uk.ac.bristol.star.cdf.record

Class BankBuf

java.lang.Object

uk.ac.bristol.star.cdf.record.BankBuf

All Implemented Interfaces:

Buf

public abstract class BankBuf
extends java.lang.Object
implements Buf

Abstract Buf implementation that divides the byte sequence into one or more contiguous data banks. Each bank contains a run of bytes short enough to be indexed by a 4-byte integer.

Since:

18 Jun 2013

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected static class	BankBuf.Bank Data bank for use within BankBuf class and its subclasses.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	BankBuf(long size, boolean isBit64, boolean isBigendian) Constructor.

Method Summary

Modifier and Type	Method and Description
java.io.InputStream	createInputStream(long offset) Returns an input stream consisting of all the bytes in this buf starting from the given offset.
static BankBuf	createMultiBankBuf(java.nio.ByteBuffer[] byteBuffers, boolean isBit64, boolean isBigendian) Returns a BankBuf based on an array of supplied ByteBuffers.
static BankBuf	createMultiBankBuf(java.nio.channels.FileChannel channel, long size, int bankSize, boolean isBit64, boolean isBigendian) Returns a BankBuf based on supplied file channel.
static BankBuf	createSingleBankBuf(java.nio.ByteBuffer byteBuffer, boolean isBit64, boolean isBigendian) Returns a BankBuf based on a single supplied ByteBuffer.
Buf	fillNewBuf(long count, java.io.InputStream in) Creates a new Buf of a given length populated from a given input stream.
protected abstract BankBuf.Bank	getBank(long offset, int count) Returns the bank which can read a given number of bytes starting at the given offset.
protected abstract java.util.Iterator<BankBuf.Bank>	getBankIterator(long offset) Returns an iterator over banks starting with the one containing the given offset.
protected abstract java.util.List<BankBuf.Bank>	getExistingBanks() Returns a list of active banks.
long	getLength() Returns the extent of this buf in bytes.
boolean	isBigendian() Determines the data encoding of this buf.
boolean	isBit64() Determines the 64bit-ness of this buf.
java.lang.String	readAsciiString(Pointer ptr, int nbyte) Reads a fixed number of bytes interpreting them as ASCII characters and returns the result as a string.
void	readDataBytes(long offset, int count, byte[] array) Reads a sequence of byte values from this buf into an array.
void	readDataDoubles(long offset, int count, double[] array) Reads a sequence of double values from this buf into an array.
void	readDataFloats(long offset, int count, float[] array) Reads a sequence of float values from this buf into an array.
void	readDataInts(long offset, int count, int[] array) Reads a sequence of int values from this buf into an array.
void	readDataLongs(long offset, int count, long[] array) Reads a sequence of long integer values from this buf into an array.
void	readDataShorts(long offset, int count, short[] array) Reads a sequence of short values from this buf into an array.
int	readInt(Pointer ptr) Reads a signed big-endian 4-byte integer from the pointer position.
long	readOffset(Pointer ptr) Reads a file offset or size from the pointer position.
int	readUnsignedByte(Pointer ptr) Reads a single byte from the pointer position, returning a value in the range 0..255.
void	setBit64(boolean isBit64) Sets the 64bit-ness of this buf.
void	setEncoding(boolean bigend) Sets the encoding for reading numeric values as performed by the readData* methods.

Methods inherited from class java.lang.Object

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

Constructor Detail

BankBuf

protected BankBuf(long size,
                  boolean isBit64,
                  boolean isBigendian)

Constructor.

Parameters:

size - total size of buffer

isBit64 - 64bit-ness of buf

isBigendian - true for big-endian data, false for little-endian

Method Detail

getBank

protected abstract BankBuf.Bank getBank(long offset,
                                        int count)
                                 throws java.io.IOException

Returns the bank which can read a given number of bytes starting at the given offset.

Implementation: in most cases this will return one of the large banks that this object has allocated. However, in the case that the requested run straddles a bank boundary it may be necessary to generate a short-lived bank just to return from this method.

