How do I properly convert a UTF-8 encoded char array to a Go string when using a C-library in Go?

Question

I'm trying to use a C library in Go. The C.PrlFoundVmInfo_GetName function writes a UTF-8 encoded string into name with length nBufSize.

// PRL_CHAR sName[1024];
var sName [1024]C.PRL_CHAR
// PRL_UINT32 nBufSize = sizeof(sName);
var nBufSize C.PRL_UINT32 = C.PRL_UINT32(unsafe.Sizeof(sName))
ret = C.PrlFoundVmInfo_GetName(hFoundVmInfo, (*C.PRL_CHAR)(unsafe.Pointer(&sName)), &nBufSize)
// printf("VM name: %s\n", sName);
var gName string = C.GoString((*C.char)(unsafe.Pointer(&sName)))
fmt.Printf("VM %d name: \"%s\"\n", nBufSize, gName)

What is the proper way to declare name (and nBufSize) and how do i convert name to a Go string? The above code dosen't work as I expect. It prints:

VM 1024 name: ""
... 

C API Documentation, extract

PrlFoundVmInfo_GetName - Parameters

PRL_RESULT PrlFoundVmInfo_GetName(
  PRL_HANDLE handle, 
  PRL_STR sName, 
  PRL_UINT32_PTR pnNameBufLength
);

• handle - A handle of type PHT_FOUND_VM_INFO identifying the container.
• sName - [out] A pointer to a buffer that receives the name. Pass a null pointer to determine the required buffer size.
• pnNameBufLength - [in] The size of the buffer used to receive the output data (in bytes). [out] The required buffer size if the buffer parameter contains a null pointer or if the specified buffer size is not large enough.

The full documentation is available at C API Documentation - PrlFoundVmInfo_GetName

Answer 1

This was the solution, create a byte array and make sName point to it. When it has been used use C.GoStringN to convert the content to a Go string.

var buf = make([]byte, 1024)
var sName C.PRL_STR = (C.PRL_STR)(unsafe.Pointer(&buf))
var nBufSize C.PRL_UINT32 = 1024
ret = C.PrlFoundVmInfo_GetName(*hFoundVmInfo, sName, &nBufSize)
gName := C.GoStringN((*_Ctype_char)(unsafe.Pointer(sName)), C.int(nBufSize))
fmt.Printf("VM %d name: \"%s\"\n", nBufSize, gName)

Answer 2

Command cgo

Go references to C

A few special functions convert between Go and C types by making copies of the data. In pseudo-Go definitions:

// C string, length to Go string
func C.GoStringN(*C.char, C.int) string

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