python計算CRC16等

python計算CRC16等

智能電能表數據通信協議DL/T 645 - 2007；本部分實現了該協議的部分功能。

'''
計算645數據域數據長度
@Source 2013-5-10 16:30
'''
def LenCal(s):
    L=''
    L=hex(len(s)/2).replace('0x','')
    if len(L)<=1:
        L=('00'+L)[-2:]

    return L

'''
對16進制字符串進行加0x33處理
@Source 2013-5-10 12:00
'''
def Add33(s):
    h=''
    for i in range(len(s)/2):
        temper=''
        temper=hex(int('33',16)+int(s[2*i:2*i+2],16)).replace('0x','')
        if len(temper)<=1:
            temper=('00'+temper).upper()[-2:]

        h=h+temper
    ##返回加0x33後的數據
    return h

'''
對16進制字符串進行減0x33處理
@Source 2013-5-10 12:10
'''
def Reduce33(s):
    h=''
    for i in range(len(s)/2):
        temper=''
        temper=hex(int(s[2*i:2*i+2],16)-int('33',16)).replace('0x','')
        ##如果餘值爲負數，去除'-'
        temper=temper.replace('-','')

        if len(temper)<=1:
            temper=('00'+temper).upper()[-2:]

        h=h+temper
    ##返回減0x33後的數據
    return h  

'''
計算16進制字符串的CRC16校驗
@Source 2013-5-10 11:00
'''
def CRC16(s):
    h='0'
    for i in range(len(s)/2):
        h=hex(int(h,16)+int(s[2*i:2*i+2],16))

    h=h.replace('0x','')
    if len(h)<=1:
        h='00'+h

    return h.upper()[-2:]

##68AAAAAAAAAAAA681300DF16
##print CRC16('68AAAAAAAAAAAA681300')
##print Add33('010101010101')
##print Reduce33('010101010101')
print LenCal('010101010101')