com.sun.labs.minion.util.buffer
Class StdBufferImpl

java.lang.Object
  com.sun.labs.minion.util.buffer.StdBufferImpl

All Implemented Interfaces:

Buffer, ReadableBuffer, WriteableBuffer

Direct Known Subclasses:

ArrayBuffer, NIOBuffer

public abstract class StdBufferImpl
extends java.lang.Object
implements WriteableBuffer, ReadableBuffer

A abstract class that implements most of the WriteableBuffer and ReadableBuffer interfaces in terms of the two implemented interfaces' get and put methods. These can be overidden in subclasses if the performance is unacceptable.

See Also:

WriteableBuffer, ReadableBuffer

Field Summary

protected static int[]	masks Bitmasks to add a single bit to a byte.
protected static long[]	maxBEValues The number of bytes that are required for encoding a number given our 7 bit encoding strategy.
protected static long[]	maxValues The maximum values that can be encoded using a given number of bytes.
protected static int[]	nBits The number of 1 bits in a byte, as a lookup table.

Constructor Summary

StdBufferImpl()

Method Summary

WriteableBuffer	append(ReadableBuffer b) Appends a readable buffer onto this buffer.
WriteableBuffer	append(ReadableBuffer b, int n) Appends a given number of bytes from a readable buffer onto this buffer.
int	byteDecode() Decodes an integer stored using the minimal number of bytes.
int	byteDecode(int nBytes) Decodes a postive integer that was coded using a specific number of bytes.
int	byteDecode(int pos, int nBytes) Decodes a postive integer that was coded using a specific number of bytes from a specific position in the buffer.
long	byteDecodeLong() Decodes a long stored using the 7 bit encoding.
long	byteDecodeLong(int nBytes) Decodes a postive long that was coded using a specific number of bytes.
long	byteDecodeLong(int pos, int nBytes) Decodes a postive long that was coded using a specific number of bytes from a given position.
WriteableBuffer	byteEncode(int pos, long n, int nBytes) Encodes a positive long directly, using a given number of bytes, starting at the given position in the units.
int	byteEncode(long n) Encodes an integer in a byte-aligned fashion, using the minimal number of bytes.
WriteableBuffer	byteEncode(long n, int nBytes) Encodes a positive long onto a writeable in a given number of bytes.
static int	bytesRequired(long n) Gets the number of bytes required to directly encode a given number.
static java.lang.String	byteToBinaryString(byte n) Build a string representation of a byte with the bits in the right order.
WriteableBuffer	clear() Clears the buffer.
int	countBits() Counts the number of bits that are set in a buffer.
protected int	countBits(int start, int end)
float	decodeFloat() Decode a float stored in 4 bytes.
WriteableBuffer	encode(java.lang.CharSequence s) Encodes a character sequence onto the buffer.
WriteableBuffer	encode(float f) Encodes a floating point value in 4 bytes.
java.lang.String	getString() Gets a string from this buffer.
WriteableBuffer	set(int bitIndex) Sets the given bit to 1 in the given buffer.
protected static int	sizeUTF8(java.lang.CharSequence s) Determines the size of the UTF-8 encoding of a character sequence.
int	skipByteEncoded() Skips an integer encoded using our 7 bit encoding without actually decoding it.
boolean	test(int bitIndex) Tests whether a given bit is true or false.
java.lang.String	toString() Gets a string representation of the bytes in this buffer.
java.lang.String	toString(int mode) Print the bits in the buffer in the order in which they actually occur.
java.lang.String	toString(int start, int end) Print the bits in the buffer in the order in which they actually occur.

