com.oracle.svm.core

Class JavaMemoryUtil

java.lang.Object

com.oracle.svm.core.JavaMemoryUtil

public final class JavaMemoryUtil
extends Object

The methods in this class are mainly used to fill or copy Java heap memory. All methods guarantee at least some level of atomicity and honor the Java memory model if they are used as documented. For more information, please read the JavaDoc of the individual methods.

The valid use cases are listed below. For all other use cases, use UnmanagedMemoryUtil instead.

• Copying between Java arrays.
• Copying between Java instance objects.
• Copying between a Java object and a Java array.
• Copying from native memory to the Java heap.
• Copying from the Java heap to unmanaged memory.
• Filling Java arrays.
• Filling Java objects.

More specialized methods (e.g., methods for copying primitive arrays) are faster than more generic ones. So, performance-wise it is best to call the most specific method that is applicable to your use case.

Method Summary

Modifier and Type	Method and Description
static void	copy(Object from, org.graalvm.word.UnsignedWord fromOffset, Object to, org.graalvm.word.UnsignedWord toOffset, org.graalvm.word.UnsignedWord size) Copy bytes from one Java object to another.
static void	copy(org.graalvm.word.Pointer from, org.graalvm.word.Pointer to, org.graalvm.word.UnsignedWord size) Copy bytes from one memory area to another.
static void	copyBackward(Object from, org.graalvm.word.UnsignedWord fromOffset, Object to, org.graalvm.word.UnsignedWord toOffset, org.graalvm.word.UnsignedWord size) Copy bytes from one Java object to another.
static void	copyBackward(org.graalvm.word.Pointer from, org.graalvm.word.Pointer to, org.graalvm.word.UnsignedWord size) Copy bytes from one memory area to another.
static void	copyForward(Object from, org.graalvm.word.UnsignedWord fromOffset, Object to, org.graalvm.word.UnsignedWord toOffset, org.graalvm.word.UnsignedWord size) Copy bytes from one Java object to another.
static void	copyForward(org.graalvm.word.Pointer from, org.graalvm.word.Pointer to, org.graalvm.word.UnsignedWord size) Copy bytes from one memory area to another.
static void	copyObjectArrayBackward(Object fromArray, int fromIndex, Object toArray, int toIndex, int length, int layoutEncoding) Copies between Java object arrays.
static void	copyObjectArrayForward(Object fromArray, int fromIndex, Object toArray, int toIndex, int length, int layoutEncoding) Copies between Java object arrays.
static void	copyObjectArrayForwardWithStoreCheck(Object fromArray, int fromIndex, Object toArray, int toIndex, int length) Copies between Java object arrays.
static void	copyPrimitiveArrayBackward(Object fromArray, int fromIndex, Object toArray, int toIndex, int length, int layoutEncoding) Copies between Java primitive arrays.
static void	copyPrimitiveArrayBackward(org.graalvm.word.Pointer fromPtr, org.graalvm.word.Pointer toPtr, org.graalvm.word.UnsignedWord size)
static void	copyPrimitiveArrayForward(Object fromArray, int fromIndex, Object toArray, int toIndex, int length, int layoutEncoding) Copies between Java primitive arrays.
static void	copyPrimitiveArrayForward(org.graalvm.word.Pointer fromPtr, org.graalvm.word.Pointer toPtr, org.graalvm.word.UnsignedWord size)
static void	copyReferencesBackward(Object from, org.graalvm.word.UnsignedWord fromOffset, Object to, org.graalvm.word.UnsignedWord toOffset, org.graalvm.word.UnsignedWord length) Copies object references from one Java object to another Java object.
static void	copyReferencesForward(Object from, org.graalvm.word.UnsignedWord fromOffset, Object to, org.graalvm.word.UnsignedWord toOffset, org.graalvm.word.UnsignedWord length) Copies object references from one Java object to another Java object.
static void	copySwap(org.graalvm.word.Pointer from, org.graalvm.word.Pointer to, org.graalvm.word.UnsignedWord size, org.graalvm.word.UnsignedWord elementSize) Copy memory from one memory area to another, unconditionally reversing bytes of an element according to the passed element size.
static void	fill(org.graalvm.word.Pointer to, org.graalvm.word.UnsignedWord size, byte value) Set the bytes of a memory area to a given value.
static void	unsafeCopyMemory(Object srcBase, long srcOffset, Object destBase, long destOffset, long bytes) Implementation of Unsafe.copyMemory.
static void	unsafeCopySwapMemory(Object srcBase, long srcOffset, Object destBase, long destOffset, long bytes, long elemSize) Implementation of Unsafe.copySwapMemory.
static void	unsafeSetMemory(Object destBase, long destOffset, long bytes, byte bvalue) Implementation of Unsafe.setMemory.

