1 // Copyright 2010 The Kyua Authors. 2 // All rights reserved. 3 // 4 // Redistribution and use in source and binary forms, with or without 5 // modification, are permitted provided that the following conditions are 6 // met: 7 // 8 // * Redistributions of source code must retain the above copyright 9 // notice, this list of conditions and the following disclaimer. 10 // * Redistributions in binary form must reproduce the above copyright 11 // notice, this list of conditions and the following disclaimer in the 12 // documentation and/or other materials provided with the distribution. 13 // * Neither the name of Google Inc. nor the names of its contributors 14 // may be used to endorse or promote products derived from this software 15 // without specific prior written permission. 16 // 17 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 18 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 19 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR 20 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT 21 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 22 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 23 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE 27 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 29 #include "utils/process/systembuf.hpp" 30 31 extern "C" { 32 #include <unistd.h> 33 } 34 35 #include "utils/auto_array.ipp" 36 #include "utils/noncopyable.hpp" 37 #include "utils/sanity.hpp" 38 39 using utils::process::systembuf; 40 41 42 /// Private implementation fields for systembuf. 43 struct systembuf::impl : utils::noncopyable { 44 /// File descriptor attached to the systembuf. 45 int _fd; 46 47 /// Size of the _read_buf and _write_buf buffers. 48 std::size_t _bufsize; 49 50 /// In-memory buffer for read operations. 51 utils::auto_array< char > _read_buf; 52 53 /// In-memory buffer for write operations. 54 utils::auto_array< char > _write_buf; 55 56 /// Initializes private implementation data. 57 /// 58 /// \param fd The file descriptor. 59 /// \param bufsize The size of the created read and write buffers. 60 impl(const int fd, const std::size_t bufsize) : 61 _fd(fd), 62 _bufsize(bufsize), 63 _read_buf(new char[bufsize]), 64 _write_buf(new char[bufsize]) 65 { 66 } 67 }; 68 69 70 /// Constructs a new systembuf based on an open file descriptor. 71 /// 72 /// This grabs ownership of the file descriptor. 73 /// 74 /// \param fd The file descriptor to wrap. Must be open and valid. 75 /// \param bufsize The size to use for the internal read/write buffers. 76 systembuf::systembuf(const int fd, std::size_t bufsize) : 77 _pimpl(new impl(fd, bufsize)) 78 { 79 setp(_pimpl->_write_buf.get(), _pimpl->_write_buf.get() + _pimpl->_bufsize); 80 } 81 82 83 /// Destroys a systembuf object. 84 /// 85 /// \post The file descriptor attached to this systembuf is closed. 86 systembuf::~systembuf(void) 87 { 88 ::close(_pimpl->_fd); 89 } 90 91 92 /// Reads new data when the systembuf read buffer underflows. 93 /// 94 /// \return The new character to be read, or EOF if no more. 95 systembuf::int_type 96 systembuf::underflow(void) 97 { 98 PRE(gptr() >= egptr()); 99 100 bool ok; 101 ssize_t cnt = ::read(_pimpl->_fd, _pimpl->_read_buf.get(), 102 _pimpl->_bufsize); 103 ok = (cnt != -1 && cnt != 0); 104 105 if (!ok) 106 return traits_type::eof(); 107 else { 108 setg(_pimpl->_read_buf.get(), _pimpl->_read_buf.get(), 109 _pimpl->_read_buf.get() + cnt); 110 return traits_type::to_int_type(*gptr()); 111 } 112 } 113 114 115 /// Writes data to the file descriptor when the write buffer overflows. 116 /// 117 /// \param c The character that causes the overflow. 118 /// 119 /// \return EOF if error, some other value for success. 120 /// 121 /// \throw something TODO(jmmv): According to the documentation, it is OK for 122 /// this method to throw in case of errors. Revisit this code to see if we 123 /// can do better. 124 systembuf::int_type 125 systembuf::overflow(int c) 126 { 127 PRE(pptr() >= epptr()); 128 if (sync() == -1) 129 return traits_type::eof(); 130 if (!traits_type::eq_int_type(c, traits_type::eof())) { 131 traits_type::assign(*pptr(), c); 132 pbump(1); 133 } 134 return traits_type::not_eof(c); 135 } 136 137 138 /// Synchronizes the stream with the file descriptor. 139 /// 140 /// \return 0 on success, -1 on error. 141 int 142 systembuf::sync(void) 143 { 144 ssize_t cnt = pptr() - pbase(); 145 146 bool ok; 147 ok = ::write(_pimpl->_fd, pbase(), cnt) == cnt; 148 149 if (ok) 150 pbump(-cnt); 151 return ok ? 0 : -1; 152 } 153