1 /* 2 * Copyright (C) 2011 The Guava Authors 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except 5 * in compliance with the License. You may obtain a copy of the License at 6 * 7 * http://www.apache.org/licenses/LICENSE-2.0 8 * 9 * Unless required by applicable law or agreed to in writing, software distributed under the License 10 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express 11 * or implied. See the License for the specific language governing permissions and limitations under 12 * the License. 13 */ 14 15 package com.google.common.hash; 16 17 import com.google.common.annotations.Beta; 18 19 import java.nio.charset.Charset; 20 21 /** 22 * A {@link PrimitiveSink} that can compute a hash code after reading the input. Each hasher should 23 * translate all multibyte values ({@link #putInt(int)}, {@link #putLong(long)}, etc) to bytes 24 * in little-endian order. 25 * 26 * <p><b>Warning:</b> The result of calling any methods after calling {@link #hash} is undefined. 27 * 28 * <p><b>Warning:</b> Using a specific character encoding when hashing a {@link CharSequence} with 29 * {@link #putString(CharSequence, Charset)} is generally only useful for cross-language 30 * compatibility (otherwise prefer {@link #putUnencodedChars}). However, the character encodings 31 * must be identical across languages. Also beware that {@link Charset} definitions may occasionally 32 * change between Java releases. 33 * 34 * <p><b>Warning:</b> Chunks of data that are put into the {@link Hasher} are not delimited. 35 * The resulting {@link HashCode} is dependent only on the bytes inserted, and the order in which 36 * they were inserted, not how those bytes were chunked into discrete put() operations. For example, 37 * the following three expressions all generate colliding hash codes: <pre> {@code 38 * 39 * newHasher().putByte(b1).putByte(b2).putByte(b3).hash() 40 * newHasher().putByte(b1).putBytes(new byte[] { b2, b3 }).hash() 41 * newHasher().putBytes(new byte[] { b1, b2, b3 }).hash()}</pre> 42 * 43 * <p>If you wish to avoid this, you should either prepend or append the size of each chunk. Keep in 44 * mind that when dealing with char sequences, the encoded form of two concatenated char sequences 45 * is not equivalent to the concatenation of their encoded form. Therefore, 46 * {@link #putString(CharSequence, Charset)} should only be used consistently with <i>complete</i> 47 * sequences and not broken into chunks. 48 * 49 * @author Kevin Bourrillion 50 * @since 11.0 51 */ 52 @Beta 53 public interface Hasher extends PrimitiveSink { 54 @Override Hasher putByte(byte b); 55 @Override Hasher putBytes(byte[] bytes); 56 @Override Hasher putBytes(byte[] bytes, int off, int len); 57 @Override Hasher putShort(short s); 58 @Override Hasher putInt(int i); 59 @Override Hasher putLong(long l); 60 61 /** 62 * Equivalent to {@code putInt(Float.floatToRawIntBits(f))}. 63 */ 64 @Override Hasher putFloat(float f); 65 66 /** 67 * Equivalent to {@code putLong(Double.doubleToRawLongBits(d))}. 68 */ 69 @Override Hasher putDouble(double d); 70 71 /** 72 * Equivalent to {@code putByte(b ? (byte) 1 : (byte) 0)}. 73 */ 74 @Override Hasher putBoolean(boolean b); 75 @Override Hasher putChar(char c); 76 77 /** 78 * Equivalent to processing each {@code char} value in the {@code CharSequence}, in order. 79 * The input must not be updated while this method is in progress. 80 * 81 * @since 15.0 (since 11.0 as putString(CharSequence)). 82 */ 83 @Override Hasher putUnencodedChars(CharSequence charSequence); 84 85 /** 86 * Equivalent to {@code putBytes(charSequence.toString().getBytes(charset))}. 87 */ 88 @Override Hasher putString(CharSequence charSequence, Charset charset); 89 90 /** 91 * A simple convenience for {@code funnel.funnel(object, this)}. 92 */ 93 <T> Hasher putObject(T instance, Funnel<? super T> funnel); 94 95 /** 96 * Computes a hash code based on the data that have been provided to this hasher. The result is 97 * unspecified if this method is called more than once on the same instance. 98 */ 99 HashCode hash(); 100 } 101
