Re: [boost] C++ Deflate (zlib-like) library

11 Mar 2020

      aOn Tue, Mar 10, 2020 at 5:49 PM Vinnie Falco 
wrote:
...
On Tue, Mar 10, 2020 at 1:31 AM Domen Vrankar 
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::spanstd::byte read(); // remains stable untill next call to
read, at that point it is auto consumed
    bool eof();
};

template
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_iteratorstd::byte begin,
std::istream_iteratorstd::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_iteratorstd::byte{str},
std::istream_iteratorstd::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