/* * Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle in the LICENSE file that accompanied this code. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package jdk.internal.misc; import jdk.internal.HotSpotIntrinsicCandidate; import jdk.internal.vm.annotation.ForceInline; import java.lang.reflect.Field; import java.security.ProtectionDomain; /** * A collection of methods for performing low-level, unsafe operations. * Although the class and all methods are public, use of this class is * limited because only trusted code can obtain instances of it. * * Note: It is the resposibility of the caller to make sure * arguments are checked before methods of this class are * called. While some rudimentary checks are performed on the input, * the checks are best effort and when performance is an overriding * priority, as when methods of this class are optimized by the * runtime compiler, some or all checks (if any) may be elided. Hence, * the caller must not rely on the checks and corresponding * exceptions! * * @author John R. Rose * @see #getUnsafe */ public final class Unsafe { private static native void registerNatives(); static { registerNatives(); } private Unsafe() {} private static final Unsafe theUnsafe = new Unsafe(); /** * Provides the caller with the capability of performing unsafe * operations. * *
The returned {@code Unsafe} object should be carefully guarded * by the caller, since it can be used to read and write data at arbitrary * memory addresses. It must never be passed to untrusted code. * *
Most methods in this class are very low-level, and correspond to a * small number of hardware instructions (on typical machines). Compilers * are encouraged to optimize these methods accordingly. * *
Here is a suggested idiom for using unsafe operations: * *
{@code * class MyTrustedClass { * private static final Unsafe unsafe = Unsafe.getUnsafe(); * ... * private long myCountAddress = ...; * public int getCount() { return unsafe.getByte(myCountAddress); } * }}* * (It may assist compilers to make the local variable {@code final}.) */ public static Unsafe getUnsafe() { return theUnsafe; } /// peek and poke operations /// (compilers should optimize these to memory ops) // These work on object fields in the Java heap. // They will not work on elements of packed arrays. /** * Fetches a value from a given Java variable. * More specifically, fetches a field or array element within the given * object {@code o} at the given offset, or (if {@code o} is null) * from the memory address whose numerical value is the given offset. *
* The results are undefined unless one of the following cases is true: *
* If one of the above cases is true, the call references a specific Java * variable (field or array element). However, the results are undefined * if that variable is not in fact of the type returned by this method. *
* This method refers to a variable by means of two parameters, and so * it provides (in effect) a double-register addressing mode * for Java variables. When the object reference is null, this method * uses its offset as an absolute address. This is similar in operation * to methods such as {@link #getInt(long)}, which provide (in effect) a * single-register addressing mode for non-Java variables. * However, because Java variables may have a different layout in memory * from non-Java variables, programmers should not assume that these * two addressing modes are ever equivalent. Also, programmers should * remember that offsets from the double-register addressing mode cannot * be portably confused with longs used in the single-register addressing * mode. * * @param o Java heap object in which the variable resides, if any, else * null * @param offset indication of where the variable resides in a Java heap * object, if any, else a memory address locating the variable * statically * @return the value fetched from the indicated Java variable * @throws RuntimeException No defined exceptions are thrown, not even * {@link NullPointerException} */ @HotSpotIntrinsicCandidate public native int getInt(Object o, long offset); /** * Stores a value into a given Java variable. *
* The first two parameters are interpreted exactly as with * {@link #getInt(Object, long)} to refer to a specific * Java variable (field or array element). The given value * is stored into that variable. *
* The variable must be of the same type as the method * parameter {@code x}. * * @param o Java heap object in which the variable resides, if any, else * null * @param offset indication of where the variable resides in a Java heap * object, if any, else a memory address locating the variable * statically * @param x the value to store into the indicated Java variable * @throws RuntimeException No defined exceptions are thrown, not even * {@link NullPointerException} */ @HotSpotIntrinsicCandidate public native void putInt(Object o, long offset, int x); /** * Returns true if the given class is a regular value type. */ public boolean isValueType(Class> c) { return c.isValue() && c == c.asValueType(); } /** * Returns true if the given class is a flattened array. */ public native boolean isFlattenedArray(Class> arrayClass); /** * Fetches a reference value from a given Java variable. * This method can return a reference to either an object or value * or a null reference. * * @see #getInt(Object, long) */ @HotSpotIntrinsicCandidate public native Object getObject(Object o, long offset); /** * Stores a reference value into a given Java variable. * This method can store a reference to either an object or value * or a null reference. *
* Unless the reference {@code x} being stored is either null
* or matches the field type, the results are undefined.
* If the reference {@code o} is non-null, card marks or
* other store barriers for that object (if the VM requires them)
* are updated.