Methods inherited from class java.lang.Object

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

Method Detail

copy

public static void copy(Object from,
                        org.graalvm.word.UnsignedWord fromOffset,
                        Object to,
                        org.graalvm.word.UnsignedWord toOffset,
                        org.graalvm.word.UnsignedWord size)

Copy bytes from one Java object to another. The copied memory areas may overlap. The caller must take care that no GC barriers are required for the operation. Furthermore, the offsets must be aligned to object field boundaries or array element boundaries in order to ensure access atomicity according to the Java memory model (Java Language Specification, 17.6).

copyForward

public static void copyForward(Object from,
                               org.graalvm.word.UnsignedWord fromOffset,
                               Object to,
                               org.graalvm.word.UnsignedWord toOffset,
                               org.graalvm.word.UnsignedWord size)

Copy bytes from one Java object to another. The caller must take care that no GC barriers are required for the operation. Furthermore, the offsets must be aligned to object field boundaries or array element boundaries in order to ensure access atomicity according to the Java memory model (Java Language Specification, 17.6).

copyBackward

public static void copyBackward(Object from,
                                org.graalvm.word.UnsignedWord fromOffset,
                                Object to,
                                org.graalvm.word.UnsignedWord toOffset,
                                org.graalvm.word.UnsignedWord size)

Copy bytes from one Java object to another. The caller must take care that no GC barriers are required for the operation. Furthermore, the offsets must be aligned to object field boundaries or array element boundaries in order to ensure access atomicity according to the Java memory model (Java Language Specification, 17.6).

copy

public static void copy(org.graalvm.word.Pointer from,
                        org.graalvm.word.Pointer to,
                        org.graalvm.word.UnsignedWord size)

Copy bytes from one memory area to another. The memory areas may overlap. If either memory area is on the Java heap, the caller must take care that no GC barriers are required for the operation and the caller must be uninterruptible or otherwise ensure that objects cannot move or be collected. When using this method to copy memory of Java objects, the addresses and size must align to object field boundaries or array element boundaries in order to ensure access atomicity according to the Java memory model (Java Language Specification, 17.6).

copyForward

public static void copyForward(org.graalvm.word.Pointer from,
                               org.graalvm.word.Pointer to,
                               org.graalvm.word.UnsignedWord size)

Copy bytes from one memory area to another. If either memory area is on the Java heap, the caller must take care that no GC barriers are required for the operation and the caller must be uninterruptible or otherwise ensure that objects cannot move or be collected. When using this method to copy memory of Java objects, the addresses and size must align to object field boundaries or array element boundaries in order to ensure access atomicity according to the Java memory model (Java Language Specification, 17.6).

copyBackward

public static void copyBackward(org.graalvm.word.Pointer from,
                                org.graalvm.word.Pointer to,
                                org.graalvm.word.UnsignedWord size)

Copy bytes from one memory area to another. If either memory area is on the Java heap, the caller must take care that no GC barriers are required for the operation and the caller must be uninterruptible or otherwise ensure that objects cannot move or be collected. When using this method to copy memory of Java objects, the addresses and size must align to object field boundaries or array element boundaries in order to ensure access atomicity according to the Java memory model (Java Language Specification, 17.6).

unsafeCopyMemory

public static void unsafeCopyMemory(Object srcBase,
                                    long srcOffset,
                                    Object destBase,
                                    long destOffset,
                                    long bytes)

Implementation of Unsafe.copyMemory.

fill

public static void fill(org.graalvm.word.Pointer to,
                        org.graalvm.word.UnsignedWord size,
                        byte value)