Parameters:

offset - start of required sequence

count - number of bytes in required sequence

Returns:

bank

Throws:

java.io.IOException

getExistingBanks

protected abstract java.util.List<BankBuf.Bank> getExistingBanks()

Returns a list of active banks. Banks which have not been created yet do not need to be included.

getBankIterator

protected abstract java.util.Iterator<BankBuf.Bank> getBankIterator(long offset)

Returns an iterator over banks starting with the one containing the given offset. If followed to the end, the returned sequence will go all the way to the end of the buf. The first bank does not need to start at the given offset, only to contain it.

Parameters:

offset - starting byte offset into buf

Returns:

iterator over data banks

getLength

public long getLength()

Description copied from interface: Buf

Returns the extent of this buf in bytes.

Specified by:

getLength in interface Buf

Returns:

buffer length

readUnsignedByte

public int readUnsignedByte(Pointer ptr)
                     throws java.io.IOException

Description copied from interface: Buf

Reads a single byte from the pointer position, returning a value in the range 0..255. Pointer position is moved on appropriately.

Specified by:

readUnsignedByte in interface Buf

Parameters:

ptr - pointer

Returns:

byte value

Throws:

java.io.IOException

readInt

public int readInt(Pointer ptr)
            throws java.io.IOException

Description copied from interface: Buf

Reads a signed big-endian 4-byte integer from the pointer position. Pointer position is moved on appropriately.

Specified by:

readInt in interface Buf

Parameters:

ptr - pointer

Returns:

integer value

Throws:

java.io.IOException

readOffset

public long readOffset(Pointer ptr)
                throws java.io.IOException

Description copied from interface: Buf

Reads a file offset or size from the pointer position. This is a signed big-endian integer, occupying either 4 or 8 bytes according to the return value of Buf.isBit64(). Pointer position is moved on appropriately.

Specified by:

readOffset in interface Buf

Returns:

buffer size or offset value

Throws:

java.io.IOException

readAsciiString

public java.lang.String readAsciiString(Pointer ptr,
                                        int nbyte)
                                 throws java.io.IOException

Description copied from interface: Buf

Reads a fixed number of bytes interpreting them as ASCII characters and returns the result as a string. If a character 0x00 appears before nbyte bytes have been read, it is taken as the end of the string. Pointer position is moved on appropriately.

Specified by:

readAsciiString in interface Buf

Parameters:

ptr - pointer

nbyte - maximum number of bytes in string

Returns:

ASCII string

Throws:

java.io.IOException

setBit64

public void setBit64(boolean isBit64)

Description copied from interface: Buf

Sets the 64bit-ness of this buf. This determines whether readOffset reads 4- or 8-byte values.

This method should be called before the readOffset method is invoked.

Specified by:

setBit64 in interface Buf

Parameters:

isBit64 - true for 8-byte offsets, false for 4-byte offsets

isBit64

public boolean isBit64()

Description copied from interface: Buf

Determines the 64bit-ness of this buf. This determines whether readOffset reads 4- or 8-byte values.

Specified by:

isBit64 in interface Buf

Returns:

true for 8-byte offsets, false for 4-byte offsets

setEncoding

public void setEncoding(boolean bigend)

Description copied from interface: Buf

Sets the encoding for reading numeric values as performed by the readData* methods.

As currently specified, there are only two possibiliies, Big-Endian and Little-Endian. Interface and implementation would need to be reworked somewhat to accommodate the (presumably, rarely seen in this day and age) D_FLOAT and G_FLOAT encodings supported by the CDF standard.

This method should be called before any of the readData* methods are invoked.

Specified by:

setEncoding in interface Buf

Parameters:

bigend - true for big-endian, false for little-endian

isBigendian

public boolean isBigendian()

Description copied from interface: Buf

Determines the data encoding of this buf.

Specified by:

isBigendian in interface Buf

Returns:

true for big-endian, false for little-endian

readDataBytes

public void readDataBytes(long offset,
                          int count,
                          byte[] array)
                   throws java.io.IOException

Description copied from interface: Buf

Reads a sequence of byte values from this buf into an array.

Specified by:

readDataBytes in interface Buf

Parameters:

offset - position sequence start in this buffer in bytes

count - number of byte values to read

array - array to receive values, starting at array element 0

Throws:

java.io.IOException

readDataShorts

public void readDataShorts(long offset,
                           int count,
                           short[] array)
                    throws java.io.IOException

Description copied from interface: Buf

Reads a sequence of short values from this buf into an array.

