org.apache.hadoop.io.file.tfile

Class Utils

java.lang.Object

org.apache.hadoop.io.file.tfile.Utils

@InterfaceAudience.Public
@InterfaceStability.Evolving
public final class Utils
extends Object

Supporting Utility classes used by TFile, and shared by users of TFile.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Utils.Version A generic Version class.

Method Summary

Methods

Modifier and Type	Method and Description
static <T> int	lowerBound(List<? extends Comparable<? super T>> list, T key) Lower bound binary search.
static <T> int	lowerBound(List<? extends T> list, T key, Comparator<? super T> cmp) Lower bound binary search.
static String	readString(DataInput in) Read a String as a VInt n, followed by n Bytes in Text format.
static int	readVInt(DataInput in) Decoding the variable-length integer.
static long	readVLong(DataInput in) Decoding the variable-length integer.
static <T> int	upperBound(List<? extends Comparable<? super T>> list, T key) Upper bound binary search.
static <T> int	upperBound(List<? extends T> list, T key, Comparator<? super T> cmp) Upper bound binary search.
static void	writeString(DataOutput out, String s) Write a String as a VInt n, followed by n Bytes as in Text format.
static void	writeVInt(DataOutput out, int n) Encoding an integer into a variable-length encoding format.
static void	writeVLong(DataOutput out, long n) Encoding a Long integer into a variable-length encoding format.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

writeVInt

public static void writeVInt(DataOutput out,
             int n)
                      throws IOException

Encoding an integer into a variable-length encoding format. Synonymous to Utils#writeVLong(out, n).

Parameters:

out - output stream

n - The integer to be encoded

Throws:

IOException

See Also:

writeVLong(DataOutput, long)

writeVLong

public static void writeVLong(DataOutput out,
              long n)
                       throws IOException

Encoding a Long integer into a variable-length encoding format.

• if n in [-32, 127): encode in one byte with the actual value. Otherwise,
• if n in [-20*2^8, 20*2^8): encode in two bytes: byte[0] = n/256 - 52; byte[1]=n&0xff. Otherwise,
• 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,
• 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:
• 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;
• 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
• 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;
• 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;
• 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;

Parameters:

out - output stream

n - the integer number

Throws:

IOException

readVInt

public static int readVInt(DataInput in)
                    throws IOException

Decoding the variable-length integer. Synonymous to (int)Utils#readVLong(in).

Parameters:

in - input stream

Returns:

the decoded integer

Throws:

IOException

See Also:

readVLong(DataInput)

readVLong

public static long readVLong(DataInput in)
                      throws IOException

Decoding the variable-length integer. Suppose the value of the first byte is FB, and the following bytes are NB[*].

• if (FB >= -32), return (long)FB;
• if (FB in [-72, -33]), return (FB+52)<<8 + NB[0]&0xff;
• if (FB in [-104, -73]), return (FB+88)<<16 + (NB[0]&0xff)<<8 + NB[1]&0xff;
• if (FB in [-120, -105]), return (FB+112)<<24 + (NB[0]&0xff)<<16 + (NB[1]&0xff)<<8 + NB[2]&0xff;
• if (FB in [-128, -121]), return interpret NB[FB+129] as a signed big-endian integer.

Parameters:

in - input stream

Returns:

the decoded long integer.

Throws:

IOException

writeString

public static void writeString(DataOutput out,
               String s)
                        throws IOException

Write a String as a VInt n, followed by n Bytes as in Text format.

Parameters:

out -

s -

Throws:

IOException

readString

public static String readString(DataInput in)
                         throws IOException

Read a String as a VInt n, followed by n Bytes in Text format.

Parameters:

in - The input stream.

Returns:

The string

Throws:

IOException

lowerBound

public static <T> int lowerBound(List<? extends T> list,
                 T key,
                 Comparator<? super T> cmp)

Lower bound binary search. Find the index to the first element in the list that compares greater than or equal to key.

Type Parameters:

T - Type of the input key.

Parameters:

list - The list

key - The input key.

cmp - Comparator for the key.

Returns:

The index to the desired element if it exists; or list.size() otherwise.

upperBound

public static <T> int upperBound(List<? extends T> list,
                 T key,
                 Comparator<? super T> cmp)

Upper bound binary search. Find the index to the first element in the list that compares greater than the input key.

Type Parameters:

T - Type of the input key.

Parameters:

list - The list

key - The input key.

cmp - Comparator for the key.

Returns:

The index to the desired element if it exists; or list.size() otherwise.

lowerBound

public static <T> int lowerBound(List<? extends Comparable<? super T>> list,
                 T key)

Lower bound binary search. Find the index to the first element in the list that compares greater than or equal to key.

Type Parameters:

T - Type of the input key.

Parameters:

list - The list

key - The input key.

Returns:

The index to the desired element if it exists; or list.size() otherwise.

upperBound

public static <T> int upperBound(List<? extends Comparable<? super T>> list,
                 T key)

Upper bound binary search. Find the index to the first element in the list that compares greater than the input key.

Type Parameters:

T - Type of the input key.

Parameters:

list - The list

key - The input key.

Returns:

The index to the desired element if it exists; or list.size() otherwise.