How to convert *_Ctype_char to *_Ctype_uchar

Question

I'm using cgo to call a function in a dynamic library whose signature looks like this:

int decompress(int, const uint8_t *, size_t, uint8_t *, size_t);

Here is my go code:

// #include statements here
import "C"
import (
    "unsafe"
)

func Decompress(comp_type int, data string, expected_size int) []byte {
    compressedData := C.CString(data)
    defer C.free(unsafe.Pointer(compressedData))
    compressedDataSize := C.ulong(len(data))

    decompressedData := C.malloc(C.ulong(C.sizeof_char * expected_size))
    defer C.free(unsafe.Pointer(decompressedData))
    decompressedDataSize := C.ulong(expected_size)

    ret_val := C.XpressDecompress(C.int(comp_type),
                                  (*C.uchar) (compressedData),
                                  compressedDataSize,
                                  (*C.uchar) (decompressedData),
                                  &decompressedDataSize)

    decompressed := C.GoBytes(decompressedData, C.int(decompressedDataSize))

    return decompressed
}

However, I'm getting this error when I try to build: cannot convert compressedData (type *_Ctype_char) to type *_Ctype_uchar

What is the best way for me to convert the input string into a const unsigned char*?

Answer 1

The following worked:

compressedData := unsafe.Pointer(data)

and

(*C.uchar) (compressedData)