rippled/beast/wsproto/detail/utf8_checker.h

//------------------------------------------------------------------------------
/*
    This file is part of Beast: https://github.com/vinniefalco/Beast
    Copyright 2013, Vinnie Falco <vinnie.falco@gmail.com>

    Permission to use, copy, modify, and/or distribute this software for any
    purpose  with  or without fee is hereby granted, provided that the above
    copyright notice and this permission notice appear in all copies.

    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
    ANY  SPECIAL ,  DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
//==============================================================================

#ifndef BEAST_WSPROTO_UTF8_CHECKER_H_INCLUDED
#define BEAST_WSPROTO_UTF8_CHECKER_H_INCLUDED

#include <boost/asio/buffer.hpp>
#include <cstdint>
#include <string> // DEPRECATED

namespace beast {
namespace wsproto {
namespace detail {

// Code adapted from
// http://bjoern.hoehrmann.de/utf-8/decoder/dfa/
/*
    Copyright (c) 2008-2009 Bjoern Hoehrmann <bjoern@hoehrmann.de>

    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. *
*/
template<class = void>
class utf8_checker_t
{
    // Table for the UTF8 decode state machine
    using lut_type = std::uint8_t[400];
    static
    lut_type const&
    lut()
    {
        // 400 elements
        static std::uint8_t constexpr tab[] = {
            0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 00..1f
            0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 20..3f
            0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 40..5f
            0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 60..7f
            1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9,9, // 80..9f
            7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7, // a0..bf
            8,8,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, // c0..df
            0xa,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x3,0x4,0x3,0x3, // e0..ef
            0xb,0x6,0x6,0x6,0x5,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8,0x8, // f0..ff
            0x0,0x1,0x2,0x3,0x5,0x8,0x7,0x1,0x1,0x1,0x4,0x6,0x1,0x1,0x1,0x1, // s0..s0
            1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,0,1,1,1,1,1,0,1,0,1,1,1,1,1,1, // s1..s2
            1,2,1,1,1,1,1,2,1,2,1,1,1,1,1,1,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,1, // s3..s4
            1,2,1,1,1,1,1,1,1,2,1,1,1,1,1,1,1,1,1,1,1,1,1,3,1,3,1,1,1,1,1,1, // s5..s6
            1,3,1,1,1,1,1,3,1,3,1,1,1,1,1,1,1,3,1,1,1,1,1,1,1,1,1,1,1,1,1,1  // s7..s8
        };
        return tab;
    }

    std::uint32_t state_ = 0;
    std::uint32_t codepoint_ = 0;

public:
    utf8_checker_t() = default;
    utf8_checker_t(utf8_checker_t&&) = default;
    utf8_checker_t(utf8_checker_t const&) = default;
    utf8_checker_t& operator=(utf8_checker_t&&) = default;
    utf8_checker_t& operator=(utf8_checker_t const&) = default;

    void
    reset();

    // Returns `true` on success
    bool
    write(void const* buffer, std::size_t size);

    // Returns `true` on success
    template<class BufferSequence>
    bool
    write(BufferSequence const& bs);

    // Returns `true` on success
    bool
    finish();
};

template<class _>
void
utf8_checker_t<_>::reset()
{
    state_ = 0;
    codepoint_ = 0;
}

template<class _>
bool
utf8_checker_t<_>::write(void const* buffer, std::size_t size)
{
    auto p = static_cast<std::uint8_t const*>(buffer);
    auto plut = &lut()[0];
    while(size)
    {
        auto const byte = *p;
        auto const type = plut[byte];
        if(state_)
            codepoint_ = (byte & 0x3fu) | (codepoint_ << 6);
        else
            codepoint_ = (0xff >> type) & byte;
        state_ = plut[256 + state_ * 16 + type];
        if(state_ == 1)
        {
            reset();
            return false;
        }
        ++p;
        --size;
    }
    return true;
}

template<class _>
template<class BufferSequence>
bool
utf8_checker_t<_>::write(BufferSequence const& bs)
{
    using boost::asio::buffer_cast;
    using boost::asio::buffer_size;
    for (auto const& b : bs)
        if(! write(buffer_cast<void const*>(b),
                buffer_size(b)))
            return false;
    return true;
}

template<class _>
bool
utf8_checker_t<_>::finish()
{
    auto const success = state_ == 0;
    reset();
    return success;
}

using utf8_checker = utf8_checker_t<>;

template<class = void>
bool
check_utf8(char const* p, std::size_t n)
{
    utf8_checker c;
    if(! c.write(p, n))
        return false;
    return c.finish();
}

} // detail
} // wsproto
} // beast

#endif