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/*
* 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 java.util.Arrays;
import static ai.vespa.airlift.zstd.UnsafeUtil.UNSAFE;
import static sun.misc.Unsafe.ARRAY_BYTE_BASE_OFFSET;
class Histogram
{
private Histogram()
{
}
// TODO: count parallel heuristic for large inputs
private static void count(Object inputBase, long inputAddress, int inputSize, int[] counts)
{
long input = inputAddress;
Arrays.fill(counts, 0);
for (int i = 0; i < inputSize; i++) {
int symbol = UNSAFE.getByte(inputBase, input) & 0xFF;
input++;
counts[symbol]++;
}
}
public static int findLargestCount(int[] counts, int maxSymbol)
{
int max = 0;
for (int i = 0; i <= maxSymbol; i++) {
if (counts[i] > max) {
max = counts[i];
}
}
return max;
}
public static int findMaxSymbol(int[] counts, int maxSymbol)
{
while (counts[maxSymbol] == 0) {
maxSymbol--;
}
return maxSymbol;
}
public static void count(byte[] input, int length, int[] counts)
{
count(input, ARRAY_BYTE_BASE_OFFSET, length, counts);
}
}
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