Specified by:

readDataShorts in interface Buf

Parameters:

offset - position sequence start in this buffer in bytes

count - number of short values to read

array - array to receive values, starting at array element 0

Throws:

java.io.IOException

readDataInts

public void readDataInts(long offset,
                         int count,
                         int[] array)
                  throws java.io.IOException

Description copied from interface: Buf

Reads a sequence of int values from this buf into an array.

Specified by:

readDataInts in interface Buf

Parameters:

offset - position sequence start in this buffer in bytes

count - number of int values to read

array - array to receive values, starting at array element 0

Throws:

java.io.IOException

readDataLongs

public void readDataLongs(long offset,
                          int count,
                          long[] array)
                   throws java.io.IOException

Description copied from interface: Buf

Reads a sequence of long integer values from this buf into an array.

Specified by:

readDataLongs in interface Buf

Parameters:

offset - position sequence start in this buffer in bytes

count - number of long values to read

array - array to receive values, starting at array element 0

Throws:

java.io.IOException

readDataFloats

public void readDataFloats(long offset,
                           int count,
                           float[] array)
                    throws java.io.IOException

Description copied from interface: Buf

Reads a sequence of float values from this buf into an array.

Specified by:

readDataFloats in interface Buf

Parameters:

offset - position sequence start in this buffer in bytes

count - number of float values to read

array - array to receive values, starting at array element 0

Throws:

java.io.IOException

readDataDoubles

public void readDataDoubles(long offset,
                            int count,
                            double[] array)
                     throws java.io.IOException

Description copied from interface: Buf

Reads a sequence of double values from this buf into an array.

Specified by:

readDataDoubles in interface Buf

Parameters:

offset - position sequence start in this buffer in bytes

count - number of double values to read

array - array to receive values, starting at array element 0

Throws:

java.io.IOException

createInputStream

public java.io.InputStream createInputStream(long offset)

Description copied from interface: Buf

Returns an input stream consisting of all the bytes in this buf starting from the given offset.

Specified by:

createInputStream in interface Buf

Parameters:

offset - position of first byte in buf that will appear in the returned stream

Returns:

input stream

fillNewBuf

public Buf fillNewBuf(long count,
                      java.io.InputStream in)
               throws java.io.IOException

Description copied from interface: Buf

Creates a new Buf of a given length populated from a given input stream. The new buf object must have the same data encoding and 64bit-ness as this one.

Specified by:

fillNewBuf in interface Buf

Parameters:

count - size of new buffer in bytes

in - input stream capable of supplying (at least) count bytes

Returns:

new buffer of length count filled with bytes from in

Throws:

java.io.IOException

createSingleBankBuf

public static BankBuf createSingleBankBuf(java.nio.ByteBuffer byteBuffer,
                                          boolean isBit64,
                                          boolean isBigendian)

Returns a BankBuf based on a single supplied ByteBuffer.

Parameters:

byteBuffer - NIO buffer containing data

isBit64 - 64bit-ness of buf

isBigendian - true for big-endian data, false for little-endian

Returns:

new buf

createMultiBankBuf

public static BankBuf createMultiBankBuf(java.nio.ByteBuffer[] byteBuffers,
                                         boolean isBit64,
                                         boolean isBigendian)

Returns a BankBuf based on an array of supplied ByteBuffers.

Parameters:

byteBuffers - NIO buffers containing data (when concatenated)

isBit64 - 64bit-ness of buf

isBigendian - true for big-endian data, false for little-endian

Returns:

new buf

createMultiBankBuf

public static BankBuf createMultiBankBuf(java.nio.channels.FileChannel channel,
                                         long size,
                                         int bankSize,
                                         boolean isBit64,
                                         boolean isBigendian)

Returns a BankBuf based on supplied file channel.

Parameters:

channel - readable file containing data

size - number of bytes in channel

bankSize - maximum size for individual data banks

isBit64 - 64bit-ness of buf

isBigendian - true for big-endian data, false for little-endian

Returns:

new buf