uk.ac.starlink.oldfits.AbstractArrayDataIO

uk.ac.starlink.oldfits.MappedFile

All Implemented Interfaces:: Closeable, DataInput, DataOutput, AutoCloseable, nom.tam.util.ArrayDataInput, nom.tam.util.ArrayDataOutput, nom.tam.util.FitsIO, nom.tam.util.InputReader, nom.tam.util.OutputWriter, nom.tam.util.RandomAccess, nom.tam.util.ReadWriteAccess

public class MappedFile extends AbstractArrayDataIO implements nom.tam.util.RandomAccess

Provides mapped access to a data buffer using a single mapped byte buffer, compatible with nom.tam.util classes.

This class implements the nom.tam.util ArrayDataInput, ArrayDataOutput and RandomAccess interfaces in the same way that nom.tam.util.BufferedFile does. Hence it can be used as a drop-in replacement for BufferedFile. Unlike BufferedFile however, it does mapped access to files (using java.nio.Buffer objects). This may be moderately more efficient for sequential access to a file, but is dramatically more efficient if very random access is required. This is because BufferedFile effectively always assumes that you are going to read sequentially, so that accessing a single datum distant from (or before) the last datum accessed always results in filling a whole buffer.

Limitations:

Files larger than Integer.MAX_VALUE bytes may not currently be accessed
Access to very large files may fail if virtual memory runs out

Since:: 30 Aug 2002
Author:: Mark Taylor (Starlink)

Nested Class Summary

Nested Classes

Modifier and Type

Class

Description

static class

MappedFile.FileTooLongException

Exception indicating that a file is too long to map.
Field Summary

Fields inherited from interface nom.tam.util.FitsIO
BITS_OF_1_BYTE, BITS_OF_2_BYTES, BITS_OF_3_BYTES, BITS_OF_4_BYTES, BITS_OF_5_BYTES, BITS_OF_6_BYTES, BITS_OF_7_BYTES, BYTE_1_OF_LONG_MASK, BYTE_2_OF_LONG_MASK, BYTE_3_OF_LONG_MASK, BYTE_4_OF_LONG_MASK, BYTE_MASK, BYTES_IN_BOOLEAN, BYTES_IN_BYTE, BYTES_IN_CHAR, BYTES_IN_DOUBLE, BYTES_IN_FLOAT, BYTES_IN_INTEGER, BYTES_IN_LONG, BYTES_IN_SHORT, DEFAULT_BUFFER_SIZE, HIGH_INTEGER_MASK, INTEGER_MASK, SHORT_MASK, SHORT_OF_LONG_MASK
Constructor Summary

Constructors

Constructor

Description

MappedFile(String filename)

Constructs a MappedFile object by mapping the whole of an existing file using read-only mode.

MappedFile(String filename, String mode)

Constructs a MappedFile object by mapping the whole of an existing file with a given mode.

MappedFile(String filename, String mode, long start, int size)

Constructs a MappedFile object by mapping part of an existing file with a given mode.

MappedFile(ByteBuffer buf)

Constructs a MappedFile object from a byte buffer.
Method Summary

Modifier and Type

Method

Description

void

close()

void

flush()

protected byte

get()

Reads one byte from the current position.

protected void

get(byte[] buf, int offset, int length)

Reads bytes into a buffer from the current position.

long

getFilePointer()

long

length()

Returns the size of this buffer.

void

mark(int readlimit)

boolean

markSupported()

protected void

put(byte b)

Writes a single byte at the current position.

protected void

put(byte[] buf, int offset, int length)

Writes bytes from a buffer to the current position.

protected long

remaining()

Returns the number of bytes remaining between the current position and the end of the file.

void

reset()

void

seek(long offsetFromStart)

long

skip(long offset)

void

skipAllBytes(int toSkip)

void

skipAllBytes(long toSkip)

int

skipBytes(int toSkip)

Methods inherited from class uk.ac.starlink.oldfits.AbstractArrayDataIO
read, read, read, read, read, read, read, read, read, read, read, read, read, read, read, read, read, readArray, readBoolean, readByte, readChar, readDouble, readFloat, readFully, readFully, readInt, readLArray, readLine, readLong, readShort, readUnsignedByte, readUnsignedShort, readUTF, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, write, writeArray, writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeDouble, writeFloat, writeInt, writeLong, writeShort, writeUTF

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

Methods inherited from interface nom.tam.util.ArrayDataInput
read, read, read, read, read, read, read, read, read, read, read, read, read, read, read, read, read, readArray, readArrayFully, readFully, readImage, readLArray

Methods inherited from interface nom.tam.util.ArrayDataOutput
write, write

Methods inherited from interface java.io.DataInput
readBoolean, readByte, readChar, readDouble, readFloat, readFully, readInt, readLine, readLong, readShort, readUnsignedByte, readUnsignedShort, readUTF

Methods inherited from interface nom.tam.util.InputReader
read, read

Methods inherited from interface nom.tam.util.OutputWriter
write, write

Methods inherited from interface nom.tam.util.RandomAccess
position, position

Constructor Details
- MappedFile
  
  public MappedFile(ByteBuffer buf)
  
  Constructs a MappedFile object from a byte buffer.
  
  Parameters:
  
  buf - byte buffer
- MappedFile
  
  public MappedFile(String filename) throws IOException
  
  Constructs a MappedFile object by mapping the whole of an existing file using read-only mode.
  
