Package com.adobe.internal.io

Class MemoryMappedByteWriter

java.lang.Object

com.adobe.internal.io.MemoryMappedByteWriter

All Implemented Interfaces:

ByteReader, ByteWriter

public final class MemoryMappedByteWriter
extends java.lang.Object
implements ByteWriter

An implementation of the ByteWriter interface that provides access to a RandomAccessFile based on the memory mapped byte writter of NIO.2 from JDK 7. This implementation also uses buffering to limit the number of calls to the methods of the RandomAccessFile class. This is because such methods use JNI and any calls to native code from Java are very slow. This class is not threadsafe. It is not safe to pass an instance of this class to multiple threads. It is not safe to pass an instance of this class to multiple users even if in the same thread. It is not safe to give the same RandomAccessFile to multiple instances of this class.

Field Summary

Fields inherited from interface com.adobe.internal.io.ByteReader

EOF

Constructor Summary

Constructors

Constructor	Description
MemoryMappedByteWriter(java.io.RandomAccessFile file)	Create a new RandomAccessFileByteReader with the given RandomAccessFile.
MemoryMappedByteWriter(java.io.RandomAccessFile file, int numberOfBuffers, int bufferSize)	Create a new RandomAccessFileByteReader with the given RandomAccessFile.

Method Summary

Modifier and Type	Method	Description
void	close()	Closes this ByteReader and releases any system resources associated with this stream.
void	flush()	Flushes this ByteWriter and forces any unwritten buffered output bytes to be written out to the underlying repository.
long	length()	Returns the number of total bytes in the repository that are visible through this API.
int	read(long position)	Read a single byte from the underlying bytes at the given position.
int	read(long position, byte[] b, int offset, int length)	Transfers bytes from the underlying repository into the given destination array.
java.lang.String	toString()
void	write(long position, byte[] b, int offset, int length)	Write an array of bytes at the position given.
void	write(long position, int b)	Write the byte given at the position given.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

MemoryMappedByteWriter

public MemoryMappedByteWriter(java.io.RandomAccessFile file,
                              int numberOfBuffers,
                              int bufferSize)

Create a new RandomAccessFileByteReader with the given RandomAccessFile. The RandomAccessFile given to this ByteWriter belongs to it and must not be used after construction of this ByteWriter. It will be closed when this ByteWriter is closed.

Parameters:

file - the location to read bytes from.

numberOfBuffers - the number of buffers to use

bufferSize - the size in bytes for the buffers

MemoryMappedByteWriter

public MemoryMappedByteWriter(java.io.RandomAccessFile file)

Create a new RandomAccessFileByteReader with the given RandomAccessFile. RandomAccessFile given to this ByteReader must not be written to during the time it is being used by this or any ByteReader.

Parameters:

file - the location to read bytes from.

Method Detail

write

public void write(long position,
                  int b)
           throws java.io.IOException

Description copied from interface: ByteWriter

Write the byte given at the position given. If during the write operation the byte to be written is beyond the end of the virtual array visible through this interface then the length of that virtual array becomes the position of the byte written plus one (because of zero based counting). length of virtual array = max(length of virtual array, position of byte written + 1)

Specified by:

write in interface ByteWriter

Parameters:

position - the zero-based offset within the byte array.

b - the byte to write.

Throws:

java.io.IOException - if an error occurs during the write operation

See Also:

ByteWriter.write(long, int)

write

public void write(long position,
                  byte[] b,
                  int offset,
                  int length)
           throws java.io.IOException

Description copied from interface: ByteWriter

Write an array of bytes at the position given. If during the write operation any of the bytes are to be written beyond the end of the virtual array visible through this interface then the length of that virtual array becomes the position of the byte written plus one (because of zero based counting). for each byte written : length of virtual array = max(length of virtual array, position of byte written + 1)

Specified by:

write in interface ByteWriter

Parameters:

position - the zero-based offset within the byte array.

b - the array of bytes to write from.

offset - the offset within the byte array to start writing from.

length - the number of bytes to write from the byte array.

Throws:

java.io.IOException - if an error occurs during the write operation

See Also:

ByteWriter.write(long, byte[], int, int)

length

public long length()
            throws java.io.IOException

Description copied from interface: ByteReader

Returns the number of total bytes in the repository that are visible through this API.

Specified by:

length in interface ByteReader

Returns:

the number of bytes in the repository.

Throws:

java.io.IOException - if an error occurs while trying to determine the length

See Also:

ByteReader.length()

flush

public void flush()
           throws java.io.IOException

Description copied from interface: ByteWriter

Flushes this ByteWriter and forces any unwritten buffered output bytes to be written out to the underlying repository.

Specified by:

flush in interface ByteWriter

Throws:

java.io.IOException - if an error occurs while trying to flush the buffer

See Also:

ByteWriter.flush()

close

public void close()
           throws java.io.IOException

Description copied from interface: ByteReader

Closes this ByteReader and releases any system resources associated with this stream.

Specified by:

close in interface ByteReader

Throws:

java.io.IOException - if an error occurs while trying to close

See Also:

ByteReader.close()

read

public int read(long position)
         throws java.io.IOException

Description copied from interface: ByteReader

Read a single byte from the underlying bytes at the given position.

Specified by:

read in interface ByteReader

Parameters:

position - the position to read the byte from.

Returns:

the byte at the postion or EOF if the position is outside of the legal range.

Throws:

java.io.IOException - if an error occurs during the read operation

See Also:

ByteReader.read(long)

read

public int read(long position,
                byte[] b,
                int offset,
                int length)
         throws java.io.IOException

Description copied from interface: ByteReader

Transfers bytes from the underlying repository into the given destination array. Copy up to length bytes from the repository starting at the postion given into the given array starting at the given offset.

Specified by:

read in interface ByteReader

Parameters:

position - the position to read the byte from.

b - the array to write the bytes into.

offset - the offset in the array at which the first byte is written.

length - the maximum number of bytes to write into the array.

Returns:

the number of bytes actually written to the array.

Throws:

java.io.IOException - if an error occurs during the read operation

See Also:

ByteReader.read(long, byte[], int, int)

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

See Also:

Object.toString()