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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 static com.google.common.base.Preconditions.checkPositionIndexes;
import static com.google.common.base.Preconditions.checkState;
import com.google.common.primitives.Chars;
import com.google.common.primitives.Ints;
import com.google.common.primitives.Longs;
import com.google.common.primitives.Shorts;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.charset.Charset;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/**
* {@link HashFunction} adapter for {@link MessageDigest}s.
*
* @author Kevin Bourrillion
* @author Dimitris Andreou
*/
final class MessageDigestHashFunction extends AbstractStreamingHashFunction {
private final String algorithmName;
private final int bits;
MessageDigestHashFunction(String algorithmName) {
this.algorithmName = algorithmName;
this.bits = getMessageDigest(algorithmName).getDigestLength() * 8;
}
public int bits() {
return bits;
}
private static MessageDigest getMessageDigest(String algorithmName) {
try {
return MessageDigest.getInstance(algorithmName);
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(e);
}
}
@Override public Hasher newHasher() {
return new MessageDigestHasher(getMessageDigest(algorithmName));
}
private static class MessageDigestHasher implements Hasher {
private final MessageDigest digest;
private final ByteBuffer scratch; // lazy convenience
private boolean done;
private MessageDigestHasher(MessageDigest digest) {
this.digest = digest;
this.scratch = ByteBuffer.allocate(8).order(ByteOrder.LITTLE_ENDIAN);
}
@Override public Hasher putByte(byte b) {
checkNotDone();
digest.update(b);
return this;
}
@Override public Hasher putBytes(byte[] bytes) {
checkNotDone();
digest.update(bytes);
return this;
}
@Override public Hasher putBytes(byte[] bytes, int off, int len) {
checkNotDone();
checkPositionIndexes(off, off + len, bytes.length);
digest.update(bytes, off, len);
return this;
}
@Override public Hasher putShort(short s) {
checkNotDone();
scratch.putShort(s);
digest.update(scratch.array(), 0, Shorts.BYTES);
scratch.clear();
return this;
}
@Override public Hasher putInt(int i) {
checkNotDone();
scratch.putInt(i);
digest.update(scratch.array(), 0, Ints.BYTES);
scratch.clear();
return this;
}
@Override public Hasher putLong(long l) {
checkNotDone();
scratch.putLong(l);
digest.update(scratch.array(), 0, Longs.BYTES);
scratch.clear();
return this;
}
@Override public Hasher putFloat(float f) {
checkNotDone();
scratch.putFloat(f);
digest.update(scratch.array(), 0, 4);
scratch.clear();
return this;
}
@Override public Hasher putDouble(double d) {
checkNotDone();
scratch.putDouble(d);
digest.update(scratch.array(), 0, 8);
scratch.clear();
return this;
}
@Override public Hasher putBoolean(boolean b) {
return putByte(b ? (byte) 1 : (byte) 0);
}
@Override public Hasher putChar(char c) {
checkNotDone();
scratch.putChar(c);
digest.update(scratch.array(), 0, Chars.BYTES);
scratch.clear();
return this;
}
@Override public Hasher putString(CharSequence charSequence) {
for (int i = 0; i < charSequence.length(); i++) {
putChar(charSequence.charAt(i));
}
return this;
}
@Override public Hasher putString(CharSequence charSequence, Charset charset) {
return putBytes(charSequence.toString().getBytes(charset));
}
@Override public <T> Hasher putObject(T instance, Funnel<? super T> funnel) {
checkNotDone();
funnel.funnel(instance, this);
return this;
}
private void checkNotDone() {
checkState(!done, "Cannot use Hasher after calling #hash() on it");
}
public HashCode hash() {
done = true;
return HashCodes.fromBytesNoCopy(digest.digest());
}
}
}
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