python中将多个参数打包为字节流的第二种方法

该方法使用ctypes模块中的memmove函数将结构体数据对应的内存移动到缓冲区对应的位置，完成打包过程，相比上种方法较为麻烦。

代码如下：

# -*- coding: utf-8 -*-#

#-------------------------------------------------------------------------------
# Name:         以结构体形式直接打包参数包
# Description:  整个包大小为64Byte，包头为0X”FAA5 FBB5 FCC4 FDD5”，包尾为0X”5FA5 5FB5 5FC5 5FD5 ”，中间不足部分补0
#               发送的参数定义（有符号整型数字）
#               cmdType = 1         # 1 Byte
#               sigType = 2         # 1 Byte
#               startFreq = 40      # 4 Byte
#               stopFreq = 400      # 4 Byte
#               deltFreq = 10       # 4 Byte
#               pulseNum = 37       # 2 Byte
#               pulseWidth = 0      # 4 Byte
#               PRF = 25000000      # 4 Byte
#               receiverFreq = 1000 # 4 Byte
# Author:       lgk
# Date:         2018/6/14
#-------------------------------------------------------------------------------

import struct
import ctypes
import binascii
import re

#字节顺序定义
byteOrders = {'Native order':'@',
              'Native standard':'=',
              'Little-endian':'<',
              'Big-endian':'>',
              'Network order':'!'}

byteOrder = 'Little-endian'

fmt_head = fmt_tail = struct.Struct(byteOrders[byteOrder] + "8B")
fmt_body = struct.Struct(byteOrders[byteOrder] + "2b3i1h3i")
bufferLength = 64

def getSendInfo(info):
    p = re.compile('.{1,2}') #匹配任意字符1-2次
    t = ' '.join(p.findall(info.upper()))
    return t

#定义本地形式结构体
class CMDParaNative(ctypes.Structure):
    _pack_ = 1
    _fields_ = [
        ('cmdType', ctypes.c_int8),
        ('sigType', ctypes.c_int8),
        ('startFreq', ctypes.c_int32),
        ('stopFreq', ctypes.c_int32),
        ('deltFreq', ctypes.c_int32),
        ('pulseNum', ctypes.c_int16),
        ('pulseWidth', ctypes.c_int32),
        ('PRF', ctypes.c_int32),
        ('receiverFreq', ctypes.c_int32)
    ]

#定义大端形式结构体
class CMDParaBigEndian(ctypes.BigEndianStructure):
    _pack_ = 1
    _fields_ = [
        ('cmdType', ctypes.c_int8),
        ('sigType', ctypes.c_int8),
        ('startFreq', ctypes.c_int32),
        ('stopFreq', ctypes.c_int32),
        ('deltFreq', ctypes.c_int32),
        ('pulseNum', ctypes.c_int16),
        ('pulseWidth', ctypes.c_int32),
        ('PRF', ctypes.c_int32),
        ('receiverFreq', ctypes.c_int32)
    ]

#定义小端形式结构体
class CMDParaLittleEndian(ctypes.LittleEndianStructure):
    _pack_ = 1
    _fields_ = [
        ('cmdType', ctypes.c_int8),
        ('sigType', ctypes.c_int8),
        ('startFreq', ctypes.c_int32),
        ('stopFreq', ctypes.c_int32),
        ('deltFreq', ctypes.c_int32),
        ('pulseNum', ctypes.c_int16),
        ('pulseWidth', ctypes.c_int32),
        ('PRF', ctypes.c_int32),
        ('receiverFreq', ctypes.c_int32)
    ]

if byteOrder == 'Little-endian':
    para = CMDParaLittleEndian(1, 2, 40, 400, 10, 37, 0, 25000000, 1000)
elif byteOrder == 'Big-endian':
    para = CMDParaBigEndian(1, 2, 40, 400, 10, 37, 0, 25000000, 1000)
else:
    para = CMDParaNative(1, 2, 40, 400, 10, 37, 0, 25000000, 1000)

headInfo = [0xFA, 0xA5, 0xFB, 0xB5, 0xFC, 0xC5, 0xFD, 0xD5]
tailInfo = [0x5F, 0xA5, 0x5F, 0xB5, 0x5F, 0xC5, 0x5F, 0xD5]

sendBuffer = ctypes.create_string_buffer(bufferLength) #创建发送缓冲区

#将待发送的参数打包到缓冲区
fmt_head.pack_into(sendBuffer, 0, *headInfo)
fmt_tail.pack_into(sendBuffer, bufferLength-fmt_tail.size, *tailInfo)
#将结构体数据对应的内存移动到缓冲区对应的位置
ctypes.memmove(ctypes.addressof(sendBuffer)+fmt_head.size, ctypes.byref(para), ctypes.sizeof(para))
# ctypes.memmove(ctypes.byref(sendBuffer, fmt_head.size), ctypes.byref(para), ctypes.sizeof(para)) #与上面一行等价

#打印出字节流的16进制信息(byteOrder = 'Little-endian')
#FA A5 FB B5 FC C5 FD D5 01 02 28 00 00 00 90 01 00 00 0A 00 00 00 25 00 00 00 00 00 40 78 7D 01 E8 03 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 5F A5 5F B5 5F C5 5F D5
print(getSendInfo(binascii.hexlify(sendBuffer)))