* @see #putInt(Object, long, int)
*/
@HotSpotIntrinsicCandidate
public native void putObject(Object o, long offset, Object x);
/**
* Fetches a value of type {@code If the native pointer is less than 64 bits wide, it is extended as
* an unsigned number to a Java long. The pointer may be indexed by any
* given byte offset, simply by adding that offset (as a simple integer) to
* the long representing the pointer. The number of bytes actually read
* from the target address may be determined by consulting {@link
* #addressSize}.
*
* @see #allocateMemory
* @see #getInt(Object, long)
*/
@ForceInline
public long getAddress(Object o, long offset) {
if (ADDRESS_SIZE == 4) {
return Integer.toUnsignedLong(getInt(o, offset));
} else {
return getLong(o, offset);
}
}
/**
* Stores a native pointer into a given memory address. If the address is
* zero, or does not point into a block obtained from {@link
* #allocateMemory}, the results are undefined.
*
* The number of bytes actually written at the target address may be
* determined by consulting {@link #addressSize}.
*
* @see #allocateMemory
* @see #putInt(Object, long, int)
*/
@ForceInline
public void putAddress(Object o, long offset, long x) {
if (ADDRESS_SIZE == 4) {
putInt(o, offset, (int)x);
} else {
putLong(o, offset, x);
}
}
// These read VM internal data.
/**
* Fetches an uncompressed reference value from a given native variable
* ignoring the VM's compressed references mode.
*
* @param address a memory address locating the variable
* @return the value fetched from the indicated native variable
*/
public native Object getUncompressedObject(long address);
// These work on values in the C heap.
/**
* Fetches a value from a given memory address. If the address is zero, or
* does not point into a block obtained from {@link #allocateMemory}, the
* results are undefined.
*
* @see #allocateMemory
*/
@ForceInline
public byte getByte(long address) {
return getByte(null, address);
}
/**
* Stores a value into a given memory address. If the address is zero, or
* does not point into a block obtained from {@link #allocateMemory}, the
* results are undefined.
*
* @see #getByte(long)
*/
@ForceInline
public void putByte(long address, byte x) {
putByte(null, address, x);
}
/** @see #getByte(long) */
@ForceInline
public short getShort(long address) {
return getShort(null, address);
}
/** @see #putByte(long, byte) */
@ForceInline
public void putShort(long address, short x) {
putShort(null, address, x);
}
/** @see #getByte(long) */
@ForceInline
public char getChar(long address) {
return getChar(null, address);
}
/** @see #putByte(long, byte) */
@ForceInline
public void putChar(long address, char x) {
putChar(null, address, x);
}
/** @see #getByte(long) */
@ForceInline
public int getInt(long address) {
return getInt(null, address);
}
/** @see #putByte(long, byte) */
@ForceInline
public void putInt(long address, int x) {
putInt(null, address, x);
}
/** @see #getByte(long) */
@ForceInline
public long getLong(long address) {
return getLong(null, address);
}
/** @see #putByte(long, byte) */
@ForceInline
public void putLong(long address, long x) {
putLong(null, address, x);
}
/** @see #getByte(long) */
@ForceInline
public float getFloat(long address) {
return getFloat(null, address);
}
/** @see #putByte(long, byte) */
@ForceInline
public void putFloat(long address, float x) {
putFloat(null, address, x);
}
/** @see #getByte(long) */
@ForceInline
public double getDouble(long address) {
return getDouble(null, address);
}
/** @see #putByte(long, byte) */
@ForceInline
public void putDouble(long address, double x) {
putDouble(null, address, x);
}
/** @see #getAddress(Object, long) */
@ForceInline
public long getAddress(long address) {
return getAddress(null, address);
}
/** @see #putAddress(Object, long, long) */
@ForceInline
public void putAddress(long address, long x) {
putAddress(null, address, x);
}
/// helper methods for validating various types of objects/values
/**
* Create an exception reflecting that some of the input was invalid
*
* Note: It is the resposibility of the caller to make
* sure arguments are checked before the methods are called. While
* some rudimentary checks are performed on the input, the checks
* are best effort and when performance is an overriding priority,
* as when methods of this class are optimized by the runtime
* compiler, some or all checks (if any) may be elided. Hence, the
* caller must not rely on the checks and corresponding
* exceptions!
