aOn Tue, Mar 10, 2020 at 5:49 PM Vinnie Falco <vinnie.falco@gmail.com> wrote:
On Tue, Mar 10, 2020 at 1:31 AM Domen Vrankar <domen.vrankar@gmail.com> wrote:
You compress/decompress in chunks so all you need is a const std::span for input and std::span for output and call decompress on a for loop.
You need to know:
1. how much input was consumed 2. how much output was produced
Now I understand what you mean. You got me confused as your compress function wasn't receiving any state (like z_stream in zlib) so I assumed that you meant to compress the entire buffer in one go.
...input iterator pair/range for input/output... ...std::istream_iterator... ...boost.spirit x3 parser... ...read->decompress->parse/process ... Whit iterators/ranges described above you wouldn't need to return std::size_t so return can be used for error codes instead.
It isn't clear what these things mean without seeing a function signature or class declaration.
Since you need to hold state I was talking about something like this: struct Reader // should be implemented for reading from vector, file stream... some provided as convinience, others user defined so an extension point { std::span<std::byte> read(); // remains stable untill next call to read, at that point it is auto consumed bool eof(); }; template<typename InReader, typename WriteBuffer> class Deflate_range { public: Deflate_range(InReader& in, WriteBuffer& write); class Deflate_iterator{...}; Deflate_iterator begin(); // can be called only once Deflate_iterator end(); private: InReader& in_; WriteBuffer& write_; z_stream zs_; // holds the compression/encryption/... state }; Polymorphic_deflate_range compress(std::istream_iterator<std::byte> begin, std::istream_iterator<std::byte> end); // it packs iterators into a Reader (an overload of compress coud also take in streams directly - it's just a convinience function) std::istringstream str{"1234567890"}; auto range = compress(std::istream_iterator<std::byte>{str}, std::istream_iterator<std::byte>{}); bool ok = boost::spirit::x3::phrase_parse(range.begin(), range.end(), ...); I haven't used std::ranges yet so perhaps such a range should be implemented differently. Then I got confused by your compress API so size_t my return comment was just me being confused and reading/replying to mails on my phone... Hope this clarifies things a bit. I'm guessing that I could use such thing in my toy game engine - not certain but perhaps I won't need the whole libarchive functionality there... To early to say. Regards, Domen
Thanks