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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.
implsystembuf::impl59 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.
systembuf(const int fd,std::size_t bufsize)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.
~systembuf(void)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
underflow(void)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
overflow(int c)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
sync(void)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