*
* @return an exception object
*/
private RuntimeException invalidInput() {
return new IllegalArgumentException();
}
/**
* Check if a value is 32-bit clean (32 MSB are all zero)
*
* @param value the 64-bit value to check
*
* @return true if the value is 32-bit clean
*/
private boolean is32BitClean(long value) {
return value >>> 32 == 0;
}
/**
* Check the validity of a size (the equivalent of a size_t)
*
* @throws RuntimeException if the size is invalid
* (Note: after optimization, invalid inputs may
* go undetected, which will lead to unpredictable
* behavior)
*/
private void checkSize(long size) {
if (ADDRESS_SIZE == 4) {
// Note: this will also check for negative sizes
if (!is32BitClean(size)) {
throw invalidInput();
}
} else if (size < 0) {
throw invalidInput();
}
}
/**
* Check the validity of a native address (the equivalent of void*)
*
* @throws RuntimeException if the address is invalid
* (Note: after optimization, invalid inputs may
* go undetected, which will lead to unpredictable
* behavior)
*/
private void checkNativeAddress(long address) {
if (ADDRESS_SIZE == 4) {
// Accept both zero and sign extended pointers. A valid
// pointer will, after the +1 below, either have produced
// the value 0x0 or 0x1. Masking off the low bit allows
// for testing against 0.
if ((((address >> 32) + 1) & ~1) != 0) {
throw invalidInput();
}
}
}
/**
* Check the validity of an offset, relative to a base object
*
* @param o the base object
* @param offset the offset to check
*
* @throws RuntimeException if the size is invalid
* (Note: after optimization, invalid inputs may
* go undetected, which will lead to unpredictable
* behavior)
*/
private void checkOffset(Object o, long offset) {
if (ADDRESS_SIZE == 4) {
// Note: this will also check for negative offsets
if (!is32BitClean(offset)) {
throw invalidInput();
}
} else if (offset < 0) {
throw invalidInput();
}
}
/**
* Check the validity of a double-register pointer
*
* Note: This code deliberately does *not* check for NPE for (at
* least) three reasons:
*
* 1) NPE is not just NULL/0 - there is a range of values all
* resulting in an NPE, which is not trivial to check for
*
* 2) It is the responsibility of the callers of Unsafe methods
* to verify the input, so throwing an exception here is not really
* useful - passing in a NULL pointer is a critical error and the
* must not expect an exception to be thrown anyway.
*
* 3) the actual operations will detect NULL pointers anyway by
* means of traps and signals (like SIGSEGV).
*
* @param o Java heap object, or null
* @param offset indication of where the variable resides in a Java heap
* object, if any, else a memory address locating the variable
* statically
*
* @throws RuntimeException if the pointer is invalid
* (Note: after optimization, invalid inputs may
* go undetected, which will lead to unpredictable
* behavior)
*/
private void checkPointer(Object o, long offset) {
if (o == null) {
checkNativeAddress(offset);
} else {
checkOffset(o, offset);
}
}
/**
* Check if a type is a primitive array type
*
* @param c the type to check
*
* @return true if the type is a primitive array type
*/
private void checkPrimitiveArray(Class> c) {
Class> componentType = c.getComponentType();
if (componentType == null || !componentType.isPrimitive()) {
throw invalidInput();
}
}
/**
* Check that a pointer is a valid primitive array type pointer
*
* Note: pointers off-heap are considered to be primitive arrays
*
* @throws RuntimeException if the pointer is invalid
* (Note: after optimization, invalid inputs may
* go undetected, which will lead to unpredictable
* behavior)
*/
private void checkPrimitivePointer(Object o, long offset) {
checkPointer(o, offset);
if (o != null) {
// If on heap, it must be a primitive array
checkPrimitiveArray(o.getClass());
}
}
/// wrappers for malloc, realloc, free:
/**
* Allocates a new block of native memory, of the given size in bytes. The
* contents of the memory are uninitialized; they will generally be
* garbage. The resulting native pointer will never be zero, and will be
* aligned for all value types. Dispose of this memory by calling {@link
* #freeMemory}, or resize it with {@link #reallocateMemory}.
*
* Note: It is the resposibility of the caller to make
* sure arguments are checked before the methods are called. While
* some rudimentary checks are performed on the input, the checks
* are best effort and when performance is an overriding priority,
* as when methods of this class are optimized by the runtime
* compiler, some or all checks (if any) may be elided. Hence, the
* caller must not rely on the checks and corresponding
* exceptions!
