cs := "你好世界, hello world. 你好世界, hello world. 你好世界, hello world."
	for k := 1; k <= 2048; k <<= 4 {
		for j := 1; j <= 64; j <<= 1 {
			b.Run(fmt.Sprintf("%d:%d", k, j), func(b *testing.B) {
				for i := 0; i < b.N; i++ {
					LastIndexAny(x[:k], cs[:j])
				}
			})
		}
	}
}

func BenchmarkTrimASCII(b *testing.B) {
	cs := "0123456789abcdef"
	for k := 1; k <= 4096; k <<= 4 {

	// #include <stdlib.h>
	//
	// static void myprint(char* s) {
	//   printf("%s\n", s);
	// }
	import "C"
	import "unsafe"

	func main() {
		cs := C.CString("Hello from stdio")
		C.myprint(cs)
		C.free(unsafe.Pointer(cs))
	}

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

	// Go string to C string