die $^E;

sub readlineMaybe {
    my $fh = shift;
    my $osfh = GetOsFHandle( $fh ) or die $^E;
    my( $bufsize, $buffer, $cAvail, $read ) = ( 1024, chr(0)x1024, 0, 
+0 );
    PeekNamedPipe( $osfh, $buffer, $bufsize, $read, $cAvail, 0 ) 
        or $^E == 109 or die $^E;
    return if $^E == 109;
    my $eolPos = 1+index $buffer, $/;
    return '' unless $eolPos;
    sysread( $fh, $buffer, $eolPos ) or die $!;
    return $buffer;
}

my $cmd = 
  'perl -le"$|++;print localtime().q[: some text] and sleep 1 for 1..1
+0" |';
my $pid = open my $pipe, $cmd or die $!;

while( defined( my $line = readlineMaybe( $pipe ) ) ) {
    Win32::Sleep( 100 ) and next unless $line;
    chomp $line;
    chop $line; ## Annoying!
    print "Got: '$line'";
}

__END__
c:\test>buk-pipe.pl
Got: 'Wed Oct  1 02:01:21 2008: some text'
Got: 'Wed Oct  1 02:01:22 2008: some text'
Got: 'Wed Oct  1 02:01:23 2008: some text'
Got: 'Wed Oct  1 02:01:24 2008: some text'
Got: 'Wed Oct  1 02:01:25 2008: some text'
Got: 'Wed Oct  1 02:01:26 2008: some text'
Got: 'Wed Oct  1 02:01:27 2008: some text'
Got: 'Wed Oct  1 02:01:28 2008: some text'
Got: 'Wed Oct  1 02:01:29 2008: some text'
Got: 'Wed Oct  1 02:01:30 2008: some text'
[download]

The only annoying thing is the need for that chop in addition to chomp.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.

"Science is about questioning the status quo. Questioning authority".

In the absence of evidence, opinion is indistinguishable from prejudice.

"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

Comment on Re^3: Non-blocking Reads from Pipe Filehandle Download Code

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Re^4: Non-blocking Reads from Pipe Filehandle by ikegami (Patriarch) on Oct 01, 2008 at 02:07 UTC
Hm, Maybe you're right, but it doesn't seem to be necessary It stopped your program from working for over a year. It's forcing you to have to OS do unnecessary and possible unwanted work. It's definitely a necessity even though though it could be fudged this time.	[reply]
Re^5: ... (Proof!) by BrowserUk (Patriarch) on Oct 01, 2008 at 03:40 UTC
It's definitely a necessity even though though it could be fudged this time. For the record. This is from API.XS: `case T_POINTER: ## If pointer params[i].t = T_POINTER; origST[i] = ST(i+1); if(has_proto) { pointerCallPack(ST(i+1), i, intypes); params[i].p = (char ) SvPV_nolen(ST(i+1)); } else { ## and no proto if(SvIOK(ST(i+1)) && SvIV(ST(i+1)) == 0) { ## and IV is OK +and zero params[i].p = NULL; ## use NULL } else { params[i].p = (char ) SvPV_nolen(ST(i+1)); ## else use th +e address of the PV } }` [download] So, if you work with the module instead of fighting it, and use 0 (zero) instead of undef to indicate that you want this pointer parameter set to null, that's what it does! Ie. it's not a "fudge", but how the author designed it! Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply] [d/l]
Re^6: ... (Proof!) by ikegami (Patriarch) on Oct 01, 2008 at 04:00 UTC
I used 0. Didn't work. But then again, `has_proto` is true for the snippet that shows the problem. What's getting you so excited? Update: Bug report. Proposed change: case T_POINTER: params[i].t = T_POINTER; origST[i] = ST(i+1); if(has_proto) { - pointerCallPack(ST(i+1), i, intypes); - params[i].p = (char ) SvPV_nolen(ST(i+1)); + if(SvOK(ST(i+1)) { + pointerCallPack(ST(i+1), i, intypes); + params[i].p = (char ) SvPV_nolen(ST(i+1)); + } else { + params[i].p = NULL; + } } else { if(SvIOK(ST(i+1)) && SvIV(ST(i+1)) == 0) { params[i].p = NULL; } else { params[i].p = (char *) SvPV_nolen(ST(i+1)); } } ... if(params[i].t == T_POINTER && has_proto) { - pointerCallUnpack(origST[i], i, intypes); + if(SvOK(origST[i]) { + pointerCallUnpack(origST[i], i, intypes); + } } [download]	[reply] [d/l] [select]
Re^7: ... (Proof!) by BrowserUk (Patriarch) on Oct 01, 2008 at 04:59 UTC
Re^8: ... (Proof!) by ikegami (Patriarch) on Oct 01, 2008 at 05:31 UTC
Re^6: ... (Proof!) by ikegami (Patriarch) on Oct 01, 2008 at 06:25 UTC
it's not a "fudge" `lpTotalBytesAvail` and `lpBytesLeftThisMessage` are both `LPDWORD`. You pass zero to both. Yet, you want me to believe doing so results in passing a non-`NULL` pointer for `lpTotalBytesAvail` and a `NULL` pointer for `lpBytesLeftThisMessage`?	[reply] [d/l] [select]
Re^7: ... (Proof!) by BrowserUk (Patriarch) on Oct 01, 2008 at 07:34 UTC
Re^5:Non-blocking Reads from Pipe Filehandle by BrowserUk (Patriarch) on Oct 01, 2008 at 02:31 UTC
It stopped your program from working for over a year. It's forcing you to have to OS do unnecessary and possible unwanted work. It's definitely a necessity even though though it could be fudged this time. Oh dear. You really do talk bollocks sometimes! My "program" was a throw away attempt at something to which I already had (and posted) a simpler, better alternative. What stopped that throw-away from working, for the whole 10 minutes I spent on it, had absolutely nothing to do with all your ballshit above about "having to manage your own buffers". As I demonstrated, that is all completely unnecessary. You (and your mentor) just like doing things the hard way for some reason. Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error. "Science is about questioning the status quo. Questioning authority". In the absence of evidence, opinion is indistinguishable from prejudice. "Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."	[reply]