// // impl/write.hpp // ~~~~~~~~~~~~~~ // // Copyright (c) 2003-2019 Christopher M. Kohlhoff (chris at kohlhoff 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) // #ifndef ASIO_IMPL_WRITE_HPP #define ASIO_IMPL_WRITE_HPP #if defined(_MSC_VER) && (_MSC_VER >= 1200) # pragma once #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) #include "asio/associated_allocator.hpp" #include "asio/associated_executor.hpp" #include "asio/buffer.hpp" #include "asio/completion_condition.hpp" #include "asio/detail/array_fwd.hpp" #include "asio/detail/base_from_completion_cond.hpp" #include "asio/detail/bind_handler.hpp" #include "asio/detail/consuming_buffers.hpp" #include "asio/detail/dependent_type.hpp" #include "asio/detail/handler_alloc_helpers.hpp" #include "asio/detail/handler_cont_helpers.hpp" #include "asio/detail/handler_invoke_helpers.hpp" #include "asio/detail/handler_type_requirements.hpp" #include "asio/detail/non_const_lvalue.hpp" #include "asio/detail/throw_error.hpp" #include "asio/detail/push_options.hpp" namespace asio { namespace detail { template std::size_t write_buffer_sequence(SyncWriteStream& s, const ConstBufferSequence& buffers, const ConstBufferIterator&, CompletionCondition completion_condition, asio::error_code& ec) { ec = asio::error_code(); asio::detail::consuming_buffers tmp(buffers); while (!tmp.empty()) { if (std::size_t max_size = detail::adapt_completion_condition_result( completion_condition(ec, tmp.total_consumed()))) tmp.consume(s.write_some(tmp.prepare(max_size), ec)); else break; } return tmp.total_consumed();; } } // namespace detail template inline std::size_t write(SyncWriteStream& s, const ConstBufferSequence& buffers, CompletionCondition completion_condition, asio::error_code& ec, typename enable_if< is_const_buffer_sequence::value >::type*) { return detail::write_buffer_sequence(s, buffers, asio::buffer_sequence_begin(buffers), ASIO_MOVE_CAST(CompletionCondition)(completion_condition), ec); } template inline std::size_t write(SyncWriteStream& s, const ConstBufferSequence& buffers, typename enable_if< is_const_buffer_sequence::value >::type*) { asio::error_code ec; std::size_t bytes_transferred = write(s, buffers, transfer_all(), ec); asio::detail::throw_error(ec, "write"); return bytes_transferred; } template inline std::size_t write(SyncWriteStream& s, const ConstBufferSequence& buffers, asio::error_code& ec, typename enable_if< is_const_buffer_sequence::value >::type*) { return write(s, buffers, transfer_all(), ec); } template inline std::size_t write(SyncWriteStream& s, const ConstBufferSequence& buffers, CompletionCondition completion_condition, typename enable_if< is_const_buffer_sequence::value >::type*) { asio::error_code ec; std::size_t bytes_transferred = write(s, buffers, ASIO_MOVE_CAST(CompletionCondition)(completion_condition), ec); asio::detail::throw_error(ec, "write"); return bytes_transferred; } #if !defined(ASIO_NO_DYNAMIC_BUFFER_V1) template std::size_t write(SyncWriteStream& s, ASIO_MOVE_ARG(DynamicBuffer_v1) buffers, CompletionCondition completion_condition, asio::error_code& ec, typename enable_if< is_dynamic_buffer_v1::type>::value && !is_dynamic_buffer_v2::type>::value >::type*) { typename decay::type b( ASIO_MOVE_CAST(DynamicBuffer_v1)(buffers)); std::size_t bytes_transferred = write(s, b.data(), ASIO_MOVE_CAST(CompletionCondition)(completion_condition), ec); b.consume(bytes_transferred); return bytes_transferred; } template inline std::size_t write(SyncWriteStream& s, ASIO_MOVE_ARG(DynamicBuffer_v1) buffers, typename enable_if< is_dynamic_buffer_v1::type>::value && !is_dynamic_buffer_v2::type>::value >::type*) { asio::error_code ec; std::size_t bytes_transferred = write(s, ASIO_MOVE_CAST(DynamicBuffer_v1)(buffers), transfer_all(), ec); asio::detail::throw_error(ec, "write"); return bytes_transferred; } template inline std::size_t write(SyncWriteStream& s, ASIO_MOVE_ARG(DynamicBuffer_v1) buffers, asio::error_code& ec, typename enable_if< is_dynamic_buffer_v1::type>::value && !is_dynamic_buffer_v2::type>::value >::type*) { return write(s, ASIO_MOVE_CAST(DynamicBuffer_v1)(buffers), transfer_all(), ec); } template inline std::size_t write(SyncWriteStream& s, ASIO_MOVE_ARG(DynamicBuffer_v1) buffers, CompletionCondition completion_condition, typename enable_if< is_dynamic_buffer_v1::type>::value && !is_dynamic_buffer_v2::type>::value >::type*) { asio::error_code ec; std::size_t bytes_transferred = write(s, ASIO_MOVE_CAST(DynamicBuffer_v1)(buffers), ASIO_MOVE_CAST(CompletionCondition)(completion_condition), ec); asio::detail::throw_error(ec, "write"); return bytes_transferred; } #if !defined(ASIO_NO_EXTENSIONS) #if !defined(ASIO_NO_IOSTREAM) template inline std::size_t write(SyncWriteStream& s, asio::basic_streambuf& b, CompletionCondition completion_condition, asio::error_code& ec) { return write(s, basic_streambuf_ref(b), ASIO_MOVE_CAST(CompletionCondition)(completion_condition), ec); } template inline std::size_t write(SyncWriteStream& s, asio::basic_streambuf& b) { return write(s, basic_streambuf_ref(b)); } template inline std::size_t write(SyncWriteStream& s, asio::basic_streambuf& b, asio::error_code& ec) { return write(s, basic_streambuf_ref(b), ec); } template inline std::size_t write(SyncWriteStream& s, asio::basic_streambuf& b, CompletionCondition completion_condition) { return write(s, basic_streambuf_ref(b), ASIO_MOVE_CAST(CompletionCondition)(completion_condition)); } #endif // !defined(ASIO_NO_IOSTREAM) #endif // !defined(ASIO_NO_EXTENSIONS) #endif // !defined(ASIO_NO_DYNAMIC_BUFFER_V1) template std::size_t write(SyncWriteStream& s, DynamicBuffer_v2 buffers, CompletionCondition completion_condition, asio::error_code& ec, typename enable_if< is_dynamic_buffer_v2::value >::type*) { std::size_t bytes_transferred = write(s, buffers.data(0, buffers.size()), ASIO_MOVE_CAST(CompletionCondition)(completion_condition), ec); buffers.consume(bytes_transferred); return bytes_transferred; } template inline std::size_t write(SyncWriteStream& s, DynamicBuffer_v2 buffers, typename enable_if< is_dynamic_buffer_v2::value >::type*) { asio::error_code ec; std::size_t bytes_transferred = write(s, ASIO_MOVE_CAST(DynamicBuffer_v2)(buffers), transfer_all(), ec); asio::detail::throw_error(ec, "write"); return bytes_transferred; } template inline std::size_t write(SyncWriteStream& s, DynamicBuffer_v2 buffers, asio::error_code& ec, typename enable_if< is_dynamic_buffer_v2::value >::type*) { return write(s, ASIO_MOVE_CAST(DynamicBuffer_v2)(buffers), transfer_all(), ec); } template inline std::size_t write(SyncWriteStream& s, DynamicBuffer_v2 buffers, CompletionCondition completion_condition, typename enable_if< is_dynamic_buffer_v2::value >::type*) { asio::error_code ec; std::size_t bytes_transferred = write(s, ASIO_MOVE_CAST(DynamicBuffer_v2)(buffers), ASIO_MOVE_CAST(CompletionCondition)(completion_condition), ec); asio::detail::throw_error(ec, "write"); return bytes_transferred; } namespace detail { template class write_op : detail::base_from_completion_cond { public: write_op(AsyncWriteStream& stream, const ConstBufferSequence& buffers, CompletionCondition& completion_condition, WriteHandler& handler) : detail::base_from_completion_cond< CompletionCondition>(completion_condition), stream_(stream), buffers_(buffers), start_(0), handler_(ASIO_MOVE_CAST(WriteHandler)(handler)) { } #if