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      1 /*
      2  * Copyright (C) 2011 The Guava Authors
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  * http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.google.common.hash;
     18 
     19 import static com.google.common.base.Preconditions.checkNotNull;
     20 
     21 import java.nio.charset.Charset;
     22 
     23 /**
     24  * An abstract composition of multiple hash functions. {@linkplain #newHasher()} delegates to the
     25  * {@code Hasher} objects of the delegate hash functions, and in the end, they are used by
     26  * {@linkplain #makeHash(Hasher[])} that constructs the final {@code HashCode}.
     27  *
     28  * @author Dimitris Andreou
     29  */
     30 abstract class AbstractCompositeHashFunction extends AbstractStreamingHashFunction {
     31   final HashFunction[] functions;
     32 
     33   AbstractCompositeHashFunction(HashFunction... functions) {
     34     for (HashFunction function : functions) {
     35       checkNotNull(function);
     36     }
     37     this.functions = functions;
     38   }
     39 
     40   /**
     41    * Constructs a {@code HashCode} from the {@code Hasher} objects of the functions. Each of them
     42    * has consumed the entire input and they are ready to output a {@code HashCode}. The order of
     43    * the hashers are the same order as the functions given to the constructor.
     44    */
     45   // this could be cleaner if it passed HashCode[], but that would create yet another array...
     46   /* protected */ abstract HashCode makeHash(Hasher[] hashers);
     47 
     48   @Override
     49   public Hasher newHasher() {
     50     final Hasher[] hashers = new Hasher[functions.length];
     51     for (int i = 0; i < hashers.length; i++) {
     52       hashers[i] = functions[i].newHasher();
     53     }
     54     return new Hasher() {
     55       @Override public Hasher putByte(byte b) {
     56         for (Hasher hasher : hashers) {
     57           hasher.putByte(b);
     58         }
     59         return this;
     60       }
     61 
     62       @Override public Hasher putBytes(byte[] bytes) {
     63         for (Hasher hasher : hashers) {
     64           hasher.putBytes(bytes);
     65         }
     66         return this;
     67       }
     68 
     69       @Override public Hasher putBytes(byte[] bytes, int off, int len) {
     70         for (Hasher hasher : hashers) {
     71           hasher.putBytes(bytes, off, len);
     72         }
     73         return this;
     74       }
     75 
     76       @Override public Hasher putShort(short s) {
     77         for (Hasher hasher : hashers) {
     78           hasher.putShort(s);
     79         }
     80         return this;
     81       }
     82 
     83       @Override public Hasher putInt(int i) {
     84         for (Hasher hasher : hashers) {
     85           hasher.putInt(i);
     86         }
     87         return this;
     88       }
     89 
     90       @Override public Hasher putLong(long l) {
     91         for (Hasher hasher : hashers) {
     92           hasher.putLong(l);
     93         }
     94         return this;
     95       }
     96 
     97       @Override public Hasher putFloat(float f) {
     98         for (Hasher hasher : hashers) {
     99           hasher.putFloat(f);
    100         }
    101         return this;
    102       }
    103 
    104       @Override public Hasher putDouble(double d) {
    105         for (Hasher hasher : hashers) {
    106           hasher.putDouble(d);
    107         }
    108         return this;
    109       }
    110 
    111       @Override public Hasher putBoolean(boolean b) {
    112         for (Hasher hasher : hashers) {
    113           hasher.putBoolean(b);
    114         }
    115         return this;
    116       }
    117 
    118       @Override public Hasher putChar(char c) {
    119         for (Hasher hasher : hashers) {
    120           hasher.putChar(c);
    121         }
    122         return this;
    123       }
    124 
    125       @Override public Hasher putUnencodedChars(CharSequence chars) {
    126         for (Hasher hasher : hashers) {
    127           hasher.putUnencodedChars(chars);
    128         }
    129         return this;
    130       }
    131 
    132       @Override public Hasher putString(CharSequence chars, Charset charset) {
    133         for (Hasher hasher : hashers) {
    134           hasher.putString(chars, charset);
    135         }
    136         return this;
    137       }
    138 
    139       @Override public <T> Hasher putObject(T instance, Funnel<? super T> funnel) {
    140         for (Hasher hasher : hashers) {
    141           hasher.putObject(instance, funnel);
    142         }
    143         return this;
    144       }
    145 
    146       @Override public HashCode hash() {
    147         return makeHash(hashers);
    148       }
    149     };
    150   }
    151 
    152   private static final long serialVersionUID = 0L;
    153 }
    154