TupleInput (Oracle - Berkeley DB Java API)
Date: 2010-04-12

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## com.sleepycat.bind.tuple
Class TupleInput

    java.lang.Object
      java.io.InputStream
          com.sleepycat.util.FastInputStream
              com.sleepycat.bind.tuple.TupleInput

All Implemented Interfaces:
  Closeable

    public class TupleInput

extends FastInputStream

An `InputStream` with `DataInput`-like methods for reading tuple fields. It is used by `TupleBinding`.

This class has many methods that have the same signatures as methods in the `DataInput` interface. The reason this class does not implement `DataInput` is because it would break the interface contract for those methods because of data format differences.

Signed numbers are stored in the buffer in MSB (most significant byte first) order with their sign bit (high-order bit) inverted to cause negative numbers to be sorted first when comparing values as unsigned byte arrays, as done in a database. Unsigned numbers, including characters, are stored in MSB order with no change to their sign bit. BigInteger values are stored with a preceding length having the same sign as the value.

Strings and character arrays are stored either as a fixed length array of unicode characters, where the length must be known by the application, or as a null-terminated UTF byte array.

- Null strings are UTF encoded as { 0xFF }, which is not allowed in a standard UTF encoding. This allows null strings, as distinct from empty or zero length strings, to be represented in a tuple. Using the default comparator, null strings will be ordered last.
- Zero (0x0000) character values are UTF encoded as non-zero values, and therefore embedded zeros in the string are supported. The sequence { 0xC0, 0x80 } is used to encode a zero character. This UTF encoding is the same one used by native Java UTF libraries. However, this encoding of zero does impact the lexicographical ordering, and zeros will not be sorted first (the natural order) or last. For all character values other than zero, the default UTF byte ordering is the same as the Unicode lexicographical character ordering.

Floats and doubles are stored using two different representations: sorted representation and integer-bit (IEEE 754) representation. If you use negative floating point numbers in a key, you should use sorted representation; alternatively you may use integer-bit representation but you will need to implement and configure a custom comparator to get correct numeric ordering for negative numbers.

To use sorted representation use this set of methods:

- `TupleOutput.writeSortedFloat(float)`
- `readSortedFloat()`
- `TupleOutput.writeSortedDouble(double)`
- `readSortedDouble()`

To use integer-bit representation use this set of methods:

- `TupleOutput.writeFloat(float)`
- `readFloat()`
- `TupleOutput.writeDouble(double)`
- `readDouble()`

Field Summary

Fields inherited from class com.sleepycat.util.FastInputStream
`buf, len, mark, off`

Constructor Summary
`TupleInput(byte[] buffer)` Creates a tuple input object for reading a byte array of tuple data.
`TupleInput(byte[] buffer, int offset, int length)` Creates a tuple input object for reading a byte array of tuple data at a given offset for a given length.
`TupleInput(TupleOutput output)` Creates a tuple input object from the data contained in a tuple output object.

