Call `gzip` in subprocess instead of gzipping in Python in http_server.

mojo/devtools/common/devtoolslib/http_server.py

Index: mojo/devtools/common/devtoolslib/http_server.py
diff --git a/mojo/devtools/common/devtoolslib/http_server.py b/mojo/devtools/common/devtoolslib/http_server.py
index d8a275770135205263026d3cba56a3aa733ddf77..6267af9531d1a062fee5eb75bb7555bc7dedce11 100644
--- a/mojo/devtools/common/devtoolslib/http_server.py
+++ b/mojo/devtools/common/devtoolslib/http_server.py
@@ -6,15 +6,14 @@ import atexit
 import datetime
 import email.utils
 import errno
-import gzip
 import hashlib
 import logging
 import math
 import os.path
-import shutil
 import socket
-import threading
+import subprocess
 import tempfile
+import threading
 
 import SimpleHTTPServer
 import SocketServer
@@ -146,24 +145,30 @@ def _get_handler_class_for_path(mappings):
           SimpleHTTPServer.SimpleHTTPRequestHandler.translate_path(self, path))
 
       for prefix, local_base_path_list in mappings:
-        if normalized_path.startswith(prefix):
-          for local_base_path in local_base_path_list:
-            candidate = os.path.join(local_base_path,
-                                     normalized_path[len(prefix):])
-            if os.path.isfile(candidate):
-              if gzipped:
-                if not self.gzipped_file:
-                  self.gzipped_file = tempfile.NamedTemporaryFile(delete=False)
-                  self.original_file_name = candidate
-                  with open(candidate, 'rb') as source:
-                    with gzip.GzipFile(fileobj=self.gzipped_file) as target:
-                      shutil.copyfileobj(source, target)
-                  self.gzipped_file.close()
-                return self.gzipped_file.name
-              return candidate
-          else:
-            self.send_response(404)
-            return None
+        if not normalized_path.startswith(prefix):
+          continue
+
+        for local_base_path in local_base_path_list:
+          candidate = os.path.join(local_base_path,
+                                   normalized_path[len(prefix):])
+          if os.path.isfile(candidate):
+            if gzipped:
+              if not self.gzipped_file:
+                self.gzipped_file = tempfile.NamedTemporaryFile(delete=False)

[piotrt, 2015/08/25 11:55:23]

I would consider extracting lines 157-166? to a separate method
called f.e. _try_gzip(..) or something similar, to separate all the 
nested conditions from actual work being done. 

[ppi, 2015/08/25 12:07:43]

Good point, done.

+                self.original_file_name = candidate
+                try:
+                  subprocess.check_call(['gzip', '-c', candidate],
+                                        stdout=self.gzipped_file)
+                except Exception:
+                  print ('http_server: call to gzip failed, make sure that '
+                         'gzip is installed on the host.')
+                  raise
+                self.gzipped_file.close()
+              return self.gzipped_file.name
+            return candidate
+        else:
+          self.send_response(404)
+          return None
       self.send_response(404)
       return None