external/bsd/kyua-cli/dist/utils/process/systembuf.cpp

   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 }