Method Summary
`int` | `getBigIntegerByteLength()` Returns the byte length of a `BigInteger`.
`int` | `getPackedIntByteLength()` Returns the byte length of a packed integer.
`int` | `getPackedLongByteLength()` Returns the byte length of a packed long integer.
`int` | `getStringByteLength()` Returns the byte length of a null-terminated UTF string in the data buffer, including the terminator.
`BigInteger` | `readBigInteger()` Reads a `BigInteger`.
`boolean` | `readBoolean()` Reads a boolean (one byte) unsigned value from the buffer and returns true if it is non-zero and false if it is zero.
`byte` | `readByte()` Reads a signed byte (one byte) value from the buffer.
`void` | `readBytes(char[] chars)` Reads the specified number of bytes from the buffer, converting each unsigned byte value to a character of the resulting array.
`String` | `readBytes(int length)` Reads the specified number of bytes from the buffer, converting each unsigned byte value to a character of the resulting string.
`char` | `readChar()` Reads a char (two byte) unsigned value from the buffer.
`void` | `readChars(char[] chars)` Reads the specified number of characters from the buffer, converting each two byte unsigned value to a character of the resulting array.
`String` | `readChars(int length)` Reads the specified number of characters from the buffer, converting each two byte unsigned value to a character of the resulting string.
`double` | `readDouble()` Reads a signed double (eight byte) value from the buffer.
`float` | `readFloat()` Reads a signed float (four byte) value from the buffer.
`int` | `readInt()` Reads a signed int (four byte) value from the buffer.
`long` | `readLong()` Reads a signed long (eight byte) value from the buffer.
`int` | `readPackedInt()` Reads a packed integer.
`long` | `readPackedLong()` Reads a packed long integer.
`short` | `readShort()` Reads a signed short (two byte) value from the buffer.
`double` | `readSortedDouble()` Reads a signed double (eight byte) value from the buffer, with support for correct default sorting of all values.
`float` | `readSortedFloat()` Reads a signed float (four byte) value from the buffer, with support for correct default sorting of all values.
`String` | `readString()` Reads a null-terminated UTF string from the data buffer and converts the data from UTF to Unicode.
`void` | `readString(char[] chars)` Reads the specified number of UTF characters string from the data buffer and converts the data from UTF to Unicode.
`String` | `readString(int length)` Reads the specified number of UTF characters string from the data buffer and converts the data from UTF to Unicode.
`int` | `readUnsignedByte()` Reads an unsigned byte (one byte) value from the buffer.
`long` | `readUnsignedInt()` Reads an unsigned int (four byte) value from the buffer.
`int` | `readUnsignedShort()` Reads an unsigned short (two byte) value from the buffer.

Methods inherited from class com.sleepycat.util.FastInputStream
`available, getBufferBytes, getBufferLength, getBufferOffset, mark, markSupported, read, read, read, readFast, readFast, readFast, reset, skip, skipFast`

Methods inherited from class java.io.InputStream
`close`

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

Constructor Detail

### TupleInput

    public TupleInput(byte[] buffer)

  Creates a tuple input object for reading a byte array of tuple data. A reference to the byte array will be kept by this object (it will not be copied) and therefore the byte array should not be modified while this object is in use.

  Parameters:
    `buffer` - is the byte array to be read and should contain data in tuple format.

### TupleInput

    public TupleInput(byte[] buffer,
                      int offset,
                      int length)

  Creates a tuple input object for reading a byte array of tuple data at a given offset for a given length. A reference to the byte array will be kept by this object (it will not be copied) and therefore the byte array should not be modified while this object is in use.

  Parameters:
    `buffer` - is the byte array to be read and should contain data in tuple format.
    `offset` - is the byte offset at which to begin reading.
    `length` - is the number of bytes to be read.

### TupleInput

    public TupleInput(TupleOutput output)

  Creates a tuple input object from the data contained in a tuple output object. A reference to the tuple output's byte array will be kept by this object (it will not be copied) and therefore the tuple output object should not be modified while this object is in use.

  Parameters:
    `output` - is the tuple output object containing the data to be read.

Method Detail

### readString

    public final String readString()
                            throws IndexOutOfBoundsException,
                                   IllegalArgumentException

  Reads a null-terminated UTF string from the data buffer and converts the data from UTF to Unicode. Reads values that were written using `TupleOutput.writeString(String)`.

  Returns:
    the converted string.
  Throws:
    `IndexOutOfBoundsException` - if no null terminating byte is found in the buffer.
    `IllegalArgumentException` - malformed UTF data is encountered.

### readChar

    public final char readChar()
                        throws IndexOutOfBoundsException

  Reads a char (two byte) unsigned value from the buffer. Reads values that were written using `TupleOutput.writeChar(int)`.

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readBoolean

    public final boolean readBoolean()
                              throws IndexOutOfBoundsException

  Reads a boolean (one byte) unsigned value from the buffer and returns true if it is non-zero and false if it is zero. Reads values that were written using `TupleOutput.writeBoolean(boolean)`.

