From: EMalenfant_at_[hidden]
Date: 2006-03-23 19:30:24
From: EMalenfant_at_[hidden]
> Consider the following, using dictionary_output_filter from
> the tutorial:
> (http://www.boost.org/libs/iostreams/doc/index.html?path=2.2.6.3)
>
> namespace io = boost::iostreams;
>
> const std::string source("This foo will be bar");
>
> io::example::dictionary dict;
> dict.add("foo", "bar");
>
> io::filtering_istream in;
> in.push(io::invert(io::example::dictionary_output_filter(dict)));
> in.push(io::array_source(source.c_str(), source.length()));
>
> io::copy(in, std::cout);
>
> Output:
> This bar will be
>
> instead of the expected:
> This bar will be bar
>
Digging a bit, I found that I could "fix" that problem by modifying
invert::read() as follows:
template<typename Source>
std::streamsize read(Source& src, char* s, std::streamsize n)
{
typedef detail::counted_array_sink<char_type> array_sink;
typedef composite<filter_ref, array_sink> filtered_array_sink;
assert((flags() & f_write) == 0);
if (flags() == 0) {
flags() = f_read;
buf().set(0, 0);
}
filtered_array_sink snk(filter(), array_sink(s, n));
int_type status;
for ( status = traits_type::good();
snk.second().count() < n && status == traits_type::good(); )
{
status = buf().fill(src);
buf().flush(snk);
}
// "Fix": When eof is reached on the input, close the filter so that it
writes
// any buffered input it may have.
if ((snk.second().count() == 0) &&
(status == traits_type::eof())){
snk.close();
}
//... "fix" ends here
return snk.second().count() == 0 &&
status == traits_type::eof()
?
-1
:
snk.second().count();
}
Looking at this, however, I wondered what would happen if the filter has
buffered more characters than what would fit in the array_sink. So I tested
with a very long (around 300) last word in the input. Result: An infinite
loop in non_blocking_adapter::write(), desperately calling write() on a full
counted_array_sink.
Guess I'll forget about invert and write an InputFilter...