*
* @throws RuntimeException if the size is negative or too large
* for the native size_t type
*
* @throws OutOfMemoryError if the allocation is refused by the system
*
* @see #getByte(long)
* @see #putByte(long, byte)
*/
public long allocateMemory(long bytes) {
allocateMemoryChecks(bytes);
if (bytes == 0) {
return 0;
}
long p = allocateMemory0(bytes);
if (p == 0) {
throw new OutOfMemoryError();
}
return p;
}
/**
* Validate the arguments to allocateMemory
*
* @throws RuntimeException if the arguments are invalid
* (Note: after optimization, invalid inputs may
* go undetected, which will lead to unpredictable
* behavior)
*/
private void allocateMemoryChecks(long bytes) {
checkSize(bytes);
}
/**
* Resizes a new block of native memory, to the given size in bytes. The
* contents of the new block past the size of the old block are
* uninitialized; they will generally be garbage. The resulting native
* pointer will be zero if and only if the requested size is zero. The
* resulting native pointer will be aligned for all value types. Dispose
* of this memory by calling {@link #freeMemory}, or resize it with {@link
* #reallocateMemory}. The address passed to this method may be null, in
* which case an allocation will be performed.
*
* Note: It is the resposibility of the caller to make
* sure arguments are checked before the methods are called. While
* some rudimentary checks are performed on the input, the checks
* are best effort and when performance is an overriding priority,
* as when methods of this class are optimized by the runtime
* compiler, some or all checks (if any) may be elided. Hence, the
* caller must not rely on the checks and corresponding
* exceptions!
*
* @throws RuntimeException if the size is negative or too large
* for the native size_t type
*
* @throws OutOfMemoryError if the allocation is refused by the system
*
* @see #allocateMemory
*/
public long reallocateMemory(long address, long bytes) {
reallocateMemoryChecks(address, bytes);
if (bytes == 0) {
freeMemory(address);
return 0;
}
long p = (address == 0) ? allocateMemory0(bytes) : reallocateMemory0(address, bytes);
if (p == 0) {
throw new OutOfMemoryError();
}
return p;
}
/**
* Validate the arguments to reallocateMemory
*
* @throws RuntimeException if the arguments are invalid
* (Note: after optimization, invalid inputs may
* go undetected, which will lead to unpredictable
* behavior)
*/
private void reallocateMemoryChecks(long address, long bytes) {
checkPointer(null, address);
checkSize(bytes);
}
/**
* Sets all bytes in a given block of memory to a fixed value
* (usually zero).
*
* This method determines a block's base address by means of two parameters,
* and so it provides (in effect) a double-register addressing mode,
* as discussed in {@link #getInt(Object,long)}. When the object reference is null,
* the offset supplies an absolute base address.
*
* The stores are in coherent (atomic) units of a size determined
* by the address and length parameters. If the effective address and
* length are all even modulo 8, the stores take place in 'long' units.
* If the effective address and length are (resp.) even modulo 4 or 2,
* the stores take place in units of 'int' or 'short'.
*
* Note: It is the resposibility of the caller to make
* sure arguments are checked before the methods are called. While
* some rudimentary checks are performed on the input, the checks
* are best effort and when performance is an overriding priority,
* as when methods of this class are optimized by the runtime
* compiler, some or all checks (if any) may be elided. Hence, the
* caller must not rely on the checks and corresponding
* exceptions!
*
* @throws RuntimeException if any of the arguments is invalid
*
* @since 1.7
*/
public void setMemory(Object o, long offset, long bytes, byte value) {
setMemoryChecks(o, offset, bytes, value);
if (bytes == 0) {
return;
}
setMemory0(o, offset, bytes, value);
}
/**
* Sets all bytes in a given block of memory to a fixed value
* (usually zero). This provides a single-register addressing mode,
* as discussed in {@link #getInt(Object,long)}.
*
* Equivalent to {@code setMemory(null, address, bytes, value)}.
*/
public void setMemory(long address, long bytes, byte value) {
setMemory(null, address, bytes, value);
}
/**
* Validate the arguments to setMemory
*
* @throws RuntimeException if the arguments are invalid
* (Note: after optimization, invalid inputs may
* go undetected, which will lead to unpredictable
* behavior)
*/
private void setMemoryChecks(Object o, long offset, long bytes, byte value) {
checkPrimitivePointer(o, offset);
checkSize(bytes);
}
/**
* Sets all bytes in a given block of memory to a copy of another
* block.
*
* This method determines each block's base address by means of two parameters,
* and so it provides (in effect) a double-register addressing mode,
* as discussed in {@link #getInt(Object,long)}. When the object reference is null,
* the offset supplies an absolute base address.
*
* The transfers are in coherent (atomic) units of a size determined
* by the address and length parameters. If the effective addresses and
* length are all even modulo 8, the transfer takes place in 'long' units.
* If the effective addresses and length are (resp.) even modulo 4 or 2,
* the transfer takes place in units of 'int' or 'short'.