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readByte

    public final byte readByte()
                        throws IndexOutOfBoundsException

  Reads a signed byte (one byte) value from the buffer. Reads values that were written using `TupleOutput.writeByte(int)`.

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readShort

    public final short readShort()
                          throws IndexOutOfBoundsException

  Reads a signed short (two byte) value from the buffer. Reads values that were written using `TupleOutput.writeShort(int)`.

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readInt

    public final int readInt()
                      throws IndexOutOfBoundsException

  Reads a signed int (four byte) value from the buffer. Reads values that were written using `TupleOutput.writeInt(int)`.

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readLong

    public final long readLong()
                        throws IndexOutOfBoundsException

  Reads a signed long (eight byte) value from the buffer. Reads values that were written using `TupleOutput.writeLong(long)`.

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readFloat

    public final float readFloat()
                          throws IndexOutOfBoundsException

  Reads a signed float (four byte) value from the buffer. Reads values that were written using `TupleOutput.writeFloat(float)`. `Float.intBitsToFloat` is used to convert the signed int value.

  Note: This method operations on byte array values that by default (without a custom comparator) do not sort correctly for negative values. Only non-negative values are sorted correctly by default. To sort all values correctly by default, use `readSortedFloat()`.

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readDouble

    public final double readDouble()
                            throws IndexOutOfBoundsException

  Reads a signed double (eight byte) value from the buffer. Reads values that were written using `TupleOutput.writeDouble(double)`. `Double.longBitsToDouble` is used to convert the signed long value.

  Note: This method operations on byte array values that by default (without a custom comparator) do not sort correctly for negative values. Only non-negative values are sorted correctly by default. To sort all values correctly by default, use `readSortedDouble()`.

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readSortedFloat

    public final float readSortedFloat()
                                throws IndexOutOfBoundsException

  Reads a signed float (four byte) value from the buffer, with support for correct default sorting of all values. Reads values that were written using `TupleOutput.writeSortedFloat(float)`.

  `Float.intBitsToFloat` and the following bit manipulations are used to convert the stored representation to a signed float value.

        int val = ... // get stored bits
        val ^= (val < 0) ? 0x80000000 : 0xffffffff;
        return Float.intBitsToFloat(val);

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readSortedDouble

    public final double readSortedDouble()
                                  throws IndexOutOfBoundsException

  Reads a signed double (eight byte) value from the buffer, with support for correct default sorting of all values. Reads values that were written using `TupleOutput.writeSortedDouble(double)`.

  `Float.longBitsToDouble` and the following bit manipulations are used to convert the stored representation to a signed double value.

        int val = ... // get stored bits
              val ^= (val < 0) ? 0x8000000000000000L : 0xffffffffffffffffL;
              return Double.longBitsToDouble(val);

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readUnsignedByte

    public final int readUnsignedByte()
                               throws IndexOutOfBoundsException

  Reads an unsigned byte (one byte) value from the buffer. Reads values that were written using `TupleOutput.writeUnsignedByte(int)`.

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readUnsignedShort

    public final int readUnsignedShort()
                                throws IndexOutOfBoundsException

  Reads an unsigned short (two byte) value from the buffer. Reads values that were written using `TupleOutput.writeUnsignedShort(int)`.

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readUnsignedInt

    public final long readUnsignedInt()
                               throws IndexOutOfBoundsException

  Reads an unsigned int (four byte) value from the buffer. Reads values that were written using `TupleOutput.writeUnsignedInt(long)`.

  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readBytes

    public final String readBytes(int length)
                           throws IndexOutOfBoundsException

  Reads the specified number of bytes from the buffer, converting each unsigned byte value to a character of the resulting string. Reads values that were written using `TupleOutput.writeBytes(java.lang.String)`. Only characters with values below 0x100 may be read using this method.

