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PROTON-2287 Improve Symbol decoding cache
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125 changes: 125 additions & 0 deletions
125
proton-j/src/main/java/org/apache/qpid/proton/codec/Hashing.java
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/* | ||
* | ||
* Licensed to the Apache Software Foundation (ASF) under one | ||
* or more contributor license agreements. See the NOTICE file | ||
* distributed with this work for additional information | ||
* regarding copyright ownership. The ASF licenses this file | ||
* to you 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 org.apache.qpid.proton.codec; | ||
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import java.nio.ByteBuffer; | ||
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public class Hashing { | ||
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private Hashing() { | ||
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} | ||
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// this const propagation should be already handled by the JIT | ||
// but we do this to make it more readable | ||
private static final int PRIME_1 = 31; | ||
private static final int PRIME_2 = PRIME_1 * PRIME_1; | ||
private static final int PRIME_3 = PRIME_2 * PRIME_1; | ||
private static final int PRIME_4 = PRIME_3 * PRIME_1; | ||
private static final int PRIME_5 = PRIME_4 * PRIME_1; | ||
private static final int PRIME_6 = PRIME_5 * PRIME_1; | ||
private static final int PRIME_7 = PRIME_6 * PRIME_1; | ||
private static final int PRIME_8 = PRIME_7 * PRIME_1; | ||
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public static int byteBufferCompatibleHashCode(ByteBuffer byteBuffer) { | ||
if (byteBuffer.hasArray()) { | ||
final int arrayOffset = byteBuffer.arrayOffset(); | ||
final int arrayPosition = arrayOffset + byteBuffer.position(); | ||
final int arrayLimit = arrayOffset + byteBuffer.limit(); | ||
return byteBufferCompatibleHashCode(byteBuffer.array(), arrayPosition, arrayLimit); | ||
} | ||
// direct ByteBuffers does have some heavy-weight bound checks and memory barriers that | ||
// we just hope JIT to be better then us! | ||
return byteBuffer.hashCode(); | ||
} | ||
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public static int byteBufferCompatibleHashCode(byte[] bytes, int position, int limit) { | ||
int h = 1; | ||
int remaining = limit - position; | ||
if (remaining == 0) { | ||
return h; | ||
} | ||
int index = limit - 1; | ||
// unrolled version | ||
final int bytesCount = remaining & 7; | ||
if (bytesCount > 0) { | ||
assert h == 1; | ||
h = unrolledHashCode(bytes, index, bytesCount, 1); | ||
index -= bytesCount; | ||
} | ||
final long longsCount = remaining >>> 3; | ||
// let's break the data dependency of each per element hash code | ||
// and save bound checks by manual unrolling 8 ops at time | ||
for (int i = 0; i < longsCount; i++) { | ||
final byte b7 = bytes[index]; | ||
final byte b6 = bytes[index - 1]; | ||
final byte b5 = bytes[index - 2]; | ||
final byte b4 = bytes[index - 3]; | ||
final byte b3 = bytes[index - 4]; | ||
final byte b2 = bytes[index - 5]; | ||
final byte b1 = bytes[index - 6]; | ||
final byte b0 = bytes[index - 7]; | ||
h = PRIME_8 * h + | ||
PRIME_7 * b7 + | ||
PRIME_6 * b6 + | ||
PRIME_5 * b5 + | ||
PRIME_4 * b4 + | ||
PRIME_3 * b3 + | ||
PRIME_2 * b2 + | ||
PRIME_1 * b1 + | ||
b0; | ||
index -= Long.BYTES; | ||
} | ||
return h; | ||
} | ||
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private static int unrolledHashCode(byte[] bytes, int index, int bytesCount, int h) { | ||
// there is still the hash data dependency but is more friendly | ||
// then a plain loop, given that we know no loop is needed here | ||
assert bytesCount > 0 && bytesCount < 8; | ||
h = PRIME_1 * h + bytes[index]; | ||
if (bytesCount == 1) { | ||
return h; | ||
} | ||
h = PRIME_1 * h + bytes[index - 1]; | ||
if (bytesCount == 2) { | ||
return h; | ||
} | ||
h = PRIME_1 * h + bytes[index - 2]; | ||
if (bytesCount == 3) { | ||
return h; | ||
} | ||
h = PRIME_1 * h + bytes[index - 3]; | ||
if (bytesCount == 4) { | ||
return h; | ||
} | ||
h = PRIME_1 * h + bytes[index - 4]; | ||
if (bytesCount == 5) { | ||
return h; | ||
} | ||
h = PRIME_1 * h + bytes[index - 5]; | ||
if (bytesCount == 6) { | ||
return h; | ||
} | ||
h = PRIME_1 * h + bytes[index - 6]; | ||
return h; | ||
} | ||
} |
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