com.graphhopper.storage

Class UnsafeDataAccess

java.lang.Object

com.graphhopper.storage.AbstractDataAccess

com.graphhopper.storage.UnsafeDataAccess

All Implemented Interfaces:

DataAccess, Storable<DataAccess>, Closeable, AutoCloseable

public class UnsafeDataAccess
extends AbstractDataAccess

This is a data structure which uses an unsafe access to native memory. The speed up compared to RAMDataAccess is roughly 10% due to index calculations and BitUtil overhead in RAMDataAccess. Notes:

1. Highly experimental. Still some bugs and access through file/MMAP should work at some point

2. Compared to MMAP no syncDAWrapper is need to make it read and write safe from multiple threads

3. Cannot be used on Android as no memory allocation methods are available there

Author:

Peter Karich

Field Summary

Fields inherited from class com.graphhopper.storage.AbstractDataAccess

bitUtil, byteOrder, closed, EMPTY, header, HEADER_OFFSET, indexDivisor, name, SEGMENT_SIZE_MIN, segmentSizeInBytes, segmentSizePower

Method Summary

Modifier and Type	Method and Description
void	close() This method makes sure that the underlying used resources are released.
DataAccess	copyTo(DataAccess da) Copies the content from this object into the specified one.
UnsafeDataAccess	create(long bytes) The first time you use a DataAccess object after configuring it you need to call this method.
boolean	ensureCapacity(long bytes) Ensures that the capacity of this object is at least the specified bytes.
void	flush() This method makes sure that the underlying data is written to the storage.
void	getBytes(long bytePos, byte[] values, int length) Get bytes from position 'index'
long	getCapacity()
int	getInt(long bytePos) Get 4 bytes from position 'bytePos'
int	getSegments()
short	getShort(long bytePos) Get 2 bytes from position 'index'
DAType	getType()
boolean	loadExisting()
void	setBytes(long bytePos, byte[] values, int length) Set bytes from position 'index' to the specified values
void	setInt(long bytePos, int value) Set 4 bytes at position 'bytePos' to the specified value
void	setShort(long bytePos, short value) Set 2 bytes at position 'index' to the specified value
void	trimTo(long bytes) Reduces the allocate space to the specified bytes.

Methods inherited from class com.graphhopper.storage.AbstractDataAccess

checkBeforeRename, copyHeader, getFullName, getHeader, getName, getSegmentSize, isClosed, isIntBased, isStoring, readHeader, rename, setHeader, setSegmentSize, toString, writeHeader

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

create

public UnsafeDataAccess create(long bytes)

Description copied from interface: DataAccess

The first time you use a DataAccess object after configuring it you need to call this method. After that first call you have to use ensureCapacity to ensure that enough space is reserved.

ensureCapacity

public final boolean ensureCapacity(long bytes)

Description copied from interface: DataAccess

Ensures that the capacity of this object is at least the specified bytes. The first time you have to call 'create' instead.

Returns:

true if size was increased

See Also:

DataAccess.create(long)

copyTo

public DataAccess copyTo(DataAccess da)

Description copied from interface: DataAccess

Copies the content from this object into the specified one.

Specified by:

copyTo in interface DataAccess

Overrides:

copyTo in class AbstractDataAccess

loadExisting

public boolean loadExisting()

Returns:

true if successfully loaded from persistent storage.

flush

public void flush()

Description copied from interface: Storable

This method makes sure that the underlying data is written to the storage. Keep in mind that a disc normally has an IO cache so that flush() is (less) probably not save against power loses.

close

public void close()

Description copied from interface: Storable

This method makes sure that the underlying used resources are released. WARNING: it does NOT flush on close!

Specified by:

close in interface Storable<DataAccess>

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Overrides:

close in class AbstractDataAccess

setInt

public final void setInt(long bytePos,
                         int value)

Description copied from interface: DataAccess

Set 4 bytes at position 'bytePos' to the specified value

getInt

public final int getInt(long bytePos)

Description copied from interface: DataAccess

Get 4 bytes from position 'bytePos'

getShort

public short getShort(long bytePos)

Description copied from interface: DataAccess

Get 2 bytes from position 'index'

setShort

public void setShort(long bytePos,
                     short value)

Description copied from interface: DataAccess

Set 2 bytes at position 'index' to the specified value

setBytes

public final void setBytes(long bytePos,
                           byte[] values,
                           int length)

Description copied from interface: DataAccess

Set bytes from position 'index' to the specified values

getBytes

public final void getBytes(long bytePos,
                           byte[] values,
                           int length)

Description copied from interface: DataAccess

Get bytes from position 'index'

values - acts as output

getCapacity

public final long getCapacity()

Returns:

the allocated storage size in bytes

getSegments

public final int getSegments()

Returns:

the number of segments.

trimTo

public final void trimTo(long bytes)

Description copied from interface: DataAccess

Reduces the allocate space to the specified bytes. Warning: it'll free the space even if it is in use!

getType

public DAType getType()

Returns:

the data access type of this object.