GZstream.h

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// SPDX-License-Identifier: LGPL-3.0-or-later
/***********************************************************************************/
/*  Copyright 2026 WSL Institute for Snow and Avalanche Research    SLF-DAVOS      */
/***********************************************************************************/
/* This file is part of MeteoIO.
    MeteoIO is free software: you can redistribute it and/or modify
    it under the terms of the GNU Lesser General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.
 
    MeteoIO is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU Lesser General Public License for more details.
 
    You should have received a copy of the GNU Lesser General Public License
    along with MeteoIO.  If not, see <http://www.gnu.org/licenses/>.
*/
 
#ifndef GZSTREAM_H
#define GZSTREAM_H
 
#include <iostream>
#include <string>
#include <memory>
#include <zlib.h>
 
namespace mio {
 
class GZstreambuf : public std::streambuf {
public:
        GZstreambuf();
        ~GZstreambuf() override;
 
        bool open(const std::string& filename, const char* mode);
 
        void close();
 
        bool is_open() const;
 
        std::streampos tell() const;
 
private:
        gzFile file; // The gzipped file handle
        static const int buffer_size = 1024*64; // Buffer size - compromise between size and speed
        char* buffer;
        bool opened; // Whether the file is currently open
 
        // Prevent copying
        GZstreambuf(const GZstreambuf&) = delete;
        GZstreambuf& operator=(const GZstreambuf&) = delete;
 
protected:
        // Override virtual functions from std::streambuf
        virtual int_type underflow() override;
        virtual int_type pbackfail(int_type c) override;
        virtual std::streamsize showmanyc() override;
        virtual std::streamsize xsgetn(char_type* s, std::streamsize n) override;
        virtual int_type overflow(int_type c) override;
        virtual int sync() override;
        virtual std::streamsize xsputn(const char_type* s, std::streamsize n) override;
};
 
class IGZstream : public std::istream {
public:
        IGZstream();
        ~IGZstream() override;
 
        explicit IGZstream(const std::string& filename);
 
        void open(const std::string& filename);
 
        void close();
 
        bool is_open() const { return buf && buf->is_open(); }
 
private:
        std::unique_ptr<GZstreambuf> buf; // The stream buffer
};
 
class OGZstream : public std::ostream {
public:
        OGZstream();
        ~OGZstream() override;
 
        explicit OGZstream(const std::string& filename);
 
        void open(const std::string& filename);
 
        void close();
 
        bool is_open() const { return buf && buf->is_open(); }
 
private:
        std::unique_ptr<GZstreambuf> buf; // The stream buffer
};
 
} // namespace mio
 
#endif // GZSTREAM_H