istream_source.hpp

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#ifndef EAGINE_SERIALIZE_ISTREAM_SOURCE_HPP
#define EAGINE_SERIALIZE_ISTREAM_SOURCE_HPP
 
#include "../assert.hpp"
#include "../memory/buffer.hpp"
#include "../memory/span_algo.hpp"
#include "data_source.hpp"
#include <istream>
 
namespace eagine {
//------------------------------------------------------------------------------
class istream_data_source : public deserializer_data_source {
public:
    istream_data_source(std::istream& in) noexcept
      : _in{in} {}
 
    auto top(span_size_t req_size) -> memory::const_block final {
        if(_cur_size < req_size) {
            while(_storage.size() < _cur_size + req_size) {
                _storage.resize(_storage.size() + _chunk_size());
            }
            read_from_stream(
              _in,
              head(skip(cover(_storage), _cur_size), req_size - _cur_size));
            _cur_size += span_size(_in.gcount());
        }
        return head(head(view(_storage), _cur_size), req_size);
    }
 
    void pop(span_size_t del_size) final {
        if(_cur_size <= del_size) {
            _cur_size = 0;
            if(_storage.size() > _chunk_size()) {
                _storage.resize(_chunk_size());
            }
        } else {
            auto sw = head(cover(_storage), _cur_size);
            memory::copy(skip(sw, del_size), sw);
            _cur_size -= del_size;
        }
        EAGINE_ASSERT(_cur_size >= 0);
    }
 
private:
    static constexpr auto _chunk_size() noexcept -> span_size_t {
        return 8 * 1024;
    }
 
    std::istream& _in;
    span_size_t _cur_size{0};
    memory::buffer _storage{};
};
//------------------------------------------------------------------------------
} // namespace eagine
 
#endif // EAGINE_SERIALIZE_ISTREAM_SOURCE_HPP