Question

我在C＃中遇到的高级问题是制作描述机器人控制网络数据包（Ethercat）的数据结构的单个副本，然后使用该单个数据结构从数据包集合中提取数据。

当尝试使用来自累积分组的数据时出现问题，因为存在具有指定类型的强制转换或调用函数的数据结构的隐式复制。为了帮助解释目标，我编写了一个python程序，它可以完成我想要的操作并希望帮助确定是否可以在C＃中执行此操作。

C＃中的挑战是单个函数“get_vector”，它返回变量数值类型的同类集合。此类型在数据包结构中定义，并且可以在不定义重新定义数据结构的情况下使用python。

import struct

# description of the complete packet
class PACKET_STRUCTURE :

# given a field name and a list of packets, return a vector
# this is the function that seems impossible in C# because the type of what is returned changes
def get_vector(self, name, packet_list):
    # locate the packet definition by the name of the vector
    result = [x for x in self.packet_def if x.field_name == name]

    # without error checking, pos contains the location of the definition
    pos = result[0].position;

    # decode ALL the pacckets in the (encoded) packet list - returning a list of [time_sec, status, position
    # in C# this step is similar to  using Marshal.PtrToStructure to transform from byte[] to a struct
    decoded_packet_list = [struct.unpack(self.fmt_str, packet) for packet in packet_list];

    # from the list of decoded_packets, extract the desired field into its own list          
    vector = [decode[pos] for decode in decoded_packet_list]

    # in C# this is similar to:
    # var CS_vector = decode_packet_list.Select(item => item.field_name).ToArray();
    # so far in C# there is no duplication of the packet structure.
    # but after this point, assume I cast CS_vector to object and return it - 
    # to use the object, I've not figured out how to avoid casting it to some type of array
    # eg double[], int32[]                        
    return vector        

    def __init__(self):
        self.packet_def = list();
        self.fmt_str = "<";
        self.cnt = 0;

    # add description of single item to the structure
    def add(self, struct_def) :
        struct_def.position = len(self.packet_def);
        self.packet_def.append(struct_def);
        self.fmt_str += struct_def.type;                

    # create a simple packet based on a counter based on the defined structure
    def make_packet(self):
        vals = [self.cnt*10+x for x in range(0, len(self.packet_def))];
        self.cnt += 1;
        pk = apply(struct.pack, [self.fmt_str] + vals)
        # print len(pk), ["%c" % x for x in pk]
        return pk

    def get_names(self):
        return [packet_items.field_name for packet_items in self.packet_def];


# the description of a single field within the packet
class PACKET_ITEM  :
    def __init__(self, field_name, type):
        self.field_name = field_name
        self.type = type;
        # self.offset = 0;
        self.position = 0;


if __name__ == "__main__" :

    INT32 = "l";
    UINT16 = "H";
    FLOAT = "f";

    packet_def = PACKET_STRUCTURE();

    # create an example packet structure - which is arbituary and could be anything - it could even be read from a file
    # this definition is the ONLY defintion of the packet structure
    # changes here require NO changes elsewhere in the program
    packet_def.add(PACKET_ITEM("time_sec", FLOAT))
    packet_def.add(PACKET_ITEM ("status",UINT16))
    packet_def.add(PACKET_ITEM ("position",INT32))

    # create a list of packets
    pk_list = list()
    for cnt in range(0,10) :
        pk_list.append(packet_def.make_packet());

    ################################
    # get the vectors without replicating the structure
    # eg no int32[] position = (int32[])get_vector()

    name_list = packet_def.get_names();
    for name in name_list :
        vector = packet_def.get_vector(name, pk_list);
        print name, vector

Answer 1

答案是将数组存储在this

类型的集合中

从集合中返回元素的函数的返回类型也应该是动态的。

以下是我more complete answer的miss-understood question ，此人试图澄清这一点。

如何返回不同类型的数组？

1 个答案: