Refactor build/android/symbolize.py to function as an output filter.

build/android/symbolize.py

 #!/usr/bin/env python
 #
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Symbolizes stack traces generated by Chromium for Android.
 
 Sample usage:
   adb logcat chromium:V | symbolize.py
@@ skipping 10 matching lines @@
                 os.path.join(constants.DIR_SOURCE_ROOT,
                             'third_party/android_platform/development/scripts'))
 import symbol
 
 # Sample output from base/debug/stack_trace_android.cc
 #00 0x693cd34f /path/to/some/libfoo.so+0x0007434f
 TRACE_LINE = re.compile('(?P<frame>\#[0-9]+ 0x[0-9a-f]{8,8}) '
                         '(?P<lib>[^+]+)\+0x(?P<addr>[0-9a-f]{8,8})')
 
 class Symbolizer(object):
-  def __init__(self, file_in, file_out):
-    self.file_in = file_in
-    self.file_out = file_out
+  def __init__(self, output):
+    self._output = output
 
-  def ProcessInput(self):
-    for line in self.file_in:
-      match = re.search(TRACE_LINE, line)
+  def write(self, data):

[bulach, 2013/07/18 09:07:03]

nit: it looks a bit weird to have "write(input_data)" :)
how about naming this method "symbolize"?

[scherkus (not reviewing), 2013/07/18 18:08:34]

The idea is that an instance of this class can act as an output text filter for
other stdout-ish / file-ish classes, similar to how StringIO emulates stdout-ish
/ file-ish API but saves the contents to a string.

+    while True:
+      match = re.search(TRACE_LINE, data)
       if not match:
-        self.file_out.write(line)
-        self.file_out.flush()
-        continue
+        self._output.write(data)
+        break
 
       frame = match.group('frame')
       lib = match.group('lib')
       addr = match.group('addr')
 
       # TODO(scherkus): Doing a single lookup per line is pretty slow,
       # especially with larger libraries. Consider caching strategies such as:
       # 1) Have Python load the libraries and do symbol lookups instead of
       #    calling out to addr2line each time.
       # 2) Have Python keep multiple addr2line instances open as subprocesses,
       #    piping addresses and reading back symbols as we find them
       # 3) Read ahead the entire stack trace until we find no more, then batch
       #    the symbol lookups.
       #
       # TODO(scherkus): These results are memoized, which could result in
       # incorrect lookups when running this script on long-lived instances
       # (e.g., adb logcat) when doing incremental development. Consider clearing
       # the cache when modification timestamp of libraries change.
       sym = symbol.SymbolInformation(lib, addr, False)[0][0]
 
       if not sym:
-        self.file_out.write(line)
-        self.file_out.flush()
+        post = match.end('addr')
+        self._output.write(data[:post])
+        data = data[post:]
         continue
 
-      pre = line[0:match.start('frame')]
-      post = line[match.end('addr'):]
+      pre = match.start('frame')
+      post = match.end('addr')
 
-      self.file_out.write(pre)
-      self.file_out.write(frame)
-      self.file_out.write(' ')
-      self.file_out.write(sym)
-      self.file_out.write(post)
-      self.file_out.flush()
+      self._output.write(data[:pre])
+      self._output.write(frame)
+      self._output.write(' ')
+      self._output.write(sym)
+
+      data = data[post:]
+
+  def flush(self):
+    self._output.flush()
 
 
 def main():
-  symbolizer = Symbolizer(sys.stdin, sys.stdout)
-  symbolizer.ProcessInput()
+  symbolizer = Symbolizer(sys.stdout)
+  for line in sys.stdin:
+    symbolizer.write(line)
+  symbolizer.flush()
 
 
 if __name__ == '__main__':
   main()