*
* Note: It is the resposibility of the caller to make
* sure arguments are checked before the methods are called. While
* some rudimentary checks are performed on the input, the checks
* are best effort and when performance is an overriding priority,
* as when methods of this class are optimized by the runtime
* compiler, some or all checks (if any) may be elided. Hence, the
* caller must not rely on the checks and corresponding
* exceptions!
*
* @throws RuntimeException if any of the arguments is invalid
*
* @since 1.7
*/
public void copyMemory(Object srcBase, long srcOffset,
Object destBase, long destOffset,
long bytes) {
copyMemoryChecks(srcBase, srcOffset, destBase, destOffset, bytes);
if (bytes == 0) {
return;
}
copyMemory0(srcBase, srcOffset, destBase, destOffset, bytes);
}
/**
* Sets all bytes in a given block of memory to a copy of another
* block. This provides a single-register addressing mode,
* as discussed in {@link #getInt(Object,long)}.
*
* Equivalent to {@code copyMemory(null, srcAddress, null, destAddress, bytes)}.
*/
public void copyMemory(long srcAddress, long destAddress, long bytes) {
copyMemory(null, srcAddress, null, destAddress, bytes);
}
/**
* Validate the arguments to copyMemory
*
* @throws RuntimeException if any of the arguments is invalid
* (Note: after optimization, invalid inputs may
* go undetected, which will lead to unpredictable
* behavior)
*/
private void copyMemoryChecks(Object srcBase, long srcOffset,
Object destBase, long destOffset,
long bytes) {
checkSize(bytes);
checkPrimitivePointer(srcBase, srcOffset);
checkPrimitivePointer(destBase, destOffset);
}
/**
* Copies all elements from one block of memory to another block,
* *unconditionally* byte swapping the elements on the fly.
*
* This method determines each block's base address by means of two parameters,
* and so it provides (in effect) a double-register addressing mode,
* as discussed in {@link #getInt(Object,long)}. When the object reference is null,
* the offset supplies an absolute base address.
*
* Note: It is the resposibility of the caller to make
* sure arguments are checked before the methods are called. While
* some rudimentary checks are performed on the input, the checks
* are best effort and when performance is an overriding priority,
* as when methods of this class are optimized by the runtime
* compiler, some or all checks (if any) may be elided. Hence, the
* caller must not rely on the checks and corresponding
* exceptions!
*
* @throws RuntimeException if any of the arguments is invalid
*
* @since 9
*/
public void copySwapMemory(Object srcBase, long srcOffset,
Object destBase, long destOffset,
long bytes, long elemSize) {
copySwapMemoryChecks(srcBase, srcOffset, destBase, destOffset, bytes, elemSize);
if (bytes == 0) {
return;
}
copySwapMemory0(srcBase, srcOffset, destBase, destOffset, bytes, elemSize);
}
private void copySwapMemoryChecks(Object srcBase, long srcOffset,
Object destBase, long destOffset,
long bytes, long elemSize) {
checkSize(bytes);
if (elemSize != 2 && elemSize != 4 && elemSize != 8) {
throw invalidInput();
}
if (bytes % elemSize != 0) {
throw invalidInput();
}
checkPrimitivePointer(srcBase, srcOffset);
checkPrimitivePointer(destBase, destOffset);
}
/**
* Copies all elements from one block of memory to another block, byte swapping the
* elements on the fly.
*
* This provides a single-register addressing mode, as
* discussed in {@link #getInt(Object,long)}.
*
* Equivalent to {@code copySwapMemory(null, srcAddress, null, destAddress, bytes, elemSize)}.
*/
public void copySwapMemory(long srcAddress, long destAddress, long bytes, long elemSize) {
copySwapMemory(null, srcAddress, null, destAddress, bytes, elemSize);
}
/**
* Disposes of a block of native memory, as obtained from {@link
* #allocateMemory} or {@link #reallocateMemory}. The address passed to
* this method may be null, in which case no action is taken.
*
* Note: It is the resposibility of the caller to make
* sure arguments are checked before the methods are called. While
* some rudimentary checks are performed on the input, the checks
* are best effort and when performance is an overriding priority,
* as when methods of this class are optimized by the runtime
* compiler, some or all checks (if any) may be elided. Hence, the
* caller must not rely on the checks and corresponding
* exceptions!
*
* @throws RuntimeException if any of the arguments is invalid
*
* @see #allocateMemory
*/
public void freeMemory(long address) {
freeMemoryChecks(address);
if (address == 0) {
return;
}
freeMemory0(address);
}
/**
* Validate the arguments to freeMemory
*
* @throws RuntimeException if the arguments are invalid
* (Note: after optimization, invalid inputs may
* go undetected, which will lead to unpredictable
* behavior)
*/
private void freeMemoryChecks(long address) {
checkPointer(null, address);
}
/// random queries
/**
* This constant differs from all results that will ever be returned from
* {@link #staticFieldOffset}, {@link #objectFieldOffset},
* or {@link #arrayBaseOffset}.
