Create Event Signature

Author: hendrikebbers

abi-parser/pom.xml

@@ -23,6 +23,10 @@
       <artifactId>jspecify</artifactId>
       <scope>compile</scope>
     </dependency>
+    <dependency>
+      <groupId>com.github.aelstad</groupId>
+      <artifactId>keccakj</artifactId>
+    </dependency>
   </dependencies>
 
   <build>

abi-parser/src/main/java/com/openelements/hiero/smartcontract/abi/model/AbiEvent.java

@@ -1,9 +1,11 @@
 package com.openelements.hiero.smartcontract.abi.model;
 
+import com.openelements.hiero.smartcontract.abi.util.HexConverter;
+import com.openelements.hiero.smartcontract.abi.util.KeccakSupport;
+import java.nio.charset.StandardCharsets;
 import java.util.List;
 import java.util.Objects;
 import org.jspecify.annotations.NonNull;
-import org.jspecify.annotations.Nullable;
 
 public record AbiEvent(@NonNull String name, @NonNull List<AbiParameter> inputs, boolean anonymous) implements AbiEntry{
 
@@ -16,4 +18,25 @@ public record AbiEvent(@NonNull String name, @NonNull List<AbiParameter> inputs,
     public AbiEntryType type() {
         return AbiEntryType.EVENT;
     }
+
+    @NonNull
+    public String createEventSignature() {
+        if(!anonymous) {
+            throw new IllegalStateException("Cannot create anonymous topic for named event");
+        }
+        final List<String> canonicalParameterTypes = inputs.stream().map(AbiParameter::getCanonicalType).toList();
+        return name + "(" + String.join(",", canonicalParameterTypes) + ")";
+    }
+
+    @NonNull
+    public byte[] createEventSignatureHash() {
+        final String eventSignature = createEventSignature();
+        return KeccakSupport.keccak256(eventSignature.getBytes(StandardCharsets.UTF_8));
+    }
+
+    @NonNull
+    public String createEventSignatureHashAsHex() {
+        final byte[] eventSignatureHash = createEventSignatureHash();
+        return HexConverter.bytesToHex(eventSignatureHash);
+    }
 }

abi-parser/src/main/java/com/openelements/hiero/smartcontract/abi/model/AbiParameter.java

@@ -18,4 +18,8 @@ public record AbiParameter(@NonNull String name, @NonNull AbiParameterType type,
         }
     }
 
+    public String getCanonicalType() {
+        return type.getCanonicalType();
+    }
+
 }

abi-parser/src/main/java/com/openelements/hiero/smartcontract/abi/model/AbiParameterType.java

@@ -18,4 +18,22 @@ public static AbiParameterType of(final String name) {
             default -> throw new IllegalArgumentException("Unknown value type: " + name);
         };
     }
+
+    public String getCanonicalType() {
+        return switch (this) {
+            case ADDRESS -> "address";
+            case STRING -> "string";
+            case BYTE32 -> "bytes32";
+            case BOOL -> "bool";
+            case UINT256 -> "uint256";
+            case TUPLE -> "tuple";
+        };
+    }
+
+    public boolean isDynamic() {
+        return switch (this) {
+            case STRING, BYTE32 -> true;
+            default -> false;
+        };
+    }
 }

abi-parser/src/main/java/com/openelements/hiero/smartcontract/abi/util/HexConverter.java

@@ -0,0 +1,23 @@
+package com.openelements.hiero.smartcontract.abi.util;
+
+import java.nio.charset.StandardCharsets;
+import java.util.Objects;
+import org.jspecify.annotations.NonNull;
+
+public class HexConverter {
+
+    private static final byte[] HEX_ARRAY = "0123456789ABCDEF".getBytes(StandardCharsets.US_ASCII);
+
+    @NonNull
+    public static String bytesToHex(@NonNull final byte[] bytes) {
+        //see https://stackoverflow.com/questions/9655181/java-convert-a-byte-array-to-a-hex-string
+        Objects.requireNonNull(bytes, "bytes");
+        final byte[] hexChars = new byte[bytes.length * 2];
+        for (int j = 0; j < bytes.length; j++) {
+            int v = bytes[j] & 0xFF;
+            hexChars[j * 2] = HEX_ARRAY[v >>> 4];
+            hexChars[j * 2 + 1] = HEX_ARRAY[v & 0x0F];
+        }
+        return new String(hexChars, StandardCharsets.UTF_8);
+    }
+}

abi-parser/src/main/java/com/openelements/hiero/smartcontract/abi/util/KeccakSupport.java

@@ -0,0 +1,25 @@
+package com.openelements.hiero.smartcontract.abi.util;
+
+import com.github.aelstad.keccakj.provider.Constants;
+import com.github.aelstad.keccakj.provider.KeccakjProvider;
+import java.security.MessageDigest;
+import java.security.Security;
+
+public class KeccakSupport {
+
+    public synchronized static MessageDigest getMessageDigest() {
+        if(Security.getProvider(Constants.PROVIDER) == null) {
+            Security.addProvider(new KeccakjProvider());
+        }
+        try {
+            return MessageDigest.getInstance(Constants.SHA3_256, Constants.PROVIDER);
+        } catch (Exception e) {
+            throw new RuntimeException("Error in Keccak provisioning", e);
+        }
+    }
+
+    public static byte[] keccak256(byte[] data) {
+        MessageDigest md = getMessageDigest();
+        return md.digest(data);
+    }
+}

abi-parser/src/main/java/module-info.java

@@ -1,5 +1,7 @@
 module com.openelements.hiero.smartcontract.abi {
     exports com.openelements.hiero.smartcontract.abi;
     exports com.openelements.hiero.smartcontract.abi.model;
+    exports com.openelements.hiero.smartcontract.abi.util;
     requires org.jspecify;
+    requires keccakj;
 }

pom.xml

@@ -65,6 +65,7 @@
     <cyclonedx-maven-plugin.version>2.8.0</cyclonedx-maven-plugin.version>
     <jreleaser-maven-plugin.version>1.9.0</jreleaser-maven-plugin.version>
     <versions-maven-plugin.version>2.17.1</versions-maven-plugin.version>
+    <keccakj.version>1.1.0</keccakj.version>
   </properties>
 
   <dependencyManagement>
@@ -191,6 +192,11 @@
         <artifactId>gson</artifactId>
         <version>${gson.version}</version>
       </dependency>
+      <dependency>
+        <groupId>com.github.aelstad</groupId>
+        <artifactId>keccakj</artifactId>
+        <version>${keccakj.version}</version>
+      </dependency>
     </dependencies>
   </dependencyManagement>