rlp: add "tail" struct tag

rlp/decode_tail_test.go

@@ -0,0 +1,33 @@
+package rlp
+
+import (
+	"bytes"
+	"fmt"
+)
+
+type structWithTail struct {
+	A, B uint
+	C    []uint `rlp:"tail"`
+}
+
+func ExampleDecode_structTagTail() {
+	// In this example, the "tail" struct tag is used to decode lists of
+	// differing length into a struct.
+	var val structWithTail
+
+	err := Decode(bytes.NewReader([]byte{0xC4, 0x01, 0x02, 0x03, 0x04}), &val)
+	fmt.Printf("with 4 elements: err=%v val=%v\n", err, val)
+
+	err = Decode(bytes.NewReader([]byte{0xC6, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06}), &val)
+	fmt.Printf("with 6 elements: err=%v val=%v\n", err, val)
+
+	// Note that at least two list elements must be present to
+	// fill fields A and B:
+	err = Decode(bytes.NewReader([]byte{0xC1, 0x01}), &val)
+	fmt.Printf("with 1 element: err=%q\n", err)
+
+	// Output:
+	// with 4 elements: err=<nil> val={1 2 [3 4]}
+	// with 6 elements: err=<nil> val={1 2 [3 4 5 6]}
+	// with 1 element: err="rlp: too few elements for rlp.structWithTail"
+}