Add Keccak256 sha3 usage.

composer.json

@@ -11,7 +11,9 @@
     ],
     "minimum-stability": "dev",
     "require": {
-        "guzzlehttp/guzzle": "~6.0"
+        "guzzlehttp/guzzle": "~6.0",
+        "PHP": "^7.1",
+        "kornrunner/keccak": "dev-master"
     },
     "require-dev": {
         "phpunit/phpunit": "~6.0"

src/Utils.php

@@ -1,11 +1,28 @@
 <?php
 
+/**
+ * This file is part of web3.php package.
+ * 
+ * (c) Kuan-Cheng,Lai <alk03073135@gmail.com>
+ * 
+ * @author Peter Lai <alk03073135@gmail.com>
+ * @license MIT
+ */
+
 namespace Web3;
 
 use InvalidArgumentException;
+use kornrunner\Keccak;
 
 class Utils
 {
+    /**
+     * SHA3_NULL_HASH
+     * 
+     * @const string
+     */
+    const SHA3_NULL_HASH = 'c5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470';
+
     /**
      * construct
      *
@@ -49,4 +66,27 @@ class Utils
 
         return pack('H*', $hexString);
     }
+
+    /**
+     * sha3
+     * keccak256
+     * 
+     * @param string $value
+     * @return string
+     */
+    public function sha3($value)
+    {
+        if (!is_string($value)) {
+            throw new InvalidArgumentException('The value to sha3 function must be string.');
+        }
+        if (preg_match('/^0x/', $value) > 0) {
+            $value = self::hexToBin($value);
+        }
+        $hash = Keccak::hash($value, 256);
+
+        if ($hash === self::SHA3_NULL_HASH) {
+            return null;
+        }
+        return '0x' . $hash;
+    }
 }

test/unit/UtilsTest.php

@@ -62,4 +62,20 @@ class UtilsTest extends TestCase
 
         $this->assertEquals($str, '七彩神仙鱼');
     }
+
+    /**
+     * testSha3
+     * 
+     * @return void
+     */
+    public function testSha3()
+    {
+        $str = Utils::sha3('');
+
+        $this->assertNull($str);
+
+        $str = Utils::sha3('baz(uint32,bool)');
+
+        $this->assertEquals(mb_substr($str, 0, 10), '0xcdcd77c0');
+    }
 }