I'm new in C++. Recently I implemented Binary reader/writer for my multiplayer game. Now reading bytes looks like this:

static int32_t readInt32(std::vector<uint8_t>& msg, int *off)
{
    if ((*off) > msg.size()) return 0;
    int32_t result; int size = sizeof (result);
    memcpy(&result, msg.data() + (*off), size); (*off) += size; 
    return result;
}

And writing byte's looks like this:

static void writeInt32(std::vector<uint8_t>* msg, int32_t value)
{
    uint8_t const * array = reinterpret_cast<uint8_t const *>(&value);

    for (std::size_t i = 0; i != sizeof(value); ++i)
    {
        (*msg).push_back(array[i]);
    }
}

How can I improve my Binary reader/writer?