132 lines
3.9 KiB
Java
132 lines
3.9 KiB
Java
/*
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* Copyright (C) 2011 The Guava Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
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* in compliance with the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under the License
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* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
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* or implied. See the License for the specific language governing permissions and limitations under
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* the License.
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*/
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package com.google.common.hash;
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import java.nio.charset.Charset;
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import com.google.common.annotations.Beta;
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/**
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* A {@link PrimitiveSink} that can compute a hash code after reading the input.
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* Each hasher should translate all multibyte values ({@link #putInt(int)},
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* {@link #putLong(long)}, etc) to bytes in little-endian order.
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*
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* <p>
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* <b>Warning:</b> The result of calling any methods after calling {@link #hash}
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* is undefined.
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*
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* <p>
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* <b>Warning:</b> Using a specific character encoding when hashing a
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* {@link CharSequence} with {@link #putString(CharSequence, Charset)} is
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* generally only useful for cross-language compatibility (otherwise prefer
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* {@link #putUnencodedChars}). However, the character encodings must be
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* identical across languages. Also beware that {@link Charset} definitions may
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* occasionally change between Java releases.
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*
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* <p>
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* <b>Warning:</b> Chunks of data that are put into the {@link Hasher} are not
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* delimited. The resulting {@link HashCode} is dependent only on the bytes
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* inserted, and the order in which they were inserted, not how those bytes were
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* chunked into discrete put() operations. For example, the following three
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* expressions all generate colliding hash codes:
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*
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* <pre>
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* {@code
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*
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* newHasher().putByte(b1).putByte(b2).putByte(b3).hash()
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* newHasher().putByte(b1).putBytes(new byte[] { b2, b3 }).hash()
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* newHasher().putBytes(new byte[] { b1, b2, b3 }).hash()}
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* </pre>
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*
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* <p>
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* If you wish to avoid this, you should either prepend or append the size of
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* each chunk. Keep in mind that when dealing with char sequences, the encoded
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* form of two concatenated char sequences is not equivalent to the
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* concatenation of their encoded form. Therefore,
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* {@link #putString(CharSequence, Charset)} should only be used consistently
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* with <i>complete</i> sequences and not broken into chunks.
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*
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* @author Kevin Bourrillion
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* @since 11.0
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*/
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@Beta
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public interface Hasher extends PrimitiveSink {
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@Override
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Hasher putByte(byte b);
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@Override
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Hasher putBytes(byte[] bytes);
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@Override
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Hasher putBytes(byte[] bytes, int off, int len);
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@Override
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Hasher putShort(short s);
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@Override
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Hasher putInt(int i);
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@Override
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Hasher putLong(long l);
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/**
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* Equivalent to {@code putInt(Float.floatToRawIntBits(f))}.
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*/
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@Override
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Hasher putFloat(float f);
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/**
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* Equivalent to {@code putLong(Double.doubleToRawLongBits(d))}.
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*/
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@Override
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Hasher putDouble(double d);
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/**
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* Equivalent to {@code putByte(b ? (byte) 1 : (byte) 0)}.
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*/
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@Override
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Hasher putBoolean(boolean b);
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@Override
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Hasher putChar(char c);
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/**
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* Equivalent to processing each {@code char} value in the {@code CharSequence},
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* in order. The input must not be updated while this method is in progress.
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*
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* @since 15.0 (since 11.0 as putString(CharSequence)).
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*/
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@Override
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Hasher putUnencodedChars(CharSequence charSequence);
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/**
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* Equivalent to {@code putBytes(charSequence.toString().getBytes(charset))}.
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*/
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@Override
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Hasher putString(CharSequence charSequence, Charset charset);
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/**
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* A simple convenience for {@code funnel.funnel(object, this)}.
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*/
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<T> Hasher putObject(T instance, Funnel<? super T> funnel);
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/**
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* Computes a hash code based on the data that have been provided to this
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* hasher. The result is unspecified if this method is called more than once on
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* the same instance.
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*/
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HashCode hash();
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}
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