#!/usr/bin/python
# -*- coding:utf-8 -*-
'''測試struct模塊'''
from struct import *
import array

def fun_calcsize():
  print 'ci:',calcsize('ci')#計算格式占內(nèi)存大小
  print '@ci:',calcsize('@ci')
  print '=ci:',calcsize('=ci')
  print '>ci:',calcsize('>ci')
  print '<ci:',calcsize('<ci')
  print 'ic:',calcsize('ic')#計算格式占內(nèi)存大小
  print '@ic:',calcsize('@ic')
  print '=ic:',calcsize('=ic')
  print '>ic:',calcsize('>ic')
  print '<ic:',calcsize('<ic')

def fun_pack(Format,msg = [0x11223344,0x55667788]):
  result = pack(Format,*msg)
  print 'pack'.ljust(10),str(type(result)).ljust(20),
  for i in result:
    print hex(ord(i)), # ord把ASCII碼表中的字符轉(zhuǎn)換成對應(yīng)的整形,hex將數(shù)值轉(zhuǎn)化為十六進(jìn)制
  print

  result = unpack(Format,result)
  print 'unpack'.ljust(10),str(type(result)).ljust(20),
  for i in result:
    print hex(i),
  print 

def fun_pack_into(Format,msg = [0x11223344,0x55667788]):
  r = array.array('c',' '*8)#大小為8的可變緩沖區(qū),writable buffer
  result = pack_into(Format,r,0,*msg)
  print 'pack_into'.ljust(10),str(type(result)).ljust(20),
  for i in r.tostring():
    print hex(ord(i)),
  print

  result = unpack_from(Format,r,0)
  print 'pack_from'.ljust(10),str(type(result)).ljust(20),
  for i in result:
    print hex(i),
  print

def IsBig_Endian():
  '''判斷本機(jī)為大/小端'''
  a = 0x12345678
  result = pack('i',a)#此時result就是一個string字符串，字符串按字節(jié)同a的二進(jìn)制存儲內(nèi)容相同。
  if hex(ord(result[0])) == '0x78':
    print '本機(jī)為小端'
  else:
    print '本機(jī)為大端'

def test():
  a = '1234'
  for i in a:
    print '字符%s的二進(jìn)制:'%i,hex(ord(i))#字符對應(yīng)ascii碼表中對應(yīng)整數(shù)的十六進(jìn)制

  '''
  不用unpack()返回的數(shù)據(jù)也是可以使用pack()函數(shù)的,只要解包的字符串符合解包格式即可,
  pack()會按照解包格式將字符串在內(nèi)存中的二進(jìn)制重新解釋(說的感覺不太好...,見下例)
  '''
  print '大端:',hex(unpack('>i',a)[0])#因為pack返回的是元組,即使只有一個元素也是元組的形式
  print '小端:',hex(unpack('<i',a)[0])


if __name__ == "__main__":
  print '判斷本機(jī)是否為大小端?',
  IsBig_Endian()

  fun_calcsize()

  print '大端:'
  Format = ">ii"
  fun_pack(Format)
  fun_pack_into(Format)

  print '小端:'
  Format = "<ii"
  fun_pack(Format)
  fun_pack_into(Format)

  print 'test'
  test()
  '''
  result:
  判斷本機(jī)是否為大小端? 本機(jī)為小端
  ci: 8
  @ci: 8
  =ci: 5
  >ci: 5
  <ci: 5
  ic: 5
  @ic: 5
  =ic: 5
  >ic: 5
  <ic: 5
  大端:
  pack    <type 'str'>     0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88
  unpack   <type 'tuple'>    0x11223344 0x55667788
  pack_into <type 'NoneType'>  0x11 0x22 0x33 0x44 0x55 0x66 0x77 0x88
  pack_from <type 'tuple'>    0x11223344 0x55667788
  小端:
  pack    <type 'str'>     0x44 0x33 0x22 0x11 0x88 0x77 0x66 0x55
  unpack   <type 'tuple'>    0x11223344 0x55667788
  pack_into <type 'NoneType'>  0x44 0x33 0x22 0x11 0x88 0x77 0x66 0x55
  pack_from <type 'tuple'>    0x11223344 0x55667788
  test
  字符1的二進(jìn)制: 0x31
  字符2的二進(jìn)制: 0x32
  字符3的二進(jìn)制: 0x33
  字符4的二進(jìn)制: 0x34
  大端:0x31323334
  小端:0x34333231
  '''