1 // Copyright 2010 Google Inc. 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/sanity.hpp" 37 38 using utils::process::systembuf; 39 40 41 /// Private implementation fields for systembuf. 42 struct systembuf::impl { 43 /// File descriptor attached to the systembuf. 44 int _fd; 45 46 /// Size of the _read_buf and _write_buf buffers. 47 std::size_t _bufsize; 48 49 /// In-memory buffer for read operations. 50 utils::auto_array< char > _read_buf; 51 52 /// In-memory buffer for write operations. 53 utils::auto_array< char > _write_buf; 54 55 /// Initializes private implementation data. 56 /// 57 /// \param fd The file descriptor. 58 /// \param bufsize The size of the created read and write buffers. 59 impl(const int fd, const std::size_t bufsize) : 60 _fd(fd), 61 _bufsize(bufsize), 62 _read_buf(new char[bufsize]), 63 _write_buf(new char[bufsize]) 64 { 65 } 66 }; 67 68 69 /// Constructs a new systembuf based on an open file descriptor. 70 /// 71 /// This grabs ownership of the file descriptor. 72 /// 73 /// \param fd The file descriptor to wrap. Must be open and valid. 74 /// \param bufsize The size to use for the internal read/write buffers. 75 systembuf::systembuf(const int fd, std::size_t bufsize) : 76 _pimpl(new impl(fd, bufsize)) 77 { 78 setp(_pimpl->_write_buf.get(), _pimpl->_write_buf.get() + _pimpl->_bufsize); 79 } 80 81 82 /// Destroys a systembuf object. 83 /// 84 /// \post The file descriptor attached to this systembuf is closed. 85 systembuf::~systembuf(void) 86 { 87 ::close(_pimpl->_fd); 88 } 89 90 91 /// Reads new data when the systembuf read buffer underflows. 92 /// 93 /// \return The new character to be read, or EOF if no more. 94 systembuf::int_type 95 systembuf::underflow(void) 96 { 97 PRE(gptr() >= egptr()); 98 99 bool ok; 100 ssize_t cnt = ::read(_pimpl->_fd, _pimpl->_read_buf.get(), 101 _pimpl->_bufsize); 102 ok = (cnt != -1 && cnt != 0); 103 104 if (!ok) 105 return traits_type::eof(); 106 else { 107 setg(_pimpl->_read_buf.get(), _pimpl->_read_buf.get(), 108 _pimpl->_read_buf.get() + cnt); 109 return traits_type::to_int_type(*gptr()); 110 } 111 } 112 113 114 /// Writes data to the file descriptor when the write buffer overflows. 115 /// 116 /// \param c The character that causes the overflow. 117 /// 118 /// \return EOF if error, some other value for success. 119 /// 120 /// \throw something TODO(jmmv): According to the documentation, it is OK for 121 /// this method to throw in case of errors. Revisit this code to see if we 122 /// can do better. 123 systembuf::int_type 124 systembuf::overflow(int c) 125 { 126 PRE(pptr() >= epptr()); 127 if (sync() == -1) 128 return traits_type::eof(); 129 if (!traits_type::eq_int_type(c, traits_type::eof())) { 130 traits_type::assign(*pptr(), c); 131 pbump(1); 132 } 133 return traits_type::not_eof(c); 134 } 135 136 137 /// Synchronizes the stream with the file descriptor. 138 /// 139 /// \return 0 on success, -1 on error. 140 int 141 systembuf::sync(void) 142 { 143 ssize_t cnt = pptr() - pbase(); 144 145 bool ok; 146 ok = ::write(_pimpl->_fd, pbase(), cnt) == cnt; 147 148 if (ok) 149 pbump(-cnt); 150 return ok ? 0 : -1; 151 } 152