Utils (Hadoop 1.2.1 API)
Date: 2013-07-22

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

    java.lang.Object
      org.apache.hadoop.io.file.tfile.Utils

    public final class Utils

extends Object

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

Nested Class Summary
`static class` | `Utils.Version` A generic Version class.

Method Summary
`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.

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