chunked_istream.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 _chunked_istream_h
#define _chunked_istream_h
 
#include "chunked_stream.h"
 
#include <stdint.h>
 
#include <istream>
#include <stdexcept>
#include <streambuf>
#include <string>
 
namespace libdap {
 
class chunked_inbuf : public std::streambuf {
private:
    std::istream &d_is;
 
    uint32_t d_buf_size; // Size of the data buffer
    char *d_buffer;      // data buffer
 
    // In the original implementation of this class, the byte order of the data stream
    // was passed in via constructors. When BYTE_ORDER_PREFIX is defined that is the
    // case. However, when it is not defined, the byte order is read from the chunk
    // header's high order byte (in bit position 2 - see chunked_stream.h). jhrg 11/24/13
 
    bool d_twiddle_bytes; // receiver-makes-right encoding (byte order)...
    bool d_set_twiddle;
 
    // If an error chunk is read, save the message here
    std::string d_error_message;
    bool d_error;

    void m_buffer_alloc() {
        delete[] d_buffer;
        d_buffer = new char[d_buf_size];
        setg(d_buffer,  // beginning of put back area
             d_buffer,  // read position
             d_buffer); // end position
    }
 
public:
    chunked_inbuf(std::istream &is, int size)
        : d_is(is), d_buf_size(size), d_buffer(0), d_twiddle_bytes(false), d_set_twiddle(false), d_error(false) {
        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");
 
        m_buffer_alloc();
    }
 
    virtual ~chunked_inbuf() { delete[] d_buffer; }
 
    int_type read_next_chunk();
 
    int bytes_in_buffer() const { return (egptr() - gptr()); }
 
    // d_twiddle_bytes is false initially and is set to the correct value
    // once the first chunk is read.
    bool twiddle_bytes() const { return d_twiddle_bytes; }
 
    bool error() const { return d_error; }
    std::string error_message() const { return d_error_message; }
 
protected:
    virtual int_type underflow();
 
    virtual std::streamsize xsgetn(char *s, std::streamsize num);
};
 
class chunked_istream : public std::istream {
protected:
    chunked_inbuf d_cbuf;
 
public:
    chunked_istream(std::istream &is, int size) : std::istream(&d_cbuf), d_cbuf(is, size) {}
 
    int read_next_chunk() { return d_cbuf.read_next_chunk(); }

    int bytes_in_buffer() const { return d_cbuf.bytes_in_buffer(); }

    bool twiddle_bytes() const { return d_cbuf.twiddle_bytes(); }
    bool error() const { return d_cbuf.error(); }
    std::string error_message() const { return d_cbuf.error_message(); }
};
 
} // namespace libdap
 
#endif // _chunked_istream_h