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The Apache Cassandra Project develops a highly scalable second-generation distributed database, bringing together Dynamo's fully distributed design and Bigtable's ColumnFamily-based data model.
/*
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// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc. All rights reserved.
// https://developers.google.com/protocol-buffers/
//
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package org.apache.cassandra.utils.vint;
import java.io.DataInput;
import java.io.IOException;
import java.nio.ByteBuffer;
import io.netty.util.concurrent.FastThreadLocal;
import net.nicoulaj.compilecommand.annotations.Inline;
import org.apache.cassandra.db.marshal.ValueAccessor;
import org.apache.cassandra.io.util.DataInputPlus;
import org.apache.cassandra.io.util.DataOutputPlus;
/**
* Borrows idea from
* https://developers.google.com/protocol-buffers/docs/encoding#varints
*/
public class VIntCoding
{
protected static final FastThreadLocal encodingBuffer = new FastThreadLocal()
{
@Override
public byte[] initialValue()
{
return new byte[9];
}
};
public static final int MAX_SIZE = 10;
/**
* Throw when attempting to decode a vint and the output type
* doesn't have enough space to fit the value that was decoded
*/
public static class VIntOutOfRangeException extends RuntimeException
{
public final long value;
private VIntOutOfRangeException(long value)
{
super(value + " is out of range for a 32-bit integer");
this.value = value;
}
}
public static long readUnsignedVInt(DataInput input) throws IOException
{
int firstByte = input.readByte();
//Bail out early if this is one byte, necessary or it fails later
if (firstByte >= 0)
return firstByte;
int size = numberOfExtraBytesToRead(firstByte);
long retval = firstByte & firstByteValueMask(size);
for (int ii = 0; ii < size; ii++)
{
byte b = input.readByte();
retval <<= 8;
retval |= b & 0xff;
}
return retval;
}
public static void skipUnsignedVInt(DataInputPlus input) throws IOException
{
int firstByte = input.readByte();
if (firstByte < 0)
input.skipBytesFully(numberOfExtraBytesToRead(firstByte));
}
/**
* Read up to a 32-bit integer back, using the unsigned (no zigzag) encoding.
*
* Note this method is the same as {@link #readUnsignedVInt(DataInput)},
* except that we do *not* block if there are not enough bytes in the buffer
* to reconstruct the value.
*
* @throws VIntOutOfRangeException If the vint doesn't fit into a 32-bit integer
*/
public static int getUnsignedVInt32(ByteBuffer input, int readerIndex)
{
return checkedCast(getUnsignedVInt(input, readerIndex));
}
public static int getVInt32(ByteBuffer input, int readerIndex)
{
return checkedCast(decodeZigZag64(getUnsignedVInt(input, readerIndex)));
}
public static long getVInt(ByteBuffer input, int readerIndex)
{
return decodeZigZag64(getUnsignedVInt(input, readerIndex));
}
public static long getUnsignedVInt(ByteBuffer input, int readerIndex)
{
return getUnsignedVInt(input, readerIndex, input.limit());
}
public static long getUnsignedVInt(ByteBuffer input, int readerIndex, int readerLimit)
{
if (readerIndex < 0)
throw new IllegalArgumentException("Reader index should be non-negative, but was " + readerIndex);
if (readerIndex >= readerLimit)
return -1;
int firstByte = input.get(readerIndex++);
//Bail out early if this is one byte, necessary or it fails later
if (firstByte >= 0)
return firstByte;
int size = numberOfExtraBytesToRead(firstByte);
if (readerIndex + size > readerLimit)
return -1;
long retval = firstByte & firstByteValueMask(size);
for (int ii = 0; ii < size; ii++)
{
byte b = input.get(readerIndex++);
retval <<= 8;
retval |= b & 0xff;
}
return retval;
}
public static int getUnsignedVInt32(V input, ValueAccessor accessor, int readerIndex)
{
return checkedCast(getUnsignedVInt(input, accessor, readerIndex));
}
public static int getVInt32(V input, ValueAccessor accessor, int readerIndex)
{
return checkedCast(decodeZigZag64(getUnsignedVInt(input, accessor, readerIndex)));
}
public static long getVInt(V input, ValueAccessor accessor, int readerIndex)
{
return decodeZigZag64(getUnsignedVInt(input, accessor, readerIndex));
}
public static long getUnsignedVInt(V input, ValueAccessor accessor, int readerIndex)
{
return getUnsignedVInt(input, accessor, readerIndex, accessor.size(input));
}
public static long getUnsignedVInt(V input, ValueAccessor accessor, int readerIndex, int readerLimit)
{
if (readerIndex < 0)
throw new IllegalArgumentException("Reader index should be non-negative, but was " + readerIndex);
if (readerIndex >= readerLimit)
return -1;
int firstByte = accessor.getByte(input, readerIndex++);
//Bail out early if this is one byte, necessary or it fails later
if (firstByte >= 0)
return firstByte;
int size = numberOfExtraBytesToRead(firstByte);
if (readerIndex + size > readerLimit)
return -1;
long retval = firstByte & firstByteValueMask(size);
for (int ii = 0; ii < size; ii++)
{
byte b = accessor.getByte(input, readerIndex++);
retval <<= 8;
retval |= b & 0xff;
}
return retval;
}
/**
* Computes size of an unsigned vint that starts at readerIndex of the provided ByteBuf.
