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

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## org.apache.hadoop.io
Class WritableUtils

    java.lang.Object
      org.apache.hadoop.io.WritableUtils

    public final class WritableUtils

extends Object

Constructor Summary
`WritableUtils()`

Method Summary
`static
`<T extends Writable> T`
` | `clone(T orig, Configuration conf)` Make a copy of a writable object using serialization to a buffer.
`static void` | `cloneInto(Writable dst, Writable src)` Deprecated. use ReflectionUtils.cloneInto instead.
`static int` | `decodeVIntSize(byte value)` Parse the first byte of a vint/vlong to determine the number of bytes
`static void` | `displayByteArray(byte[] record)`
`static int` | `getVIntSize(long i)` Get the encoded length if an integer is stored in a variable-length format
`static boolean` | `isNegativeVInt(byte value)` Given the first byte of a vint/vlong, determine the sign
`static byte[]` | `readCompressedByteArray(DataInput in)`
`static String` | `readCompressedString(DataInput in)`
`static String[]` | `readCompressedStringArray(DataInput in)`
`static
`<T extends Enum<T>> T`
` | `readEnum(DataInput in, Class<T> enumType)` Read an Enum value from DataInput, Enums are read and written using String values.
`static String` | `readString(DataInput in)`
`static String[]` | `readStringArray(DataInput in)`
`static int` | `readVInt(DataInput stream)` Reads a zero-compressed encoded integer from input stream and returns it.
`static long` | `readVLong(DataInput stream)` Reads a zero-compressed encoded long from input stream and returns it.
`static void` | `skipCompressedByteArray(DataInput in)`
`static void` | `skipFully(DataInput in, int len)` Skip len number of bytes in input streamin
`static byte[]` | `toByteArray(Writable... writables)` Convert writables to a byte array
`static int` | `writeCompressedByteArray(DataOutput out, byte[] bytes)`
`static int` | `writeCompressedString(DataOutput out, String s)`
`static void` | `writeCompressedStringArray(DataOutput out, String[] s)`
`static void` | `writeEnum(DataOutput out, Enum<?> enumVal)` writes String value of enum to DataOutput.
`static void` | `writeString(DataOutput out, String s)`
`static void` | `writeStringArray(DataOutput out, String[] s)`
`static void` | `writeVInt(DataOutput stream, int i)` Serializes an integer to a binary stream with zero-compressed encoding.
`static void` | `writeVLong(DataOutput stream, long i)` Serializes a long to a binary stream with zero-compressed encoding.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

### WritableUtils

    public WritableUtils()

Method Detail

### readCompressedByteArray

    public static byte[] readCompressedByteArray(DataInput in)
                                          throws IOException

  Throws:
    `IOException`

### skipCompressedByteArray

    public static void skipCompressedByteArray(DataInput in)
                                        throws IOException

  Throws:
    `IOException`

### writeCompressedByteArray

    public static int writeCompressedByteArray(DataOutput out,
                                               byte[] bytes)
                                        throws IOException

  Throws:
    `IOException`

### readCompressedString

    public static String readCompressedString(DataInput in)
                                       throws IOException

  Throws:
    `IOException`

### writeCompressedString

    public static int writeCompressedString(DataOutput out,
                                            String s)
                                     throws IOException

  Throws:
    `IOException`

### writeString

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

  Throws:
    `IOException`

### readString

    public static String readString(DataInput in)
                             throws IOException

  Throws:
    `IOException`

### writeStringArray

    public static void writeStringArray(DataOutput out,
                                        String[] s)
                                 throws IOException

  Throws:
    `IOException`

### writeCompressedStringArray

    public static void writeCompressedStringArray(DataOutput out,
                                                  String[] s)
                                           throws IOException

  Throws:
    `IOException`

### readStringArray

    public static String[] readStringArray(DataInput in)
                                    throws IOException

  Throws:
    `IOException`

### readCompressedStringArray

    public static String[] readCompressedStringArray(DataInput in)
                                              throws IOException

  Throws:
    `IOException`

### displayByteArray

    public static void displayByteArray(byte[] record)

### clone

    public static <T extends Writable> T clone(T orig,
                                               Configuration conf)

  Make a copy of a writable object using serialization to a buffer.