Methods inherited from class java.lang.Object

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

Methods inherited from interface com.sun.labs.minion.util.buffer.WriteableBuffer

capacity, getReadableBuffer, or, put, put, write, write, write, write, xor

Methods inherited from interface com.sun.labs.minion.util.buffer.ReadableBuffer

duplicate, get, get, slice

Methods inherited from interface com.sun.labs.minion.util.buffer.Buffer

limit, limit, position, position, remaining

Field Detail

maxValues

protected static long[] maxValues

The maximum values that can be encoded using a given number of bytes.

maxBEValues

protected static long[] maxBEValues

The number of bytes that are required for encoding a number given our 7 bit encoding strategy.

nBits

protected static int[] nBits

The number of 1 bits in a byte, as a lookup table.

masks

protected static int[] masks

Bitmasks to add a single bit to a byte.

Constructor Detail

StdBufferImpl

public StdBufferImpl()

Method Detail

bytesRequired

public static int bytesRequired(long n)

Gets the number of bytes required to directly encode a given number.

Parameters:

n - The number that we want to encode.

Returns:

The number of bytes required to directly encode the number.

byteEncode

public WriteableBuffer byteEncode(long n,
                                  int nBytes)

Encodes a positive long onto a writeable in a given number of bytes.

Specified by:

byteEncode in interface WriteableBuffer

Parameters:

n - The number to encode.

nBytes - The number of bytes to use in the encoding.

Returns:

The buffer, to allow chained invocations.

byteEncode

public WriteableBuffer byteEncode(int pos,
                                  long n,
                                  int nBytes)

Encodes a positive long directly, using a given number of bytes, starting at the given position in the units.

Specified by:

byteEncode in interface WriteableBuffer

Parameters:

pos - The position to start encoding.

n - The number to encode.

nBytes - The number of bytes to use in the encoding.

Returns:

The buffer, to allow chained invocations.

byteEncode

public int byteEncode(long n)

Encodes an integer in a byte-aligned fashion, using the minimal number of bytes. The basic idea: use the 7 lower order bits of a byte to encode a number. If the 8th bit is 0, then there are no further bytes in this number. If the 8th bit is one, then the next byte continues the number. Note that this means that a number that would completly fill an integer will take 5 bytes to encode.

Specified by:

byteEncode in interface WriteableBuffer

Parameters:

n - The number to encode.

Returns:

the number of bytes used to encode the number.

encode

public WriteableBuffer encode(float f)

Encodes a floating point value in 4 bytes.

Specified by:

encode in interface WriteableBuffer

Parameters:

f - the floating point number to encode

Returns:

the number of bytes used to encode the float, which is always 4.

sizeUTF8

protected static int sizeUTF8(java.lang.CharSequence s)

Determines the size of the UTF-8 encoding of a character sequence.

Parameters:

s - The sequence that we wish to encode.

Returns:

The number of bytes in the UTF-8 encoding of the sequence.

append

public WriteableBuffer append(ReadableBuffer b)

Appends a readable buffer onto this buffer.

Specified by:

append in interface WriteableBuffer

Parameters:

b - The buffer that we wish to append onto this buffer.

Returns:

The buffer, to allow chained invocations.

append

public WriteableBuffer append(ReadableBuffer b,
                              int n)

Appends a given number of bytes from a readable buffer onto this buffer.

Specified by:

append in interface WriteableBuffer

Parameters:

b - The buffer that we wish to append onto this buffer.

n - The number of bytes from the given buffer to append onto this buffer.

Returns:

The buffer, to allow chained invocations.

encode

public WriteableBuffer encode(java.lang.CharSequence s)

Encodes a character sequence onto the buffer. The sequence is encoded in the following way: first, the number of bytes used to encode the string is encoded using the byteEncode method. Then, the characters in the sequence are encoded using a UTF-8 encoding.

Specified by:

encode in interface WriteableBuffer

Parameters:

s - The sequence that we wish to encode.

Returns:

This buffer, for chained invocations.

set

public WriteableBuffer set(int bitIndex)

Sets the given bit to 1 in the given buffer.

Specified by:

set in interface WriteableBuffer

Parameters:

bitIndex - the index of the bit to set to 1.

