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Fork of https://github.com/airlift/aircompressor (zstd only).
This module is temporary until we get an official release that includes the
ZstdInputStream API (which is already implemented by two different people
but neither PR shows any progress).
/*
* 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 ai.vespa.airlift.zstd;
import static ai.vespa.airlift.zstd.Constants.SIZE_OF_LONG;
import static ai.vespa.airlift.zstd.UnsafeUtil.UNSAFE;
import static sun.misc.Unsafe.ARRAY_BYTE_BASE_OFFSET;
class SequenceStore
{
public final byte[] literalsBuffer;
public int literalsLength;
public final int[] offsets;
public final int[] literalLengths;
public final int[] matchLengths;
public int sequenceCount;
public final byte[] literalLengthCodes;
public final byte[] matchLengthCodes;
public final byte[] offsetCodes;
public LongField longLengthField;
public int longLengthPosition;
public enum LongField
{
LITERAL, MATCH
}
private static final byte[] LITERAL_LENGTH_CODE = {0, 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 11, 12, 13, 14, 15,
16, 16, 17, 17, 18, 18, 19, 19,
20, 20, 20, 20, 21, 21, 21, 21,
22, 22, 22, 22, 22, 22, 22, 22,
23, 23, 23, 23, 23, 23, 23, 23,
24, 24, 24, 24, 24, 24, 24, 24,
24, 24, 24, 24, 24, 24, 24, 24};
private static final byte[] MATCH_LENGTH_CODE = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31,
32, 32, 33, 33, 34, 34, 35, 35, 36, 36, 36, 36, 37, 37, 37, 37,
38, 38, 38, 38, 38, 38, 38, 38, 39, 39, 39, 39, 39, 39, 39, 39,
40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40,
41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41,
42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42,
42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42};
public SequenceStore(int blockSize, int maxSequences)
{
offsets = new int[maxSequences];
literalLengths = new int[maxSequences];
matchLengths = new int[maxSequences];
literalLengthCodes = new byte[maxSequences];
matchLengthCodes = new byte[maxSequences];
offsetCodes = new byte[maxSequences];
literalsBuffer = new byte[blockSize];
reset();
}
public void appendLiterals(Object inputBase, long inputAddress, int inputSize)
{
UNSAFE.copyMemory(inputBase, inputAddress, literalsBuffer, ARRAY_BYTE_BASE_OFFSET + literalsLength, inputSize);
literalsLength += inputSize;
}
public void storeSequence(Object literalBase, long literalAddress, int literalLength, int offsetCode, int matchLengthBase)
{
long input = literalAddress;
long output = ARRAY_BYTE_BASE_OFFSET + literalsLength;
int copied = 0;
do {
UNSAFE.putLong(literalsBuffer, output, UNSAFE.getLong(literalBase, input));
input += SIZE_OF_LONG;
output += SIZE_OF_LONG;
copied += SIZE_OF_LONG;
}
while (copied < literalLength);
literalsLength += literalLength;
if (literalLength > 65535) {
longLengthField = LongField.LITERAL;
longLengthPosition = sequenceCount;
}
literalLengths[sequenceCount] = literalLength;
offsets[sequenceCount] = offsetCode + 1;
if (matchLengthBase > 65535) {
longLengthField = LongField.MATCH;
longLengthPosition = sequenceCount;
}
matchLengths[sequenceCount] = matchLengthBase;
sequenceCount++;
}
public void reset()
{
literalsLength = 0;
sequenceCount = 0;
longLengthField = null;
}
public void generateCodes()
{
for (int i = 0; i < sequenceCount; ++i) {
literalLengthCodes[i] = (byte) literalLengthToCode(literalLengths[i]);
offsetCodes[i] = (byte) Util.highestBit(offsets[i]);
matchLengthCodes[i] = (byte) matchLengthToCode(matchLengths[i]);
}
if (longLengthField == LongField.LITERAL) {
literalLengthCodes[longLengthPosition] = Constants.MAX_LITERALS_LENGTH_SYMBOL;
}
if (longLengthField == LongField.MATCH) {
matchLengthCodes[longLengthPosition] = Constants.MAX_MATCH_LENGTH_SYMBOL;
}
}
private static int literalLengthToCode(int literalLength)
{
if (literalLength >= 64) {
return Util.highestBit(literalLength) + 19;
}
else {
return LITERAL_LENGTH_CODE[literalLength];
}
}
/*
* matchLengthBase = matchLength - MINMATCH
* (that's how it's stored in SequenceStore)
*/
private static int matchLengthToCode(int matchLengthBase)
{
if (matchLengthBase >= 128) {
return Util.highestBit(matchLengthBase) + 36;
}
else {
return MATCH_LENGTH_CODE[matchLengthBase];
}
}
}