org.glowroot.shaded.HdrHistogram.ShortCountsHistogram Maven / Gradle / Ivy
/**
* Written by Gil Tene of Azul Systems, and released to the public domain,
* as explained at http://creativecommons.org/publicdomain/zero/1.0/
*
* @author Gil Tene
*/
package org.glowroot.shaded.HdrHistogram;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.nio.ByteBuffer;
import java.nio.ShortBuffer;
import java.util.Arrays;
import java.util.zip.DataFormatException;
/**
* A High Dynamic Range (HDR) Histogram using a short count type
*
* See package description for {@link org.glowroot.shaded.HdrHistogram} for details.
*/
public class ShortCountsHistogram extends AbstractHistogram {
long totalCount;
short[] counts;
int normalizingIndexOffset;
@Override
long getCountAtIndex(final int index) {
return counts[normalizeIndex(index, normalizingIndexOffset, countsArrayLength)];
}
@Override
long getCountAtNormalizedIndex(final int index) {
return counts[index];
}
@Override
void incrementCountAtIndex(final int index) {
int normalizedIndex = normalizeIndex(index, normalizingIndexOffset, countsArrayLength);
short currentCount = counts[normalizedIndex];
short newCount = (short) (currentCount + 1);
if (newCount < 0) {
throw new IllegalStateException("would overflow short integer count");
}
counts[normalizedIndex] = newCount;
}
@Override
void addToCountAtIndex(final int index, final long value) {
int normalizedIndex = normalizeIndex(index, normalizingIndexOffset, countsArrayLength);
short currentCount = counts[normalizedIndex];
if ((value < 0) || (value > Short.MAX_VALUE)) {
throw new IllegalArgumentException("would overflow short integer count");
}
short newCount = (short) (currentCount + value);
if (newCount < 0) {
throw new IllegalStateException("would overflow short integer count");
}
counts[normalizedIndex] = newCount;
}
@Override
void setCountAtIndex(int index, long value) {
setCountAtNormalizedIndex(normalizeIndex(index, normalizingIndexOffset, countsArrayLength), value);
}
@Override
void setCountAtNormalizedIndex(int index, long value) {
if ((value < 0) || (value > Short.MAX_VALUE)) {
throw new IllegalArgumentException("would overflow short integer count");
}
counts[index] = (short) value;
}
@Override
int getNormalizingIndexOffset() {
return normalizingIndexOffset;
}
@Override
void setNormalizingIndexOffset(int normalizingIndexOffset) {
this.normalizingIndexOffset = normalizingIndexOffset;
}
@Override
void shiftNormalizingIndexByOffset(int offsetToAdd, boolean lowestHalfBucketPopulated) {
nonConcurrentNormalizingIndexShift(offsetToAdd, lowestHalfBucketPopulated);
}
@Override
void clearCounts() {
java.util.Arrays.fill(counts, (short) 0);
totalCount = 0;
}
@Override public ShortCountsHistogram copy() {
ShortCountsHistogram copy = new ShortCountsHistogram(this);
copy.add(this);
return copy;
}
@Override
public ShortCountsHistogram copyCorrectedForCoordinatedOmission(final long expectedIntervalBetweenValueSamples) {
ShortCountsHistogram toHistogram = new ShortCountsHistogram(this);
toHistogram.addWhileCorrectingForCoordinatedOmission(this, expectedIntervalBetweenValueSamples);
return toHistogram;
}
@Override
public long getTotalCount() {
return totalCount;
}
@Override
void setTotalCount(final long totalCount) {
this.totalCount = totalCount;
}
@Override
void incrementTotalCount() {
totalCount++;
}
@Override
void addToTotalCount(long value) {
totalCount += value;
}
@Override
int _getEstimatedFootprintInBytes() {
return (512 + (2 * counts.length));
}
@Override
void resize(long newHighestTrackableValue) {
int oldNormalizedZeroIndex = normalizeIndex(0, normalizingIndexOffset, countsArrayLength);
establishSize(newHighestTrackableValue);
int countsDelta = countsArrayLength - counts.length;
counts = Arrays.copyOf(counts, countsArrayLength);
if (oldNormalizedZeroIndex != 0) {
// We need to shift the stuff from the zero index and up to the end of the array:
int newNormalizedZeroIndex = oldNormalizedZeroIndex + countsDelta;
int lengthToCopy = (countsArrayLength - countsDelta) - oldNormalizedZeroIndex;
System.arraycopy(counts, oldNormalizedZeroIndex, counts, newNormalizedZeroIndex, lengthToCopy);
}
}
/**
* Construct an auto-resizing ShortCountsHistogram with a lowest discernible value of 1 and an auto-adjusting
* highestTrackableValue. Can auto-resize up to track values up to (Long.MAX_VALUE / 2).
*
* @param numberOfSignificantValueDigits Specifies the precision to use. This is the number of significant
* decimal digits to which the histogram will maintain value resolution
* and separation. Must be a non-negative integer between 0 and 5.
