java.lang.Object
- uk.ac.starlink.fits.AbstractArrayDataIO
- - uk.ac.starlink.fits.MappedFile

All Implemented Interfaces:

java.io.Closeable, java.io.DataInput, java.io.DataOutput, java.lang.AutoCloseable, nom.tam.util.ArrayDataInput, nom.tam.util.ArrayDataOutput, nom.tam.util.FitsIO, nom.tam.util.RandomAccess
```
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(java.lang.String filename)`	Constructs a MappedFile object by mapping the whole of an existing file using read-only mode.
`MappedFile(java.lang.String filename, java.lang.String mode)`	Constructs a MappedFile object by mapping the whole of an existing file with a given mode.
`MappedFile(java.lang.String filename, java.lang.String mode, long start, int size)`	Constructs a MappedFile object by mapping part of an existing file with a given mode.
`MappedFile(java.nio.ByteBuffer buf)`	Constructs a MappedFile object from a byte buffer.

Method Summary

All Methods Instance Methods Concrete Methods
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.fits.AbstractArrayDataIO
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, readArray, readFully, readLArray

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

- Constructor Detail
  - MappedFile
```
public MappedFile(java.nio.ByteBuffer buf)
```
    Constructs a MappedFile object from a byte buffer.
    
    Parameters:
    
    buf - byte buffer
  - MappedFile
```
public MappedFile(java.lang.String filename)
           throws java.io.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
    
    java.io.IOException
  - MappedFile
```
public MappedFile(java.lang.String filename,
                  java.lang.String mode)
           throws java.io.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
    
    java.io.IOException
  - MappedFile
```
public MappedFile(java.lang.String filename,
                  java.lang.String mode,
                  long start,
                  int size)
           throws java.io.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:
    
    java.io.IOException
- Method Detail
  - seek
```
public void seek(long offsetFromStart)
          throws java.io.IOException
```
    Specified by:
    
    seek in interface nom.tam.util.RandomAccess
    
    Throws:
    
    java.io.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 java.io.DataInput
  - skipAllBytes
```
public void skipAllBytes(long toSkip)
                  throws java.io.IOException
```
    Specified by:
    
    skipAllBytes in interface nom.tam.util.ArrayDataInput
    
    Throws:
    
    java.io.IOException
  - skipAllBytes
```
public void skipAllBytes(int toSkip)
                  throws java.io.IOException
```
    Specified by:
    
    skipAllBytes in interface nom.tam.util.ArrayDataInput
    
    Throws:
    
    java.io.IOException
  - markSupported
```
public boolean markSupported()
```
  - mark
```
public void mark(int readlimit)
```
    Specified by:
    
    mark in interface nom.tam.util.ArrayDataInput
  - reset
```
public void reset()
           throws java.io.IOException
```
    Specified by:
    
    reset in interface nom.tam.util.ArrayDataInput
    
    Throws:
    
    java.io.IOException
  - get
```
protected byte get()
            throws java.io.IOException
```
    Description copied from class: AbstractArrayDataIO
    
    Reads one byte from the current position.
    
    Specified by:
    
    get in class AbstractArrayDataIO
    
    Returns:
    
    next byte
    
    Throws:
    
    java.io.IOException
  - get
```
protected void get(byte[] buf,
                   int offset,
                   int length)
            throws java.io.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:
    
    java.io.IOException
  - put
```
protected void put(byte b)
            throws java.io.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:
    
    java.io.IOException
  - put
```
protected void put(byte[] buf,
                   int offset,
                   int length)
            throws java.io.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:
    
    java.io.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 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 java.lang.AutoCloseable
    
    Specified by:
    
    close in interface java.io.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.fits.AbstractArrayDataIO

Methods inherited from class java.lang.Object

Methods inherited from interface nom.tam.util.ArrayDataInput

Methods inherited from interface java.io.DataInput

Constructor Detail

MappedFile

MappedFile

MappedFile

MappedFile

Method Detail

seek

skip

getFilePointer

skipBytes

skipAllBytes

skipAllBytes

markSupported

mark

reset

get

get

put

put

length

remaining

close

flush