Parent copy loop. Copies pty master -> standard output (master_read) standard input -> pty master (stdin_read)
(master_fd, master_read=_read, stdin_read=_read)
| 91 | return os.read(fd, 1024) |
| 92 | |
| 93 | def _copy(master_fd, master_read=_read, stdin_read=_read): |
| 94 | """Parent copy loop. |
| 95 | Copies |
| 96 | pty master -> standard output (master_read) |
| 97 | standard input -> pty master (stdin_read)""" |
| 98 | if os.get_blocking(master_fd): |
| 99 | # If we write more than tty/ndisc is willing to buffer, we may block |
| 100 | # indefinitely. So we set master_fd to non-blocking temporarily during |
| 101 | # the copy operation. |
| 102 | os.set_blocking(master_fd, False) |
| 103 | try: |
| 104 | _copy(master_fd, master_read=master_read, stdin_read=stdin_read) |
| 105 | finally: |
| 106 | # restore blocking mode for backwards compatibility |
| 107 | os.set_blocking(master_fd, True) |
| 108 | return |
| 109 | high_waterlevel = 4096 |
| 110 | stdin_avail = master_fd != STDIN_FILENO |
| 111 | stdout_avail = master_fd != STDOUT_FILENO |
| 112 | i_buf = b'' |
| 113 | o_buf = b'' |
| 114 | while 1: |
| 115 | rfds = [] |
| 116 | wfds = [] |
| 117 | if stdin_avail and len(i_buf) < high_waterlevel: |
| 118 | rfds.append(STDIN_FILENO) |
| 119 | if stdout_avail and len(o_buf) < high_waterlevel: |
| 120 | rfds.append(master_fd) |
| 121 | if stdout_avail and len(o_buf) > 0: |
| 122 | wfds.append(STDOUT_FILENO) |
| 123 | if len(i_buf) > 0: |
| 124 | wfds.append(master_fd) |
| 125 | |
| 126 | rfds, wfds, _xfds = select(rfds, wfds, []) |
| 127 | |
| 128 | if STDOUT_FILENO in wfds: |
| 129 | try: |
| 130 | n = os.write(STDOUT_FILENO, o_buf) |
| 131 | o_buf = o_buf[n:] |
| 132 | except OSError: |
| 133 | stdout_avail = False |
| 134 | |
| 135 | if master_fd in rfds: |
| 136 | # Some OSes signal EOF by returning an empty byte string, |
| 137 | # some throw OSErrors. |
| 138 | try: |
| 139 | data = master_read(master_fd) |
| 140 | except OSError: |
| 141 | data = b"" |
| 142 | if not data: # Reached EOF. |
| 143 | return # Assume the child process has exited and is |
| 144 | # unreachable, so we clean up. |
| 145 | o_buf += data |
| 146 | |
| 147 | if master_fd in wfds: |
| 148 | n = os.write(master_fd, i_buf) |
| 149 | i_buf = i_buf[n:] |
| 150 |
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