[3 of 4] Speedup GetRegistryLengthImpl() by seeding the DAFSA in reverse

net/tools/dafsa/make_dafsa.py

Index: net/tools/dafsa/make_dafsa.py
diff --git a/net/tools/dafsa/make_dafsa.py b/net/tools/dafsa/make_dafsa.py
index 5c9082d372c18007b853a9e9599c57b5e253f736..358be16ee89f0845e4685f0a415c8dcb091d2039 100755
--- a/net/tools/dafsa/make_dafsa.py
+++ b/net/tools/dafsa/make_dafsa.py
@@ -192,8 +192,19 @@ The bytes in the generated array has the following meaning:
 10: 0x82 <return_value> 0x82 & 0x0F -> return 2
 """
 
+import argparse
 import sys
 
+
+parser = argparse.ArgumentParser()
+parser.add_argument('infile', nargs='?', type=argparse.FileType('r'))
+parser.add_argument('outfile', nargs='?', type=argparse.FileType('w'))
+parser.add_argument('--reverse_inputs', action='store_true',
+                    help='Generates a DAFSA on reversed input strings; this is '
+                         'useful for suffix queries')
+args = parser.parse_args()
+
+
 class InputError(Exception):
   """Exception raised for errors in the input file."""
 
@@ -453,14 +464,17 @@ def parse_gperf(infile):
     if not line.endswith(('0', '1', '2', '3', '4', '5', '6', '7')):
       raise InputError('Expected value to be in the range of 0-7, found "%s"' %
                        line[-1])
-  return [line[:-3] + line[-1] for line in lines]
-
+  result = []
+  for line in lines:
+    word, result_code = line[:-3], line[-1]
+    if args.reverse_inputs:
+      word = word[::-1]
+    result.append(word + result_code)
+  result.sort()
+  return result
 
 def main():
-  if len(sys.argv) != 3:
-    print('usage: %s infile outfile' % sys.argv[0])
-    return 1
-  with open(sys.argv[1], 'r') as infile, open(sys.argv[2], 'w') as outfile:
+  with args.infile as infile, args.outfile as outfile:
     outfile.write(words_to_cxx(parse_gperf(infile)))
   return 0