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java/org/apache/tomcat/util/security/MD5Encoder.java

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+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.tomcat.util.security;
+
+/**
+ * Encode an MD5 digest into a String.
+ * <p>
+ * The 128 bit MD5 hash is converted into a 32 character long String.
+ * Each character of the String is the hexadecimal representation of 4 bits
+ * of the digest.
+ *
+ * @author Remy Maucherat
+ */
+public final class MD5Encoder {
+
+
+    private MD5Encoder() {
+        // Hide default constructor for utility class
+    }
+
+
+    private static final char[] hexadecimal = {'0', '1', '2', '3', '4', '5',
+        '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+
+
+    /**
+     * Encodes the 128 bit (16 bytes) MD5 into a 32 character String.
+     *
+     * @param binaryData Array containing the digest
+     *
+     * @return Encoded MD5, or null if encoding failed
+     */
+    public static String encode(byte[] binaryData) {
+
+        if (binaryData.length != 16)
+            return null;
+
+        char[] buffer = new char[32];
+
+        for (int i=0; i<16; i++) {
+            int low = binaryData[i] & 0x0f;
+            int high = (binaryData[i] & 0xf0) >> 4;
+            buffer[i*2] = hexadecimal[high];
+            buffer[i*2 + 1] = hexadecimal[low];
+        }
+
+        return new String(buffer);
+    }
+}
+