*
* @return -1 if there are not enough bytes in the input to calculate the size; else, the vint unsigned value size in bytes.
*/
public static int computeUnsignedVIntSize(ByteBuffer input, int readerIndex)
{
return computeUnsignedVIntSize(input, readerIndex, input.limit());
}
public static int computeUnsignedVIntSize(ByteBuffer input, int readerIndex, int readerLimit)
{
if (readerIndex >= readerLimit)
return -1;
int firstByte = input.get(readerIndex);
return 1 + ((firstByte >= 0) ? 0 : numberOfExtraBytesToRead(firstByte));
}
public static long readVInt(DataInput input) throws IOException
{
return decodeZigZag64(readUnsignedVInt(input));
}
/**
* Read up to a signed 32-bit integer back.
*
* Assumes the vint was written using {@link #writeVInt32(int, DataOutputPlus)} or similar
* that zigzag encodes the integer.
*
* @throws VIntOutOfRangeException If the vint doesn't fit into a 32-bit integer
*/
public static int readVInt32(DataInput input) throws IOException
{
return checkedCast(decodeZigZag64(readUnsignedVInt(input)));
}
/**
* Read up to a 32-bit integer.
*
* This method assumes the original integer was written using {@link #writeUnsignedVInt32(int, DataOutputPlus)}
* or similar that doesn't zigzag encodes the vint.
*
* @throws VIntOutOfRangeException If the vint doesn't fit into a 32-bit integer
*/
public static int readUnsignedVInt32(DataInput input) throws IOException
{
return checkedCast(readUnsignedVInt(input));
}
// & this with the first byte to give the value part for a given extraBytesToRead encoded in the byte
public static int firstByteValueMask(int extraBytesToRead)
{
// by including the known 0bit in the mask, we can use this for encodeExtraBytesToRead
return 0xff >> extraBytesToRead;
}
public static int encodeExtraBytesToRead(int extraBytesToRead)
{
// because we have an extra bit in the value mask, we just need to invert it
return ~firstByteValueMask(extraBytesToRead);
}
public static int numberOfExtraBytesToRead(int firstByte)
{
// we count number of set upper bits; so if we simply invert all of the bits, we're golden
// this is aided by the fact that we only work with negative numbers, so when upcast to an int all
// of the new upper bits are also set, so by inverting we set all of them to zero
return Integer.numberOfLeadingZeros(~firstByte) - 24;
}
/** @deprecated See CASSANDRA-18099 */
@Deprecated(since = "5.0")
public static void writeUnsignedVInt(int value, DataOutputPlus output) throws IOException
{
throw new UnsupportedOperationException("Use writeUnsignedVInt32/readUnsignedVInt32");
}
@Inline
public static void writeUnsignedVInt(long value, DataOutputPlus output) throws IOException
{
int size = VIntCoding.computeUnsignedVIntSize(value);
if (size == 1)
{
output.writeByte((int) value);
}
else if (size < 9)
{
int shift = (8 - size) << 3;
int extraBytes = size - 1;
long mask = (long)VIntCoding.encodeExtraBytesToRead(extraBytes) << 56;
long register = (value << shift) | mask;
output.writeMostSignificantBytes(register, size);
}
else if (size == 9)
{
output.write((byte) 0xFF);
output.writeLong(value);
}
else
{
throw new AssertionError();
}
}
public static void writeUnsignedVInt32(int value, DataOutputPlus output) throws IOException
{
writeUnsignedVInt((long)value, output);
}
/** @deprecated See CASSANDRA-18099 */
@Deprecated(since = "5.0")
public static void writeUnsignedVInt(int value, ByteBuffer output) throws IOException
{
throw new UnsupportedOperationException("Use writeUnsignedVInt32/getUnsignedVInt32");
}
@Inline
public static void writeUnsignedVInt(long value, ByteBuffer output)
{
int size = VIntCoding.computeUnsignedVIntSize(value);
if (size == 1)
{
output.put((byte) (value));
}
else if (size < 9)
{
int limit = output.limit();
int pos = output.position();
if (limit - pos >= 8)
{
int shift = (8 - size) << 3;
int extraBytes = size - 1;
long mask = (long)VIntCoding.encodeExtraBytesToRead(extraBytes) << 56;
long register = (value << shift) | mask;
output.putLong(pos, register);
output.position(pos + size);
}
else
{
output.put(VIntCoding.encodeUnsignedVInt(value, size), 0, size);
}
}
else if (size == 9)
{
output.put((byte) 0xFF);
output.putLong(value);
}
else
{
throw new AssertionError();
}
}
@Inline
public static int writeVInt(long value, V output, int offset, ValueAccessor accessor)
{
return writeUnsignedVInt(encodeZigZag64(value), output, offset, accessor);
}
@Inline
public static int writeVInt32(int value, V output, int offset, ValueAccessor accessor)
