1 files changed, 96 insertions, 0 deletions
diff --git a/chromium/tools/resources/ar.py b/chromium/tools/resources/ar.py
new file mode 100755
index 00000000000..19c294fba54
--- /dev/null
+++ b/chromium/tools/resources/ar.py
@@ -0,0 +1,96 @@
+#!/usr/bin/env python3
+# Copyright 2018 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.
+"""Logic for reading .a files.
+
+Copied from //tools/binary_size/libsupersize/ar.py"""
+
+import os
+
+
+def _ResolveThinObjectPath(archive_path, subpath):
+  """Given the .a path and .o subpath, returns the .o path."""
+  # |subpath| is path complete under Gold, and incomplete under LLD. Check its
+  # prefix to test completeness, and if not, use |archive_path| to supply the
+  # required prefix.
+  if subpath.startswith('obj/'):
+    return subpath
+  # .o subpaths in thin archives are relative to the directory of the .a.
+  parent_path = os.path.dirname(archive_path)
+  return os.path.normpath(os.path.join(parent_path, subpath))
+
+
+def _IterThinPaths(path):
+  """Given the .a path, yields all nested .o paths."""
+  # File format reference:
+  # https://github.com/pathscale/binutils/blob/master/gold/archive.cc
+  with open(path, 'rb') as f:
+    header = f.read(8)
+    is_thin = header == b'!<thin>\n'
+    if not is_thin and header != b'!<arch>\n':
+      raise Exception('Invalid .a: ' + path)
+    if not is_thin:
+      return
+
+    def read_payload(size):
+      ret = f.read(size)
+      # Entries are 2-byte aligned.
+      if size & 1 != 0:
+        f.read(1)
+      return ret
+
+    while True:
+      entry = f.read(60)
+      if not entry:
+        return
+      entry_name = entry[:16].rstrip()
+      entry_size = int(entry[48:58].rstrip())
+
+      if entry_name in (b'', b'/', b'//', b'/SYM64/'):
+        payload = read_payload(entry_size)
+        # Metadata sections we don't care about.
+        if entry_name == b'//':
+          name_list = payload
+        continue
+
+      if entry_name[0:1] == b'/':
+        # Name is specified as location in name table.
+        # E.g.: /123
+        name_offset = int(entry_name[1:])
+        # String table enties are delimited by \n (e.g. "browser.o/\n").
+        end_idx = name_list.index(b'\n', name_offset)
+        entry_name = name_list[name_offset:end_idx]
+      else:
+        # Name specified inline with spaces for padding (e.g. "browser.o/    ").
+        entry_name = entry_name.rstrip()
+
+      yield entry_name.rstrip(b'/').decode('ascii')
+
+
+def ExpandThinArchives(paths):
+  """Expands all thin archives found in |paths| into .o paths.
+
+  Args:
+    paths: List of paths relative to |output_directory|.
+    output_directory: Output directory.
+
+  Returns:
+    * A new list of paths with all archives replaced by .o paths.
+  """
+  expanded_paths = []
+  for path in paths:
+    if not path.endswith('.a'):
+      expanded_paths.append(path)
+      continue
+
+    with open(path, 'rb') as f:
+      header = f.read(8)
+      is_thin = header == b'!<thin>\n'
+      if is_thin:
+        for subpath in _IterThinPaths(path):
+          expanded_paths.append(_ResolveThinObjectPath(path, subpath))
+      elif header != b'!<arch>\n':
+        raise Exception('Invalid .a: ' + path)
+
+  return expanded_paths