blob: 19c294fba54b353df1af1998c97ffe08c19c0e44 [file] [log] [blame]
#!/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/"""
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:
with open(path, 'rb') as f:
header =
is_thin = header == b'!<thin>\n'
if not is_thin and header != b'!<arch>\n':
raise Exception('Invalid .a: ' + path)
if not is_thin:
def read_payload(size):
ret =
# Entries are 2-byte aligned.
if size & 1 != 0:
return ret
while True:
entry =
if not entry:
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
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]
# 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.
paths: List of paths relative to |output_directory|.
output_directory: Output directory.
* A new list of paths with all archives replaced by .o paths.
expanded_paths = []
for path in paths:
if not path.endswith('.a'):
with open(path, 'rb') as f:
header =
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