boost/log/detail/attachable_sstream_buf.hpp
/* * Copyright Andrey Semashev 2007 - 2016. * 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) */ /*! * \file attachable_sstream_buf.hpp * \author Andrey Semashev * \date 29.07.2007 * * \brief This header is the Boost.Log library implementation, see the library documentation * at http://www.boost.org/doc/libs/release/libs/log/doc/html/index.html. */ #ifndef BOOST_LOG_ATTACHABLE_SSTREAM_BUF_HPP_INCLUDED_ #define BOOST_LOG_ATTACHABLE_SSTREAM_BUF_HPP_INCLUDED_ #include <cstddef> #include <memory> #include <locale> #include <string> #include <streambuf> #include <boost/assert.hpp> #include <boost/cstdint.hpp> #include <boost/type_traits/integral_constant.hpp> #include <boost/log/detail/config.hpp> #include <boost/log/detail/header.hpp> #ifdef BOOST_HAS_PRAGMA_ONCE #pragma once #endif namespace boost { BOOST_LOG_OPEN_NAMESPACE namespace aux { //! A streambuf that puts the formatted data to an external string template< typename CharT, typename TraitsT = std::char_traits< CharT >, typename AllocatorT = std::allocator< CharT > > class basic_ostringstreambuf : public std::basic_streambuf< CharT, TraitsT > { //! Self type typedef basic_ostringstreambuf< CharT, TraitsT, AllocatorT > this_type; //! Base type typedef std::basic_streambuf< CharT, TraitsT > base_type; //! Buffer size enum { buffer_size = 16 }; public: //! Character type typedef typename base_type::char_type char_type; //! Traits type typedef typename base_type::traits_type traits_type; //! String type typedef std::basic_string< char_type, traits_type, AllocatorT > string_type; //! Size type typedef typename string_type::size_type size_type; //! Int type typedef typename base_type::int_type int_type; struct storage_state { //! A reference to the string that will be filled string_type* storage; //! Max size of the storage, in characters size_type max_size; //! Indicates that storage overflow happened bool overflow; BOOST_CONSTEXPR storage_state() BOOST_NOEXCEPT : storage(NULL), max_size(0u), overflow(false) { } }; private: //! Buffer storage state storage_state m_storage_state; //! A buffer used to temporarily store output char_type m_buffer[buffer_size]; public: //! Constructor basic_ostringstreambuf() BOOST_NOEXCEPT { base_type::setp(m_buffer, m_buffer + (sizeof(m_buffer) / sizeof(*m_buffer))); } //! Constructor explicit basic_ostringstreambuf(string_type& storage) BOOST_NOEXCEPT { base_type::setp(m_buffer, m_buffer + (sizeof(m_buffer) / sizeof(*m_buffer))); attach(storage); } storage_state const& get_storage_state() const BOOST_NOEXCEPT { return m_storage_state; } void set_storage_state(storage_state const& st) BOOST_NOEXCEPT { m_storage_state = st; } //! Detaches the buffer from the string void detach() { if (m_storage_state.storage) { this_type::sync(); m_storage_state.storage = NULL; m_storage_state.max_size = 0u; m_storage_state.overflow = false; } } //! Attaches the buffer to another string void attach(string_type& storage) { attach(storage, storage.max_size()); } //! Attaches the buffer to another string void attach(string_type& storage, size_type max_size) { detach(); m_storage_state.storage = &storage; this->max_size(max_size); } //! Returns a pointer to the attached string string_type* storage() const BOOST_NOEXCEPT { return m_storage_state.storage; } //! Returns the maximum size of the storage size_type max_size() const BOOST_NOEXCEPT { return m_storage_state.max_size; } //! Sets the maximum size of the storage void max_size(size_type size) { if (m_storage_state.storage) { const size_type storage_max_size = m_storage_state.storage->max_size(); size = size > storage_max_size ? storage_max_size : size; } m_storage_state.max_size = size; ensure_max_size(); } //! Makes sure the storage does not exceed the max size limit. Should be called after the storage is modified externally. void ensure_max_size() { if (m_storage_state.storage && m_storage_state.storage->size() > m_storage_state.max_size) { const size_type len = length_until_boundary(m_storage_state.storage->c_str(), m_storage_state.storage->size(), m_storage_state.max_size); m_storage_state.storage->resize(len); m_storage_state.overflow = true; } } //! Returns true if the max size limit has been exceeded bool storage_overflow() const BOOST_NOEXCEPT { return m_storage_state.overflow; } //! Sets the overflow flag void storage_overflow(bool f) BOOST_NOEXCEPT { m_storage_state.overflow = f; } //! Returns the size left in the storage size_type size_left() const BOOST_NOEXCEPT { BOOST_ASSERT(m_storage_state.storage != NULL); const size_type size = m_storage_state.storage->size(); return size < m_storage_state.max_size ? m_storage_state.max_size - size : static_cast< size_type >(0u); } //! Appends a string to the storage