Add some more notes to self

- Add the test script used in python-triogh-928 to decipher Window's port reuse
  semantics
- Note the existence of the 'tree-format' package (found thanks to
  @itamarst)

notes-to-self/how-does-windows-so-reuseaddr-work.py

@@ -0,0 +1,61 @@
+# There are some tables here:
+#   https://web.archive.org/web/20120206195747/https://msdn.microsoft.com/en-us/library/windows/desktop/ms740621(v=vs.85).aspx
+# They appear to be wrong.
+#
+# See https://github.com/python-trio/trio/issues/928 for details and context
+
+import socket
+import errno
+
+modes = ["default", "SO_REUSEADDR", "SO_EXCLUSIVEADDRUSE"]
+bind_types = ["wildcard", "specific"]
+
+def sock(mode):
+    s = socket.socket(family=socket.AF_INET)
+    if mode == "SO_REUSEADDR":
+        s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
+    elif mode == "SO_EXCLUSIVEADDRUSE":
+        s.setsockopt(socket.SOL_SOCKET, socket.SO_EXCLUSIVEADDRUSE, 1)
+    return s
+
+def bind(sock, bind_type):
+    if bind_type == "wildcard":
+        sock.bind(("0.0.0.0", 12345))
+    elif bind_type == "specific":
+        sock.bind(("127.0.0.1", 12345))
+    else:
+        assert False
+
+def table_entry(mode1, bind_type1, mode2, bind_type2):
+    with sock(mode1) as sock1:
+        bind(sock1, bind_type1)
+        try:
+            with sock(mode2) as sock2:
+                bind(sock2, bind_type2)
+        except OSError as exc:
+            if exc.winerror == errno.WSAEADDRINUSE:
+                return "INUSE"
+            elif exc.winerror == errno.WSAEACCES:
+                return "ACCESS"
+            raise
+        else:
+            return "Success"
+
+print("""
+                                                       second bind
+                               | default           | SO_REUSEADDR      | SO_EXCLUSIVEADDRUSE
+                               | specific| wildcard| specific| wildcard| specific| wildcard
+first bind                     ------------------------------------------------------------"""
+#           default | wildcard |   INUSE | Success |  ACCESS | Success |   INUSE | Success
+)
+
+for i, mode1 in enumerate(modes):
+    for j, bind_type1 in enumerate(bind_types):
+        row = []
+        for k, mode2 in enumerate(modes):
+            for l, bind_type2 in enumerate(bind_types):
+                entry = table_entry(mode1, bind_type1, mode2, bind_type2)
+                row.append(entry)
+                #print(mode1, bind_type1, mode2, bind_type2, entry)
+        print("%19s | %8s | " % (mode1, bind_type1)
+              + " | ".join(["%7s" % entry for entry in row]))

notes-to-self/print-task-tree.py

@@ -1,3 +1,7 @@
+# NOTE:
+# possibly it would be easier to use https://pypi.org/project/tree-format/
+# instead of formatting by hand like this code does...
+
 """
 Demo/exploration of how to print a task tree. Outputs: