我有一个读取长八位字符串的解析器，我希望它根据解析细节打印出较小的字符串。它读入一个hexstring，如下所示
字符串的格式如下：
01046574683001000004677265300000000266010000
十六进制中包含的接口格式如下：
version:length_of_name:name:op_status:priority:reserved_byte
==
01:04:65746830:01:00:00
==（从十六进制转换时）
01:04:eth0:01:00:00
^这是字符串的1段，代表eth0（我插入了：使其更容易阅读）。但是，在那一刻，我的代码返回一个空白列表，我不知道为什么。请有人帮帮我！
def octetChop(long_hexstring, from_ssh_):
startpoint_of_interface_def=0
# As of 14/8/13 , the network operator has not been implemented
network_operator_implemented=False
version_has_been_read = False
position_of_interface=0
chopped_octet_list = []
#This while loop moves through the string of the interface, based on the full length of the container
try:
while startpoint_of_interface_def < len(long_hexstring):
if version_has_been_read == True:
pass
else:
if startpoint_of_interface_def == 0:
startpoint_of_interface_def = startpoint_of_interface_def + 2
version_has_been_read = True
endpoint_of_interface_def = startpoint_of_interface_def+2
length_of_interface_name = long_hexstring[startpoint_of_interface_def:endpoint_of_interface_def]
length_of_interface_name_in_bytes = int(length_of_interface_name) * 2 #multiply by 2 because its calculating bytes
end_of_interface_name_point = endpoint_of_interface_def + length_of_interface_name_in_bytes
hex_name = long_hexstring[endpoint_of_interface_def:end_of_interface_name_point]
text_name = hex_name.decode("hex")
print "the text_name is " + text_name
operational_status_hex = long_hexstring[end_of_interface_name_point:end_of_interface_name_point+2]
startpoint_of_priority = end_of_interface_name_point+2
priority_hex = long_hexstring[startpoint_of_priority:startpoint_of_priority+2]
#Skip the reserved byte
network_operator_length_startpoint = startpoint_of_priority+4
single_interface_string = long_hexstring[startpoint_of_interface_def:startpoint_of_priority+4]
print single_interface_string + " is chopped from the octet string"# - keep for possible debugging
startpoint_of_interface_def = startpoint_of_priority+4
if network_operator_implemented == True:
network_operator_length = long_hexstring[network_operator_length_startpoint:network_operator_length_startpoint+2]
network_operator_length = int(network_operator_length) * 2
network_operator_start_point = network_operator_length_startpoint+2
network_operator_end_point = network_operator_start_point + network_operator_length
network_operator = long_hexstring[network_operator_start_point:network_operator_end_point]
#
single_interface_string = long_hexstring[startpoint_of_interface_def:network_operator_end_point]
#set the next startpoint if there is one
startpoint_of_interface_def = network_operator_end_point+1
else:
self.network_operator = None
print single_interface_string + " is chopped from the octet string"# - keep for possible debugging
#This is where each individual interface is stored, in a list for comparison.
chopped_octet_list.append(single_interface_string)
finally:
return chopped_octet_list
答案 0 :(得分：1)
我希望我帮到你。你有一个包含各种接口定义的十六进制字符串。在每个接口定义中，第二个八位字节描述接口名称的长度。
假设字符串包含接口eth0和eth01，看起来像这样（eth0的长度为4，eth01的长度为5）：
01046574683001000001056574683031010000
然后你可以像这样分开它：
def splitIt (s):
tokens = []
while s:
length = int (s [2:4], 16) * 2 + 10 #name length * 2 + 10 digits for rest
tokens.append (s [:length] )
s = s [length:]
return tokens
这会产生：
['010465746830010000', '01056574683031010000']
答案 1 :(得分：1)
您的代码返回空白列表的原因如下：在此行中：
else:
self.network_operator = None
self未定义，因此您获得 NameError 异常。这意味着try直接跳转到finally子句而不执行您所在的部分：
chopped_octet_list.append(single_interface_string)
结果列表仍然是空的。无论如何，代码对于这样的任务来说过于复杂，我会遵循其他一个答案。
答案 2 :(得分：0)
要添加到Hyperboreus的答案，这是分割界面字符串时解析界面字符串的简单方法：
def parse(s):
version = int(s[:2], 16)
name_len = int(s[2:4], 16)
name_end = 4 + name_len * 2
name = s[4:name_end].decode('hex')
op_status = int(s[name_end:name_end+2], 16)
priority = int(s[name_end+2:name_end+4], 16)
reserved = s[name_end+4:name_end+6]
return version, name_len, name, op_status, priority, reserved
这是输出：
>>> parse('010465746830010000')
(1, 4, 'eth0', 1, 0, '00')
答案 3 :(得分：0)
检查以下内容是否有帮助。调用下面的parse方法并将字符串流传递给它，然后迭代获取卡片信息（希望我能帮到你:)）parse将返回所需信息的元组。
>>> def getbytes(hs):
"""Returns a generator of bytes from a hex string"""
return (int(hs[i:i+2],16) for i in range(0,len(hs)-1,2))
>>> def get_single_card_info(g):
"""Fetches a single card info from a byte generator"""
v = g.next()
l = g.next()
name = "".join(chr(x) for x in map(lambda y: y.next(),[g]*l))
return (str(v),name,g.next(),g.next(),g.next())
>>> def parse(hs):
"""Parses a hex string stream and returns a generator of card infos"""
bs = getbytes(hs)
while True:
yield get_single_card_info(bs)
>>> c = 1
>>> for card in parse("01046574683001000001056574683031010000"):
print "Card:{0} -> Version:{1}, Id:{2}, Op_stat:{3}, priority:{4}, reserved:{5} bytes".format(c,*card)
c = c + 1
Card:1 -> Version:1, Id:eth0, Op_stat:1, priority:0, reserved:0 bytes
Card:2 -> Version:1, Id:eth01, Op_stat:1, priority:0, reserved:0 bytes
答案 4 :(得分：0)
Pyparsing包含一个内置表达式，用于解析计数的元素数组，因此这将很好地处理您的“名称”字段。这是整个解析器：
from pyparsing import Word,hexnums,countedArray
# read in 2 hex digits, convert to integer at parse time
octet = Word(hexnums,exact=2).setParseAction(lambda t:int(t[0],16))
# read in a counted array of octets, convert to string
nameExpr = countedArray(octet, intExpr=octet)
nameExpr.setParseAction(lambda t: ''.join(map(chr,t[0])))
# define record expression, with named results
recordExpr = (octet('version') + nameExpr('name') + octet('op_status') +
octet('priority') #+ octet('reserved'))
解析您的样本：
sample = "01046574683001000004677265300000000266010000"
for rec in recordExpr.searchString(sample):
print rec.dump()
给出：
[1, 'eth0', 1, 0]
- name: eth0
- op_status: 1
- priority: 0
- version: 1
[0, 'gre0', 0, 0]
- name: gre0
- op_status: 0
- priority: 0
- version: 0
[0, 'f\x01', 0, 0]
- name: f
- op_status: 0
- priority: 0
- version: 0
dump（）方法显示可用于访问单独解析位的结果名称，如rec.name或rec.version。
（我注释掉了保留字节，否则第二个条目将无法正确解析。另外，第三个条目包含一个带有\ x01字节的名称。）