Boost C++ Libraries

boost/beast/core/impl/static_buffer.ipp

//
// Copyright (c) 2016-2019 Vinnie Falco (vinnie dot falco at gmail dot com)
//
// 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)
//
// Official repository: https://github.com/boostorg/beast
//

#ifndef BOOST_BEAST_IMPL_STATIC_BUFFER_IPP
#define BOOST_BEAST_IMPL_STATIC_BUFFER_IPP

#include <boost/beast/core/static_buffer.hpp>
#include <boost/asio/buffer.hpp>
#include <boost/throw_exception.hpp>
#include <stdexcept>

namespace boost {
namespace beast {

static_buffer_base::
static_buffer_base(
    void* p, std::size_t size) noexcept
    : begin_(static_cast<char*>(p))
    , capacity_(size)
{
}

void
static_buffer_base::
clear() noexcept
{
    in_off_ = 0;
    in_size_ = 0;
    out_size_ = 0;
}

auto
static_buffer_base::
data() const noexcept ->
    const_buffers_type
{
    if(in_off_ + in_size_ <= capacity_)
        return {
            net::const_buffer{
                begin_ + in_off_, in_size_},
            net::const_buffer{
                begin_, 0}};
    return {
        net::const_buffer{
            begin_ + in_off_, capacity_ - in_off_},
        net::const_buffer{
            begin_, in_size_ - (capacity_ - in_off_)}};
}

auto
static_buffer_base::
data() noexcept ->
    mutable_buffers_type
{
    if(in_off_ + in_size_ <= capacity_)
        return {
            net::mutable_buffer{
                begin_ + in_off_, in_size_},
            net::mutable_buffer{
                begin_, 0}};
    return {
        net::mutable_buffer{
            begin_ + in_off_, capacity_ - in_off_},
        net::mutable_buffer{
            begin_, in_size_ - (capacity_ - in_off_)}};
}

auto
static_buffer_base::
prepare(std::size_t n) ->
    mutable_buffers_type
{
    using net::mutable_buffer;
    if(n > capacity_ - in_size_)
        BOOST_THROW_EXCEPTION(std::length_error{
            "static_buffer overflow"});
    out_size_ = n;
    auto const out_off =
        (in_off_ + in_size_) % capacity_;
    if(out_off + out_size_ <= capacity_ )
        return {
            net::mutable_buffer{
                begin_ + out_off, out_size_},
            net::mutable_buffer{
                begin_, 0}};
    return {
        net::mutable_buffer{
            begin_ + out_off, capacity_ - out_off},
        net::mutable_buffer{
            begin_, out_size_ - (capacity_ - out_off)}};
}

void
static_buffer_base::
commit(std::size_t n) noexcept
{
    in_size_ += (std::min)(n, out_size_);
    out_size_ = 0;
}

void
static_buffer_base::
consume(std::size_t n) noexcept
{
    if(n < in_size_)
    {
        in_off_ = (in_off_ + n) % capacity_;
        in_size_ -= n;
    }
    else
    {
        // rewind the offset, so the next call to prepare
        // can have a longer contiguous segment. this helps
        // algorithms optimized for larger buffers.
        in_off_ = 0;
        in_size_ = 0;
    }
}

} // beast
} // boost

#endif