  Parameters:
    `orig` - The object to copy
  Returns:
    The copied object

### cloneInto

    @Deprecated
    public static void cloneInto(Writable dst,
                                            Writable src)
                          throws IOException

  Deprecated. use ReflectionUtils.cloneInto instead.

  Make a copy of the writable object using serialiation to a buffer

  Parameters:
    `dst` - the object to copy from
    `src` - the object to copy into, which is destroyed
  Throws:
    `IOException`

### writeVInt

    public static void writeVInt(DataOutput stream,
                                 int i)
                          throws IOException

  Serializes an integer to a binary stream with zero-compressed encoding. For -120 <= i <= 127, only one byte is used with the actual value. For other values of i, the first byte value indicates whether the integer is positive or negative, and the number of bytes that follow. If the first byte value v is between -121 and -124, the following integer is positive, with number of bytes that follow are -(v+120). If the first byte value v is between -125 and -128, the following integer is negative, with number of bytes that follow are -(v+124). Bytes are stored in the high-non-zero-byte-first order.

  Parameters:
    `stream` - Binary output stream
    `i` - Integer to be serialized
  Throws:
    `IOException`

### writeVLong

    public static void writeVLong(DataOutput stream,
                                  long i)
                           throws IOException

  Serializes a long to a binary stream with zero-compressed encoding. For -112 <= i <= 127, only one byte is used with the actual value. For other values of i, the first byte value indicates whether the long is positive or negative, and the number of bytes that follow. If the first byte value v is between -113 and -120, the following long is positive, with number of bytes that follow are -(v+112). If the first byte value v is between -121 and -128, the following long is negative, with number of bytes that follow are -(v+120). Bytes are stored in the high-non-zero-byte-first order.

  Parameters:
    `stream` - Binary output stream
    `i` - Long to be serialized
  Throws:
    `IOException`

### readVLong

    public static long readVLong(DataInput stream)
                          throws IOException

  Reads a zero-compressed encoded long from input stream and returns it.

  Parameters:
    `stream` - Binary input stream
  Returns:
    deserialized long from stream.
  Throws:
    `IOException`

### readVInt

    public static int readVInt(DataInput stream)
                        throws IOException

  Reads a zero-compressed encoded integer from input stream and returns it.

  Parameters:
    `stream` - Binary input stream
  Returns:
    deserialized integer from stream.
  Throws:
    `IOException`

### isNegativeVInt

    public static boolean isNegativeVInt(byte value)

  Given the first byte of a vint/vlong, determine the sign

  Parameters:
    `value` - the first byte
  Returns:
    is the value negative

### decodeVIntSize

    public static int decodeVIntSize(byte value)

  Parse the first byte of a vint/vlong to determine the number of bytes

  Parameters:
    `value` - the first byte of the vint/vlong
  Returns:
    the total number of bytes (1 to 9)

### getVIntSize

    public static int getVIntSize(long i)

  Get the encoded length if an integer is stored in a variable-length format

  Returns:
    the encoded length

### readEnum

    public static <T extends Enum<T>> T readEnum(DataInput in,
                                                 Class<T> enumType)
                                      throws IOException

  Read an Enum value from DataInput, Enums are read and written using String values.

  Type Parameters:
    `T` - Enum type
  Parameters:
    `in` - DataInput to read from
    `enumType` - Class type of Enum
  Returns:
    Enum represented by String read from DataInput
  Throws:
    `IOException`

### writeEnum

    public static void writeEnum(DataOutput out,
                                 Enum<?> enumVal)
                          throws IOException

  writes String value of enum to DataOutput.

  Parameters:
    `out` - Dataoutput stream
    `enumVal` - enum value
  Throws:
    `IOException`

### skipFully

    public static void skipFully(DataInput in,
                                 int len)
                          throws IOException

  Skip len number of bytes in input streamin

  Parameters:
    `in` - input stream
    `len` - number of bytes to skip
  Throws:
    `IOException` - when skipped less number of bytes

### toByteArray

    public static byte[] toByteArray(Writable... writables)

  Convert writables to a byte array

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