[tor-commits] [stem/master] Don't modify list of descriptor lines

[atagar at torproject.org]

commit e607f9127657b47439a72661e8814e1cb9a80361
Author: Damian Johnson <atagar at torproject.org>
Date:   Sun Jan 25 12:53:21 2015 -0800

    Don't modify list of descriptor lines
    
    In theory popping from the head of our unread lines is inefficient since we
    create a new list with every line read. However, oddly changeing this doesn't
    seem to have a benefit in terms of performance...
    
    It's more readable how it was so including this commit and reversion in our
    history so we can loop back and include this if we later discover it is
    beneficial.
---
 stem/descriptor/__init__.py |   33 +++++++++++++++++++--------------
 1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/stem/descriptor/__init__.py b/stem/descriptor/__init__.py
index 0d2295d..da4e5e7 100644
--- a/stem/descriptor/__init__.py
+++ b/stem/descriptor/__init__.py
@@ -587,23 +587,25 @@ def _read_until_keywords(keywords, descriptor_file, inclusive = False, ignore_fi
     return content
 
 
-def _get_pseudo_pgp_block(remaining_contents):
+def _get_pseudo_pgp_block(lines, i):
   """
   Checks if given contents begins with a pseudo-Open-PGP-style block and, if
   so, pops it off and provides it back to the caller.
 
-  :param list remaining_contents: lines to be checked for a public key block
+  :param list lines: lines to be checked for a public key block
+  :param int i: line to start reading from
 
-  :returns: **tuple** of the (block_type, content) or None if it doesn't exist
+  :returns: **tuple** of the (block_type, content, read_until) or None if it
+    doesn't exist
 
   :raises: **ValueError** if the contents starts with a key block but it's
     malformed (for instance, if it lacks an ending line)
   """
 
-  if not remaining_contents:
+  if len(lines) <= i:
     return None  # nothing left
 
-  block_match = PGP_BLOCK_START.match(remaining_contents[0])
+  block_match = PGP_BLOCK_START.match(lines[i])
 
   if block_match:
     block_type = block_match.groups()[0]
@@ -611,14 +613,15 @@ def _get_pseudo_pgp_block(remaining_contents):
     end_line = PGP_BLOCK_END % block_type
 
     while True:
-      if not remaining_contents:
+      if len(lines) <= i:
         raise ValueError("Unterminated pgp style block (looking for '%s'):\n%s" % (end_line, '\n'.join(block_lines)))
 
-      line = remaining_contents.pop(0)
+      line = lines[i]
       block_lines.append(line)
+      i += 1
 
       if line == end_line:
-        return (block_type, '\n'.join(block_lines))
+        return (block_type, '\n'.join(block_lines), i)
   else:
     return None
 
@@ -654,10 +657,12 @@ def _get_descriptor_components(raw_contents, validate, extra_keywords = ()):
 
   entries = OrderedDict()
   extra_entries = []  # entries with a keyword in extra_keywords
-  remaining_lines = raw_contents.split('\n')
+  lines = raw_contents.split('\n')
+  skip_until = None  # _get_pseudo_pgp_block() reads ahead, so we should skip lines its read
 
-  while remaining_lines:
-    line = remaining_lines.pop(0)
+  for i, line in enumerate(lines):
+    if skip_until and i < skip_until:
+      continue
 
     # V2 network status documents explicitly can contain blank lines...
     #
@@ -691,12 +696,12 @@ def _get_descriptor_components(raw_contents, validate, extra_keywords = ()):
       value = ''
 
     try:
-      block_attr = _get_pseudo_pgp_block(remaining_lines)
+      block_attr = _get_pseudo_pgp_block(lines, i + 1)
 
       if block_attr:
-        block_type, block_contents = block_attr
+        block_type, block_contents, skip_until = block_attr
       else:
-        block_type, block_contents = None, None
+        block_type, block_contents, skip_until = None, None, None
     except ValueError as exc:
       if not validate:
         continue