如何从字符串中存储和检索char *？

Question

const char *RecBuffer, int *packetLength point to the data and the size

    string packet(RecBuffer,*packetLength);//store here
     ...do some stuff
    RecBuffer = packet.c_str();//retrieve it later

now what is happening is that my Recbuffer contains lots of floats, and ints packet together which I receive as a UDP packet. But when I store and retrieve it from the string it contains garbage.

Where am I going wrong?

Answer 1

I suspect the std::string instance named packet is being destructed, or modified, before RecBuffer is being used, meaning RecBuffer is a dangling pointer. You need to copy the content of packet rather than store a reference to an internal member of it. Instead of dynamically allocating a char* suggest using a std::vector<char> (as commented by Bartek) instead:

std::vector<char> RecBuffer(packet.begin(), packet.end());

Use &RecBuffer[0] (or RecBuffer.data() if available, introduced in c++11) to access the internal array.

Answer 2

Use memcpy:

RecBuffer[packet.size()]=0;
memcpy(RecBuffer, packet.c_str(), packet.size());