defined(ASIO_HAS_MOVE) write_op(const write_op& other) : detail::base_from_completion_cond(other), stream_(other.stream_), buffers_(other.buffers_), start_(other.start_), handler_(other.handler_) { } write_op(write_op&& other) : detail::base_from_completion_cond( ASIO_MOVE_CAST(detail::base_from_completion_cond< CompletionCondition>)(other)), stream_(other.stream_), buffers_(ASIO_MOVE_CAST(buffers_type)(other.buffers_)), start_(other.start_), handler_(ASIO_MOVE_CAST(WriteHandler)(other.handler_)) { } #endif // defined(ASIO_HAS_MOVE) void operator()(const asio::error_code& ec, std::size_t bytes_transferred, int start = 0) { std::size_t max_size; switch (start_ = start) { case 1: max_size = this->check_for_completion(ec, buffers_.total_consumed()); do { stream_.async_write_some(buffers_.prepare(max_size), ASIO_MOVE_CAST(write_op)(*this)); return; default: buffers_.consume(bytes_transferred); if ((!ec && bytes_transferred == 0) || buffers_.empty()) break; max_size = this->check_for_completion(ec, buffers_.total_consumed()); } while (max_size > 0); handler_(ec, buffers_.total_consumed()); } } //private: typedef asio::detail::consuming_buffers buffers_type; AsyncWriteStream& stream_; buffers_type buffers_; int start_; WriteHandler handler_; }; template inline void* asio_handler_allocate(std::size_t size, write_op* this_handler) { return asio_handler_alloc_helpers::allocate( size, this_handler->handler_); } template inline void asio_handler_deallocate(void* pointer, std::size_t size, write_op* this_handler) { asio_handler_alloc_helpers::deallocate( pointer, size, this_handler->handler_); } template inline bool asio_handler_is_continuation( write_op* this_handler) { return this_handler->start_ == 0 ? true : asio_handler_cont_helpers::is_continuation( this_handler->handler_); } template inline void asio_handler_invoke(Function& function, write_op* this_handler) { asio_handler_invoke_helpers::invoke( function, this_handler->handler_); } template inline void asio_handler_invoke(const Function& function, write_op* this_handler) { asio_handler_invoke_helpers::invoke( function, this_handler->handler_); } template inline void start_write_buffer_sequence_op(AsyncWriteStream& stream, const ConstBufferSequence& buffers, const ConstBufferIterator&, CompletionCondition& completion_condition, WriteHandler& handler) { detail::write_op( stream, buffers, completion_condition, handler)( asio::error_code(), 0, 1); } struct initiate_async_write_buffer_sequence { template void operator()(ASIO_MOVE_ARG(WriteHandler) handler, AsyncWriteStream* s, const ConstBufferSequence& buffers, ASIO_MOVE_ARG(CompletionCondition) completion_cond) const { // If you get an error on the following line it means that your handler // does not meet the documented type requirements for a WriteHandler. ASIO_WRITE_HANDLER_CHECK(WriteHandler, handler) type_check; non_const_lvalue handler2(handler); non_const_lvalue completion_cond2(completion_cond); start_write_buffer_sequence_op(*s, buffers, asio::buffer_sequence_begin(buffers), completion_cond2.value, handler2.value); } }; } // namespace detail #if !defined(GENERATING_DOCUMENTATION) template struct associated_allocator< detail::write_op, Allocator> { typedef typename associated_allocator::type type; static type get( const detail::write_op& h, const Allocator& a = Allocator()) ASIO_NOEXCEPT { return associated_allocator::get(h.handler_, a); } }; template struct associated_executor< detail::write_op, Executor> { typedef typename associated_executor::type type; static type get( const detail::write_op& h, const Executor& ex = Executor()) ASIO_NOEXCEPT { return associated_executor::get(h.handler_, ex); } }; #endif // !defined(GENERATING_DOCUMENTATION) template