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/*******************************************************************************
* Copyright 2014 Trevor Robinson
*
* 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.scurrilous.circe.impl;
import java.nio.ByteBuffer;
import com.scurrilous.circe.IncrementalIntHash;
import com.scurrilous.circe.StatefulIntHash;
/**
* Base implementation for incremental stateless integer hash functions.
*/
public abstract class AbstractIncrementalIntHash implements IncrementalIntHash {
@Override
public boolean supportsUnsafe() {
return false;
}
@Override
public StatefulIntHash createStateful() {
return new IncrementalIntStatefulHash(this);
}
@Override
public int calculate(byte[] input) {
return resume(initial(), input);
}
@Override
public int calculate(byte[] input, int index, int length) {
return resume(initial(), input, index, length);
}
@Override
public int calculate(ByteBuffer input) {
return resume(initial(), input);
}
@Override
public int calculate(long address, long length) {
return resume(initial(), address, length);
}
@Override
public int resume(int current, byte[] input) {
return resumeUnchecked(current, input, 0, input.length);
}
@Override
public int resume(int current, byte[] input, int index, int length) {
if (length < 0)
throw new IllegalArgumentException();
if (index < 0 || index + length > input.length)
throw new IndexOutOfBoundsException();
return resumeUnchecked(current, input, index, length);
}
@Override
public int resume(int current, ByteBuffer input) {
final byte[] array;
final int index;
final int length = input.remaining();
if (input.hasArray()) {
array = input.array();
index = input.arrayOffset() + input.position();
input.position(input.limit());
} else {
array = new byte[length];
index = 0;
input.get(array);
}
return resumeUnchecked(current, array, index, length);
}
@Override
public int resume(int current, long address, long length) {
throw new UnsupportedOperationException();
}
/**
* The initial state of the hash function, which is the same as the output
* value for an empty input sequence.
*
* @return the initial hash state/output
*/
protected abstract int initial();
/**
* Evaluates this hash function as if the given range of the given input
* array were appended to the previously hashed input. The index and length
* parameters have already been validated.
*
* @param current the hash output for input hashed so far
* @param input the input array
* @param index the starting index of the first input byte
* @param length the length of the input range
* @return the output of the hash function for the concatenated input
*/
protected abstract int resumeUnchecked(int current, byte[] input, int index, int length);
}
