chunked_ostream.h

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// -*- mode: c++; c-basic-offset:4 -*-
 
// This file is part of libdap, A C++ implementation of the OPeNDAP Data
// Access Protocol.
 
// Copyright (c) 2013 OPeNDAP, Inc.
// Author: James Gallagher <jgallagher@opendap.org>
//
// This library 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 2.1 of the License, or (at your option) any later version.
//
// This library 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 this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
//
// You can contact OPeNDAP, Inc. at PO Box 112, Saunderstown, RI. 02874-0112.
//
// Portions of this code were taken verbatim from  Josuttis,
// "The C++ Standard Library," p.672
 
#ifndef _chunkedostream_h
#define _chunkedostream_h
 
#include "chunked_stream.h"
 
#include <ostream>
#include <stdexcept> // std::out_of_range
#include <streambuf>
 
#include "util.h"
 
namespace libdap {
 
class chunked_ostream;

class chunked_outbuf : public std::streambuf {
    friend class chunked_ostream;
 
protected:
    std::ostream &d_os;      // Write stuff here
    unsigned int d_buf_size; // Size of the data buffer
    char *d_buffer;          // Data buffer
    bool d_big_endian;
 
public:
    chunked_outbuf(std::ostream &os, unsigned int buf_size) : d_os(os), d_buf_size(buf_size), d_buffer(0) {
        if (d_buf_size & CHUNK_TYPE_MASK)
            throw std::out_of_range(
                "A chunked_outbuf (or chunked_ostream) was built using a buffer larger than 0x00ffffff");
 
        d_big_endian = is_host_big_endian();
        d_buffer = new char[buf_size];
        // Trick: making the pointers think the buffer is one char smaller than it
        // really is ensures that overflow() will be called when there's space for
        // one more character.
        setp(d_buffer, d_buffer + (buf_size - 1));
    }
 
    virtual ~chunked_outbuf() {
        // call end_chunk() and not sync()
        end_chunk();
 
        delete[] d_buffer;
    }
 
protected:
    // data_chunk and end_chunk might not be needed because they
    // are called via flush() and ~chunked_outbuf(), resp. jhrg 9/13/13
    int_type data_chunk(); // sync() and overflow() call this
    int_type end_chunk();
 
    int_type err_chunk(const std::string &msg);
 
    virtual std::streamsize xsputn(const char *s, std::streamsize num);
    // Manipulate the buffer pointers using pbump() after filling the buffer
    // and then call data_chunk(). Leave remainder in buffer. Or copy logic
    // for data_chunk() into loop in this code.
 
    virtual int_type overflow(int c);
    virtual int_type sync();
};

class chunked_ostream : public std::ostream {
protected:
    chunked_outbuf d_cbuf;
 
public:
    chunked_ostream(std::ostream &os, unsigned int buf_size) : std::ostream(&d_cbuf), d_cbuf(os, buf_size) {}

    int_type write_end_chunk() { return d_cbuf.end_chunk(); }

    int_type write_data_chunk() { return d_cbuf.data_chunk(); }

    int_type write_err_chunk(const std::string &msg) { return d_cbuf.err_chunk(msg); }
};
 
} // namespace libdap
 
#endif // _chunkedostream_h