GetAdapterAddresses function with NEW instead of MALLOC

Question

I would use the GetAdaptersAddresses() function of windows to get some informations about the adapters of the computer. In this MSDN page there is a big example of how to use it. But I'm using C++ so I would stick with the new keyword and not malloc (C native). How can I rewrite the parts that uses malloc with new?

EDIT 1

std::vector<PIP_ADAPTER_ADDRESSES> buffer;
ULONG outBufferLen = 0;

if (GetAdaptersAddresses(AF_INET, GAA_FLAG_INCLUDE_PREFIX, NULL, NULL, &outBufferLen) == ERROR_BUFFER_OVERFLOW)
{
    buffer.resize(outBufferLen);

    PIP_ADAPTER_ADDRESSES addresses = reinterpret_cast<PIP_ADAPTER_ADDRESSES>(buffer.data());

    if (GetAdaptersAddresses(AF_INET, GAA_FLAG_INCLUDE_PREFIX, NULL, addresses, &outBufferLen) == NO_ERROR)
    {
        for (; addresses != NULL; addresses = addresses->Next)
        {
            ...
        }
    }
}

EDIT 2

ULONG outBufferLen = 0;

if (GetAdaptersAddresses(AF_INET, GAA_FLAG_INCLUDE_PREFIX, NULL, NULL, &outBufferLen) == ERROR_BUFFER_OVERFLOW)
{
    PIP_ADAPTER_ADDRESSES p = new IP_ADAPTER_ADDRESSES[outBufferLen / sizeof(IP_ADAPTER_ADDRESSES)];

    if (GetAdaptersAddresses(AF_INET, GAA_FLAG_INCLUDE_PREFIX, NULL, p, &outBufferLen) == NO_ERROR)
    {
        ....
    }
}

The easier solution is to use a `std::vector`, and resize that. — MSalters, Nov 25 '11 at 15:06
@MSalters could I do something like what I wrote in the EDIT 2? — Stefano, Nov 25 '11 at 15:44
Well, that rounds down instead of up. Unless `outBufferLen` is a mulitple of `sizeof(IP_ADAPTER_ADDRESSES)`, you've got a buffer overflow. Also, please note that you won't actually get a `IP_ADAPTER_ADDRESSES[]` from `GetAdaptersAddresses`. — MSalters, Nov 25 '11 at 16:00
@MSalters ok so, could you please make me an example of how should I implement vector to get the code working? — Stefano, Nov 25 '11 at 16:15

score 1 · Answer 1 · answered Nov 24 '11 at 15:39

1

You can't directly rewrite that code using new/delete, because introducing new would induce risk of exceptions and that code is not exceptions safe. A dumb way would be to call ::operator new( size_t, const nothrow_t&) instead of malloc() - but this is really ugly.

The real solution is to rewrite all code using proper C++ classes. std::vector would be a good fit for pAddresses and you'd need a RAII wrapper for lpMsgBuf.

answered Nov 24 '11 at 15:39

sharptooth

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Using `nothrow new` is ugly enough to not be recommended IMHO. – Alok Save Nov 24 '11 at 15:40
@Als: That often happens to dumb decisions. – sharptooth Nov 24 '11 at 15:43
@sharptooth I'm missing what is a RAII wrapper. Can you explain me? – Stefano Nov 24 '11 at 15:44
@sharptooth Ok, but how can I use a function that accepts raw pointers with std::vector? – Stefano Nov 24 '11 at 15:48
@Stefano: Just resize the vector to hold enough data and get a raw pointer to its first element - http://stackoverflow.com/q/1339470/57428 – sharptooth Nov 25 '11 at 06:42
@sharptooth using vectors means that I cannot eventually use iterators to cycle throught all the adapters, is this right? – Stefano Nov 25 '11 at 13:50
@Stefano: I see no reason why you can't use iterators. – sharptooth Nov 25 '11 at 13:59
@sharptooth I've edited my question with the actual code that I have. GetAdaptersAddresses returns a linked list, using vectors means that with that code I will create a vector of outBufferLen elements. – Stefano Nov 25 '11 at 14:10

GetAdapterAddresses function with NEW instead of MALLOC

1 Answers1