SendARP not writing out to mac array - c++

Question

SendARP is not setting my mac array, so likewise when I try to convert the mac array to BYTE to convert it to human readable, it also gets random characters in it. also the memset does not seem to make MacAddr 0!
std::wstring GetMacAddress(IPAddr destip)
{
DWORD ret;
ULONG MacAddr[2] = {0}; //initialize instead of memset
ULONG PhyAddrLen = 6; /* default to length of six bytes */
unsigned char mac[6];
//memset(MacAddr, 0, sizeof(MacAddr)); //MacAddr doesn't get set to 0!
//Send an arp packet
ret = SendARP(destip , 0, MacAddr , &PhyAddrLen); //MacAddr stays
//Prepare the mac address
if (ret == NO_ERROR)
{
BYTE *bMacAddr = (BYTE *) & MacAddr;
if(PhyAddrLen)
{
for (int i = 0; i < (int) PhyAddrLen; i++)
{
mac[i] = (char)bMacAddr[i];
}
}
}
}
I have tried numerous ways to get MacAddr to get set by the SendARP function, but it doesn't seem to work and it doesn't return an error.

Answer 1

Casting to char does not convert to a textual representation. If you want to convert to a textual representation one option is to use std::wstringstream
#include <sstream>
#include <string>
#include <iomanip>
std::wstring GetMacAddress(IPAddr destip)
{
// ... snip ...
std::wstringstream out;
for (int i = 0; i < (int) PhyAddrLen; i++)
{
out << std::setw(2) << std::setfill(L'0') << bMacAddr[i];
}
return out.str();
}

Answer 2

Try this:
static const wchar_t *HexChars = L"0123456789ABCDEF";
std::wstring GetMacAddress(IPAddr destip)
{
DWORD ret;
BYTE MacAddr[sizeof(ULONG)*2];
ULONG PhyAddrLen = sizeof(MacAddr);
std::wstring MacAddrStr;
ret = SendARP(destip, 0, (PULONG)MacAddr, &PhyAddrLen);
if ((ret == NO_ERROR) && (PhyAddrLen != 0))
{
MacAddrStr.resize((PhyAddrLen * 2) + (PhyAddrLen-1));
MacAddrStr[0] = HexChars[(MacAddr[0] & 0xF0) >> 4];
MacAddrStr[1] = HexChars[MacAddr[0] & 0x0F];
for (ULONG i = 1, j = 2; i < PhyAddrLen; ++i, j += 3)
{
MacAddrStr[j+0] = L':';
MacAddrStr[j+1] = HexChars[(MacAddr[i] & 0xF0) >> 4];
MacAddrStr[j+2] = HexChars[MacAddr[i] & 0x0F];
}
}
return MacAddrStr;
}