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/*
* Copyright (C) 2011 The Guava Authors
*
* Licensed 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 com.google.common.hash;
import com.google.common.base.Preconditions;
import com.google.common.base.Throwables;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.charset.Charset;
/**
* Skeleton implementation of {@link HashFunction}, appropriate for non-streaming algorithms.
* All the hash computation done using {@linkplain #newHasher()} are delegated to the {@linkplain
* #hashBytes(byte[], int, int)} method.
*
* @author Dimitris Andreou
*/
abstract class AbstractNonStreamingHashFunction implements HashFunction {
@Override
public Hasher newHasher() {
return new BufferingHasher(32);
}
@Override
public Hasher newHasher(int expectedInputSize) {
Preconditions.checkArgument(expectedInputSize >= 0);
return new BufferingHasher(expectedInputSize);
}
@Override public HashCode hashString(CharSequence input) {
int len = input.length();
Hasher hasher = newHasher(len * 2);
for (int i = 0; i < len; i++) {
hasher.putChar(input.charAt(i));
}
return hasher.hash();
}
@Override public HashCode hashString(CharSequence input, Charset charset) {
return hashBytes(input.toString().getBytes(charset));
}
@Override public HashCode hashInt(int input) {
return newHasher(4).putInt(input).hash();
}
@Override public HashCode hashLong(long input) {
return newHasher(8).putLong(input).hash();
}
@Override public HashCode hashBytes(byte[] input) {
return hashBytes(input, 0, input.length);
}
/**
* In-memory stream-based implementation of Hasher.
*/
private final class BufferingHasher extends AbstractHasher {
final ExposedByteArrayOutputStream stream;
static final int BOTTOM_BYTE = 0xFF;
BufferingHasher(int expectedInputSize) {
this.stream = new ExposedByteArrayOutputStream(expectedInputSize);
}
@Override
public Hasher putByte(byte b) {
stream.write(b);
return this;
}
@Override
public Hasher putBytes(byte[] bytes) {
try {
stream.write(bytes);
} catch (IOException e) {
throw Throwables.propagate(e);
}
return this;
}
@Override
public Hasher putBytes(byte[] bytes, int off, int len) {
stream.write(bytes, off, len);
return this;
}
@Override
public Hasher putShort(short s) {
stream.write(s & BOTTOM_BYTE);
stream.write((s >>> 8) & BOTTOM_BYTE);
return this;
}
@Override
public Hasher putInt(int i) {
stream.write(i & BOTTOM_BYTE);
stream.write((i >>> 8) & BOTTOM_BYTE);
stream.write((i >>> 16) & BOTTOM_BYTE);
stream.write((i >>> 24) & BOTTOM_BYTE);
return this;
}
@Override
public Hasher putLong(long l) {
for (int i = 0; i < 64; i += 8) {
stream.write((byte) ((l >>> i) & BOTTOM_BYTE));
}
return this;
}
@Override
public Hasher putChar(char c) {
stream.write(c & BOTTOM_BYTE);
stream.write((c >>> 8) & BOTTOM_BYTE);
return this;
}
@Override
public <T> Hasher putObject(T instance, Funnel<? super T> funnel) {
funnel.funnel(instance, this);
return this;
}
@Override
public HashCode hash() {
return hashBytes(stream.byteArray(), 0, stream.length());
}
}
// Just to access the byte[] without introducing an unnecessary copy
private static final class ExposedByteArrayOutputStream extends ByteArrayOutputStream {
ExposedByteArrayOutputStream(int expectedInputSize) {
super(expectedInputSize);
}
byte[] byteArray() {
return buf;
}
int length() {
return count;
}
}
}
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