inline ASIO_INITFN_RESULT_TYPE(WriteHandler, void (asio::error_code, std::size_t)) async_write(AsyncWriteStream& s, const ConstBufferSequence& buffers, CompletionCondition completion_condition, ASIO_MOVE_ARG(WriteHandler) handler, typename enable_if< is_const_buffer_sequence::value >::type*) { return async_initiate( detail::initiate_async_write_buffer_sequence(), handler, &s, buffers, ASIO_MOVE_CAST(CompletionCondition)(completion_condition)); } template inline ASIO_INITFN_RESULT_TYPE(WriteHandler, void (asio::error_code, std::size_t)) async_write(AsyncWriteStream& s, const ConstBufferSequence& buffers, ASIO_MOVE_ARG(WriteHandler) handler, typename enable_if< is_const_buffer_sequence::value >::type*) { return async_initiate( detail::initiate_async_write_buffer_sequence(), handler, &s, buffers, transfer_all()); } #if !defined(ASIO_NO_DYNAMIC_BUFFER_V1) namespace detail { template class write_dynbuf_v1_op { public: template write_dynbuf_v1_op(AsyncWriteStream& stream, ASIO_MOVE_ARG(BufferSequence) buffers, CompletionCondition& completion_condition, WriteHandler& handler) : stream_(stream), buffers_(ASIO_MOVE_CAST(BufferSequence)(buffers)), completion_condition_( ASIO_MOVE_CAST(CompletionCondition)(completion_condition)), handler_(ASIO_MOVE_CAST(WriteHandler)(handler)) { } #if defined(ASIO_HAS_MOVE) write_dynbuf_v1_op(const write_dynbuf_v1_op& other) : stream_(other.stream_), buffers_(other.buffers_), completion_condition_(other.completion_condition_), handler_(other.handler_) { } write_dynbuf_v1_op(write_dynbuf_v1_op&& other) : stream_(other.stream_), buffers_(ASIO_MOVE_CAST(DynamicBuffer_v1)(other.buffers_)), completion_condition_( ASIO_MOVE_CAST(CompletionCondition)( other.completion_condition_)), handler_(ASIO_MOVE_CAST(WriteHandler)(other.handler_)) { } #endif // defined(ASIO_HAS_MOVE) void operator()(const asio::error_code& ec, std::size_t bytes_transferred, int start = 0) { switch (start) { case 1: async_write(stream_, buffers_.data(), ASIO_MOVE_CAST(CompletionCondition)(completion_condition_), ASIO_MOVE_CAST(write_dynbuf_v1_op)(*this)); return; default: buffers_.consume(bytes_transferred); handler_(ec, static_cast(bytes_transferred)); } } //private: AsyncWriteStream& stream_; DynamicBuffer_v1 buffers_; CompletionCondition completion_condition_; WriteHandler handler_; }; template inline void* asio_handler_allocate(std::size_t size, write_dynbuf_v1_op* this_handler) { return asio_handler_alloc_helpers::allocate( size, this_handler->handler_); } template inline void asio_handler_deallocate(void* pointer, std::size_t size, write_dynbuf_v1_op* this_handler) { asio_handler_alloc_helpers::deallocate( pointer, size, this_handler->handler_); } template inline bool asio_handler_is_continuation( write_dynbuf_v1_op* this_handler) { return asio_handler_cont_helpers::is_continuation( this_handler->handler_); } template inline void asio_handler_invoke(Function& function, write_dynbuf_v1_op* this_handler) { asio_handler_invoke_helpers::invoke( function, this_handler->handler_); } template inline void asio_handler_invoke(const Function& function, write_dynbuf_v1_op* this_handler) { asio_handler_invoke_helpers::invoke( function, this_handler->handler_); } struct initiate_async_write_dynbuf_v1 { template void operator()(ASIO_MOVE_ARG(WriteHandler) handler, AsyncWriteStream* s, ASIO_MOVE_ARG(DynamicBuffer_v1) buffers, ASIO_MOVE_ARG(CompletionCondition) completion_cond) const { // If you get an error on the following line it means that your handler // does not meet the documented type requirements for a WriteHandler. ASIO_WRITE_HANDLER_CHECK(WriteHandler, handler) type_check; non_const_lvalue handler2(handler); non_const_lvalue