package com.indeed.mph.serializers;
import com.indeed.mph.LinearDiophantineEquation;
import javax.annotation.Nonnull;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
/**
* @author alexs
*/
public class SmartVLongSerializer extends AbstractSmartLongSerializer {
private static final LinearDiophantineEquation ONE_PLUS = LinearDiophantineEquation.slopeIntercept(1L, 1L);
private static final long serialVersionUID = 2147053399;
@Override
public void write(@Nonnull final Long n, final DataOutput out) throws IOException {
writeVLong(out, n);
}
@Override
public Long read(final DataInput in) throws IOException {
return readVLong(in);
}
@Override
public long sizeOf(final Long n) throws IOException {
if ((n < 128) && (n >= -32)) {
return 1L;
}
return super.sizeOf(n);
}
@Override
public LinearDiophantineEquation size() {
return ONE_PLUS;
}
/**
* Borrowed from Hadoop org.apache.hadoop.io.file.tfile.Utils
*/
/**
* Encoding a Long integer into a variable-length encoding format.
* <ul>
* <li>if n in [-32, 127): encode in one byte with the actual value.
* Otherwise,
* <li>if n in [-20*2^8, 20*2^8): encode in two bytes: byte[0] = n/256 - 52;
* byte[1]=n&0xff. Otherwise,
* <li>if n IN [-16*2^16, 16*2^16): encode in three bytes: byte[0]=n/2^16 -
* 88; byte[1]=(n>>8)&0xff; byte[2]=n&0xff. Otherwise,
* <li>if n in [-8*2^24, 8*2^24): encode in four bytes: byte[0]=n/2^24 - 112;
* byte[1] = (n>>16)&0xff; byte[2] = (n>>8)&0xff; byte[3]=n&0xff. Otherwise:
* <li>if n in [-2^31, 2^31): encode in five bytes: byte[0]=-125; byte[1] =
* (n>>24)&0xff; byte[2]=(n>>16)&0xff; byte[3]=(n>>8)&0xff; byte[4]=n&0xff;
* <li>if n in [-2^39, 2^39): encode in six bytes: byte[0]=-124; byte[1] =
* (n>>32)&0xff; byte[2]=(n>>24)&0xff; byte[3]=(n>>16)&0xff;
* byte[4]=(n>>8)&0xff; byte[5]=n&0xff
* <li>if n in [-2^47, 2^47): encode in seven bytes: byte[0]=-123; byte[1] =
* (n>>40)&0xff; byte[2]=(n>>32)&0xff; byte[3]=(n>>24)&0xff;
* byte[4]=(n>>16)&0xff; byte[5]=(n>>8)&0xff; byte[6]=n&0xff;
* <li>if n in [-2^55, 2^55): encode in eight bytes: byte[0]=-122; byte[1] =
* (n>>48)&0xff; byte[2] = (n>>40)&0xff; byte[3]=(n>>32)&0xff;
* byte[4]=(n>>24)&0xff; byte[5]=(n>>16)&0xff; byte[6]=(n>>8)&0xff;
* byte[7]=n&0xff;
* <li>if n in [-2^63, 2^63): encode in nine bytes: byte[0]=-121; byte[1] =
* (n>>54)&0xff; byte[2] = (n>>48)&0xff; byte[3] = (n>>40)&0xff;
* byte[4]=(n>>32)&0xff; byte[5]=(n>>24)&0xff; byte[6]=(n>>16)&0xff;
* byte[7]=(n>>8)&0xff; byte[8]=n&0xff;
* </ul>
*
* @param out output stream
* @param n the integer number
* @throws java.io.IOException if unable to write to out
*/
@SuppressWarnings("fallthrough")
static void writeVLong(final DataOutput out, final long n) throws IOException {
if ((n < 128) && (n >= -32)) {
out.writeByte((int) n);
return;
}
final long un = (n < 0) ? ~n : n;
// how many bytes do we need to represent the number with sign bit?
final int len = ((Long.SIZE - Long.numberOfLeadingZeros(un)) / 8) + 1;
int firstByte = (int) (n >> ((len - 1) * 8));
switch (len) {
case 1:
// fall it through to firstByte==-1, len=2.
firstByte >>= 8;
case 2:
if ((firstByte < 20) && (firstByte >= -20)) {
out.writeByte(firstByte - 52);
out.writeByte((int) n);
return;
}
// fall it through to firstByte==0/-1, len=3.
firstByte >>= 8;
case 3:
if ((firstByte < 16) && (firstByte >= -16)) {
out.writeByte(firstByte - 88);
out.writeShort((int) n);
return;
}
// fall it through to firstByte==0/-1, len=4.
firstByte >>= 8;
case 4:
if ((firstByte < 8) && (firstByte >= -8)) {
out.writeByte(firstByte - 112);
out.writeShort(((int) n) >>> 8);
out.writeByte((int) n);
return;
}
out.writeByte(len - 129);
out.writeInt((int) n);
return;
case 5:
out.writeByte(len - 129);
out.writeInt((int) (n >>> 8));
out.writeByte((int) n);
return;
case 6:
out.writeByte(len - 129);
out.writeInt((int) (n >>> 16));
out.writeShort((int) n);
return;
case 7:
out.writeByte(len - 129);
out.writeInt((int) (n >>> 24));
out.writeShort((int) (n >>> 8));
out.writeByte((int) n);
return;
case 8:
out.writeByte(len - 129);
out.writeLong(n);
return;
default:
throw new RuntimeException("Internal error");
}
}
/**
* Decoding the variable-length integer. Suppose the value of the first byte
* is FB, and the following bytes are NB[*].
* <ul>
* <li>if (FB >= -32), return (long)FB;
* <li>if (FB in [-72, -33]), return (FB+52)<<8 + NB[0]&0xff;
* <li>if (FB in [-104, -73]), return (FB+88)<<16 + (NB[0]&0xff)<<8 +
* NB[1]&0xff;
* <li>if (FB in [-120, -105]), return (FB+112)<<24 + (NB[0]&0xff)<<16 +
* (NB[1]&0xff)<<8 + NB[2]&0xff;
* <li>if (FB in [-128, -121]), return interpret NB[FB+129] as a signed
* big-endian integer.
* </ul>
*
* @param in input stream
* @return the decoded long integer.
* @throws java.io.IOException if unable to read from in
*/
public static long readVLong(final DataInput in) throws IOException {
final int firstByte = in.readByte();
if (firstByte >= -32) {
return firstByte;
}
switch ((firstByte + 128) / 8) {
case 11:
case 10:
case 9:
case 8:
case 7:
return ((firstByte + 52) << 8) | in.readUnsignedByte();
case 6:
case 5:
case 4:
case 3:
return ((firstByte + 88) << 16) | in.readUnsignedShort();
case 2:
case 1:
return ((firstByte + 112) << 24) | (in.readUnsignedShort() << 8)
| in.readUnsignedByte();
case 0:
final int len = firstByte + 129;
switch (len) {
case 4:
return in.readInt();
case 5:
return (((long) in.readInt()) << 8) | in.readUnsignedByte();
case 6:
return (((long) in.readInt()) << 16) | in.readUnsignedShort();
case 7:
return (((long) in.readInt()) << 24) | (in.readUnsignedShort() << 8)
| in.readUnsignedByte();
case 8:
return in.readLong();
default:
throw new IOException("Corrupted VLong encoding");
}
default:
throw new RuntimeException("Internal error");
}
}
}
