Buffer.hpp

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// The Reactive C++ Toolbox.
// Copyright (C) 2013-2019 Swirly Cloud Limited
// Copyright (C) 2021 Reactive Markets Limited
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
 
#ifndef TOOLBOX_IO_BUFFER_HPP
#define TOOLBOX_IO_BUFFER_HPP
 
#include <toolbox/Config.h>
 
#include <boost/asio/buffer.hpp>
#include <boost/container/vector.hpp>
 
namespace toolbox {
inline namespace io {
 
using ConstBuffer = boost::asio::const_buffer;
using MutableBuffer = boost::asio::mutable_buffer;
 
using boost::asio::buffer_cast;
using boost::asio::buffer_size;
 
class TOOLBOX_API Buffer {
  public:
    explicit Buffer(std::size_t capacity) { buf_.reserve(capacity); }
    Buffer() = default;
    ~Buffer() = default;
 
    // Copy.
    Buffer(const Buffer&) = default;
    Buffer& operator=(const Buffer&) = default;
 
    // Move.
    Buffer(Buffer&&) noexcept = default;
    Buffer& operator=(Buffer&&) noexcept = default;
 
    ConstBuffer data() const noexcept { return {rptr(), size()}; }
 
    ConstBuffer data(std::size_t limit) const noexcept { return {rptr(), std::min(limit, size())}; }
 
    std::string_view str() const noexcept { return {rptr(), size()}; }
 
    std::string_view front(std::size_t size) const noexcept
    {
        const auto limit = this->size();
        return {rptr(), std::min(size, limit)};
    }
    std::string_view back(std::size_t size) const noexcept
    {
        const auto limit = this->size();
        size = std::min(size, limit);
        return {rptr() + limit - size, size};
    }
 
    bool empty() const noexcept { return size() == 0U; };
 
    std::size_t size() const noexcept { return wpos_ - rpos_; }
 
    void clear() noexcept { rpos_ = wpos_ = 0; }
 
    void commit(std::size_t count) noexcept { wpos_ += count; }
 
    void consume(std::size_t count) noexcept;
 
    MutableBuffer prepare(std::size_t size)
    {
        if (const auto avail = available(); size > avail) {
            // More buffer space required.
            const auto diff = size - avail;
            buf_.resize(buf_.size() + diff);
        }
        return {wptr(), size};
    }
 
    void reserve(std::size_t capacity) { buf_.reserve(capacity); }
 
  private:
    const char* rptr() const noexcept { return buf_.data() + rpos_; }
    char* wptr() noexcept { return buf_.data() + wpos_; }
    std::size_t available() const noexcept { return buf_.size() - wpos_; }
 
    std::size_t rpos_{}, wpos_{};
    boost::container::vector<char> buf_;
};
 
TOOLBOX_API ConstBuffer advance(ConstBuffer buf, std::size_t n) noexcept;
TOOLBOX_API MutableBuffer advance(MutableBuffer buf, std::size_t n) noexcept;
 
} // namespace io
} // namespace toolbox
 
#endif // TOOLBOX_IO_BUFFER_HPP