tools/generate_library_loader/generate_library_loader.py

   1 #!/usr/bin/env python
   2 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
   3 # Use of this source code is governed by a BSD-style license that can be
   4 # found in the LICENSE file.
   5
   6 """
   7 Creates a library loader (a header and implementation file),
   8 which is a wrapper for dlopen or direct linking with given library.
   9
  10 The loader makes it possible to have the same client code for both cases,
  11 and also makes it easier to write code using dlopen (and also provides
  12 a standard way to do so, and limits the ugliness just to generated files).
  13
  14 For more info refer to http://crbug.com/162733 .
  15 """
  16
  17
  18 import optparse
  19 import os.path
  20 import re
  21 import sys
  22
  23
  24 HEADER_TEMPLATE = """// This is generated file. Do not modify directly.
  25 // Path to the code generator: %(generator_path)s .
  26
  27 #ifndef %(unique_prefix)s
  28 #define %(unique_prefix)s
  29
  30 %(wrapped_header_include)s
  31
  32 #include <string>
  33
  34 class %(class_name)s {
  35  public:
  36   %(class_name)s();
  37   ~%(class_name)s();
  38
  39   bool Load(const std::string& library_name)
  40       __attribute__((warn_unused_result));
  41
  42   bool loaded() const { return loaded_; }
  43
  44 %(member_decls)s
  45
  46  private:
  47   void CleanUp(bool unload);
  48
  49 #if defined(%(unique_prefix)s_DLOPEN)
  50   void* library_;
  51 #endif
  52
  53   bool loaded_;
  54
  55   // Disallow copy constructor and assignment operator.
  56   %(class_name)s(const %(class_name)s&);
  57   void operator=(const %(class_name)s&);
  58 };
  59
  60 #endif  // %(unique_prefix)s
  61 """
  62
  63
  64 HEADER_MEMBER_TEMPLATE = """  typeof(&::%(function_name)s) %(function_name)s;
  65 """
  66
  67
  68 IMPL_TEMPLATE = """// This is generated file. Do not modify directly.
  69 // Path to the code generator: %(generator_path)s .
  70
  71 #include "%(generated_header_name)s"
  72
  73 #include <dlfcn.h>
  74
  75 // Put these sanity checks here so that they fire at most once
  76 // (to avoid cluttering the build output).
  77 #if !defined(%(unique_prefix)s_DLOPEN) && !defined(%(unique_prefix)s_DT_NEEDED)
  78 #error neither %(unique_prefix)s_DLOPEN nor %(unique_prefix)s_DT_NEEDED defined
  79 #endif
  80 #if defined(%(unique_prefix)s_DLOPEN) && defined(%(unique_prefix)s_DT_NEEDED)
  81 #error both %(unique_prefix)s_DLOPEN and %(unique_prefix)s_DT_NEEDED defined
  82 #endif
  83
  84 %(class_name)s::%(class_name)s() : loaded_(false) {
  85 }
  86
  87 %(class_name)s::~%(class_name)s() {
  88   CleanUp(loaded_);
  89 }
  90
  91 bool %(class_name)s::Load(const std::string& library_name) {
  92   if (loaded_)
  93     return false;
  94
  95 #if defined(%(unique_prefix)s_DLOPEN)
  96   library_ = dlopen(library_name.c_str(), RTLD_LAZY);
  97   if (!library_)
  98     return false;
  99 #endif
 100
 101 %(member_init)s
 102
 103   loaded_ = true;
 104   return true;
 105 }
 106
 107 void %(class_name)s::CleanUp(bool unload) {
 108 #if defined(%(unique_prefix)s_DLOPEN)
 109   if (unload) {
 110     dlclose(library_);
 111     library_ = NULL;
 112   }
 113 #endif
 114   loaded_ = false;
 115 %(member_cleanup)s
 116 }
 117 """
 118
 119 IMPL_MEMBER_INIT_TEMPLATE = """
 120 #if defined(%(unique_prefix)s_DLOPEN)
 121   %(function_name)s =
 122       reinterpret_cast<typeof(this->%(function_name)s)>(
 123           dlsym(library_, "%(function_name)s"));
 124 #endif
 125 #if defined(%(unique_prefix)s_DT_NEEDED)
 126   %(function_name)s = &::%(function_name)s;
 127 #endif
 128   if (!%(function_name)s) {
 129     CleanUp(true);
 130     return false;
 131   }
 132 """
 133
 134 IMPL_MEMBER_CLEANUP_TEMPLATE = """  %(function_name)s = NULL;
 135 """
 136
 137 def main():
 138   parser = optparse.OptionParser()
 139   parser.add_option('--name')
 140   parser.add_option('--output-cc')
 141   parser.add_option('--output-h')
 142   parser.add_option('--header')
 143
 144   parser.add_option('--bundled-header')
 145   parser.add_option('--use-extern-c', action='store_true', default=False)
 146   parser.add_option('--link-directly', type=int, default=0)
 147
 148   options, args = parser.parse_args()
 149
 150   if not options.name:
 151     parser.error('Missing --name parameter')
 152   if not options.output_cc:
 153     parser.error('Missing --output-cc parameter')
 154   if not options.output_h:
 155     parser.error('Missing --output-h parameter')
 156   if not options.header:
 157     parser.error('Missing --header paramater')
 158   if not args:
 159     parser.error('No function names specified')
 160
 161   # Make sure we are always dealing with paths relative to source tree root
 162   # to avoid issues caused by different relative path roots.
