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 import com.google.errorprone.annotations.CanIgnoreReturnValue; 19 import java.nio.ByteBuffer; 20 import java.nio.charset.Charset; 21 import org.checkerframework.checker.nullness.qual.Nullable; 22 23 /** 24 * A {@link PrimitiveSink} that can compute a hash code after reading the input. Each hasher should 25 * translate all multibyte values ({@link #putInt(int)}, {@link #putLong(long)}, etc) to bytes in 26 * little-endian order. 27 * 28 * <p><b>Warning:</b> The result of calling any methods after calling {@link #hash} is undefined. 29 * 30 * <p><b>Warning:</b> Using a specific character encoding when hashing a {@link CharSequence} with 31 * {@link #putString(CharSequence, Charset)} is generally only useful for cross-language 32 * compatibility (otherwise prefer {@link #putUnencodedChars}). However, the character encodings 33 * must be identical across languages. Also beware that {@link Charset} definitions may occasionally 34 * change between Java releases. 35 * 36 * <p><b>Warning:</b> Chunks of data that are put into the {@link Hasher} are not delimited. The 37 * resulting {@link HashCode} is dependent only on the bytes inserted, and the order in which they 38 * were inserted, not how those bytes were chunked into discrete put() operations. For example, the 39 * following three expressions all generate colliding hash codes: 40 * 41 * <pre>{@code 42 * newHasher().putByte(b1).putByte(b2).putByte(b3).hash() 43 * newHasher().putByte(b1).putBytes(new byte[] { b2, b3 }).hash() 44 * newHasher().putBytes(new byte[] { b1, b2, b3 }).hash() 45 * }</pre> 46 * 47 * <p>If you wish to avoid this, you should either prepend or append the size of each chunk. Keep in 48 * mind that when dealing with char sequences, the encoded form of two concatenated char sequences 49 * is not equivalent to the concatenation of their encoded form. Therefore, {@link 50 * #putString(CharSequence, Charset)} should only be used consistently with <i>complete</i> 51 * sequences and not broken into chunks. 52 * 53 * @author Kevin Bourrillion 54 * @since 11.0 55 */ 56 @Beta 57 @CanIgnoreReturnValue 58 @ElementTypesAreNonnullByDefault 59 public interface Hasher extends PrimitiveSink { 60 @Override putByte(byte b)61 Hasher putByte(byte b); 62 63 @Override putBytes(byte[] bytes)64 Hasher putBytes(byte[] bytes); 65 66 @Override putBytes(byte[] bytes, int off, int len)67 Hasher putBytes(byte[] bytes, int off, int len); 68 69 @Override putBytes(ByteBuffer bytes)70 Hasher putBytes(ByteBuffer bytes); 71 72 @Override putShort(short s)73 Hasher putShort(short s); 74 75 @Override putInt(int i)76 Hasher putInt(int i); 77 78 @Override putLong(long l)79 Hasher putLong(long l); 80 81 /** Equivalent to {@code putInt(Float.floatToRawIntBits(f))}. */ 82 @Override putFloat(float f)83 Hasher putFloat(float f); 84 85 /** Equivalent to {@code putLong(Double.doubleToRawLongBits(d))}. */ 86 @Override putDouble(double d)87 Hasher putDouble(double d); 88 89 /** Equivalent to {@code putByte(b ? (byte) 1 : (byte) 0)}. */ 90 @Override putBoolean(boolean b)91 Hasher putBoolean(boolean b); 92 93 @Override putChar(char c)94 Hasher putChar(char c); 95 96 /** 97 * Equivalent to processing each {@code char} value in the {@code CharSequence}, in order. In 98 * other words, no character encoding is performed; the low byte and high byte of each {@code 99 * char} are hashed directly (in that order). The input must not be updated while this method is 100 * in progress. 101 * 102 * <p><b>Warning:</b> This method will produce different output than most other languages do when 103 * running the same hash function on the equivalent input. For cross-language compatibility, use 104 * {@link #putString}, usually with a charset of UTF-8. For other use cases, use {@code 105 * putUnencodedChars}. 106 * 107 * @since 15.0 (since 11.0 as putString(CharSequence)). 108 */ 109 @Override putUnencodedChars(CharSequence charSequence)110 Hasher putUnencodedChars(CharSequence charSequence); 111 112 /** 113 * Equivalent to {@code putBytes(charSequence.toString().getBytes(charset))}. 114 * 115 * <p><b>Warning:</b> This method, which reencodes the input before hashing it, is useful only for 116 * cross-language compatibility. For other use cases, prefer {@link #putUnencodedChars}, which is 117 * faster, produces the same output across Java releases, and hashes every {@code char} in the 118 * input, even if some are invalid. 119 */ 120 @Override putString(CharSequence charSequence, Charset charset)121 Hasher putString(CharSequence charSequence, Charset charset); 122 123 /** A simple convenience for {@code funnel.funnel(object, this)}. */ putObject( @arametricNullness T instance, Funnel<? super T> funnel)124 <T extends @Nullable Object> Hasher putObject( 125 @ParametricNullness T instance, Funnel<? super T> funnel); 126 127 /** 128 * Computes a hash code based on the data that have been provided to this hasher. The result is 129 * unspecified if this method is called more than once on the same instance. 130 */ hash()131 HashCode hash(); 132 133 /** 134 * {@inheritDoc} 135 * 136 * @deprecated This returns {@link Object#hashCode()}; you almost certainly mean to call {@code 137 * hash().asInt()}. 138 */ 139 @Override 140 @Deprecated hashCode()141 int hashCode(); 142 } 143