Converting managed Byte array to unmanaged string

Question

I am trying to convert a managed byte array to std::string in my C++/CLI wrapper; however, I am seeing some corrupt memory in the heap later on. Just wanted to check if I am doing the conversion right. Below is my method is CLI:

string ByteArrayToStr(array<Byte>^ byteArray)
{
    int size = byteArray.Length;
    IntPtr pnt = Marshal::AllocHGlobal(size + 1);
    char* chararray = (char*)pnt.ToPointer();
    try
    {
        Marshal::Copy(byteArray, 0, pnt, size);
        *(chararray + size) = 0;
        return string(chararray);
    }
    finally
    {
        Marshal::FreeHGlobal(pnt);
    }
}

Does anything seem wrong in above code?

I don't see any problems in that code. I would change the second line in the try block to use chararray[site], but that would be just more readable, it wouldn't change what the code does. — svick
– svick, Commented Mar 14, 2012 at 0:42
You don't typically need a lot of help from C++/CLI code to corrupt the heap. This isn't it. — Hans Passant
– Hans Passant, Commented Mar 14, 2012 at 0:43
Thank you for the validation. There must be some bug my code elsewhere; I shall take a look. Thank you, Raj. — user392005
– user392005, Commented Mar 14, 2012 at 3:29

alexisdm · Accepted Answer · 2012-03-14 14:29:44Z

3

You are doing an unnecessary explicit copy and playing with a manual memory allocation.

You could just pass the raw pinned pointer to std::string constructor:

string ByteArrayToStr(array<Byte>^ byteArray)
{
    pin_ptr<unsigned char> temp = &byteArray[0];
    return string(reinterpret_cast<char*>(temp), byteArray->Length);
}

edited Mar 14, 2012 at 14:29

answered Mar 14, 2012 at 3:00

alexisdm

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3 Comments

user392005 Over a year ago

That's definitely much simpler. I believe the 'str' in the second line was a typo though. Thank you.

user392005 Over a year ago

BTW, pin_ptr goes out of scope when the function returns. Does std::string constructor do the copying of managed data pointed to by 'temp' into unmanaged data so that the returned string can be used later?

alexisdm Over a year ago

@user392005 Yes, std::string copies the data in its own internal buffer.

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