*/
public static final int INVALID_FIELD_OFFSET = -1;
/**
* Reports the location of a given field in the storage allocation of its
* class. Do not expect to perform any sort of arithmetic on this offset;
* it is just a cookie which is passed to the unsafe heap memory accessors.
*
* Any given field will always have the same offset and base, and no
* two distinct fields of the same class will ever have the same offset
* and base.
*
* As of 1.4.1, offsets for fields are represented as long values,
* although the Sun JVM does not use the most significant 32 bits.
* However, JVM implementations which store static fields at absolute
* addresses can use long offsets and null base pointers to express
* the field locations in a form usable by {@link #getInt(Object,long)}.
* Therefore, code which will be ported to such JVMs on 64-bit platforms
* must preserve all bits of static field offsets.
* @see #getInt(Object, long)
*/
public long objectFieldOffset(Field f) {
if (f == null) {
throw new NullPointerException();
}
return objectFieldOffset0(f);
}
/**
* Reports the location of the field with a given name in the storage
* allocation of its class.
*
* @throws NullPointerException if any parameter is {@code null}.
* @throws InternalError if there is no field named {@code name} declared
* in class {@code c}, i.e., if {@code c.getDeclaredField(name)}
* would throw {@code java.lang.NoSuchFieldException}.
*
* @see #objectFieldOffset(Field)
*/
public long objectFieldOffset(Class> c, String name) {
if (c == null || name == null) {
throw new NullPointerException();
}
return objectFieldOffset1(c, name);
}
/**
* Reports the location of a given static field, in conjunction with {@link
* #staticFieldBase}.
* Do not expect to perform any sort of arithmetic on this offset;
* it is just a cookie which is passed to the unsafe heap memory accessors.
*
* Any given field will always have the same offset, and no two distinct
* fields of the same class will ever have the same offset.
*
* As of 1.4.1, offsets for fields are represented as long values,
* although the Sun JVM does not use the most significant 32 bits.
* It is hard to imagine a JVM technology which needs more than
* a few bits to encode an offset within a non-array object,
* However, for consistency with other methods in this class,
* this method reports its result as a long value.
* @see #getInt(Object, long)
*/
public long staticFieldOffset(Field f) {
if (f == null) {
throw new NullPointerException();
}
return staticFieldOffset0(f);
}
/**
* Reports the location of a given static field, in conjunction with {@link
* #staticFieldOffset}.
* Fetch the base "Object", if any, with which static fields of the
* given class can be accessed via methods like {@link #getInt(Object,
* long)}. This value may be null. This value may refer to an object
* which is a "cookie", not guaranteed to be a real Object, and it should
* not be used in any way except as argument to the get and put routines in
* this class.
*/
public Object staticFieldBase(Field f) {
if (f == null) {
throw new NullPointerException();
}
return staticFieldBase0(f);
}
/**
* Detects if the given class may need to be initialized. This is often
* needed in conjunction with obtaining the static field base of a
* class.
* @return false only if a call to {@code ensureClassInitialized} would have no effect
*/
public boolean shouldBeInitialized(Class> c) {
if (c == null) {
throw new NullPointerException();
}
return shouldBeInitialized0(c);
}
/**
* Ensures the given class has been initialized. This is often
* needed in conjunction with obtaining the static field base of a
* class.
*/
public void ensureClassInitialized(Class> c) {
if (c == null) {
throw new NullPointerException();
}
ensureClassInitialized0(c);
}
/**
* Reports the offset of the first element in the storage allocation of a
* given array class. If {@link #arrayIndexScale} returns a non-zero value
* for the same class, you may use that scale factor, together with this
* base offset, to form new offsets to access elements of arrays of the
* given class.