completion_cond2(completion_cond); write_dynbuf_v1_op::type, CompletionCondition, typename decay::type>( *s, ASIO_MOVE_CAST(DynamicBuffer_v1)(buffers), completion_cond2.value, handler2.value)( asio::error_code(), 0, 1); } }; } // namespace detail #if !defined(GENERATING_DOCUMENTATION) template struct associated_allocator< detail::write_dynbuf_v1_op, Allocator> { typedef typename associated_allocator::type type; static type get( const detail::write_dynbuf_v1_op& h, const Allocator& a = Allocator()) ASIO_NOEXCEPT { return associated_allocator::get(h.handler_, a); } }; template struct associated_executor< detail::write_dynbuf_v1_op, Executor> { typedef typename associated_executor::type type; static type get( const detail::write_dynbuf_v1_op& h, const Executor& ex = Executor()) ASIO_NOEXCEPT { return associated_executor::get(h.handler_, ex); } }; #endif // !defined(GENERATING_DOCUMENTATION) template inline ASIO_INITFN_RESULT_TYPE(WriteHandler, void (asio::error_code, std::size_t)) async_write(AsyncWriteStream& s, ASIO_MOVE_ARG(DynamicBuffer_v1) buffers, ASIO_MOVE_ARG(WriteHandler) handler, typename enable_if< is_dynamic_buffer_v1::type>::value && !is_dynamic_buffer_v2::type>::value >::type*) { return async_write(s, ASIO_MOVE_CAST(DynamicBuffer_v1)(buffers), transfer_all(), ASIO_MOVE_CAST(WriteHandler)(handler)); } template inline ASIO_INITFN_RESULT_TYPE(WriteHandler, void (asio::error_code, std::size_t)) async_write(AsyncWriteStream& s, ASIO_MOVE_ARG(DynamicBuffer_v1) buffers, CompletionCondition completion_condition, ASIO_MOVE_ARG(WriteHandler) handler, typename enable_if< is_dynamic_buffer_v1::type>::value && !is_dynamic_buffer_v2::type>::value >::type*) { return async_initiate( detail::initiate_async_write_dynbuf_v1(), handler, &s, ASIO_MOVE_CAST(DynamicBuffer_v1)(buffers), ASIO_MOVE_CAST(CompletionCondition)(completion_condition)); } #if !defined(ASIO_NO_EXTENSIONS) #if !defined(ASIO_NO_IOSTREAM) template inline ASIO_INITFN_RESULT_TYPE(WriteHandler, void (asio::error_code, std::size_t)) async_write(AsyncWriteStream& s, asio::basic_streambuf& b, ASIO_MOVE_ARG(WriteHandler) handler) { return async_write(s, basic_streambuf_ref(b), ASIO_MOVE_CAST(WriteHandler)(handler)); } template inline ASIO_INITFN_RESULT_TYPE(WriteHandler, void (asio::error_code, std::size_t)) async_write(AsyncWriteStream& s, asio::basic_streambuf& b, CompletionCondition completion_condition, ASIO_MOVE_ARG(WriteHandler) handler) { return async_write(s, basic_streambuf_ref(b), ASIO_MOVE_CAST(CompletionCondition)(completion_condition), ASIO_MOVE_CAST(WriteHandler)(handler)); } #endif // !defined(ASIO_NO_IOSTREAM) #endif // !defined(ASIO_NO_EXTENSIONS) #endif // !defined(ASIO_NO_DYNAMIC_BUFFER_V1) namespace detail { template class write_dynbuf_v2_op { public: template write_dynbuf_v2_op(AsyncWriteStream& stream, ASIO_MOVE_ARG(BufferSequence) buffers, CompletionCondition& completion_condition, WriteHandler& handler) : stream_(stream), buffers_(ASIO_MOVE_CAST(BufferSequence)(buffers)), completion_condition_( ASIO_MOVE_CAST(CompletionCondition)(completion_condition)), handler_(ASIO_MOVE_CAST(WriteHandler)(handler)) { } #if defined(ASIO_HAS_MOVE) write_dynbuf_v2_op(const write_dynbuf_v2_op& other) : stream_(other.stream_), buffers_(other.buffers_), completion_condition_(other.completion_condition_), handler_(other.handler_) { } write_dynbuf_v2_op(write_dynbuf_v2_op&& other) : stream_(other.stream_), buffers_(ASIO_MOVE_CAST(DynamicBuffer_v2)(other.buffers_)), completion_condition_( ASIO_MOVE_CAST(CompletionCondition)( other.completion_condition_)), handler_(ASIO_MOVE_CAST(WriteHandler)(other.handler_)) { } #endif // defined(ASIO_HAS_MOVE) void operator()(const