在Python 2.4.3中使用软件包代替Pack_into

Question

以下代码用于模拟嵌入式设备上的Modbus接口。不幸的是，它有一个更老的Python（2.4.3）。该代码适用于2.7，但不适用于2.4.3，因为我使用的Python版本不支持struct.pack_into，只支持struct.pack。我可以就如何解决这个问题得到一些建议吗？我想我需要使用一个字符串也许并转换为一个字节缓冲区。这涉及非Python代码，所以我相信pickle不能用。

import socket 
import sys 
import array 
import struct 

def hexdump(src, length=16): 
    FILTER = ''.join([(len(repr(chr(x))) == 3) and chr(x) or '.' for x in range(256)]) 
    lines = [] 
    for c in xrange(0, len(src), length): 
     chars = src[c:c+length] 
     hex = ' '.join(["%02x" % ord(x) for x in chars]) 
     printable = ''.join(["%s" % ((ord(x) <= 127 and FILTER[ord(x)]) or '.') for x in chars]) 
     lines.append("%04x %-*s %s\n" % (c, length*3, hex, printable)) 
    return ''.join(lines) 

HOST = '192.168.1.187' 
PORT = 502 
s = socket.socket(socket.AF_INET,socket.SOCK_STREAM) 
s.bind((HOST,PORT)) 
s.listen(1) 
conn, addr = s.accept() 
data = [] 
datatran = array.array('B', '\x00' * 14) 
data = conn.recv(1024) 
print 'Connect by', addr 
while (data): 
    sys.stdout.write(hexdump(data)) 
    TransID , ProtoColID, PacketLength, UnitID, FC, StartAddress, RegisterCount = struct.unpack_from(">hhhBBhh", data) 
    print TransID, ProtoColID, PacketLength, UnitID 
    print FC, StartAddress, RegisterCount 
    struct.pack_into(">hhhBBBh", datatran, 0, TransID , ProtoColID, PacketLength+2, UnitID, FC, 2, 51) 
    conn.sendall(datatran) 
    data = conn.recv(1024) 

conn.close() 
s.close() 

感谢

Answer 1

随着比特位数的计算，应该可以使用pack和unpack代替：

import socket 
import sys 
import array 
import struct 

def hexdump(src, length=16): 
    FILTER = ''.join([(len(repr(chr(x))) == 3) and chr(x) or '.' for x in range(256)]) 
    lines = [] 
    for c in xrange(0, len(src), length): 
     chars = src[c:c+length] 
     hex = ' '.join(["%02x" % ord(x) for x in chars]) 
     printable = ''.join(["%s" % ((ord(x) <= 127 and FILTER[ord(x)]) or '.') for x in chars]) 
     lines.append("%04x %-*s %s\n" % (c, length*3, hex, printable)) 
    return ''.join(lines) 

HOST = '192.168.1.187' 
PORT = 502 
s = socket.socket(socket.AF_INET,socket.SOCK_STREAM) 
s.bind((HOST,PORT)) 
s.listen(1) 
conn, addr = s.accept() 
datatranStruct = '>hhhBBBh' 
datatranStructSize = struct.calcsize(datatranStruct) 
datatranFormat = '%s%dx' % (datatranStruct, 14 - datatranStructSize) 
recvStruct = '>hhhBBhh' 
recvStructSize = struct.calcsize(recvStruct) 
data = conn.recv(1024) 
print 'Connect by', addr 
while (data): 
    sys.stdout.write(hexdump(data)) 
    recvFormat = '%s%dx' % (recvStruct, len(data) - recvStructSize) 
    TransID , ProtoColID, PacketLength, UnitID, FC, StartAddress, RegisterCount = struct.unpack(recvFormat, data) 
    print TransID, ProtoColID, PacketLength, UnitID 
    print FC, StartAddress, RegisterCount 
    datatran = struct.pack(datatranFormat, TransID , ProtoColID, PacketLength+2, UnitID, FC, 2, 51) 
    conn.sendall(datatran) 
    data = conn.recv(1024) 

conn.close() 
s.close()