org.apache.cassandra.io.util.SizedInts Maven / Gradle / Ivy
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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.cassandra.io.util;
import java.io.IOException;
import java.nio.ByteBuffer;
/**
* Utility class for sizing, writing and reading ints with length stored separately.
* Used for trie payloads.
*/
public class SizedInts
{
/**
* Returns the number of bytes we need to store the given position.
* This method understands 0 to need 1 byte.
*
* If your use case permits 0 to be encoded in 0 length, use {@link #sizeAllowingZero} below.
*/
public static int nonZeroSize(long value)
{
if (value < 0)
value = ~value;
int lz = Long.numberOfLeadingZeros(value); // 1 <= lz <= 64
return (64 - lz + 1 + 7) / 8; // significant bits, +1 for sign, rounded up. At least 1, at most 8.
}
/**
* Returns the number of bytes we need to store the given position. Returns 0 for 0 argument.
*/
public static int sizeAllowingZero(long value)
{
if (value == 0)
return 0;
return nonZeroSize(value);
}
public static long read(ByteBuffer src, int startPos, int bytes)
{
switch (bytes)
{
case 0:
return 0;
case 1:
return src.get(startPos);
case 2:
return src.getShort(startPos);
case 3:
{
long high = src.get(startPos);
return (high << 16L) | (src.getShort(startPos + 1) & 0xFFFFL);
}
case 4:
return src.getInt(startPos);
case 5:
{
long high = src.get(startPos);
return (high << 32L) | (src.getInt(startPos + 1) & 0xFFFFFFFFL);
}
case 6:
{
long high = src.getShort(startPos);
return (high << 32L) | (src.getInt(startPos + 2) & 0xFFFFFFFFL);
}
case 7:
{
long high = src.get(startPos);
high = (high << 16L) | (src.getShort(startPos + 1) & 0xFFFFL);
return (high << 32L) | (src.getInt(startPos + 3) & 0xFFFFFFFFL);
}
case 8:
return src.getLong(startPos);
default:
throw new AssertionError();
}
}
public static long readUnsigned(ByteBuffer src, int startPos, int bytes)
{
if (bytes == 8)
return src.getLong(startPos);
else
return read(src, startPos, bytes) & ((1L << (bytes * 8)) - 1);
}
public static void write(DataOutputPlus dest, long value, int size) throws IOException
{
dest.writeMostSignificantBytes(value << ((8 - size) * 8), size);
}
}