  Parameters:
  
  filename - name of the file to map
  
  Throws:
  
  MappedFile.FileTooLongException - if the file is too long to map
  
  IOException
- MappedFile
  
  public MappedFile(String filename, String mode) throws IOException
  
  Constructs a MappedFile object by mapping the whole of an existing file with a given mode.
  
  Parameters:
  
  filename - name of the file to map
  
  mode - mode
  
  Throws:
  
  MappedFile.FileTooLongException - if the file is too long to map
  
  IOException
- MappedFile
  
  public MappedFile(String filename, String mode, long start, int size) throws IOException
  
  Constructs a MappedFile object by mapping part of an existing file with a given mode.
  
  Parameters:
  
  filename - name of the file to map
  
  mode - mode
  
  start - offset of region to map
  
  size - length of region to map
  
  Throws:
  
  IOException
Method Details
- seek
  
  public void seek(long offsetFromStart) throws IOException
  
  Specified by:
  
  seek in interface nom.tam.util.RandomAccess
  
  Throws:
  
  IOException
- skip
  
  public long skip(long offset)
  
  Specified by:
  
  skip in interface nom.tam.util.ArrayDataInput
- getFilePointer
  
  public long getFilePointer()
  
  Specified by:
  
  getFilePointer in interface nom.tam.util.RandomAccess
- skipBytes
  
  public int skipBytes(int toSkip)
  
  Specified by:
  
  skipBytes in interface DataInput
- skipAllBytes
  
  public void skipAllBytes(long toSkip) throws IOException
  
  Specified by:
  
  skipAllBytes in interface nom.tam.util.ArrayDataInput
  
  Throws:
  
  IOException
- skipAllBytes
  
  public void skipAllBytes(int toSkip) throws IOException
  
  Specified by:
  
  skipAllBytes in interface nom.tam.util.ArrayDataInput
  
  Throws:
  
  IOException
- markSupported
  
  public boolean markSupported()
  
  Specified by:
  
  markSupported in interface nom.tam.util.ArrayDataInput
- mark
  
  public void mark(int readlimit)
  
  Specified by:
  
  mark in interface nom.tam.util.ArrayDataInput
- reset
  
  public void reset() throws IOException
  
  Specified by:
  
  reset in interface nom.tam.util.ArrayDataInput
  
  Throws:
  
  IOException
- get
  
  protected byte get() throws IOException
  
  Description copied from class: AbstractArrayDataIO
  
  Reads one byte from the current position.
  
  Specified by:
  
  get in class AbstractArrayDataIO
  
  Returns:
  
  next byte
  
  Throws:
  
  IOException
- get
  
  protected void get(byte[] buf, int offset, int length) throws IOException
  
  Description copied from class: AbstractArrayDataIO
  
  Reads bytes into a buffer from the current position.
  
  Specified by:
  
  get in class AbstractArrayDataIO
  
  Parameters:
  
  buf - destination buffer
  
  offset - offset of first byte in buf to be written
  
  length - maximum number of bytes to be written to buf
  
  Throws:
  
  IOException
- put
  
  protected void put(byte b) throws IOException
  
  Description copied from class: AbstractArrayDataIO
  
  Writes a single byte at the current position.
  
  Specified by:
  
  put in class AbstractArrayDataIO
  
  Parameters:
  
  b - output byte
  
  Throws:
  
  IOException
- put
  
  protected void put(byte[] buf, int offset, int length) throws IOException
  
  Description copied from class: AbstractArrayDataIO
  
  Writes bytes from a buffer to the current position.
  
  Specified by:
  
  put in class AbstractArrayDataIO
  
  Parameters:
  
  buf - source buffer
  
  offset - offset of first byte in buf to be read
  
  length - number of bytes from buf to be read
  
  Throws:
  
  IOException
- length
  
  public long length()
  
  Description copied from class: AbstractArrayDataIO
  
  Returns the size of this buffer. May be -1 if not known/unlimited.
  
  Specified by:
  
  length in interface nom.tam.util.ReadWriteAccess
  
  Specified by:
  
  length in class AbstractArrayDataIO
  
  Returns:
  
  length or -1
- remaining
  
  protected long remaining()
  
  Description copied from class: AbstractArrayDataIO
  
  Returns the number of bytes remaining between the current position and the end of the file. If there is no end to the file, it is permissible to return Long.MAX_VALUE;
  
  Specified by:
  
  remaining in class AbstractArrayDataIO
  
  Returns:
  
  number of bytes left in file
- close
  
  public void close()
  
  Specified by:
  
  close in interface AutoCloseable
  
  Specified by:
  
  close in interface Closeable
  
  Specified by:
  
  close in interface nom.tam.util.FitsIO
- flush
  
  public void flush()
  
  Specified by:
  
  flush in interface nom.tam.util.ArrayDataOutput

Class MappedFile

Limitations:

Nested Class Summary

Field Summary

Fields inherited from interface nom.tam.util.FitsIO

Constructor Summary

Method Summary

Methods inherited from class uk.ac.starlink.oldfits.AbstractArrayDataIO

Methods inherited from class java.lang.Object

Methods inherited from interface nom.tam.util.ArrayDataInput

Methods inherited from interface nom.tam.util.ArrayDataOutput

Methods inherited from interface java.io.DataInput

Methods inherited from interface nom.tam.util.InputReader

Methods inherited from interface nom.tam.util.OutputWriter

Methods inherited from interface nom.tam.util.RandomAccess

Constructor Details

MappedFile

MappedFile

MappedFile

MappedFile

Method Details

seek

skip

getFilePointer

skipBytes

skipAllBytes

skipAllBytes

markSupported

mark

reset

get

get

put

put

length

remaining

close

flush