Fix select() deadlock on BSD OSes (#18)

.travis.yml

@@ -10,17 +10,15 @@ jobs:
         - python: 3.8-dev
           dist: xenial
           sudo: true
-        - python: nightly
-          dist: xenial
-          sudo: true
+        - os: osx
+          language: generic
 
-matrix:
-    allow_failures:
-        - python: nightly
+before_install:
+    - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then brew update && brew upgrade python && pip3 install --upgrade pip setuptools wheel; fi
 
 install:
-    - pip install -U -e .[dev]
-    - pip freeze
+    - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then sudo pip3 install -U -e .[dev]; else pip install -U -e .[dev]; fi
+    - if [[ "$TRAVIS_OS_NAME" == "osx" ]]; then pip3 freeze; else pip freeze; fi
 
 script:
     - coverage run --branch --source termtosvg -m unittest -v

termtosvg/term.py

@@ -3,7 +3,7 @@
 import logging
 import os
 import pty
-import selectors
+import select
 import struct
 import termios
 import tty
@@ -117,24 +117,24 @@ def _capture_data(input_fileno, output_fileno, master_fd, buffer_size=1024):
     generator.
     See https://github.com/python/cpython/blob/master/Lib/pty.py
     """
-    sel = selectors.DefaultSelector()
-    sel.register(master_fd, selectors.EVENT_READ)
-    sel.register(input_fileno, selectors.EVENT_READ)
+    rlist = [input_fileno, master_fd]
+    xlist = [input_fileno, output_fileno, master_fd]
 
-    while {master_fd, input_fileno} <= set(sel.get_map()):
-        events = sel.select()
-        for key, _ in events:
+    xfds = []
+    while not xfds:
+        rfds, _, xfds = select.select(rlist, [], xlist)
+        for fd in rfds:
             try:
-                data = os.read(key.fileobj, buffer_size)
+                data = os.read(fd, buffer_size)
             except OSError:
-                sel.unregister(key.fileobj)
+                xfds.append(fd)
                 continue
 
             if not data:
-                sel.unregister(key.fileobj)
+                xfds.append(fd)
                 continue
 
-            if key.fileobj == input_fileno:
+            if fd == input_fileno:
                 write_fileno = master_fd
             else:
                 write_fileno = output_fileno