如何将结构内容复制到另一个数组结构

Question

I have this c++ struct

struct PACKET
{
    BOOL isTCPPacket;
    BOOL isUDPPacket;
    BOOL isICMPPacket;
    BOOL isIGMPPacket;
    BOOL isARPPacket;
    BOOL isIPPacket;

    struct PETHER_HEADER
    {
        string  DestinationHost;
        string  SourceHost;
        struct PROTOCOL_TYPE
        {
            string  Name;
            WORD    Identifier;
        } ProtocolType;
    } EthernetHeader;
};

and i have

PACKET* Packet;
PACKET* Packets[6];

how can i copy contents of Packet into Packets[3] for example, knowing that the Packet contents will vary for each array in Packets[INDEX]

I have tried memcpy as

memcpy((void*)&Packets[i],(void*)&Packet,sizeof(PACKET));

with no luck

Answer 1

How about Packets[3] = Packet; ? This does exactly what you asked (copies the content of Packet , which is a pointer, into Packets[3] ).

If you want to copy the values, you can use assignment as well: *(Packets[3]) = *Packet; , assuming the pointers are valid. The compiler generated assignment operator for PACKET should work just fine.

I'd avoid memcpy in this case, since some of the members are std::string - you're bound to run into trouble.

Answer 2

Hope Packet contains valid object. Also Packets[i] point to allocated objects.

Do this: Packet[i] = Packet;

As string objects store pointers in their objects and can only be duplicated using assignment operator.

Answer 3

Ah! Just one thing:

PACKET* Packets[6];

is different than:

PACKET (*Packets)[6];

Former is an array of pointer (ie 6-pointers), but latter is a pointer to hold address-of a PACKET[6] array!

In either case, you must allocate memory for your Packet variable. memcpy or assignment will not work, unless some heap or stack memory is allocated.