kh2reg.py: refactor main program to bottom of file.

Now most of the program consists of function and class definitions,
and the code that activates it all is localised in one place at the
bottom instead of interleaved between the definitions.

contrib/kh2reg.py

@@ -52,8 +52,6 @@ def warn(s):
     sys.stderr.write("%s:%d: %s\n"
                      % (fileinput.filename(), fileinput.filelineno(), s))
 
-output_type = 'windows'
-
 def invert(n, p):
     """Compute inverse mod p."""
     if n % p == 0:
@@ -163,21 +161,6 @@ nist_curves = {
     "ecdsa-sha2-nistp521": NistCurve(0x01ffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff, 0x01fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffc, 0x0051953eb9618e1c9a1f929a21a0b68540eea2da725b99b315f3b8b489918ef109e156193951ec7e937b1652c0bd3bb1bf073573df883d2c34f1ef451fd46b503f00),
 }
 
-try:
-    optlist, args = getopt.getopt(sys.argv[1:], '', [ 'win', 'unix' ])
-    if any(x[0] == '--unix' for x in optlist):
-        output_type = 'unix'
-except getopt.error as e:
-    sys.stderr.write(str(e) + "\n")
-    sys.exit(1)
-
-if output_type == 'windows':
-    # Output REG file header.
-    sys.stdout.write("""REGEDIT4
-
-[HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\SshHostKeys]
-""")
-
 class BlankInputLine(Exception):
     pass
 
@@ -189,9 +172,7 @@ class KeyFormatError(Exception):
     def __init__(self, msg):
         self.msg = msg
 
-# Now process all known_hosts input.
+def handle_line(line, output_formatter):
-for line in fileinput.input(args):
-
     try:
         # Remove leading/trailing whitespace (should zap CR and LF)
         line = line.strip()
@@ -346,14 +327,7 @@ for line in fileinput.input(args):
                     lambda x: x if isinstance(x, str)
                     else x.decode('ASCII') if isinstance(x, bytes)
                     else inttohex(x), keyparams))
-                if output_type == 'unix':
+                output_formatter.key(key, value)
-                    # Unix format.
-                    sys.stdout.write('%s %s\n' % (key, value))
-                else:
-                    # Windows format.
-                    # XXX: worry about double quotes?
-                    sys.stdout.write("\"%s\"=\"%s\"\n"
-                                     % (winmungestr(key), value))
 
     except UnknownKeyType as k:
         warn("unknown SSH key type '%s', skipping" % k.keytype)
@@ -362,13 +336,54 @@ for line in fileinput.input(args):
     except BlankInputLine:
         pass
 
-# The spec at http://support.microsoft.com/kb/310516 says we need
+class OutputFormatter(object):
-# a blank line at the end of the reg file:
+    def __init__(self, fh):
-#
+        self.fh = fh
-#   Note the registry file should contain a blank line at the
+    def header(self):
-#   bottom of the file.
+        pass
-#
+    def trailer(self):
-if output_type == 'windows':
+        pass
-    # Output REG file header.
+
-    sys.stdout.write("\n")
+class WindowsOutputFormatter(OutputFormatter):
-            
+    def header(self):
+        # Output REG file header.
+        self.fh.write("""REGEDIT4
+
+[HKEY_CURRENT_USER\Software\SimonTatham\PuTTY\SshHostKeys]
+""")
+
+    def key(self, key, value):
+        # XXX: worry about double quotes?
+        self.fh.write("\"%s\"=\"%s\"\n" % (winmungestr(key), value))
+
+    def trailer(self):
+        # The spec at http://support.microsoft.com/kb/310516 says we need
+        # a blank line at the end of the reg file:
+        #
+        #   Note the registry file should contain a blank line at the
+        #   bottom of the file.
+        #
+        self.fh.write("\n")
+
+class UnixOutputFormatter(OutputFormatter):
+    def key(self, key, value):
+        self.fh.write('%s %s\n' % (key, value))
+
+def main():
+    output_formatter_class = WindowsOutputFormatter
+    try:
+        optlist, args = getopt.getopt(sys.argv[1:], '', [ 'win', 'unix' ])
+        if any(x[0] == '--unix' for x in optlist):
+            output_formatter_class = UnixOutputFormatter
+    except getopt.error as e:
+        sys.stderr.write(str(e) + "\n")
+        sys.exit(1)
+
+    output_formatter = output_formatter_class(sys.stdout)
+    output_formatter.header()
+    for line in fileinput.input(args):
+        handle_line(line, output_formatter)
+    output_formatter.trailer()
+
+if __name__ == "__main__":
+    main()