Returns:

This buffer, for chained invocations.

clear

public WriteableBuffer clear()

Clears the buffer. This default implementation simply sets the position to 0.

Specified by:

clear in interface WriteableBuffer

Returns:

This buffer, for chained invocations.

byteDecode

public int byteDecode(int nBytes)

Decodes a postive integer that was coded using a specific number of bytes.

Specified by:

byteDecode in interface ReadableBuffer

Parameters:

nBytes - The number of bytes to use.

Returns:

the decoded number.

byteDecode

public int byteDecode(int pos,
                      int nBytes)

Decodes a postive integer that was coded using a specific number of bytes from a specific position in the buffer.

Specified by:

byteDecode in interface ReadableBuffer

Parameters:

pos - The position to decode from.

nBytes - The number of bytes to use.

Returns:

the decoded number.

byteDecodeLong

public long byteDecodeLong(int nBytes)

Decodes a postive long that was coded using a specific number of bytes.

Specified by:

byteDecodeLong in interface ReadableBuffer

Parameters:

nBytes - The number of bytes to use.

Returns:

the decoded number.

byteDecodeLong

public long byteDecodeLong(int pos,
                           int nBytes)

Decodes a postive long that was coded using a specific number of bytes from a given position.

Specified by:

byteDecodeLong in interface ReadableBuffer

Parameters:

pos - The position to decode from.

nBytes - The number of bytes to use.

Returns:

the decoded number.

byteDecode

public int byteDecode()

Decodes an integer stored using the minimal number of bytes.

Specified by:

byteDecode in interface ReadableBuffer

Returns:

the decoded integer.

See Also:

byteEncode(long, int)

byteDecodeLong

public long byteDecodeLong()

Decodes a long stored using the 7 bit encoding.

Specified by:

byteDecodeLong in interface ReadableBuffer

Returns:

the decoded long.

See Also:

byteEncode(long, int)

decodeFloat

public float decodeFloat()

Decode a float stored in 4 bytes.

Specified by:

decodeFloat in interface ReadableBuffer

Returns:

the decoded float.

skipByteEncoded

public int skipByteEncoded()

Skips an integer encoded using our 7 bit encoding without actually decoding it.

Specified by:

skipByteEncoded in interface ReadableBuffer

Returns:

the number of bytes skipped.

See Also:

WriteableBuffer.byteEncode(long, int)

test

public boolean test(int bitIndex)

Tests whether a given bit is true or false.

Specified by:

test in interface ReadableBuffer

Parameters:

bitIndex - the index of the bit to test.

Returns:

true if the bit is 1, false if it is 0

countBits

public int countBits()

Counts the number of bits that are set in a buffer.

Specified by:

countBits in interface ReadableBuffer

Returns:

The number of 1 bits in the buffer.

countBits

protected int countBits(int start,
                        int end)

getString

public java.lang.String getString()

Gets a string from this buffer.

Specified by:

getString in interface ReadableBuffer

Returns:

The decoded string.

See Also:

WriteableBuffer.encode(CharSequence)

toString

public java.lang.String toString()

Gets a string representation of the bytes in this buffer.

Overrides:

toString in class java.lang.Object

Returns:

A string representation of the buffer.

toString

public java.lang.String toString(int mode)

Print the bits in the buffer in the order in which they actually occur.

Parameters:

mode - The type of print out required.

Returns:

A string representation of the buffer.

toString

public java.lang.String toString(int start,
                                 int end)

Print the bits in the buffer in the order in which they actually occur.

Parameters:

start - The starting position in the buffer from which to display the bytes.

end - The (exclusive) ending position in the buffer.

Returns:

A string representation of the buffer.

byteToBinaryString

public static java.lang.String byteToBinaryString(byte n)

Build a string representation of a byte with the bits in the right order.

Parameters:

n - The number to represent

Returns:

A string containing a representation of the bits in this byte.