Linux: create a library loader code generator for dlopen and use it for libpci.

tools/generate_library_loader/generate_library_loader.py

+#!/usr/bin/env python
+# Copyright (c) 2012 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.
+
+"""
+Creates a library loader (a header and implementation file),
+which is a wrapper for dlopen or direct linking with given library.
+
+The loader makes it possible to have the same client code for both cases,
+and also makes it easier to write code using dlopen (and also provides
+a standard way to do so, and limits the ugliness just to generated files).
+
+For more info refer to http://crbug.com/162733 .
+"""
+
+
+import optparse
+import os.path
+import re
+import sys
+
+
+HEADER_TEMPLATE = """// This is generated file. Do not modify directly.
+// Path to the code generator: %(generator_path)s .
+
+#ifndef %(unique_prefix)s_H_
+#define %(unique_prefix)s_H_
+
+%(wrapped_header_include)s
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#ifdef %(unique_prefix)s_DLOPEN
+#include "base/native_library.h"
+#endif
+
+class %(class_name)s {
+ public:
+  %(class_name)s();
+  ~%(class_name)s();
+
+  bool Load(const std::string& library_name) WARN_UNUSED_RESULT;
+
+%(member_decls)s
+
+ private:
+#ifdef %(unique_prefix)s_DLOPEN
+  base::NativeLibrary library_;
+#endif
+
+  bool loaded_;
+
+  DISALLOW_COPY_AND_ASSIGN(%(class_name)s);
+};
+
+#endif  // %(unique_prefix)s_H_
+"""
+
+
+HEADER_MEMBER_TEMPLATE = """  typeof(&::%(function_name)s) %(function_name)s;
+"""
+
+
+IMPL_TEMPLATE = """// This is generated file. Do not modify directly.
+// Path to the code generator: %(generator_path)s .
+
+#include "%(generated_header_name)s"
+
+#include "base/file_path.h"
+#include "base/logging.h"
+
+%(class_name)s::%(class_name)s() : loaded_(false) {
+}
+
+%(class_name)s::~%(class_name)s() {
+#ifdef %(unique_prefix)s_DLOPEN
+  if (loaded_)
+    base::UnloadNativeLibrary(library_);
+#endif
+}
+
+bool %(class_name)s::Load(const std::string& library_name) {
+  if (loaded_) {
+    NOTREACHED();
+    return false;
+  }
+
+#ifdef %(unique_prefix)s_DLOPEN
+  library_ = base::LoadNativeLibrary(FilePath(library_name), NULL);
+  if (library_) {
+#endif
+
+%(member_init)s
+
+    loaded_ = true;
+    return true;
+#ifdef %(unique_prefix)s_DLOPEN
+  }
+
+  return false;
+#endif
+}
+"""
+
+IMPL_MEMBER_TEMPLATE = """
+#ifdef %(unique_prefix)s_DLOPEN
+    this->%(function_name)s =
+        reinterpret_cast<typeof(this->%(function_name)s)>(
+            base::GetFunctionPointerFromNativeLibrary(
+                library_, "%(function_name)s"));
+    if (!this->%(function_name)s) {
+      base::UnloadNativeLibrary(library_);
+      return false;
+    }
+#else
+  this->%(function_name)s = &::%(function_name)s;
+#endif
+"""
+
+
+def main():
+  parser = optparse.OptionParser()
+  parser.add_option('--name')
+  parser.add_option('--output')
+  parser.add_option('--header')
+
+  parser.add_option('--use-extern-c', action='store_true', default=False)
+  parser.add_option('--link-directly', type=int, default=0)
+
+  options, args = parser.parse_args()
+
+  if not options.name:
+    parser.error('Missing --name parameter')
+  if not options.output:
+    parser.error('Missing --output parameter')
+  if not options.header:
+    parser.error('Missing --header paramater')
+  if not args:
+    parser.error('No function names specified')
+
+  # Create a unique prefix, e.g. for header guards.
+  unique_prefix = re.sub(r'[\W]', '_', options.output).upper();
+
+  member_decls = []
+  member_init = []
+  for fn in args:
+    member_decls += HEADER_MEMBER_TEMPLATE % {
+      'function_name': fn,
+      'unique_prefix': unique_prefix
+    }
+    member_init += IMPL_MEMBER_TEMPLATE % {
+      'function_name': fn,
+      'unique_prefix': unique_prefix
+    }
+
+  wrapped_header_include = '#include %s' % options.header
+
+  # Some libraries (e.g. libpci) have headers that cannot be included
+  # without extern "C", otherwise they cause the link to fail.
+  if options.use_extern_c:
+    wrapped_header_include = 'extern "C" {\n%s\n}\n' % wrapped_header_include
+
+  # It seems cleaner just to have a single #define here and #ifdefs in bunch
+  # of places, rather than having a different set of templates, duplicating
+  # or complicating more code.
+  if options.link_directly == 0:
+    wrapped_header_include += '#define %s_DLOPEN\n' % unique_prefix
+
+  # Make it easier for people to find the code generator just in case.
+  # Doing it this way is more maintainable, because it's going to work
+  # even if file gets moved without updating the contents.
+  generator_path = os.path.abspath(__file__)
+
+  header_contents = HEADER_TEMPLATE % {
+    'generator_path': generator_path,
+    'unique_prefix': unique_prefix,
+    'wrapped_header_include': wrapped_header_include,
+    'class_name': options.name,
+    'member_decls': ''.join(member_decls),
+  }
+
+  impl_contents = IMPL_TEMPLATE % {
+    'generator_path': generator_path,
+    'unique_prefix': unique_prefix,
+    'generated_header_name': options.output + '.h',
+    'class_name': options.name,
+    'member_init': ''.join(member_init),
+  }
+
+  header_file = open(options.output + '.h', 'w')
+  try:
+    header_file.write(header_contents)
+  finally:
+    header_file.close()
+
+  impl_file = open(options.output + '.cc', 'w')
+  try:
+    impl_file.write(impl_contents)
+  finally:
+    impl_file.close()
+
+  return 0
+
+if __name__ == '__main__':
+  sys.exit(main())