[tor-commits] [stem/master] Caching for stem.process.get_version()

[atagar at torproject.org]

commit 11b2a71d3a6ae24365ebd1e9a30c323a6a3ce275
Author: Damian Johnson <atagar at torproject.org>
Date:   Thu Oct 27 09:17:26 2011 -0700

    Caching for stem.process.get_version()
    
    Caching results of the stem.process.get_version() function to avoid unnecessary
    lookups.
---
 stem/process.py |   48 +++++++++++++++++++++++++++---------------------
 1 files changed, 27 insertions(+), 21 deletions(-)

diff --git a/stem/process.py b/stem/process.py
index 0baa5dd..934a9c1 100644
--- a/stem/process.py
+++ b/stem/process.py
@@ -15,6 +15,9 @@ from stem.util import system
 # number of seconds before we time out our attempt to start a tor instance
 DEFAULT_INIT_TIMEOUT = 90
 
+# cache for the get_version function
+VERSION_CACHE = {}
+
 def get_version(tor_cmd = "tor"):
   """
   Provides the version of tor.
@@ -29,29 +32,32 @@ def get_version(tor_cmd = "tor"):
     IOError if unable to query or parse the version
   """
   
-  try:
-    version_cmd = "%s --version" % tor_cmd
-    version_output = system.call(version_cmd)
-  except OSError, exc:
-    raise IOError(exc)
-  
-  if version_output:
-    # output example:
-    # Oct 21 07:19:27.438 [notice] Tor v0.2.1.30. This is experimental software. Do not rely on it for strong anonymity. (Running on Linux i686)
-    # Tor version 0.2.1.30.
+  if not tor_cmd in VERSION_CACHE:
+    try:
+      version_cmd = "%s --version" % tor_cmd
+      version_output = system.call(version_cmd)
+    except OSError, exc:
+      raise IOError(exc)
     
-    last_line = version_output[-1]
-    
-    if last_line.startswith("Tor version ") and last_line.endswith("."):
-      try:
-        version_str = last_line[12:-1]
-        return stem.types.get_version(version_str)
-      except ValueError, exc:
-        raise IOError(exc)
+    if version_output:
+      # output example:
+      # Oct 21 07:19:27.438 [notice] Tor v0.2.1.30. This is experimental software. Do not rely on it for strong anonymity. (Running on Linux i686)
+      # Tor version 0.2.1.30.
+      
+      last_line = version_output[-1]
+      
+      if last_line.startswith("Tor version ") and last_line.endswith("."):
+        try:
+          version_str = last_line[12:-1]
+          VERSION_CACHE[tor_cmd] = stem.types.get_version(version_str)
+        except ValueError, exc:
+          raise IOError(exc)
+      else:
+        raise IOError("Unexpected response from '%s': %s" % (version_cmd, last_line))
     else:
-      raise IOError("Unexpected response from '%s': %s" % (version_cmd, last_line))
-  else:
-    raise IOError("'%s' didn't have any output" % version_cmd)
+      raise IOError("'%s' didn't have any output" % version_cmd)
+  
+  return VERSION_CACHE[tor_cmd]
 
 def launch_tor(torrc_path, completion_percent = 100, init_msg_handler = None, timeout = DEFAULT_INIT_TIMEOUT):
   """