RubyInline C experimentation

rb_c_xor_file_contents_extension.rb

# run with  Piece.xor_files 'output_filepath', ['infilepath1','infilepath2']

require 'inline'
Class Piece
  inline do |builder|
    builder.include '<stdlib.h>'
    builder.include '<stdio.h>'
    builder.c_singleton <<-C_CODE
    /*
    rb_input_paths_array should be a ruby array of strings, 
    where the files referenced by path are of equal size
    result_path should be the path of the desired result file
    */
    static int xor_files(char* result_path, VALUE rb_input_paths){
      int counter;

      //set up files for reading
      int input_files_length = RARRAY(rb_input_paths)->len;
      FILE *input_files[input_files_length];
      for(counter=0; counter < input_files_length; counter++){
        char* path = RSTRING(rb_ary_shift(rb_input_paths))->ptr;
        input_files[counter] = fopen(path, "rb");
      }

      //read bytes and xor to output
      int byte = 0;
      FILE* output = fopen(result_path, "wb");
      while ((byte = fgetc(input_files[0])) != EOF) {
        for (counter = 1; counter < input_files_length; counter++) { 
          byte ^= fgetc(input_files[counter]);
        }
        fputc(byte, output);
      }

      //clean up
      for(counter=0; counter<input_files_length; counter++) { fclose(input_files[counter]); }
      fclose(output);
      return 0;
    }
    C_CODE
  end
end

rb_string_array_arg_example.rb

# demonstrate ruby string -> C char[] param passing, and an array
# in irb run with
# require 'piece'; Piece.print_strings('foo', ['a','b'])
# hi
# foo
# a
# b

require 'inline'
Class Piece
    inline do |builder|
      builder.c_singleton <<-C_CODE
      static int print_strings(VALUE rb_result_file_path, VALUE rb_input_file_paths){
        printf("hi\\n");
        printf("%s\\n", RSTRING(rb_result_file_path)->ptr);
        int input_files = RARRAY(rb_input_file_paths)->len;
        int counter;
        for(counter=0; counter < input_files; counter++){
          printf("%s\\n", RSTRING(rb_ary_shift(rb_input_file_paths))->ptr);
        }
        return 0;
      }
      C_CODE
    end
end