#!/usr/bin/env python
#
# Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
#
# Use of this source code is governed by a BSD-style license
# that can be found in the LICENSE file in the root of the source
# tree. An additional intellectual property rights grant can be found
# in the file PATENTS.  All contributing project authors may
# be found in the AUTHORS file in the root of the source tree.

"""This script is a tool to generate special header files from input
C source files.

It first assembles the input source files to generate intermediate assembly
files (*.s). Then it parses the .s files and finds declarations of variables
whose names start with the string specified as the third argument in the
command-line, translates the variable names and values into constant defines
and writes them into header files.
"""

import os
import re
import subprocess
import sys
from optparse import OptionParser

def main(argv):
  parser = OptionParser()
  usage = 'Usage: %prog [options] input_filename'
  parser.set_usage(usage)
  parser.add_option('--compiler', default = 'gcc', help = 'compiler name')
  parser.add_option('--options', default = '-S', help = 'compiler options')
  parser.add_option('--pattern', default = 'offset_', help = 'A match pattern'
                    ' used for searching the relevant constants.')
  parser.add_option('--dir', default = '.', help = 'output directory')
  (options, args) = parser.parse_args()

  # Generate complete intermediate and header file names.
  input_filename = args[0]
  output_root = (options.dir + '/' +
      os.path.splitext(os.path.basename(input_filename))[0])
  interim_filename = output_root + '.s'
  out_filename = output_root + '.h'

  # Set the shell command with the compiler and options inputs.
  compiler_command = (options.compiler + " " + options.options + " " +
      input_filename + " -o " + interim_filename)

  # Run the shell command and generate the intermediate file.
  subprocess.check_call(compiler_command, shell=True)

  interim_file = open(interim_filename)  # The intermediate file.
  out_file = open(out_filename, 'w')  # The output header file.

  # Generate the output header file.
  while True:
    line = interim_file.readline()
    if not line: break
    if line.startswith(options.pattern):
      # Find name of the next constant and write to the output file.
      const_name = re.sub(r'^_', '', line.split(':')[0])
      out_file.write('#define %s ' % const_name)

      # Find value of the constant we just found and write to the output file.
      line = interim_file.readline()
      const_value = filter(str.isdigit, line.split(' ')[0])
      if const_value != '':
        out_file.write('%s\n' % const_value)

  interim_file.close()
  out_file.close()

if __name__ == "__main__":
  main(sys.argv[1:])