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Diffstat (limited to 'lib/asio/basic_streambuf.hpp')
| -rw-r--r-- | lib/asio/basic_streambuf.hpp | 452 |
1 files changed, 452 insertions, 0 deletions
diff --git a/lib/asio/basic_streambuf.hpp b/lib/asio/basic_streambuf.hpp new file mode 100644 index 0000000..14f85d2 --- /dev/null +++ b/lib/asio/basic_streambuf.hpp @@ -0,0 +1,452 @@ +// +// basic_streambuf.hpp +// ~~~~~~~~~~~~~~~~~~~ +// +// Copyright (c) 2003-2018 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_BASIC_STREAMBUF_HPP +#define ASIO_BASIC_STREAMBUF_HPP + +#if defined(_MSC_VER) && (_MSC_VER >= 1200) +# pragma once +#endif // defined(_MSC_VER) && (_MSC_VER >= 1200) + +#include "asio/detail/config.hpp" + +#if !defined(ASIO_NO_IOSTREAM) + +#include <algorithm> +#include <cstring> +#include <stdexcept> +#include <streambuf> +#include <vector> +#include "asio/basic_streambuf_fwd.hpp" +#include "asio/buffer.hpp" +#include "asio/detail/limits.hpp" +#include "asio/detail/noncopyable.hpp" +#include "asio/detail/throw_exception.hpp" + +#include "asio/detail/push_options.hpp" + +namespace asio { + +/// Automatically resizable buffer class based on std::streambuf. +/** + * The @c basic_streambuf class is derived from @c std::streambuf to associate + * the streambuf's input and output sequences with one or more character + * arrays. These character arrays are internal to the @c basic_streambuf + * object, but direct access to the array elements is provided to permit them + * to be used efficiently with I/O operations. Characters written to the output + * sequence of a @c basic_streambuf object are appended to the input sequence + * of the same object. + * + * The @c basic_streambuf class's public interface is intended to permit the + * following implementation strategies: + * + * @li A single contiguous character array, which is reallocated as necessary + * to accommodate changes in the size of the character sequence. This is the + * implementation approach currently used in Asio. + * + * @li A sequence of one or more character arrays, where each array is of the + * same size. Additional character array objects are appended to the sequence + * to accommodate changes in the size of the character sequence. + * + * @li A sequence of one or more character arrays of varying sizes. Additional + * character array objects are appended to the sequence to accommodate changes + * in the size of the character sequence. + * + * The constructor for basic_streambuf accepts a @c size_t argument specifying + * the maximum of the sum of the sizes of the input sequence and output + * sequence. During the lifetime of the @c basic_streambuf object, the following + * invariant holds: + * @code size() <= max_size()@endcode + * Any member function that would, if successful, cause the invariant to be + * violated shall throw an exception of class @c std::length_error. + * + * The constructor for @c basic_streambuf takes an Allocator argument. A copy + * of this argument is used for any memory allocation performed, by the + * constructor and by all member functions, during the lifetime of each @c + * basic_streambuf object. + * + * @par Examples + * Writing directly from an streambuf to a socket: + * @code + * asio::streambuf b; + * std::ostream os(&b); + * os << "Hello, World!\n"; + * + * // try sending some data in input sequence + * size_t n = sock.send(b.data()); + * + * b.consume(n); // sent data is removed from input sequence + * @endcode + * + * Reading from a socket directly into a streambuf: + * @code + * asio::streambuf b; + * + * // reserve 512 bytes in output sequence + * asio::streambuf::mutable_buffers_type bufs = b.prepare(512); + * + * size_t n = sock.receive(bufs); + * + * // received data is "committed" from output sequence to input sequence + * b.commit(n); + * + * std::istream is(&b); + * std::string s; + * is >> s; + * @endcode + */ +#if defined(GENERATING_DOCUMENTATION) +template <typename Allocator = std::allocator<char> > +#else +template <typename Allocator> +#endif +class basic_streambuf + : public std::streambuf, + private noncopyable +{ +public: +#if defined(GENERATING_DOCUMENTATION) + /// The type used to represent the input sequence as a list of buffers. + typedef implementation_defined const_buffers_type; + + /// The type used to represent the output sequence as a list of buffers. + typedef implementation_defined mutable_buffers_type; +#else + typedef ASIO_CONST_BUFFER const_buffers_type; + typedef