 163   source_tree_root = os.path.abspath(
 164     os.path.join(os.path.dirname(__file__), '..', '..'))
 165   options.output_cc = os.path.relpath(options.output_cc, source_tree_root)
 166   options.output_h = os.path.relpath(options.output_h, source_tree_root)
 167
 168   # Create a unique prefix, e.g. for header guards.
 169   # Stick a known string at the beginning to ensure this doesn't begin
 170   # with an underscore, which is reserved for the C++ implementation.
 171   unique_prefix = ('LIBRARY_LOADER_' +
 172                    re.sub(r'[\W]', '_', options.output_h).upper())
 173
 174   member_decls = []
 175   member_init = []
 176   member_cleanup = []
 177   for fn in args:
 178     member_decls.append(HEADER_MEMBER_TEMPLATE % {
 179       'function_name': fn,
 180       'unique_prefix': unique_prefix
 181     })
 182     member_init.append(IMPL_MEMBER_INIT_TEMPLATE % {
 183       'function_name': fn,
 184       'unique_prefix': unique_prefix
 185     })
 186     member_cleanup.append(IMPL_MEMBER_CLEANUP_TEMPLATE % {
 187       'function_name': fn,
 188       'unique_prefix': unique_prefix
 189     })
 190
 191   header = options.header
 192   if options.link_directly == 0 and options.bundled_header:
 193     header = options.bundled_header
 194   wrapped_header_include = '#include %s\n' % header
 195
 196   # Some libraries (e.g. libpci) have headers that cannot be included
 197   # without extern "C", otherwise they cause the link to fail.
 198   # TODO(phajdan.jr): This is a workaround for broken headers. Remove it.
 199   if options.use_extern_c:
 200     wrapped_header_include = 'extern "C" {\n%s\n}\n' % wrapped_header_include
 201
 202   # It seems cleaner just to have a single #define here and #ifdefs in bunch
 203   # of places, rather than having a different set of templates, duplicating
 204   # or complicating more code.
 205   if options.link_directly == 0:
 206     wrapped_header_include += '#define %s_DLOPEN\n' % unique_prefix
 207   elif options.link_directly == 1:
 208     wrapped_header_include += '#define %s_DT_NEEDED\n' % unique_prefix
 209   else:
 210     parser.error('Invalid value for --link-directly. Should be 0 or 1.')
 211
 212   # Make it easier for people to find the code generator just in case.
 213   # Doing it this way is more maintainable, because it's going to work
 214   # even if file gets moved without updating the contents.
 215   generator_path = os.path.relpath(__file__, source_tree_root)
 216
 217   header_contents = HEADER_TEMPLATE % {
 218     'generator_path': generator_path,
 219     'unique_prefix': unique_prefix,
 220     'wrapped_header_include': wrapped_header_include,
 221     'class_name': options.name,
 222     'member_decls': ''.join(member_decls),
 223   }
 224
 225   impl_contents = IMPL_TEMPLATE % {
 226     'generator_path': generator_path,
 227     'unique_prefix': unique_prefix,
 228     'generated_header_name': options.output_h,
 229     'class_name': options.name,
 230     'member_init': ''.join(member_init),
 231     'member_cleanup': ''.join(member_cleanup),
 232   }
 233
 234   header_file = open(os.path.join(source_tree_root, options.output_h), 'w')
 235   try:
 236     header_file.write(header_contents)
 237   finally:
 238     header_file.close()
 239
 240   impl_file = open(os.path.join(source_tree_root, options.output_cc), 'w')
 241   try:
 242     impl_file.write(impl_contents)
 243   finally:
 244     impl_file.close()
 245
 246   return 0
 247
 248 if __name__ == '__main__':
 249   sys.exit(main())