com.oracle.svm.core

Class UnmanagedMemoryUtil

java.lang.Object

com.oracle.svm.core.UnmanagedMemoryUtil

public final class UnmanagedMemoryUtil
extends Object

The methods in this class are mainly used to fill or copy unmanaged (i.e., non-Java heap) memory. None of the methods cares about Java semantics like GC barriers or the Java memory model. The valid use cases are listed below. For all other use cases, use JavaMemoryUtil instead.

• Copying between unmanaged memory.
• Filling unmanaged memory.

All operations in this class that copy memory guarantee to always use the largest-possible data type for each individual read and write operation, e.g.:

• Copying 60 bytes may be split into 7 operations that copy 8, 8, 8, 8, 8, 8 and 4 bytes. However, it is guaranteed that no operation will copy less than 4 bytes.
• Copying 15 bytes may be split into 4 operations that copy 8, 4, 2, and 1 bytes.

In some situations (e.g., during a serial GC or if it is guaranteed that all involved objects are not yet visible to other threads), the methods in this class may also be used for objects the live in the Java heap. However, those usages should be kept to a minimum.

Method Summary

Modifier and Type	Method and Description
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(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(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	copyLongsBackward(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	copyLongsForward(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	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	fillLongs(org.graalvm.word.Pointer to, org.graalvm.word.UnsignedWord size, long longValue) Set the bytes of a memory area to a given value.

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(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. Guarantees to use the largest-possible data type for each individual read and write operation.

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. Guarantees to use the largest-possible data type for each individual read and write operation.

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. Guarantees to use the largest-possible data type for each individual read and write operation.

copyLongsForward

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

Copy bytes from one memory area to another.

copyLongsBackward

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

Copy bytes from one memory area to another.

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. Does *NOT* guarantee any size for the individual read/write operations and therefore does not guarantee any atomicity.

fillLongs

public static void fillLongs(org.graalvm.word.Pointer to,
                             org.graalvm.word.UnsignedWord size,
                             long longValue)

Set the bytes of a memory area to a given value.