{
return writeVInt(value, output, offset, accessor);
}
@Inline
public static int writeUnsignedVInt32(int value, V output, int offset, ValueAccessor accessor)
{
return writeUnsignedVInt(value, output, offset, accessor);
}
@Inline
public static int writeUnsignedVInt(long value, V output, int offset, ValueAccessor accessor)
{
int size = VIntCoding.computeUnsignedVIntSize(value);
int written = 0;
if (size == 1)
{
written += accessor.putByte(output, offset, (byte) (value));
}
else if (size < 9)
{
if (accessor.remaining(output, offset) >= 8)
{
int shift = (8 - size) << 3;
int extraBytes = size - 1;
long mask = (long)VIntCoding.encodeExtraBytesToRead(extraBytes) << 56;
long register = (value << shift) | mask;
accessor.putLong(output, offset, register);
written += size;
}
else
{
written += accessor.putBytes(output, offset, VIntCoding.encodeUnsignedVInt(value, size), 0, size);
}
}
else if (size == 9)
{
written += accessor.putByte(output, offset, (byte) 0xFF);
written += accessor.putLong(output, offset + written, value);
}
else
{
throw new AssertionError();
}
return written;
}
@Inline
public static void writeUnsignedVInt32(int value, ByteBuffer output)
{
writeUnsignedVInt((long)value, output);
}
/** @deprecated See CASSANDRA-18099 */
@Deprecated(since = "5.0")
public static void writeVInt(int value, DataOutputPlus output) throws IOException
{
throw new UnsupportedOperationException("Use writeVInt32/readVInt32");
}
@Inline
public static void writeVInt(long value, DataOutputPlus output) throws IOException
{
writeUnsignedVInt(encodeZigZag64(value), output);
}
@Inline
public static void writeVInt32(int value, DataOutputPlus output) throws IOException
{
writeVInt((long)value, output);
}
/** @deprecated See CASSANDRA-18099 */
@Deprecated(since = "5.0")
public static void writeVInt(int value, ByteBuffer output)
{
throw new UnsupportedOperationException("Use writeVInt32/getVInt32");
}
@Inline
public static void writeVInt(long value, ByteBuffer output)
{
writeUnsignedVInt(encodeZigZag64(value), output);
}
@Inline
public static void writeVInt32(int value, ByteBuffer output)
{
writeVInt((long)value, output);
}
/**
* @return a TEMPORARY THREAD LOCAL BUFFER containing the encoded bytes of the value
* This byte[] must be discarded by the caller immediately, and synchronously
*/
@Inline
private static byte[] encodeUnsignedVInt(long value, int size)
{
byte[] encodingSpace = encodingBuffer.get();
int extraBytes = size - 1;
for (int i = extraBytes ; i >= 0; --i)
{
encodingSpace[i] = (byte) value;
value >>= 8;
}
encodingSpace[0] |= VIntCoding.encodeExtraBytesToRead(extraBytes);
return encodingSpace;
}
/**
* Decode a ZigZag-encoded 64-bit value. ZigZag encodes signed integers
* into values that can be efficiently encoded with varint. (Otherwise,
* negative values must be sign-extended to 64 bits to be varint encoded,
* thus always taking 10 bytes on the wire.)
*
* @param n An unsigned 64-bit integer, stored in a signed int because
* Java has no explicit unsigned support.
* @return A signed 64-bit integer.
*/
public static long decodeZigZag64(final long n)
{
return (n >>> 1) ^ -(n & 1);
}
/**
* Encode a ZigZag-encoded 64-bit value. ZigZag encodes signed integers
* into values that can be efficiently encoded with varint. (Otherwise,
* negative values must be sign-extended to 64 bits to be varint encoded,
* thus always taking 10 bytes on the wire.)
*
* @param n A signed 64-bit integer.
* @return An unsigned 64-bit integer, stored in a signed int because
* Java has no explicit unsigned support.
*/
public static long encodeZigZag64(final long n)
{
// Note: the right-shift must be arithmetic
return (n << 1) ^ (n >> 63);
}
/** Compute the number of bytes that would be needed to encode a varint. */
public static int computeVIntSize(final long param)
{
return computeUnsignedVIntSize(encodeZigZag64(param));
}
/** Compute the number of bytes that would be needed to encode an unsigned varint. */
public static int computeUnsignedVIntSize(final long value)
{
int magnitude = Long.numberOfLeadingZeros(value | 1); // | with 1 to ensure magntiude <= 63, so (63 - 1) / 7 <= 8
// the formula below is hand-picked to match the original 9 - ((magnitude - 1) / 7)
return (639 - magnitude * 9) >> 6;
}
public static int checkedCast(long value)
{
int result = (int)value;
if ((long)result != value)
throw new VIntOutOfRangeException(value);
return result;
}
}