*/
public ShortCountsHistogram(final int numberOfSignificantValueDigits) {
this(1, 2, numberOfSignificantValueDigits);
setAutoResize(true);
}
/**
* Construct a ShortCountsHistogram given the Highest value to be tracked and a number of significant decimal digits. The
* histogram will be constructed to implicitly track (distinguish from 0) values as low as 1.
*
* @param highestTrackableValue The highest value to be tracked by the histogram. Must be a positive
* integer that is {@literal >=} 2.
* @param numberOfSignificantValueDigits Specifies the precision to use. This is the number of significant
* decimal digits to which the histogram will maintain value resolution
* and separation. Must be a non-negative integer between 0 and 5.
*/
public ShortCountsHistogram(final long highestTrackableValue, final int numberOfSignificantValueDigits) {
this(1, highestTrackableValue, numberOfSignificantValueDigits);
}
/**
* Construct a ShortCountsHistogram given the Lowest and Highest values to be tracked and a number of significant
* decimal digits. Providing a lowestDiscernibleValue is useful is situations where the units used
* for the histogram's values are much smaller that the minimal accuracy required. E.g. when tracking
* time values stated in nanosecond units, where the minimal accuracy required is a microsecond, the
* proper value for lowestDiscernibleValue would be 1000.
*
* @param lowestDiscernibleValue The lowest value that can be tracked (distinguished from 0) by the histogram.
* Must be a positive integer that is {@literal >=} 1. May be internally rounded
* down to nearest power of 2.
* @param highestTrackableValue The highest value to be tracked by the histogram. Must be a positive
* integer that is {@literal >=} (2 * lowestDiscernibleValue).
* @param numberOfSignificantValueDigits Specifies the precision to use. This is the number of significant
* decimal digits to which the histogram will maintain value resolution
* and separation. Must be a non-negative integer between 0 and 5.
*/
public ShortCountsHistogram(final long lowestDiscernibleValue, final long highestTrackableValue,
final int numberOfSignificantValueDigits) {
super(lowestDiscernibleValue, highestTrackableValue, numberOfSignificantValueDigits);
counts = new short[countsArrayLength];
wordSizeInBytes = 2;
}
/**
* Construct a histogram with the same range settings as a given source histogram,
* duplicating the source's start/end timestamps (but NOT it's contents)
* @param source The source histogram to duplicate
*/
public ShortCountsHistogram(final AbstractHistogram source) {
super(source);
counts = new short[countsArrayLength];
wordSizeInBytes = 2;
}
/**
* Construct a new histogram by decoding it from a ByteBuffer.
* @param buffer The buffer to decode from
* @param minBarForHighestTrackableValue Force highestTrackableValue to be set at least this high
* @return The newly constructed histogram
*/
public static ShortCountsHistogram decodeFromByteBuffer(final ByteBuffer buffer,
final long minBarForHighestTrackableValue) {
return (ShortCountsHistogram) decodeFromByteBuffer(buffer, ShortCountsHistogram.class,
minBarForHighestTrackableValue);
}
/**
* Construct a new histogram by decoding it from a compressed form in a ByteBuffer.
* @param buffer The buffer to decode from
* @param minBarForHighestTrackableValue Force highestTrackableValue to be set at least this high
* @return The newly constructed histogram
* @throws DataFormatException on error parsing/decompressing the buffer
*/
public static ShortCountsHistogram decodeFromCompressedByteBuffer(final ByteBuffer buffer,
final long minBarForHighestTrackableValue) throws DataFormatException {
return (ShortCountsHistogram) decodeFromCompressedByteBuffer(buffer, ShortCountsHistogram.class,
minBarForHighestTrackableValue);
}
private void readObject(final ObjectInputStream o)
throws IOException, ClassNotFoundException {
o.defaultReadObject();
}
@Override
synchronized void fillCountsArrayFromBuffer(final ByteBuffer buffer, final int length) {
buffer.asShortBuffer().get(counts, 0, length);
}
// We try to cache the LongBuffer used in output cases, as repeated
// output form the same histogram using the same buffer is likely:
private ShortBuffer cachedDstShortBuffer = null;
private ByteBuffer cachedDstByteBuffer = null;
private int cachedDstByteBufferPosition = 0;
@Override
synchronized void fillBufferFromCountsArray(final ByteBuffer buffer, final int length) {
if ((cachedDstShortBuffer == null) ||
(buffer != cachedDstByteBuffer) ||
(buffer.position() != cachedDstByteBufferPosition)) {
cachedDstByteBuffer = buffer;
cachedDstByteBufferPosition = buffer.position();
cachedDstShortBuffer = buffer.asShortBuffer();
}
cachedDstShortBuffer.rewind();
int zeroIndex = normalizeIndex(0, getNormalizingIndexOffset(), countsArrayLength);
int lengthFromZeroIndexToEnd = Math.min(length, (countsArrayLength - zeroIndex));
int remainingLengthFromNormalizedZeroIndex = length - lengthFromZeroIndexToEnd;
cachedDstShortBuffer.put(counts, zeroIndex, lengthFromZeroIndexToEnd);
cachedDstShortBuffer.put(counts, 0, remainingLengthFromNormalizedZeroIndex);
}
}