Reland of V2 of //tools/binary_size rewrite (diffs).

tools/binary_size/file_format.py

Index: tools/binary_size/file_format.py
diff --git a/tools/binary_size/file_format.py b/tools/binary_size/file_format.py
new file mode 100644
index 0000000000000000000000000000000000000000..4f1bbb9180bb67ed2dbd89b9f26a52fad747a748
--- /dev/null
+++ b/tools/binary_size/file_format.py
@@ -0,0 +1,85 @@
+# Copyright 2017 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.
+
+"""Deals with loading & saving .size files."""
+
+import ast
+import gzip
+import models
+
+
+# File format version for .size files.
+_SERIALIZATION_VERSION = 1
+
+
+def EndsWithMaybeGz(path, suffix):
+  return path.endswith(suffix) or path.endswith(suffix + '.gz')
+
+
+def OpenMaybeGz(path, mode=None):
+  """Calls `gzip.open()` if |path| ends in ".gz", otherwise calls `open()`."""
+  if path.endswith('.gz'):
+    if mode and 'w' in mode:
+      return gzip.GzipFile(path, mode, 1)
+    return gzip.open(path, mode)
+  return open(path, mode or 'r')
+
+
+def _SaveSizeInfoToFile(result, file_obj):
+  """Saves the result to the given file object."""
+  # Store one bucket per line.
+  file_obj.write('%d\n' % _SERIALIZATION_VERSION)
+  file_obj.write('%r\n' % result.section_sizes)
+  file_obj.write('%d\n' % len(result.symbols))
+  prev_section_name = None
+  # Store symbol fields as tab-separated.
+  # Store only non-derived fields.
+  for symbol in result.symbols:
+    if symbol.section_name != prev_section_name:
+      file_obj.write('%s\n' % symbol.section_name)
+      prev_section_name = symbol.section_name
+    # Don't write padding nor name since these are derived values.
+    file_obj.write('%x\t%x\t%s\t%s\n' % (
+        symbol.address, symbol.size_without_padding,
+        symbol.function_signature or symbol.name, symbol.path))
+
+
+def _LoadSizeInfoFromFile(file_obj):
+  """Loads a result from the given file."""
+  lines = iter(file_obj)
+  actual_version = int(next(lines))
+  assert actual_version == _SERIALIZATION_VERSION, (
+      'Version mismatch. Need to write some upgrade code.')
+
+  section_sizes = ast.literal_eval(next(lines))
+  num_syms = int(next(lines))
+  symbol_list = [None] * num_syms
+  section_name = None
+  for i in xrange(num_syms):
+    line = next(lines)[:-1]
+    if '\t' not in line:
+      section_name = line
+      line = next(lines)[:-1]
+    new_sym = models.Symbol.__new__(models.Symbol)
+    parts = line.split('\t')
+    new_sym.section_name = section_name
+    new_sym.address = int(parts[0], 16)
+    new_sym.size = int(parts[1], 16)
+    new_sym.name = parts[2]
+    new_sym.path = parts[3]
+    new_sym.padding = 0  # Derived
+    new_sym.function_signature = None  # Derived
+    symbol_list[i] = new_sym
+
+  return models.SizeInfo(models.SymbolGroup(symbol_list), section_sizes)
+
+
+def SaveSizeInfo(result, path):
+  with OpenMaybeGz(path, 'wb') as f:
+    _SaveSizeInfoToFile(result, f)
+
+
+def LoadSizeInfo(path):
+  with OpenMaybeGz(path) as f:
+    return _LoadSizeInfoFromFile(f)