cmd/rlpdump: add support for text to rlp (#23745)

This PR adds support for the rlpdump tool to go from text format to RLP.

cmd/rlpdump/rlpdump_test.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"strings"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+)
+
+func TestRoundtrip(t *testing.T) {
+	for i, want := range []string{
+		"0xf880806482520894d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0d0a1010000000000000000000000000000000000000000000000000000000000000001801ba0c16787a8e25e941d67691954642876c08f00996163ae7dfadbbfd6cd436f549da06180e5626cae31590f40641fe8f63734316c4bfeb4cdfab6714198c1044d2e28",
+		"0xd5c0d3cb84746573742a2a808213378667617a6f6e6b",
+		"0xc780c0c1c0825208",
+	} {
+		var out strings.Builder
+		err := rlpToText(bytes.NewReader(common.FromHex(want)), &out)
+		if err != nil {
+			t.Fatal(err)
+		}
+		text := out.String()
+		rlpBytes, err := textToRlp(strings.NewReader(text))
+		if err != nil {
+			t.Errorf("test %d: error %v", i, err)
+			continue
+		}
+		have := fmt.Sprintf("0x%x", rlpBytes)
+		if have != want {
+			t.Errorf("test %d: have\n%v\nwant:\n%v\n", i, have, want)
+		}
+	}
+}
+
+func TestTextToRlp(t *testing.T) {
+	type tc struct {
+		text string
+		want string
+	}
+	cases := []tc{
+		{
+			text: `[
+  "",
+  [],
+[     
+ [],
+    ],
+  5208,
+]`,
+			want: "0xc780c0c1c0825208",
+		},
+	}
+	for i, tc := range cases {
+		have, err := textToRlp(strings.NewReader(tc.text))
+		if err != nil {
+			t.Errorf("test %d: error %v", i, err)
+			continue
+		}
+		if hexutil.Encode(have) != tc.want {
+			t.Errorf("test %d:\nhave %v\nwant %v", i, hexutil.Encode(have), tc.want)
+		}
+	}
+}