1 files changed, 45 insertions, 0 deletions
diff --git a/common/hexutil/json_example_test.go b/common/hexutil/json_example_test.go
new file mode 100644
index 000000000..80180d918
--- /dev/null
+++ b/common/hexutil/json_example_test.go
@@ -0,0 +1,45 @@
+// Copyright 2017 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package hexutil_test
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/common/hexutil"
+)
+
+type MyType [5]byte
+
+func (v *MyType) UnmarshalText(input []byte) error {
+	return hexutil.UnmarshalFixedText("MyType", input, v[:])
+}
+
+func (v MyType) String() string {
+	return hexutil.Bytes(v[:]).String()
+}
+
+func ExampleUnmarshalFixedText() {
+	var v1, v2 MyType
+	fmt.Println("v1 error:", json.Unmarshal([]byte(`"0x01"`), &v1))
+	fmt.Println("v2 error:", json.Unmarshal([]byte(`"0x0101010101"`), &v2))
+	fmt.Println("v2:", v2)
+	// Output:
+	// v1 error: hex string has length 2, want 10 for MyType
+	// v2 error: <nil>
+	// v2: 0x0101010101
+}