From []byte to char*

Question

I want to wrap a C function that takes a char* pointing to (the first element of) a non-empty buffer of bytes. I'm trying to wrap that in a Go function using CGo so that I can pass it a []byte, but I don't know how to do the conversion. A simplified version of the C function's signature is

void foo(char const *buf, size_t n);

I tried passing a pointer to the first byte in the slice with

C.foo(&b[0], C.size_t(n))

That doesn't compile, though:

cannot use &b[0] (type *byte) as type *_Ctype_char in function argument

So what's the correct procedure here? The go-wiki only describes the reverse situation.

Answer 1

Ok, that turned out to be much easier than I thought:

(*C.char)(unsafe.Pointer(&b[0]))

does the trick. (Found this at golang-nuts.)