com.scurrilous.circe.IncrementalLongHash Maven / Gradle / Ivy
/*******************************************************************************
* 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;
import java.nio.ByteBuffer;
/**
* Incremental stateless long integer hash function, which has the property that
* its output is the same as (or easily derivable from) its state. Specifically,
* for any sequence M partitioned arbitrarily into two subsequences
* M1 M2:
*
*
* h(M) = h'(h(M1), M2)
*
*
* where h corresponds to the {@link StatelessLongHash#calculate calculate}
* function and h' corresponds to the {@link #resume} function.
*
* Note that stateful hash functions obtained from incremental stateless hash
* functions are also {@linkplain StatefulHash#supportsIncremental incremental}.
*/
public interface IncrementalLongHash extends StatelessLongHash {
/**
* Evaluates this hash function as if the entire given input array were
* appended to the previously hashed input.
*
* @param current the hash output for input hashed so far
* @param input the input array
* @return the output of the hash function for the concatenated input
*/
long resume(long current, byte[] input);
/**
* Evaluates this hash function as if the given range of the given input
* array were appended to the previously hashed input.
*
* @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
* @throws IndexOutOfBoundsException if index is negative or
* {@code index + length} is greater than the array length
*/
long resume(long current, byte[] input, int index, int length);
/**
* Evaluates this hash function as if the remaining contents of the given
* input buffer were appended to the previously hashed input. This method
* leaves the buffer position at the limit.
*
* @param current the hash output for input hashed so far
* @param input the input buffer
* @return the output of the hash function for the concatenated input
*/
long resume(long current, ByteBuffer input);
/**
* Evaluates this hash function as if the memory with the given address and
* length were appended to the previously hashed input. The arguments are
* generally not checked in any way and will likely lead to a VM crash or
* undefined results if invalid.
*
* @param current the hash output for input hashed so far
* @param address the base address of the input
* @param length the length of the input
* @return the output of the hash function for the concatenated input
* @throws UnsupportedOperationException if this function does not support
* unsafe memory access
* @see #supportsUnsafe()
*/
long resume(long current, long address, long length);
}