asio::error_code& ec, std::size_t bytes_transferred, int start = 0) { switch (start) { case 1: async_write(stream_, buffers_.data(0, buffers_.size()), ASIO_MOVE_CAST(CompletionCondition)(completion_condition_), ASIO_MOVE_CAST(write_dynbuf_v2_op)(*this)); return; default: buffers_.consume(bytes_transferred); handler_(ec, static_cast(bytes_transferred)); } } //private: AsyncWriteStream& stream_; DynamicBuffer_v2 buffers_; CompletionCondition completion_condition_; WriteHandler handler_; }; template inline void* asio_handler_allocate(std::size_t size, write_dynbuf_v2_op* this_handler) { return asio_handler_alloc_helpers::allocate( size, this_handler->handler_); } template inline void asio_handler_deallocate(void* pointer, std::size_t size, write_dynbuf_v2_op* this_handler) { asio_handler_alloc_helpers::deallocate( pointer, size, this_handler->handler_); } template inline bool asio_handler_is_continuation( write_dynbuf_v2_op* this_handler) { return asio_handler_cont_helpers::is_continuation( this_handler->handler_); } template inline void asio_handler_invoke(Function& function, write_dynbuf_v2_op* this_handler) { asio_handler_invoke_helpers::invoke( function, this_handler->handler_); } template inline void asio_handler_invoke(const Function& function, write_dynbuf_v2_op* this_handler) { asio_handler_invoke_helpers::invoke( function, this_handler->handler_); } struct initiate_async_write_dynbuf_v2 { template void operator()(ASIO_MOVE_ARG(WriteHandler) handler, AsyncWriteStream* s, ASIO_MOVE_ARG(DynamicBuffer_v2) buffers, ASIO_MOVE_ARG(CompletionCondition) completion_cond) const { // If you get an error on the following line it means that your handler // does not meet the documented type requirements for a WriteHandler. ASIO_WRITE_HANDLER_CHECK(WriteHandler, handler) type_check; non_const_lvalue handler2(handler); non_const_lvalue completion_cond2(completion_cond); write_dynbuf_v2_op::type, CompletionCondition, typename decay::type>( *s, ASIO_MOVE_CAST(DynamicBuffer_v2)(buffers), completion_cond2.value, handler2.value)( asio::error_code(), 0, 1); } }; } // namespace detail #if !defined(GENERATING_DOCUMENTATION) template struct associated_allocator< detail::write_dynbuf_v2_op, Allocator> { typedef typename associated_allocator::type type; static type get( const detail::write_dynbuf_v2_op& h, const Allocator& a = Allocator()) ASIO_NOEXCEPT { return associated_allocator::get(h.handler_, a); } }; template struct associated_executor< detail::write_dynbuf_v2_op, Executor> { typedef typename associated_executor::type type; static type get( const detail::write_dynbuf_v2_op& h, const Executor& ex = Executor()) ASIO_NOEXCEPT { return associated_executor::get(h.handler_, ex); } }; #endif // !defined(GENERATING_DOCUMENTATION) template inline ASIO_INITFN_RESULT_TYPE(WriteHandler, void (asio::error_code, std::size_t)) async_write(AsyncWriteStream& s, DynamicBuffer_v2 buffers, ASIO_MOVE_ARG(WriteHandler) handler, typename enable_if< is_dynamic_buffer_v2::value >::type*) { return async_write(s, ASIO_MOVE_CAST(DynamicBuffer_v2)(buffers), transfer_all(), ASIO_MOVE_CAST(WriteHandler)(handler)); } template inline ASIO_INITFN_RESULT_TYPE(WriteHandler, void (asio::error_code, std::size_t)) async_write(AsyncWriteStream& s, DynamicBuffer_v2 buffers, CompletionCondition completion_condition, ASIO_MOVE_ARG(WriteHandler) handler, typename enable_if< is_dynamic_buffer_v2::value >::type*) { return async_initiate( detail::initiate_async_write_dynbuf_v2(), handler, &s, ASIO_MOVE_CAST(DynamicBuffer_v2)(buffers), ASIO_MOVE_CAST(CompletionCondition)(completion_condition)); } } // namespace asio #include "asio/detail/pop_options.hpp" #endif // ASIO_IMPL_WRITE_HPP