and returns the number of written characters size_type append(const char_type* s, size_type n) { if (!m_storage_state.overflow) { BOOST_ASSERT(m_storage_state.storage != NULL); size_type left = size_left(); BOOST_LOG_ASSUME(left <= m_storage_state.storage->max_size()); if (BOOST_LIKELY(n <= left)) { m_storage_state.storage->append(s, n); return n; } else { // We have to find out where the last character that fits before the limit ends left = length_until_boundary(s, n, left); m_storage_state.storage->append(s, left); m_storage_state.overflow = true; return left; } } return 0u; } //! Appends the specified number of characters to the storage and returns the number of written characters size_type append(size_type n, char_type c) { if (!m_storage_state.overflow) { BOOST_ASSERT(m_storage_state.storage != NULL); const size_type left = size_left(); BOOST_LOG_ASSUME(left <= m_storage_state.storage->max_size()); if (BOOST_LIKELY(n <= left)) { m_storage_state.storage->append(n, c); return n; } else { m_storage_state.storage->append(left, c); m_storage_state.overflow = true; return left; } } return 0u; } //! Appends a character to the storage and returns the number of written characters size_type push_back(char_type c) { if (!m_storage_state.overflow) { BOOST_ASSERT(m_storage_state.storage != NULL); BOOST_LOG_ASSUME(m_storage_state.max_size <= m_storage_state.storage->max_size()); if (BOOST_LIKELY(m_storage_state.storage->size() < m_storage_state.max_size)) { m_storage_state.storage->push_back(c); return 1u; } else { m_storage_state.overflow = true; return 0u; } } return 0u; } protected: //! Puts all buffered data to the string int sync() BOOST_OVERRIDE { char_type* pBase = this->pbase(); char_type* pPtr = this->pptr(); if (pBase != pPtr) { this->append(pBase, static_cast< size_type >(pPtr - pBase)); this->pbump(static_cast< int >(pBase - pPtr)); } return 0; } //! Puts an unbuffered character to the string int_type overflow(int_type c) BOOST_OVERRIDE { this_type::sync(); if (!traits_type::eq_int_type(c, traits_type::eof())) { this->push_back(traits_type::to_char_type(c)); return c; } else return traits_type::not_eof(c); } //! Puts a character sequence to the string std::streamsize xsputn(const char_type* s, std::streamsize n) BOOST_OVERRIDE { this_type::sync(); return static_cast< std::streamsize >(this->append(s, static_cast< size_type >(n))); } //! Finds the string length so that it includes only complete characters, and does not exceed \a max_size size_type length_until_boundary(const char_type* s, size_type n, size_type max_size) const { BOOST_ASSERT(max_size <= n); return length_until_boundary(s, n, max_size, boost::integral_constant< std::size_t, sizeof(char_type) >()); } private: //! Finds the string length so that it includes only complete characters, and does not exceed \a max_size size_type length_until_boundary(const char_type* s, size_type n, size_type max_size, boost::integral_constant< std::size_t, 1u >) const { std::locale loc = this->getloc(); std::codecvt< wchar_t, char, std::mbstate_t > const& fac = std::use_facet< std::codecvt< wchar_t, char, std::mbstate_t > >(loc); std::mbstate_t mbs = std::mbstate_t(); return static_cast< size_type >(fac.length(mbs, s, s + max_size, n)); } //! Finds the string length so that it includes only complete characters, and does not exceed \a max_size static size_type length_until_boundary(const char_type* s, size_type n, size_type max_size, boost::integral_constant< std::size_t, 2u >) { // Note: Although it's not required to be true for wchar_t, here we assume that the string has Unicode encoding (UTF-16 or UCS-2). // Compilers use some version of Unicode for wchar_t on all tested platforms, and std::locale doesn't offer a way // to find the character boundary for character types other than char anyway. size_type pos = max_size; while (pos > 0u) { --pos; uint_fast16_t c = static_cast< uint_fast16_t >(s[pos]); // Check if this is a leading surrogate if ((c & 0xFC00u) != 0xD800u) return pos + 1u; } return 0u; } //! Finds the string length so that it includes only complete characters, and does not exceed \a max_size static size_type length_until_boundary(const char_type* s, size_type n, size_type max_size, boost::integral_constant< std::size_t, 4u >) { // In UTF-32 and UCS-4 one code point is encoded as one code unit return max_size; } //! Copy constructor (closed) BOOST_DELETED_FUNCTION(basic_ostringstreambuf(basic_ostringstreambuf const& that)) //! Assignment (closed) BOOST_DELETED_FUNCTION(basic_ostringstreambuf& operator= (basic_ostringstreambuf const& that)) }; } // namespace aux BOOST_LOG_CLOSE_NAMESPACE // namespace log } // namespace boost #include <boost/log/detail/footer.hpp> #endif // BOOST_LOG_ATTACHABLE_SSTREAM_BUF_HPP_INCLUDED_