Program Listing for File streambuf.hpp

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//          Copyright Maarten L. Hekkelman, 2020
// Distributed under the Boost Software License, Version 1.0.
//    (See accompanying file LICENSE_1_0.txt or copy at
//          http://www.boost.org/LICENSE_1_0.txt)

#pragma once


#include <zeep/config.hpp>

#include <cassert>
#include <cstring>

#include <streambuf>

namespace zeep
{

// --------------------------------------------------------------------

class char_streambuf : public std::streambuf
{
  public:

    char_streambuf(const char* buffer, size_t length)
        : m_begin(buffer), m_end(buffer + length), m_current(buffer)
    {
        assert(std::less_equal<const char*>()(m_begin, m_end));
    }

    char_streambuf(const char* buffer)
        : m_begin(buffer), m_end(buffer + strlen(buffer)), m_current(buffer)
    {
    }

    char_streambuf(const char_streambuf&) = delete;
    char_streambuf &operator=(const char_streambuf&) = delete;

  private:

    int_type underflow()
    {
        if (m_current == m_end)
            return traits_type::eof();

        return traits_type::to_int_type(*m_current);
    }

    int_type uflow()
    {
        if (m_current == m_end)
            return traits_type::eof();

        return traits_type::to_int_type(*m_current++);
    }

    int_type pbackfail(int_type ch)
    {
        if (m_current == m_begin or (ch != traits_type::eof() and ch != m_current[-1]))
            return traits_type::eof();

        return traits_type::to_int_type(*--m_current);
    }

    std::streamsize showmanyc()
    {
        assert(std::less_equal<const char*>()(m_current, m_end));
        return m_end - m_current;
    }

    pos_type seekoff(std::streambuf::off_type off, std::ios_base::seekdir dir, std::ios_base::openmode /*which*/)
    {
        switch (dir)
        {
            case std::ios_base::beg:
                m_current = m_begin + off;
                break;

            case std::ios_base::end:
                m_current = m_end + off;
                break;

            case std::ios_base::cur:
                m_current += off;
                break;

            default:
                break;
        }

        if (m_current < m_begin)
            m_current = m_begin;

        if (m_current > m_end)
            m_current = m_end;

        return m_current - m_begin;
    }

    pos_type seekpos(std::streambuf::pos_type pos, std::ios_base::openmode /*which*/)
    {
        m_current = m_begin + pos;

        if (m_current < m_begin)
            m_current = m_begin;

        if (m_current > m_end)
            m_current = m_end;

        return m_current - m_begin;
    }

  private:
    const char* const m_begin;
    const char* const m_end;
    const char* m_current;
};

} // namespace zeep