python计算CRC16等

'''
计算645数据域数据长度
@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

'''
对16进制字符串进行加0x33处理
@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后的数据
    return h

'''
对16进制字符串进行减0x33处理
@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','')
        ##如果余值为负数，去除'-'
        temper=temper.replace('-','')

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

        h=h+temper
    ##返回减0x33后的数据
    return h  

'''
计算16进制字符串的CRC16校验
@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')