*
* @see #getInt(Object, long)
* @see #putInt(Object, long, int)
*/
public int arrayBaseOffset(Class> arrayClass) {
if (arrayClass == null) {
throw new NullPointerException();
}
return arrayBaseOffset0(arrayClass);
}
/** The value of {@code arrayBaseOffset(boolean[].class)} */
public static final int ARRAY_BOOLEAN_BASE_OFFSET
= theUnsafe.arrayBaseOffset(boolean[].class);
/** The value of {@code arrayBaseOffset(byte[].class)} */
public static final int ARRAY_BYTE_BASE_OFFSET
= theUnsafe.arrayBaseOffset(byte[].class);
/** The value of {@code arrayBaseOffset(short[].class)} */
public static final int ARRAY_SHORT_BASE_OFFSET
= theUnsafe.arrayBaseOffset(short[].class);
/** The value of {@code arrayBaseOffset(char[].class)} */
public static final int ARRAY_CHAR_BASE_OFFSET
= theUnsafe.arrayBaseOffset(char[].class);
/** The value of {@code arrayBaseOffset(int[].class)} */
public static final int ARRAY_INT_BASE_OFFSET
= theUnsafe.arrayBaseOffset(int[].class);
/** The value of {@code arrayBaseOffset(long[].class)} */
public static final int ARRAY_LONG_BASE_OFFSET
= theUnsafe.arrayBaseOffset(long[].class);
/** The value of {@code arrayBaseOffset(float[].class)} */
public static final int ARRAY_FLOAT_BASE_OFFSET
= theUnsafe.arrayBaseOffset(float[].class);
/** The value of {@code arrayBaseOffset(double[].class)} */
public static final int ARRAY_DOUBLE_BASE_OFFSET
= theUnsafe.arrayBaseOffset(double[].class);
/** The value of {@code arrayBaseOffset(Object[].class)} */
public static final int ARRAY_OBJECT_BASE_OFFSET
= theUnsafe.arrayBaseOffset(Object[].class);
/**
* Reports the scale factor for addressing elements in the storage
* allocation of a given array class. However, arrays of "narrow" types
* will generally not work properly with accessors like {@link
* #getByte(Object, long)}, so the scale factor for such classes is reported
* as zero.
*
* @see #arrayBaseOffset
* @see #getInt(Object, long)
* @see #putInt(Object, long, int)
*/
public int arrayIndexScale(Class> arrayClass) {
if (arrayClass == null) {
throw new NullPointerException();
}
return arrayIndexScale0(arrayClass);
}
/** The value of {@code arrayIndexScale(boolean[].class)} */
public static final int ARRAY_BOOLEAN_INDEX_SCALE
= theUnsafe.arrayIndexScale(boolean[].class);
/** The value of {@code arrayIndexScale(byte[].class)} */
public static final int ARRAY_BYTE_INDEX_SCALE
= theUnsafe.arrayIndexScale(byte[].class);
/** The value of {@code arrayIndexScale(short[].class)} */
public static final int ARRAY_SHORT_INDEX_SCALE
= theUnsafe.arrayIndexScale(short[].class);
/** The value of {@code arrayIndexScale(char[].class)} */
public static final int ARRAY_CHAR_INDEX_SCALE
= theUnsafe.arrayIndexScale(char[].class);
/** The value of {@code arrayIndexScale(int[].class)} */
public static final int ARRAY_INT_INDEX_SCALE
= theUnsafe.arrayIndexScale(int[].class);
/** The value of {@code arrayIndexScale(long[].class)} */
public static final int ARRAY_LONG_INDEX_SCALE
= theUnsafe.arrayIndexScale(long[].class);
/** The value of {@code arrayIndexScale(float[].class)} */
public static final int ARRAY_FLOAT_INDEX_SCALE
= theUnsafe.arrayIndexScale(float[].class);
/** The value of {@code arrayIndexScale(double[].class)} */
public static final int ARRAY_DOUBLE_INDEX_SCALE
= theUnsafe.arrayIndexScale(double[].class);
/** The value of {@code arrayIndexScale(Object[].class)} */
public static final int ARRAY_OBJECT_INDEX_SCALE
= theUnsafe.arrayIndexScale(Object[].class);
/**
* Reports the size in bytes of a native pointer, as stored via {@link
* #putAddress}. This value will be either 4 or 8. Note that the sizes of
* other primitive types (as stored in native memory blocks) is determined
* fully by their information content.
*/
public int addressSize() {
return ADDRESS_SIZE;
}
/** The value of {@code addressSize()} */
public static final int ADDRESS_SIZE = theUnsafe.addressSize0();
/**
* Reports the size in bytes of a native memory page (whatever that is).
* This value will always be a power of two.
*/
public native int pageSize();
/// random trusted operations from JNI:
/**
* Tells the VM to define a class, without security checks. By default, the
* class loader and protection domain come from the caller's class.
*/
public Class> defineClass(String name, byte[] b, int off, int len,
ClassLoader loader,
ProtectionDomain protectionDomain) {
if (b == null) {
throw new NullPointerException();
}
if (len < 0) {
throw new ArrayIndexOutOfBoundsException();
}
return defineClass0(name, b, off, len, loader, protectionDomain);
}
public native Class> defineClass0(String name, byte[] b, int off, int len,
ClassLoader loader,
ProtectionDomain protectionDomain);
/**
* Defines a class but does not make it known to the class loader or system dictionary.
