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Often I have a task to read/write data to/from pipes without perl buffered IO (because same pipes used in select()). AFAIK this should be implemented via sysread/syswrite, and sysread/syswrite are documented to sometimes return less data, than available and sometimes return EINTR (let's talk about blocking pipes for now). So every time I end up with the following wrappers:

# args: ($file, $buffer, $length)
# returns data in $buffer and number of bytes read, or undef on EOF
sub sysreadfull
{
    my ($file, $len) = ($_[0], $_[2]);
    my $n = 0;
    while ($len - $n) {
        my $i = sysread($file, $_[1], $len - $n, $n);
        if (defined($i)) {
            if ($i == 0) {
                return $n;
            } else {
                $n += $i;
            }
        } elsif ($!{EINTR}) {
            redo;
        } else {
            return $n ? $n : undef;
        }
    }
    return $n;
}

# args: ($file, $buffer)
# returns number of bytes actually written
sub syswritefull
{
    my ($file, $len) = ($_[0], length($_[1]));
    my $n = 0;
    while ($len - $n) {
        my $i = syswrite($file, $_[1], $len - $n, $n);
        if (defined($i)) {
            $n += $i;
        } elsif ($!{EINTR}) {
            redo;
        } else {
            return $n ? $n : undef;
        }
    }
    return $n;
}
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Question is: It's should be very common problem for everyone who deals with IPC or network programming, why nobody wrote CPAN module with such wrappers? Maybe because there is easier way ? Maybe ":raw" handles? I saw similar code only here (but for non-blocking), but seems it has bug

In reply to sysread/syswrite wrappers by vsespb

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