From bf61f86a4c2e06f7d952b3d9f9ccf8fb275aeb9b Mon Sep 17 00:00:00 2001
From: Nischal Sharma <nischal@web3labs.com>
Date: Mon, 20 Jan 2025 14:40:37 +0530
Subject: [PATCH] labelHash function added (#2140)

Signed-off-by: Nischal Sharma <nischal@web3labs.com>
---
 .../src/main/java/org/web3j/ens/NameHash.java | 13 ++++++++++++
 .../test/java/org/web3j/ens/NameHashTest.java | 20 +++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/core/src/main/java/org/web3j/ens/NameHash.java b/core/src/main/java/org/web3j/ens/NameHash.java
index 9e24de122..85cbe80df 100644
--- a/core/src/main/java/org/web3j/ens/NameHash.java
+++ b/core/src/main/java/org/web3j/ens/NameHash.java
@@ -107,4 +107,17 @@ public static String dnsEncode(String name) throws IOException {
 
         return Numeric.toHexString(outputStream.toByteArray()) + "00";
     }
+
+    public static String labelHash(String ensName) {
+        if (ensName.isEmpty()) {
+            return Numeric.toHexString(EMPTY);
+        } else {
+            String normalisedEnsName = normalise(ensName);
+            return Numeric.toHexString(Hash.sha3(normalisedEnsName.split("\\.")[0].getBytes(StandardCharsets.UTF_8)));
+        }
+    }
+
+    public static byte[] labelHashAsBytes(String ensName) {
+        return Numeric.hexStringToByteArray(labelHash(ensName));
+    }
 }
diff --git a/core/src/test/java/org/web3j/ens/NameHashTest.java b/core/src/test/java/org/web3j/ens/NameHashTest.java
index 186577113..baa1aa105 100644
--- a/core/src/test/java/org/web3j/ens/NameHashTest.java
+++ b/core/src/test/java/org/web3j/ens/NameHashTest.java
@@ -18,6 +18,7 @@
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.fail;
+import static org.web3j.ens.NameHash.labelHash;
 import static org.web3j.ens.NameHash.nameHash;
 import static org.web3j.ens.NameHash.normalise;
 
@@ -42,6 +43,25 @@ void testNameHash() {
                 ("0xf7de5954cda078ee481b14cff677e8066fe805a89b5c87b4a9b866338049b04a"));
     }
 
+    @Test
+    void testLabelHash() {
+        assertEquals(
+                labelHash(""),
+                ("0x0000000000000000000000000000000000000000000000000000000000000000"));
+
+        assertEquals(
+                labelHash("label"),
+                ("0x1b036544434cea9770a413fd03e0fb240e1ccbd10a452f7dba85c8eca9ca3eda"));
+
+        assertEquals(
+                labelHash("label.eth"),
+                ("0x1b036544434cea9770a413fd03e0fb240e1ccbd10a452f7dba85c8eca9ca3eda"));
+
+        assertEquals(
+                labelHash("\uD83D\uDC8E.gmcafe.art"),
+                ("0xed2cc33b0587afe42a04579d79c23b72b25c5416efcb50c674f3f59e2db9cce6"));
+    }
+
     @Test
     void testNormalise() {
         assertEquals(normalise("foo"), ("foo"));