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

On Wed, Mar 11, 2020 at 7:12 AM Domen Vrankar wrote:

aOn Tue, Mar 10, 2020 at 5:49 PM Vinnie Falco wrote:

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On Tue, Mar 10, 2020 at 1:31 AM Domen Vrankar wrote:

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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.

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...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);

Sry... I meant to write std::spanstd::byte instead of WriteBuffer template but completely forgot while composing the mail... It's a temporary buffer used by deflate process to be used for iterator buffering. Just replace it while reading ;)

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

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Thanks