Package org.eclipse.mat.hprof

Class ChunkedGZIPRandomAccessFile

java.lang.Object

java.io.RandomAccessFile

org.eclipse.mat.hprof.ChunkedGZIPRandomAccessFile

All Implemented Interfaces:

Closeable, DataInput, DataOutput, AutoCloseable

public class ChunkedGZIPRandomAccessFile
extends RandomAccessFile

This class can be used to get random access to chunked gzipped hprof files like the openjdk can create them. As described in https://tools.ietf.org/html/rfc1952, a gzip file consists of a number of "members". The openjdk gzipped dumps have a maximum size of data compressed in each "member". This makes it possible to start decompression at each start of a member. In case of the openjdk dumps the maximum size of uncompressed data in a "member" is stored in a comment in the first member. This is used to detect those files (without having to uncompress the whole file).

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ChunkedGZIPRandomAccessFile.ChunkedGZIPOutputStream

Method Summary

Modifier and Type	Method	Description
void	close()
static void	compressFileChunked(File toCompress, File compressed)	Compressed a file to a chunked gzipped file.
static void	compressFileChunked2(File toCompress, File compressed)	Compressed a file to a chunked gzipped file.
static void	compressFileUnchunked(File toCompress, File compressed)	Compressed a file to an unchunked gzipped file, but with more header fields compared to GZIPOutputStream.
static void	forget(File file)	Forget all cached version of the file.
static ChunkedGZIPRandomAccessFile	get(RandomAccessFile raf, File file, String prefix)	Returns the random access file for the given file or null if not supported for the file.
long	getFilePointer()
long	getLastPhysicalReadPosition()	Returns an estimation of the last physical position we read from.
static boolean	isChunkedGZIPFile(RandomAccessFile raf)	Checks if the given file is a chunked gzipped file.
long	length()	Unknown length is Long.MAX_VALUE
int	read()
int	read(byte[] buf)
int	read(byte[] buf, int off, int len)
int	read(long offset, byte[] b, int off, int len)	Reads bytes from the gzip file.
void	seek(long pos)

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, write, write, write, writeBoolean, writeByte, writeBytes, writeChar, writeChars, writeDouble, writeFloat, writeInt, writeLong, writeShort, writeUTF

Methods inherited from class java.lang.Object

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

Method Details

seek

public void seek(long pos)
          throws IOException

Overrides:

seek in class RandomAccessFile

Throws:

IOException

getFilePointer

public long getFilePointer()

Overrides:

getFilePointer in class RandomAccessFile

length

public long length()

Unknown length is Long.MAX_VALUE

Overrides:

length in class RandomAccessFile

read

public int read()
         throws IOException

Overrides:

read in class RandomAccessFile

Throws:

IOException

read

public int read(byte[] buf)
         throws IOException

Overrides:

read in class RandomAccessFile

Throws:

IOException

read

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

Overrides:

read in class RandomAccessFile

Throws:

IOException

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Overrides:

close in class RandomAccessFile

Throws:

IOException

getLastPhysicalReadPosition

public long getLastPhysicalReadPosition()

Returns an estimation of the last physical position we read from.

Returns:

The last physical position.

read

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

Reads bytes from the gzip file.

Parameters:

offset - The offset from which to start the read.

b - The array to read into.

off - The offset in the array to use.

len - The number of bytes to read at most.

Returns:

The number of bytes read or -1 if we are at the end of the file.

Throws:

IOException - On error.

isChunkedGZIPFile

public static boolean isChunkedGZIPFile(RandomAccessFile raf)
                                 throws IOException

Checks if the given file is a chunked gzipped file.

Parameters:

raf - The file to check.

Returns:

true if the file is a chunked gzip file.

Throws:

IOException - On error.

get

public static ChunkedGZIPRandomAccessFile get(RandomAccessFile raf,
 File file,
 String prefix)
                                       throws IOException

Returns the random access file for the given file or null if not supported for the file.

Parameters:

raf - The random access file.

file - The file name.

prefix - The prefix of the snapshot.

Returns:

The random access file or null.

Throws:

IOException - problem reading the file

forget

public static void forget(File file)

Forget all cached version of the file.

Parameters:

file - The file to forget.

compressFileChunked

public static void compressFileChunked(File toCompress,
 File compressed)
                                throws IOException

Compressed a file to a chunked gzipped file.

Parameters:

toCompress - The file to gzip.

compressed - The gzipped file.

Throws:

IOException - On error.

compressFileUnchunked

public static void compressFileUnchunked(File toCompress,
 File compressed)
                                  throws IOException

Compressed a file to an unchunked gzipped file, but with more header fields compared to GZIPOutputStream.

Parameters:

toCompress - The file to gzip.

compressed - The gzipped file.

Throws:

IOException - On error.

compressFileChunked2

public static void compressFileChunked2(File toCompress,
 File compressed)
                                 throws IOException

Compressed a file to a chunked gzipped file. Note that there is no header CRC.

Parameters:

toCompress - The file to gzip.

compressed - The gzipped file.

Throws:

IOException - On error.