com.couchbase.client.core.deps.org.HdrHistogram.ZigZagEncoding Maven / Gradle / Ivy
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The official Couchbase JVM Core IO Library
/**
* 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 com.couchbase.client.core.deps.org.HdrHistogram;
import java.nio.ByteBuffer;
/**
* This class provides encoding and decoding methods for writing and reading
* ZigZag-encoded LEB128-64b9B-variant (Little Endian Base 128) values to/from a
* {@link ByteBuffer}. LEB128's variable length encoding provides for using a
* smaller nuber of bytes for smaller values, and the use of ZigZag encoding
* allows small (closer to zero) negative values to use fewer bytes. Details
* on both LEB128 and ZigZag can be readily found elsewhere.
*
* The LEB128-64b9B-variant encoding used here diverges from the "original"
* LEB128 as it extends to 64 bit values: In the original LEB128, a 64 bit
* value can take up to 10 bytes in the stream, where this variant's encoding
* of a 64 bit values will max out at 9 bytes.
*
* As such, this encoder/decoder should NOT be used for encoding or decoding
* "standard" LEB128 formats (e.g. Google Protocol Buffers).
*/
class ZigZagEncoding {
/**
* Writes a long value to the given buffer in LEB128 ZigZag encoded format
* @param buffer the buffer to write to
* @param value the value to write to the buffer
*/
static void putLong(ByteBuffer buffer, long value) {
value = (value << 1) ^ (value >> 63);
if (value >>> 7 == 0) {
buffer.put((byte) value);
} else {
buffer.put((byte) ((value & 0x7F) | 0x80));
if (value >>> 14 == 0) {
buffer.put((byte) (value >>> 7));
} else {
buffer.put((byte) (value >>> 7 | 0x80));
if (value >>> 21 == 0) {
buffer.put((byte) (value >>> 14));
} else {
buffer.put((byte) (value >>> 14 | 0x80));
if (value >>> 28 == 0) {
buffer.put((byte) (value >>> 21));
} else {
buffer.put((byte) (value >>> 21 | 0x80));
if (value >>> 35 == 0) {
buffer.put((byte) (value >>> 28));
} else {
buffer.put((byte) (value >>> 28 | 0x80));
if (value >>> 42 == 0) {
buffer.put((byte) (value >>> 35));
} else {
buffer.put((byte) (value >>> 35 | 0x80));
if (value >>> 49 == 0) {
buffer.put((byte) (value >>> 42));
} else {
buffer.put((byte) (value >>> 42 | 0x80));
if (value >>> 56 == 0) {
buffer.put((byte) (value >>> 49));
} else {
buffer.put((byte) (value >>> 49 | 0x80));
buffer.put((byte) (value >>> 56));
}
}
}
}
}
}
}
}
}
/**
* Writes an int value to the given buffer in LEB128-64b9B ZigZag encoded format
* @param buffer the buffer to write to
* @param value the value to write to the buffer
*/
static void putInt(ByteBuffer buffer, int value) {
value = (value << 1) ^ (value >> 31);
if (value >>> 7 == 0) {
buffer.put((byte) value);
} else {
buffer.put((byte) ((value & 0x7F) | 0x80));
if (value >>> 14 == 0) {
buffer.put((byte) (value >>> 7));
} else {
buffer.put((byte) (value >>> 7 | 0x80));
if (value >>> 21 == 0) {
buffer.put((byte) (value >>> 14));
} else {
buffer.put((byte) (value >>> 14 | 0x80));
if (value >>> 28 == 0) {
buffer.put((byte) (value >>> 21));
} else {
buffer.put((byte) (value >>> 21 | 0x80));
buffer.put((byte) (value >>> 28));
}
}
}
}
}
/**
* Read an LEB128-64b9B ZigZag encoded long value from the given buffer
* @param buffer the buffer to read from
* @return the value read from the buffer
*/
static long getLong(ByteBuffer buffer) {
long v = buffer.get();
long value = v & 0x7F;
if ((v & 0x80) != 0) {
v = buffer.get();
value |= (v & 0x7F) << 7;
if ((v & 0x80) != 0) {
v = buffer.get();
value |= (v & 0x7F) << 14;
if ((v & 0x80) != 0) {
v = buffer.get();
value |= (v & 0x7F) << 21;
if ((v & 0x80) != 0) {
v = buffer.get();
value |= (v & 0x7F) << 28;
if ((v & 0x80) != 0) {
v = buffer.get();
value |= (v & 0x7F) << 35;
if ((v & 0x80) != 0) {
v = buffer.get();
value |= (v & 0x7F) << 42;
if ((v & 0x80) != 0) {
v = buffer.get();
value |= (v & 0x7F) << 49;
if ((v & 0x80) != 0) {
v = buffer.get();
value |= v << 56;
}
}
}
}
}
}
}
}
value = (value >>> 1) ^ (-(value & 1));
return value;
}
/**
* Read an LEB128-64b9B ZigZag encoded int value from the given buffer
* @param buffer the buffer to read from
* @return the value read from the buffer
*/
static int getInt (ByteBuffer buffer) {
int v = buffer.get();
int value = v & 0x7F;
if ((v & 0x80) != 0) {
v = buffer.get();
value |= (v & 0x7F) << 7;
if ((v & 0x80) != 0) {
v = buffer.get();
value |= (v & 0x7F) << 14;
if ((v & 0x80) != 0) {
v = buffer.get();
value |= (v & 0x7F) << 21;
if ((v & 0x80) != 0) {
v = buffer.get();
value |= (v & 0x7F) << 28;
}
}
}
}
value = (value >>> 1) ^ (-(value & 1));
return value;
}
}