It works! thanks On Thu, Apr 7, 2016 at 4:36 PM, llonesmiz <jorge.navalon@gmail.com> wrote:
Cherotek Music wrote
Hey, I'm new to boost and need a seekable input filter that will operate on bytes read from an ifstream. This is what I currently have:
struct my_filter : boost::iostreams::seekable_filter{ template <typename Source> int get(Source& src) { int byte = boost::iostreams::get(src); if(byte != EOF && byte != boost::iostreams::WOULD_BLOCK) { // Do something with byte } return byte; }
template <typename Sink> bool put(Sink&, char) { // No need to actually implement put because this filter is only used with ifstream return true; }
template <typename T> std::streampos seek(T& t, boost::iostreams::stream_offset off, std::ios_base::seekdir way, std::ios_base::openmode which = std::ios_base::in | std::ios_base::out) { return boost::iostreams::seek(t, off, way, which); }};
It works but I would like to get rid of the useless put method. The boost documentation here
http://www.boost.org/doc/libs/1_60_0/libs/iostreams/doc/concepts/filter.html
says there is an InputSeekableFilter refinement of Filter but I can't seem to understand how to use it (there are no input_seekable_filter_tag or input_seekable_filter structs that I could use).
Thanks
"boost::iostreams::seekable_filter" seems to just be a typedef for "boost::iostreams::filter<boost::iostreams::seekable>". I don't know for sure, but I think it would make sense that deriving your "struct my_filter" from "boost::iostreams::filter<boost::iostreams::input_seekable>" would accomplish what you want.
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