Updated stats-viewer.py to work with chromium.

Review URL: http://codereview.chromium.org/473002

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3463 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

tools/stats-viewer.py

+#!/usr/bin/env python
+#
 # Copyright 2008 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
@@ -49,8 +51,9 @@ UPDATE_INTERVAL_MS = 100
 COUNTER_LABELS = {"t": "%i ms.", "c": "%i"}
 
 
-# The magic number used to check if a file is not a counters file
+# The magic numbers used to check if a file is not a counters file
 COUNTERS_FILE_MAGIC_NUMBER = 0xDEADFACE
+CHROME_COUNTERS_FILE_MAGIC_NUMBER = 0x13131313
 
 
 class StatsViewer(object):
@@ -99,10 +102,12 @@ class StatsViewer(object):
     fileno = data_file.fileno()
     self.shared_mmap = mmap.mmap(fileno, size, access=mmap.ACCESS_READ)
     data_access = SharedDataAccess(self.shared_mmap)
-    if data_access.IntAt(0) != COUNTERS_FILE_MAGIC_NUMBER:
-      print "File %s is not stats data." % self.data_name
-      sys.exit(1)
-    return CounterCollection(data_access)
+    if data_access.IntAt(0) == COUNTERS_FILE_MAGIC_NUMBER:
+      return CounterCollection(data_access)
+    elif data_access.IntAt(0) == CHROME_COUNTERS_FILE_MAGIC_NUMBER:
+      return ChromeCounterCollection(data_access)
+    print "File %s is not stats data." % self.data_name
+    sys.exit(1)
 
   def CleanUp(self):
     """Cleans up the memory mapped file if necessary."""
@@ -356,6 +361,72 @@ class CounterCollection(object):
     return 4 + self.max_name_size
 
 
+class ChromeCounter(object):
+  """A pointer to a single counter withing a binary counters file."""
+
+  def __init__(self, data, name_offset, value_offset):
+    """Create a new instance.
+
+    Args:
+      data: the shared data access object containing the counter
+      name_offset: the byte offset of the start of this counter's name
+      value_offset: the byte offset of the start of this counter's value
+    """
+    self.data = data
+    self.name_offset = name_offset
+    self.value_offset = value_offset
+
+  def Value(self):
+    """Return the integer value of this counter."""
+    return self.data.IntAt(self.value_offset)
+
+  def Name(self):
+    """Return the ascii name of this counter."""
+    result = ""
+    index = self.name_offset
+    current = self.data.ByteAt(index)
+    while current:
+      result += chr(current)
+      index += 1
+      current = self.data.ByteAt(index)
+    return result
+
+
+class ChromeCounterCollection(object):
+  """An overlay over a counters file that provides access to the
+  individual counters contained in the file."""
+
+  _HEADER_SIZE = 4 * 4
+  _NAME_SIZE = 32
+
+  def __init__(self, data):
+    """Create a new instance.
+
+    Args:
+      data: the shared data access object
+    """
+    self.data = data
+    self.max_counters = data.IntAt(8)
+    self.max_threads = data.IntAt(12)
+    self.counter_names_offset = \
+        self._HEADER_SIZE + self.max_threads * (self._NAME_SIZE + 2 * 4)
+    self.counter_values_offset = \
+        self.counter_names_offset + self.max_counters * self._NAME_SIZE
+
+  def CountersInUse(self):
+    """Return the number of counters in active use."""
+    for i in xrange(self.max_counters):
+      if self.data.ByteAt(self.counter_names_offset + i * self._NAME_SIZE) == 0:
+        return i
+    return self.max_counters
+
+  def Counter(self, i):
+    """Return the i'th counter."""
+    return ChromeCounter(self.data,
+                         self.counter_names_offset + i * self._NAME_SIZE,
+                         self.counter_values_offset + i * self.max_threads * 4)
+
+
 def Main(data_file):
   """Run the stats counter.