ASIO_MUTABLE_BUFFER mutable_buffers_type; +#endif + + /// Construct a basic_streambuf object. + /** + * Constructs a streambuf with the specified maximum size. The initial size + * of the streambuf's input sequence is 0. + */ + explicit basic_streambuf( + std::size_t maximum_size = (std::numeric_limits<std::size_t>::max)(), + const Allocator& allocator = Allocator()) + : max_size_(maximum_size), + buffer_(allocator) + { + std::size_t pend = (std::min<std::size_t>)(max_size_, buffer_delta); + buffer_.resize((std::max<std::size_t>)(pend, 1)); + setg(&buffer_[0], &buffer_[0], &buffer_[0]); + setp(&buffer_[0], &buffer_[0] + pend); + } + + /// Get the size of the input sequence. + /** + * @returns The size of the input sequence. The value is equal to that + * calculated for @c s in the following code: + * @code + * size_t s = 0; + * const_buffers_type bufs = data(); + * const_buffers_type::const_iterator i = bufs.begin(); + * while (i != bufs.end()) + * { + * const_buffer buf(*i++); + * s += buf.size(); + * } + * @endcode + */ + std::size_t size() const ASIO_NOEXCEPT + { + return pptr() - gptr(); + } + + /// Get the maximum size of the basic_streambuf. + /** + * @returns The allowed maximum of the sum of the sizes of the input sequence + * and output sequence. + */ + std::size_t max_size() const ASIO_NOEXCEPT + { + return max_size_; + } + + /// Get the current capacity of the basic_streambuf. + /** + * @returns The current total capacity of the streambuf, i.e. for both the + * input sequence and output sequence. + */ + std::size_t capacity() const ASIO_NOEXCEPT + { + return buffer_.capacity(); + } + + /// Get a list of buffers that represents the input sequence. + /** + * @returns An object of type @c const_buffers_type that satisfies + * ConstBufferSequence requirements, representing all character arrays in the + * input sequence. + * + * @note The returned object is invalidated by any @c basic_streambuf member + * function that modifies the input sequence or output sequence. + */ + const_buffers_type data() const ASIO_NOEXCEPT + { + return asio::buffer(asio::const_buffer(gptr(), + (pptr() - gptr()) * sizeof(char_type))); + } + + /// Get a list of buffers that represents the output sequence, with the given + /// size. + /** + * Ensures that the output sequence can accommodate @c n characters, + * reallocating character array objects as necessary. + * + * @returns An object of type @c mutable_buffers_type that satisfies + * MutableBufferSequence requirements, representing character array objects + * at the start of the output sequence such that the sum of the buffer sizes + * is @c n. + * + * @throws std::length_error If <tt>size() + n > max_size()</tt>. + * + * @note The returned object is invalidated by any @c basic_streambuf member + * function that modifies the input sequence or output sequence. + */ + mutable_buffers_type prepare(std::size_t n) + { + reserve(n); + return asio::buffer(asio::mutable_buffer( + pptr(), n * sizeof(char_type))); + } + + /// Move characters from the output sequence to the input sequence. + /** + * Appends @c n characters from the start of the output sequence to the input + * sequence. The beginning of the output sequence is advanced by @c n + * characters. + * + * Requires a preceding call <tt>prepare(x)</tt> where <tt>x >= n</tt>, and + * no intervening operations that modify the input or output sequence. + * + * @note If @c n is greater than the size of the output sequence, the entire + * output sequence is moved to the input sequence and no error is issued. + */ + void commit(std::size_t n) + { + n = std::min<std::size_t>(n, epptr() - pptr()); + pbump(static_cast<int>(n)); + setg(eback(), gptr(), pptr()); + } + + /// Remove characters from the input sequence. + /** + * Removes @c n characters from the beginning of the input sequence. + * + * @note If @c n is greater than the size of the input sequence, the entire + * input sequence is consumed and no error is issued. + */ + void consume(std::size_t n) + { + if (egptr() < pptr()) + setg(&buffer_[0], gptr(), pptr()); + if (gptr() + n > pptr()) + n = pptr() - gptr(); + gbump(static_cast<int>(n)); + } + +protected: + enum { buffer_delta = 128 }; + + /// Override std::streambuf behaviour. + /** + * Behaves according to the specification of @c std::streambuf::underflow(). + */ + int_type underflow() + { + if (gptr() < pptr()) + { + setg(&buffer_[0], gptr(), pptr()); + return traits_type::to_int_type(*gptr()); + } + else + { + return traits_type::eof(); + } + } + + /// Override std::streambuf behaviour. + /** + * Behaves according to the specification of @c std::streambuf::overflow(), + * with the specialisation that @c std::length_error is thrown if appending + * the character to the input sequence would require the condition + * <tt>size() > max_size()</tt> to be true. + */ + int_type overflow(int_type c) + { + if (!traits_type::eq_int_type(c, traits_type::eof())) + { + if (pptr() == epptr()) + { + std::size_t buffer_size = pptr() - gptr(); + if (buffer_size < max_size_ && max_size_ - buffer_size < buffer_delta) + { + reserve(max_size_ - buffer_size); + } + else + { + reserve(buffer_delta); + } + } + + *pptr() = traits_type::to_char_type(c); + pbump(1); + return c; + } + + return traits_type::not_eof(c); + } + + void reserve(std::size_t n) + { + // Get current stream positions as offsets. + std::size_t gnext = gptr() - &buffer_[0]; + std::size_t pnext = pptr() - &buffer_[0]; + std::size_t pend = epptr() - &buffer_[0]; + + // Check if there is already enough space in the put area. + if (n <= pend - pnext) + { + return; + } + + // Shift existing contents of get area to start of buffer. + if (gnext > 0) + { + pnext -= gnext; + std::memmove(&buffer_[0], &buffer_[0] + gnext, pnext); + } + + // Ensure buffer is large enough to hold at least the specified size. + if (n > pend - pnext) + { + if (n <= max_size_ && pnext <= max_size_ - n) + { + pend = pnext + n; + buffer_.resize((std::max<std::size_t>)(pend, 1)); + } + else + { + std::length_error ex("asio::streambuf too long"); + asio::detail::throw_exception(ex); + } + } + + // Update stream positions. + setg(&buffer_[0], &buffer_[0], &buffer_[0] + pnext); + setp(&buffer_[0] + pnext, &buffer_[0] + pend); + } + +private: + std::size_t max_size_; + std::vector<char_type, Allocator> buffer_; + + // Helper function to get the preferred size for reading data. + friend std::size_t read_size_helper( + basic_streambuf& sb, std::size_t max_size) + { + return std::min<std::size_t>( + std::max<std::size_t>(512, sb.buffer_.capacity() - sb.size()), + std::min<std::size_t>(max_size, sb.max_size() - sb.size())); + } +}; + +/// Adapts basic_streambuf to the dynamic buffer sequence type requirements. +#if defined(GENERATING_DOCUMENTATION) +template <typename Allocator = std::allocator<char> > +#else +template <typename Allocator> +#endif +class basic_streambuf_ref +{ +public: + /// The type used to represent the input sequence as a list of buffers. + typedef typename basic_streambuf<Allocator>::const_buffers_type + const_buffers_type; + + /// The type used to represent the output sequence as a list of buffers. + typedef typename basic_streambuf<Allocator>::mutable_buffers_type + mutable_buffers_type; + + /// Construct a basic_streambuf_ref for the given basic_streambuf object. + explicit basic_streambuf_ref(basic_streambuf<Allocator>& sb) + : sb_(sb) + { + } + + /// Copy construct a basic_streambuf_ref. + basic_streambuf_ref(const basic_streambuf_ref& other) ASIO_NOEXCEPT + : sb_(other.sb_) + { + } + +#if defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION) + /// Move construct a basic_streambuf_ref. + basic_streambuf_ref(basic_streambuf_ref&& other) ASIO_NOEXCEPT + : sb_(other.sb_) + { + } +#endif // defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION) + + /// Get the size of the input sequence. + std::size_t size() const ASIO_NOEXCEPT + { + return sb_.size(); + } + + /// Get the maximum size of the dynamic buffer. + std::size_t max_size() const ASIO_NOEXCEPT + { + return sb_.max_size(); + } + + /// Get the current capacity of the dynamic buffer. + std::size_t capacity() const ASIO_NOEXCEPT + { + return sb_.capacity(); + } + + /// Get a list of buffers that represents the input sequence. + const_buffers_type data() const ASIO_NOEXCEPT + { + return sb_.data(); + } + + /// Get a list of buffers that represents the output sequence, with the given + /// size. + mutable_buffers_type prepare(std::size_t n) + { + return sb_.prepare(n); + } + + /// Move bytes from the output sequence to the input sequence. + void commit(std::size_t n) + { + return sb_.commit(n); + } + + /// Remove characters from the input sequence. + void consume(std::size_t n) + { + return sb_.consume(n); + } + +private: + basic_streambuf<Allocator>& sb_; +}; + +} // namespace asio + +#include "asio/detail/pop_options.hpp" + +#endif // !defined(ASIO_NO_IOSTREAM) + +#endif // ASIO_BASIC_STREAMBUF_HPP |