ffi.go

func ExampleExecute_ffi() {
	// enable FFI
	vm.EnableFFI()

	cfg := &Config{
		DisableJit: true,
		// create ffi model and functions
		Ffi: vm.Ffi{
			0: func(in []byte) ([]byte, error) {
				reverse := make([]byte, len(in))
				for i := 0; i < len(in); i++ {
					reverse[len(in)-i-1] = in[i]
				}

				return reverse, nil
			},
		},
	}

	// hello push string
	helloPush := append([]byte{byte(vm.PUSH11)}, []byte("hello world")...)
	ret, _ := Execute(append(helloPush, []byte{
		byte(vm.PUSH1), 0, // push 0'th offset as start pos for mem write
		byte(vm.MSTORE),                       // write hello world to 0th offset
		byte(vm.PUSH1), 32, byte(vm.PUSH1), 0, // push 0 to 32 for input mem read
		byte(vm.PUSH1), 32, byte(vm.PUSH1), 0, // push 0 to 32 for ret mem write
		byte(vm.PUSH1), 0x0, // push FFI address 0
		byte(vm.FFI),                          // execute FFI 0 addr
		byte(vm.PUSH1), 32, byte(vm.PUSH1), 0, // push 0 to 32 for return mem read
		byte(vm.RETURN), // return memory
	}...), nil, cfg)
	fmt.Printf("%x\n", ret)
	// Output:
	// 646c726f77206f6c6c6568000000000000000000000000000000000000000000
}