  Parameters:
    `length` - is the number of bytes to be read.
  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readChars

    public final String readChars(int length)
                           throws IndexOutOfBoundsException

  Reads the specified number of characters from the buffer, converting each two byte unsigned value to a character of the resulting string. Reads values that were written using `TupleOutput.writeChars(java.lang.String)`.

  Parameters:
    `length` - is the number of characters to be read.
  Returns:
    the value read from the buffer.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readBytes

    public final void readBytes(char[] chars)
                         throws IndexOutOfBoundsException

  Reads the specified number of bytes from the buffer, converting each unsigned byte value to a character of the resulting array. Reads values that were written using `TupleOutput.writeBytes(java.lang.String)`. Only characters with values below 0x100 may be read using this method.

  Parameters:
    `chars` - is the array to receive the data and whose length is used to determine the number of bytes to be read.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readChars

    public final void readChars(char[] chars)
                         throws IndexOutOfBoundsException

  Reads the specified number of characters from the buffer, converting each two byte unsigned value to a character of the resulting array. Reads values that were written using `TupleOutput.writeChars(java.lang.String)`.

  Parameters:
    `chars` - is the array to receive the data and whose length is used to determine the number of characters to be read.
  Throws:
    `IndexOutOfBoundsException` - if not enough bytes are available in the buffer.

### readString

    public final String readString(int length)
                            throws IndexOutOfBoundsException,
                                   IllegalArgumentException

  Reads the specified number of UTF characters string from the data buffer and converts the data from UTF to Unicode. Reads values that were written using `TupleOutput.writeString(char[])`.

  Parameters:
    `length` - is the number of characters to be read.
  Returns:
    the converted string.
  Throws:
    `IndexOutOfBoundsException` - if no null terminating byte is found in the buffer.
    `IllegalArgumentException` - malformed UTF data is encountered.

### readString

    public final void readString(char[] chars)
                          throws IndexOutOfBoundsException,
                                 IllegalArgumentException

  Reads the specified number of UTF characters string from the data buffer and converts the data from UTF to Unicode. Reads values that were written using `TupleOutput.writeString(char[])`.

  Parameters:
    `chars` - is the array to receive the data and whose length is used to determine the number of characters to be read.
  Throws:
    `IndexOutOfBoundsException` - if no null terminating byte is found in the buffer.
    `IllegalArgumentException` - malformed UTF data is encountered.

### getStringByteLength

    public final int getStringByteLength()
                                  throws IndexOutOfBoundsException,
                                         IllegalArgumentException

  Returns the byte length of a null-terminated UTF string in the data buffer, including the terminator. Used with string values that were written using `TupleOutput.writeString(String)`.

  Throws:
    `IndexOutOfBoundsException` - if no null terminating byte is found in the buffer.
    `IllegalArgumentException` - malformed UTF data is encountered.

### readPackedInt

    public final int readPackedInt()

  Reads a packed integer. Note that packed integers are not appropriate for sorted values (keys) unless a custom comparator is used.

  See Also:
    `PackedInteger`

### getPackedIntByteLength

    public final int getPackedIntByteLength()

  Returns the byte length of a packed integer.

  See Also:
    `PackedInteger`

### readPackedLong

    public final long readPackedLong()

  Reads a packed long integer. Note that packed integers are not appropriate for sorted values (keys) unless a custom comparator is used.

  See Also:
    `PackedInteger`

### getPackedLongByteLength

    public final int getPackedLongByteLength()

  Returns the byte length of a packed long integer.

  See Also:
    `PackedInteger`

### readBigInteger

    public final BigInteger readBigInteger()

  Reads a `BigInteger`.

  See Also:
    `TupleOutput.writeBigInteger(java.math.BigInteger)`

### getBigIntegerByteLength

    public final int getBigIntegerByteLength()

  Returns the byte length of a `BigInteger`.

  See Also:
    `TupleOutput.writeBigInteger(java.math.BigInteger)`

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