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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.checkArgument;
import static com.google.common.base.Preconditions.checkNotNull;
import static com.google.common.base.Preconditions.checkState;
import com.google.common.annotations.Beta;
import com.google.common.primitives.UnsignedInts;
import java.io.Serializable;
/**
* Static factories for creating {@link HashCode} instances; most users should never have to use
* this. All returned instances are {@link Serializable}.
*
* @author Dimitris Andreou
* @since 12.0
*/
@Beta
public final class HashCodes {
private HashCodes() {}
/**
* Creates a 32-bit {@code HashCode}, of which the bytes will form the passed int, interpreted
* in little endian order.
*/
public static HashCode fromInt(int hash) {
return new IntHashCode(hash);
}
private static final class IntHashCode extends HashCode implements Serializable {
final int hash;
IntHashCode(int hash) {
this.hash = hash;
}
@Override public int bits() {
return 32;
}
@Override public byte[] asBytes() {
return new byte[] {
(byte) hash,
(byte) (hash >> 8),
(byte) (hash >> 16),
(byte) (hash >> 24)};
}
@Override public int asInt() {
return hash;
}
@Override public long asLong() {
throw new IllegalStateException("this HashCode only has 32 bits; cannot create a long");
}
@Override
public long padToLong() {
return UnsignedInts.toLong(hash);
}
private static final long serialVersionUID = 0;
}
/**
* Creates a 64-bit {@code HashCode}, of which the bytes will form the passed long, interpreted
* in little endian order.
*/
public static HashCode fromLong(long hash) {
return new LongHashCode(hash);
}
private static final class LongHashCode extends HashCode implements Serializable {
final long hash;
LongHashCode(long hash) {
this.hash = hash;
}
@Override public int bits() {
return 64;
}
@Override public byte[] asBytes() {
return new byte[] {
(byte) hash,
(byte) (hash >> 8),
(byte) (hash >> 16),
(byte) (hash >> 24),
(byte) (hash >> 32),
(byte) (hash >> 40),
(byte) (hash >> 48),
(byte) (hash >> 56)};
}
@Override public int asInt() {
return (int) hash;
}
@Override public long asLong() {
return hash;
}
@Override
public long padToLong() {
return hash;
}
private static final long serialVersionUID = 0;
}
/**
* Creates a {@code HashCode} from a byte array. The array is defensively copied to preserve
* the immutability contract of {@code HashCode}. The array cannot be empty.
*/
public static HashCode fromBytes(byte[] bytes) {
checkArgument(bytes.length >= 1, "A HashCode must contain at least 1 byte.");
return fromBytesNoCopy(bytes.clone());
}
/**
* Creates a {@code HashCode} from a byte array. The array is <i>not</i> copied defensively,
* so it must be handed-off so as to preserve the immutability contract of {@code HashCode}.
*/
static HashCode fromBytesNoCopy(byte[] bytes) {
return new BytesHashCode(bytes);
}
private static final class BytesHashCode extends HashCode implements Serializable {
final byte[] bytes;
BytesHashCode(byte[] bytes) {
this.bytes = checkNotNull(bytes);
}
@Override public int bits() {
return bytes.length * 8;
}
@Override public byte[] asBytes() {
return bytes.clone();
}
@Override public int asInt() {
checkState(bytes.length >= 4,
"HashCode#asInt() requires >= 4 bytes (it only has %s bytes).", bytes.length);
return (bytes[0] & 0xFF)
| ((bytes[1] & 0xFF) << 8)
| ((bytes[2] & 0xFF) << 16)
| ((bytes[3] & 0xFF) << 24);
}
@Override public long asLong() {
checkState(bytes.length >= 8,
"HashCode#asLong() requires >= 8 bytes (it only has %s bytes).", bytes.length);
return (bytes[0] & 0xFFL)
| ((bytes[1] & 0xFFL) << 8)
| ((bytes[2] & 0xFFL) << 16)
| ((bytes[3] & 0xFFL) << 24)
| ((bytes[4] & 0xFFL) << 32)
| ((bytes[5] & 0xFFL) << 40)
| ((bytes[6] & 0xFFL) << 48)
| ((bytes[7] & 0xFFL) << 56);
}
@Override
public long padToLong() {
return (bytes.length < 8) ? UnsignedInts.toLong(asInt()) : asLong();
}
@Override
public int hashCode() {
if (bytes.length >= 4) {
return asInt();
} else {
int val = (bytes[0] & 0xFF);
for (int i = 1; i < bytes.length; i++) {
val |= ((bytes[i] & 0xFF) << (i * 8));
}
return val;
}
}
private static final long serialVersionUID = 0;
}
}
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