Parent copy loop. Copies pty master -> standard output (master_read) standard input -> pty master (stdin_read)
(master_fd, master_read=_read, stdin_read=_read)
| 126 | return os.read(fd, 1024) |
| 127 | |
| 128 | def _copy(master_fd, master_read=_read, stdin_read=_read): |
| 129 | """Parent copy loop. |
| 130 | Copies |
| 131 | pty master -> standard output (master_read) |
| 132 | standard input -> pty master (stdin_read)""" |
| 133 | if os.get_blocking(master_fd): |
| 134 | # If we write more than tty/ndisc is willing to buffer, we may block |
| 135 | # indefinitely. So we set master_fd to non-blocking temporarily during |
| 136 | # the copy operation. |
| 137 | os.set_blocking(master_fd, False) |
| 138 | try: |
| 139 | _copy(master_fd, master_read=master_read, stdin_read=stdin_read) |
| 140 | finally: |
| 141 | # restore blocking mode for backwards compatibility |
| 142 | os.set_blocking(master_fd, True) |
| 143 | return |
| 144 | high_waterlevel = 4096 |
| 145 | stdin_avail = master_fd != STDIN_FILENO |
| 146 | stdout_avail = master_fd != STDOUT_FILENO |
| 147 | i_buf = b'' |
| 148 | o_buf = b'' |
| 149 | while 1: |
| 150 | rfds = [] |
| 151 | wfds = [] |
| 152 | if stdin_avail and len(i_buf) < high_waterlevel: |
| 153 | rfds.append(STDIN_FILENO) |
| 154 | if stdout_avail and len(o_buf) < high_waterlevel: |
| 155 | rfds.append(master_fd) |
| 156 | if stdout_avail and len(o_buf) > 0: |
| 157 | wfds.append(STDOUT_FILENO) |
| 158 | if len(i_buf) > 0: |
| 159 | wfds.append(master_fd) |
| 160 | |
| 161 | rfds, wfds, _xfds = select(rfds, wfds, []) |
| 162 | |
| 163 | if STDOUT_FILENO in wfds: |
| 164 | try: |
| 165 | n = os.write(STDOUT_FILENO, o_buf) |
| 166 | o_buf = o_buf[n:] |
| 167 | except OSError: |
| 168 | stdout_avail = False |
| 169 | |
| 170 | if master_fd in rfds: |
| 171 | # Some OSes signal EOF by returning an empty byte string, |
| 172 | # some throw OSErrors. |
| 173 | try: |
| 174 | data = master_read(master_fd) |
| 175 | except OSError: |
| 176 | data = b"" |
| 177 | if not data: # Reached EOF. |
| 178 | return # Assume the child process has exited and is |
| 179 | # unreachable, so we clean up. |
| 180 | o_buf += data |
| 181 | |
| 182 | if master_fd in wfds: |
| 183 | n = os.write(master_fd, i_buf) |
| 184 | i_buf = i_buf[n:] |
| 185 |