org.apache.hudi.common.util

Class BufferedRandomAccessFile

java.lang.Object

java.io.RandomAccessFile

org.apache.hudi.common.util.BufferedRandomAccessFile

All Implemented Interfaces:

Closeable, DataInput, DataOutput, AutoCloseable

public final class BufferedRandomAccessFile
extends RandomAccessFile

Use a private buffer for the read/write/seek operations of the RandomAccessFile to reduce the number of disk operations. S C L/E Buffer: |----+---| File: +---------------D-------------------+ S. startPosition - file position of start of the buffer. C. currentPosition - file position of current pointer in the buffer. L. validLastPosition - file position of the last byte in the buffer. (This is same as endPosition of the buffer. Except for the last file block). S-C--L--E (A) Buffer: |-+--+--| File: +-----------------------------------D E. endPosition() - end file position of the current buffer. D. DiskPosition - Position in the file pointed by underlying RandomAccessFile. When reading from the file, diskPosition aligns with startPosition. When writing to the file, diskPosition(D) aligns with validLastPosition(L/E). A. AvailableSpace - Space between validLastPosition(L) and EndPosition(E) is the available space in buffer, when writing/appending records into the buffer/file. Note: Based on BufferedRandomAccessFile implementation in Apache/Cassandra. - adopted from org.apache.cassandra.io Copyright: 2015-2019 The Apache Software Foundation Home page: http://cassandra.apache.org/ License: http://www.apache.org/licenses/LICENSE-2.0

Constructor Summary

Constructors

Constructor and Description
BufferedRandomAccessFile(File file, String mode)
BufferedRandomAccessFile(File file, String mode, int size)
BufferedRandomAccessFile(String name, String mode)
BufferedRandomAccessFile(String name, String mode, int size)

Method Summary

Modifier and Type	Method and Description
void	close() Close the file, after flushing data in the buffer.
void	flush() If the file is writable, flush any bytes in the buffer that have not yet been written to disk.
long	getFilePointer()
long	length() Returns the length of the file, depending on whether buffer has more data (to be flushed).
int	read()
int	read(byte[] b)
int	read(byte[] b, int off, int len) Read specified number of bytes into given array starting at given offset.
void	seek(long pos) If the new seek position is in the buffer, adjust the currentPosition.
void	write(byte[] b) write an array of bytes to the buffer/file.
void	write(byte[] b, int off, int len) Write specified number of bytes into buffer/file, with given starting offset and length.
void	write(int v) write a byte to the buffer/file.

Methods inherited from class java.io.RandomAccessFile

getChannel, getFD, readBoolean, readByte, readChar, readDouble, readFloat, readFully, readFully, readInt, readLine, readLong, readShort, readUnsignedByte, readUnsignedShort, readUTF, setLength, skipBytes, 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

Constructor Detail

BufferedRandomAccessFile

public BufferedRandomAccessFile(File file,
                                String mode)
                         throws IOException

Parameters:

file - - file name

mode - - "r" for read only; "rw" for read write

Throws:

IOException

BufferedRandomAccessFile

public BufferedRandomAccessFile(File file,
                                String mode,
                                int size)
                         throws IOException

Parameters:

file - - file name

mode - - "r" for read only; "rw" for read write

size - - size/capacity of the buffer.

Throws:

IOException

BufferedRandomAccessFile

public BufferedRandomAccessFile(String name,
                                String mode)
                         throws IOException

Parameters:

name - - name of the file

mode - - "r" for read only; "rw" for read write

Throws:

IOException

BufferedRandomAccessFile

public BufferedRandomAccessFile(String name,
                                String mode,
                                int size)
                         throws FileNotFoundException

Parameters:

name - - name of the file

mode - - "r" for read only; "rw" for read write

size - - size/capacity of the buffer

Throws:

FileNotFoundException

Method Detail

close

public void close()
           throws IOException

Close the file, after flushing data in the buffer.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Overrides:

close in class RandomAccessFile

Throws:

IOException

flush

public void flush()
           throws IOException

If the file is writable, flush any bytes in the buffer that have not yet been written to disk.

Throws:

IOException

seek

public void seek(long pos)
          throws IOException

If the new seek position is in the buffer, adjust the currentPosition. If the new seek position is outside of the buffer, flush the contents to the file and reload the buffer corresponding to the position. We logically view the file as group blocks, where each block will perfectly fit into the buffer (except for the last block). Given a position to seek, we identify the block to be loaded using BUFFER_BOUNDARY_MASK. When dealing with the last block, we will have extra space between validLastPosition and endPosition of the buffer.

Overrides:

seek in class RandomAccessFile

Parameters:

pos - - position in the file to be loaded to the buffer.

Throws:

IOException

getFilePointer

public long getFilePointer()

Overrides:

getFilePointer in class RandomAccessFile

Returns:

current file position

length

public long length()
            throws IOException

Returns the length of the file, depending on whether buffer has more data (to be flushed).

Overrides:

length in class RandomAccessFile

Returns:

- length of the file (including data yet to be flushed to the file).

Throws:

IOException

read

public int read()
         throws IOException

Overrides:

read in class RandomAccessFile

Returns:

- returns a byte as an integer.

Throws:

IOException

read

public int read(byte[] b)
         throws IOException

Overrides:

read in class RandomAccessFile

Parameters:

b - - byte array into which to read data.

Returns:

- returns number of bytes read.

Throws:

IOException

read

public int read(byte[] b,
                int off,
                int len)
         throws IOException

Read specified number of bytes into given array starting at given offset.

Overrides:

read in class RandomAccessFile

Parameters:

b - - byte array

off - - start offset

len - - length of bytes to be read

Returns:

- number of bytes read.

Throws:

IOException

write

public void write(int v)
           throws IOException

write a byte to the buffer/file.

Specified by:

write in interface DataOutput

Overrides:

write in class RandomAccessFile

Parameters:

v - - value to be written

Throws:

IOException

write

public void write(byte[] b)
           throws IOException

write an array of bytes to the buffer/file.

Specified by:

write in interface DataOutput

Overrides:

write in class RandomAccessFile

Parameters:

b - - byte array with data to be written

Throws:

IOException

write

public void write(byte[] b,
                  int off,
                  int len)
           throws IOException

Write specified number of bytes into buffer/file, with given starting offset and length.

Specified by:

write in interface DataOutput

Overrides:

write in class RandomAccessFile

Parameters:

b - - byte array with data to be written

off - - starting offset.

len - - length of bytes to be written

Throws:

IOException