org.neo4j.unsafe.impl.internal.dragons

Class UnsafeUtil

java.lang.Object

org.neo4j.unsafe.impl.internal.dragons.UnsafeUtil

public final class UnsafeUtil
extends Object

Always check that the Unsafe utilities are available with the assertHasUnsafe() method, before calling any of the other methods. Avoid `import static` for these individual methods. Always qualify method usages with `UnsafeUtil` so use sites show up in code greps.

Field Summary

Fields

Modifier and Type	Field and Description
static boolean	allowUnalignedMemoryAccess
static boolean	storeByteOrderIsNative

Constructor Summary

Constructors

Constructor and Description
UnsafeUtil()

Method Summary

Methods

Modifier and Type	Method and Description
static int	arrayBaseOffset(Class klass)
static int	arrayIndexScale(Class klass)
static int	arrayOffset(int index, int base, int scale)
static void	assertHasUnsafe()
static boolean	compareAndSwapLong(Object obj, long offset, long expected, long update) Atomically compare the current value of the given long field with the expected value, and if they are the equal, set the field to the updated value and return true.
static boolean	compareAndSwapObject(Object obj, long offset, Object expected, Object update) Same as compareAndSwapLong, but for object references.
static void	free(long pointer) Free the memory that was allocated with malloc(long).
static int	getAndAddInt(Object obj, long offset, int delta) Atomically add the given delta to the int field, and return its previous value.
static Object	getAndSetObject(Object obj, long offset, Object newValue) Same as getAndAddInt, but for object references.
static byte	getByte(long address)
static byte	getByteVolatile(Object obj, long offset)
static long	getFieldOffset(Class<?> type, String field) Get the object-relative field offset.
static int	getInt(long address)
static int	getIntVolatile(Object obj, long offset)
static long	getLong(long address)
static long	getLongVolatile(Object obj, long offset)
static Object	getObjectVolatile(Object obj, long offset)
static short	getShort(long address)
static long	malloc(long sizeInBytes) Allocate a slab of memory of the given size in bytes, and return a pointer to that memory.
static ByteBuffer	newDirectByteBuffer(long addr, int cap) Create a new DirectByteBuffer that wraps the given address and has the given capacity.
static void	putByte(long address, byte value)
static void	putByteVolatile(Object obj, long offset, byte value)
static void	putInt(long address, int value)
static void	putLong(long address, long value)
static void	putLong(Object obj, long offset, long value)
static void	putObjectVolatile(Object obj, long offset, Object value)
static void	putShort(long address, short value)
static void	setMemory(long address, long bytes, byte value) Set the given number of bytes to the given value, starting from the given address.

Methods inherited from class java.lang.Object

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

Field Detail

allowUnalignedMemoryAccess

public static final boolean allowUnalignedMemoryAccess

storeByteOrderIsNative

public static final boolean storeByteOrderIsNative

Constructor Detail

UnsafeUtil

public UnsafeUtil()

Method Detail

assertHasUnsafe

public static void assertHasUnsafe()

Throws:

LinkageError - if the Unsafe tools are not available on in this JVM.

getFieldOffset

public static long getFieldOffset(Class<?> type,
                  String field)

Get the object-relative field offset.

getAndAddInt

public static int getAndAddInt(Object obj,
               long offset,
               int delta)

Atomically add the given delta to the int field, and return its previous value. This has the memory visibility semantics of a volatile read followed by a volatile write.

compareAndSwapLong

public static boolean compareAndSwapLong(Object obj,
                         long offset,
                         long expected,
                         long update)

Atomically compare the current value of the given long field with the expected value, and if they are the equal, set the field to the updated value and return true. Otherwise return false. If this method returns true, then it has the memory visibility semantics of a volatile read followed by a volatile write.

compareAndSwapObject

public static boolean compareAndSwapObject(Object obj,
                           long offset,
                           Object expected,
                           Object update)

Same as compareAndSwapLong, but for object references.

getAndSetObject

public static Object getAndSetObject(Object obj,
                     long offset,
                     Object newValue)

Same as getAndAddInt, but for object references.

malloc

public static long malloc(long sizeInBytes)

Allocate a slab of memory of the given size in bytes, and return a pointer to that memory. The memory is aligned such that it can be used for any data type. The memory is cleared, so all bytes are zero.

free

public static void free(long pointer)

Free the memory that was allocated with malloc(long).

getByte

public static byte getByte(long address)

putByte

public static void putByte(long address,
           byte value)

getByteVolatile

public static byte getByteVolatile(Object obj,
                   long offset)

putByteVolatile

public static void putByteVolatile(Object obj,
                   long offset,
                   byte value)

getLong

public static long getLong(long address)

putLong

public static void putLong(long address,
           long value)

getInt

public static int getInt(long address)

putInt

public static void putInt(long address,
          int value)

getShort

public static short getShort(long address)

putShort

public static void putShort(long address,
            short value)

putLong

public static void putLong(Object obj,
           long offset,
           long value)

getLongVolatile

public static long getLongVolatile(Object obj,
                   long offset)

getIntVolatile

public static int getIntVolatile(Object obj,
                 long offset)

getObjectVolatile

public static Object getObjectVolatile(Object obj,
                       long offset)

putObjectVolatile

public static void putObjectVolatile(Object obj,
                     long offset,
                     Object value)

arrayBaseOffset

public static int arrayBaseOffset(Class klass)

arrayIndexScale

public static int arrayIndexScale(Class klass)

arrayOffset

public static int arrayOffset(int index,
              int base,
              int scale)

setMemory

public static void setMemory(long address,
             long bytes,
             byte value)

Set the given number of bytes to the given value, starting from the given address.

newDirectByteBuffer

public static ByteBuffer newDirectByteBuffer(long addr,
                             int cap)
                                      throws Exception

Create a new DirectByteBuffer that wraps the given address and has the given capacity. The ByteBuffer does NOT create a Cleaner, or otherwise register the pointer for freeing.

Throws:

Exception