// itlib-rstream v1.00

//

// std::stream-like classes which impose more restrictions on reading

// thus allowing somewhat optimal stream redirection

//

// SPDX-License-Identifier: MIT

// MIT License:

// Copyright(c) 2020 Borislav Stanimirov

//

// Permission is hereby granted, free of charge, to any person obtaining

// a copy of this software and associated documentation files(the

// "Software"), to deal in the Software without restriction, including

// without limitation the rights to use, copy, modify, merge, publish,

// distribute, sublicense, and / or sell copies of the Software, and to

// permit persons to whom the Software is furnished to do so, subject to

// the following conditions :

//

// The above copyright notice and this permission notice shall be

// included in all copies or substantial portions of the Software.

//

// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

// NONINFRINGEMENT.IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE

// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION

// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION

// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

//

//

// VERSION HISTORY

//

// 1.00 (2020-10-21) Initial release

//

//

// DOCUMENTATION

//

// Simply include this file wherever you need.

// It defines two classes

// itlib::rstream (read stream) which wraps a std::istream and allows reads,

// but does not allow seeks. Thus can be sure that all ops in the stream are

// sequential and don't have to worry that seeks might mess-up your reades.

//

// This allows us to define the second class which is called redirect_rstream

// it allows you to to have a rstream from a specific pos within an existing

// std::stream. redirect_rstream seeks to the position when created and seeks

// back to the original position within the wrapped std::stream when destroyed

//

// Configuration:

// You can optionally define ITLIB_RSTREAM_OVERLOAD_RSHIFT to make rstream

// provide a `>>` operator like the one in std::istream.

//

// It is not enabled by default, because it is DANGEROUS when used with

// redirect_stream

//

// The point of having a redirect_stream is to potentially wrap several objects

// which you can read from an rstream into a single block (file, memory...)

// Then, if the packing is tight, reading the last element with >> from an

// object can overflow into the next. Only allow `operator >>` if you know what

// you're doing.

//

//

// TESTS

//

// You can find unit tests in the official repo:

// https://github.com/iboB/itlib/blob/master/test/

//

#pragma once

#include <istream>

namespace itlib

{

template <typename Stream>

class basic_rstream

{

public:

using stream_type = Stream;

using char_type = typename Stream::char_type;

basic_rstream(Stream& in)

: m_in(in)

{}

virtual ~basic_rstream() = default;

basic_rstream& read(char_type* buf, std::streamsize count)

{

m_in.read(buf, count);

return *this;

}

bool fail() const { return m_in.fail(); }

explicit operator bool() const { return !fail(); }

bool good() const { return m_in.good(); }

bool eof() const { return m_in.eof(); }

#if ITLIB_RSTREAM_OVERLOAD_RSHIFT

template <typename T>

friend basic_rstream& operator>>(basic_rstream& in, T& t)

{

in.m_in >> t;

return in;

}

#endif

protected:

Stream& m_in;

};

using rstream = basic_rstream<std::istream>;

template <typename Stream>

class basic_redirect_rstream : public basic_rstream<Stream>

{

public:

basic_redirect_rstream(Stream& in, std::streampos pos)

: basic_rstream<Stream>(in)

, m_restore(pos)

{

m_restore = in.tellg();

in.seekg(pos);

}

~basic_redirect_rstream()

{

this->m_in.seekg(m_restore);

}

private:

std::streampos m_restore;

};

using redirect_rstream = basic_redirect_rstream<std::istream>;

}