Set the bytes of a memory area to a given value. If either memory area is on the Java heap, the caller must take care that no GC barriers are required for the operation and the caller must be uninterruptible or otherwise ensure that objects cannot move or be collected. When using this method to copy memory of Java objects, the address and size must align to object field boundaries or array element boundaries in order to ensure access atomicity according to the Java memory model (Java Language Specification, 17.6).

unsafeSetMemory

public static void unsafeSetMemory(Object destBase,
                                   long destOffset,
                                   long bytes,
                                   byte bvalue)

Implementation of Unsafe.setMemory.

copySwap

public static void copySwap(org.graalvm.word.Pointer from,
                            org.graalvm.word.Pointer to,
                            org.graalvm.word.UnsignedWord size,
                            org.graalvm.word.UnsignedWord elementSize)

Copy memory from one memory area to another, unconditionally reversing bytes of an element according to the passed element size. The memory areas may overlap. If either memory area is on the Java heap, the caller must take care that no GC barriers are required for the operation and the caller must be uninterruptible or otherwise ensure that objects cannot move or be collected.

unsafeCopySwapMemory

public static void unsafeCopySwapMemory(Object srcBase,
                                        long srcOffset,
                                        Object destBase,
                                        long destOffset,
                                        long bytes,
                                        long elemSize)

Implementation of Unsafe.copySwapMemory.

copyObjectArrayForward

public static void copyObjectArrayForward(Object fromArray,
                                          int fromIndex,
                                          Object toArray,
                                          int toIndex,
                                          int length,
                                          int layoutEncoding)

Copies between Java object arrays. Emits the necessary read/write barriers but does *NOT* perform any array store checks (i.e., it is up to the caller to ensure that the arrays are compatible).

copyObjectArrayBackward

public static void copyObjectArrayBackward(Object fromArray,
                                           int fromIndex,
                                           Object toArray,
                                           int toIndex,
                                           int length,
                                           int layoutEncoding)

Copies between Java object arrays. Emits the necessary read/write barriers but does *NOT* perform any array store checks (i.e., it is up to the caller to ensure that the arrays are compatible).

copyReferencesForward

public static void copyReferencesForward(Object from,
                                         org.graalvm.word.UnsignedWord fromOffset,
                                         Object to,
                                         org.graalvm.word.UnsignedWord toOffset,
                                         org.graalvm.word.UnsignedWord length)

Copies object references from one Java object to another Java object. Emits the necessary read/write barriers but does *NOT* perform any array store checks (i.e., if this is used for copying between arrays, it is up to the caller to ensure that the arrays are compatible).

copyReferencesBackward

public static void copyReferencesBackward(Object from,
                                          org.graalvm.word.UnsignedWord fromOffset,
                                          Object to,
                                          org.graalvm.word.UnsignedWord toOffset,
                                          org.graalvm.word.UnsignedWord length)

Copies object references from one Java object to another Java object. Emits the necessary read/write barriers but does *NOT* perform any array store checks (i.e., if this is used for copying between arrays, it is up to the caller to ensure that the arrays are compatible).

copyObjectArrayForwardWithStoreCheck

public static void copyObjectArrayForwardWithStoreCheck(Object fromArray,
                                                        int fromIndex,
                                                        Object toArray,
                                                        int toIndex,
                                                        int length)

Copies between Java object arrays. Emits the necessary read/write barriers and also performs array store checks.

copyPrimitiveArrayForward

public static void copyPrimitiveArrayForward(Object fromArray,
                                             int fromIndex,
                                             Object toArray,
                                             int toIndex,
                                             int length,
                                             int layoutEncoding)

Copies between Java primitive arrays.

copyPrimitiveArrayForward

public static void copyPrimitiveArrayForward(org.graalvm.word.Pointer fromPtr,
                                             org.graalvm.word.Pointer toPtr,
                                             org.graalvm.word.UnsignedWord size)

copyPrimitiveArrayBackward

public static void copyPrimitiveArrayBackward(Object fromArray,
                                              int fromIndex,
                                              Object toArray,
                                              int toIndex,
                                              int length,
                                              int layoutEncoding)

Copies between Java primitive arrays.

copyPrimitiveArrayBackward

public static void copyPrimitiveArrayBackward(org.graalvm.word.Pointer fromPtr,
                                              org.graalvm.word.Pointer toPtr,
                                              org.graalvm.word.UnsignedWord size)