# coding=utf-8
import time

from codeobject import CodeObject


class Parser(object):
 def __init__(self, file_path):
 self._pyc_file = open(file_path, 'r')
 self.magic_number = None
 self.modify_time = None
 self.code_object = None

 self._string_table = []

 def parse(self):
 self.magic_number = "0x{:08x}".format(self._read_int())
 # python2.7 的魔数是 0x0a0df303
 assert self.magic_number == "0x0a0df303"

 self.modify_time = time.ctime(self._read_int())

 # 根据规定, 后面的一个字符一定是 c, 表示代码段
 assert self._pyc_file.read(1) == 'c'

 return self._get_code_object()

 def _get_code_object(self):
 code_object = CodeObject()

 code_object.arg_count = self._read_int()
 code_object.nlocals = self._read_int()
 code_object.stack_size = self._read_int()
 code_object.flag = self._read_int()
 code_object.byte_codes = self._get_byte_code()
 code_object.consts = self._get_consts()
 code_object.names = self._get_names()
 code_object.var_names = self._get_var_names()
 code_object.free_vars = self._get_free_vars()
 code_object.cell_vars = self._get_var_names()
 code_object.file_name = self._get_file_name()
 code_object.co_name = self._get_name()
 code_object.line_no = self._read_int()
 code_object.lnotable = self._get_no_table()

 return code_object

 def _read_int(self):
 data = bytearray(self._read(4))
 m = data[0]
 m |= data[1] << 8
 m |= data[2] << 16
 m |= data[3] << 24
 return m

 def _get_byte_code(self):
 assert self._read(1) == 's'
 return self._get_string()

 def _get_consts(self):
 if self._read(1) == '(':
 return self._get_tuple()
 self._read_back(1)
 return []

 def _get_names(self):
 if self._read(1) == '(':
 return self._get_tuple()
 self._read_back(1)
 return []

 def _get_var_names(self):
 if self._read(1) == '(':
 return self._get_tuple()
 self._read_back(1)
 return []

 def _get_free_vars(self):
 if self._read(1) == '(':
 return self._get_tuple()
 self._read_back(1)
 return []

 def _get_cell_vars(self):
 if self._read(1) == '(':
 return self._get_tuple()
 self._read_back(1)
 return []

 def _get_file_name(self):
 return self._get_name()

 def _get_no_table(self):
 ch = self._read(1)
 if ch not in ['s', 't']:
 return None

 return self._get_string()

 def _get_tuple(self):
 length = self._read_int()
 l = []
 for _ in range(length):
 obj_type = self._read(1)

 if obj_type == 'c':
 l.append(self._get_code_object())
 elif obj_type == 'i':
 l.append(self._read_int())
 elif obj_type == 'N':
 l.append(None)
 elif obj_type == 't':
 s = self._get_string()
 l.append(s)
 self._string_table.append(s)
 elif obj_type == 's':
 l.append(self._get_string())
 elif obj_type == 'R':
 index = self._read_int()
 l.append(self._string_table[index])
 else:
 print("Parser Failed. Unknown Type :", obj_type)
 return l

 def _get_name(self):
 ch = self._read(1)

 if ch == 's':
 return self._get_string()
 elif ch == 't':
 s = self._get_string()
 self._string_table.append(s)
 return s
 elif ch == 'R':
 index = self._read_int()
 return self._string_table[index]
 else:
 return None

 def _get_string(self):
 length = self._read_int()
 data = self._read(length)
 return data

 def _read(self, n):
 return self._pyc_file.read(n)

 def _read_back(self, n):
 """
 将当前读取的游标回退n个字节
 :param n: 回退的个数
 :return:
 """
 # 第二个参数 1 代表从当前位置当做起始点
 self._pyc_file.seek(-n, 1)

 def close(self):
 self._pyc_file.close()


if __name__ == '__main__':
 pyc_file_path = 'test/simple_test.pyc'
 parser = Parser(pyc_file_path)
 c = parser.parse()
 parser.close()
 print(parser.magic_number, parser.modify_time)