# -*- coding: utf-8 -*-
import Tkinter
import tkFileDialog
WIDTH = 16
TOPBIT = (1 << (WIDTH - 1))
crcTable = {}
class FindLocation(object):
  def __init__(self):
    #创建主窗口，用于容纳其它组件
    self.root = Tkinter.Tk()
    #给主窗口设置标题内容
    self.root.title("获取bin文件的crc校验码")
    #创建一个输入框，并设置尺寸
    self.default_value = Tkinter.StringVar()
    self.default_value.set('请输入bin文件全路径')
    self.ip_input = Tkinter.Entry(self.root,width=30,textvariable = self.default_value)
    #创建一个回显列表
    self.display_info = Tkinter.Listbox(self.root,width=50)
    #创建一个搜索文件的按钮
    self.getPath_button = Tkinter.Button(self.root,command = self.getPath,text = "获取文件")
    #创建一个查询结果的按钮
    self.result_button = Tkinter.Button(self.root,command = self.crcFast,text = "获取校验码")
  def gui_arrang(self):
    self.ip_input.pack()
    self.display_info.pack()
    self.getPath_button.pack()
    self.result_button.pack()
  def getPath(self):
    self.fname = tkFileDialog.askopenfilename()
    self.default_value.set(self.fname)
  def crcInit(self):
    SHIFT = WIDTH - 8
    for step in range(0,256):
      remainder = step << SHIFT
      for bit in range(8,0,-1):
        if remainder & TOPBIT:
          remainder = ((remainder << 1) & 0xFFFF) ^0x1021
        else:
          remainder = remainder <<1
      crcTable[step]=remainder
      #print("%x"%remainder)
  def crc16(self,cCRC,szData,rLen):
    for len in range(rLen):
      data = (cCRC  8) ^ ord(szData[len])
      cCRC = crcTable[data] ^ (cCRC << 8) & 0xFFFF
    return cCRC
  def crcFast(self):
    filePath = self.ip_input.get()
    tLen = 0
    rLen = 0
    szData = 0
    cCRC = 0
    self.crcInit()
    fp = open(filePath,'rb')
    fp.seek(0,2)
    iFileLen = fp.tell()
    fp.seek(0,0)
    while True:
      if (iFileLen - tLen) < 8192:
        rLen = iFileLen - tLen
      else:
        rLen = 8192
      szData = fp.read(rLen)
      cCRC = self.crc16(cCRC,szData,rLen)
      tLen += rLen
      if tLen >= iFileLen:
        break
    print "crc is %x\n" % cCRC
    fp.close()
    self.display_info.insert(0,"%x"%cCRC)
    self.display_info.insert(0,"this bin crc is :")  
def main():
  #初始化对象
  FL = FindLocation()
  #进行布局
  FL.gui_arrang()
  #主程序执行
  Tkinter.mainloop()
if __name__ == '__main__':
  main()