*
* For each CP entry, the corresponding CP patch must either be null or have
* the a format that matches its tag:
*
* This method should only be used in the very rare cases where a high-performance code
* overwrites the destination array completely, and compilers cannot assist in zeroing elimination.
* In an overwhelming majority of cases, a normal Java allocation should be used instead.
*
* Users of this method are required to overwrite the initial (garbage) array contents
* before allowing untrusted code, or code in other threads, to observe the reference
* to the newly allocated array. In addition, the publication of the array reference must be
* safe according to the Java Memory Model requirements.
*
* The safest approach to deal with an uninitialized array is to keep the reference to it in local
* variable at least until the initialization is complete, and then publish it once, either
* by writing it to a volatile field, or storing it into a final field in constructor,
* or issuing a {@link #storeFence} before publishing the reference.
*
* @implnote This method can only allocate primitive arrays, to avoid garbage reference
* elements that could break heap integrity.
*
* @param componentType array component type to allocate
* @param length array size to allocate
* @throws IllegalArgumentException if component type is null, or not a primitive class;
* or the length is negative
*/
public Object allocateUninitializedArray(Class> componentType, int length) {
if (componentType == null) {
throw new IllegalArgumentException("Component type is null");
}
if (!componentType.isPrimitive()) {
throw new IllegalArgumentException("Component type is not primitive");
}
if (length < 0) {
throw new IllegalArgumentException("Negative length");
}
return allocateUninitializedArray0(componentType, length);
}
@HotSpotIntrinsicCandidate
private Object allocateUninitializedArray0(Class> componentType, int length) {
// These fallbacks provide zeroed arrays, but intrinsic is not required to
// return the zeroed arrays.
if (componentType == byte.class) return new byte[length];
if (componentType == boolean.class) return new boolean[length];
if (componentType == short.class) return new short[length];
if (componentType == char.class) return new char[length];
if (componentType == int.class) return new int[length];
if (componentType == float.class) return new float[length];
if (componentType == long.class) return new long[length];
if (componentType == double.class) return new double[length];
return null;
}
/** Throws the exception without telling the verifier. */
public native void throwException(Throwable ee);
/**
* Atomically updates Java variable to {@code x} if it is currently
* holding {@code expected}.
*
* This operation has memory semantics of a {@code volatile} read
* and write. Corresponds to C11 atomic_compare_exchange_strong.
*
* @return {@code true} if successful
*/
@HotSpotIntrinsicCandidate
public final native boolean compareAndSetObject(Object o, long offset,
Object expected,
Object x);
@ForceInline
public final This operation has memory semantics of a {@code volatile} read
* and write. Corresponds to C11 atomic_compare_exchange_strong.
*
* @return {@code true} if successful
*/
@HotSpotIntrinsicCandidate
public final native boolean compareAndSetInt(Object o, long offset,
int expected,
int x);
@HotSpotIntrinsicCandidate
public final native int compareAndExchangeInt(Object o, long offset,
int expected,
int x);
@HotSpotIntrinsicCandidate
public final int compareAndExchangeIntAcquire(Object o, long offset,
int expected,
int x) {
return compareAndExchangeInt(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final int compareAndExchangeIntRelease(Object o, long offset,
int expected,
int x) {
return compareAndExchangeInt(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetIntPlain(Object o, long offset,
int expected,
int x) {
return compareAndSetInt(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetIntAcquire(Object o, long offset,
int expected,
int x) {
return compareAndSetInt(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetIntRelease(Object o, long offset,
int expected,
int x) {
return compareAndSetInt(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetInt(Object o, long offset,
int expected,
int x) {
return compareAndSetInt(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final byte compareAndExchangeByte(Object o, long offset,
byte expected,
byte x) {
long wordOffset = offset & ~3;
int shift = (int) (offset & 3) << 3;
if (BE) {
shift = 24 - shift;
}
int mask = 0xFF << shift;
int maskedExpected = (expected & 0xFF) << shift;
int maskedX = (x & 0xFF) << shift;
int fullWord;
do {
fullWord = getIntVolatile(o, wordOffset);
if ((fullWord & mask) != maskedExpected)
return (byte) ((fullWord & mask) >> shift);
} while (!weakCompareAndSetInt(o, wordOffset,
fullWord, (fullWord & ~mask) | maskedX));
return expected;
}
@HotSpotIntrinsicCandidate
public final boolean compareAndSetByte(Object o, long offset,
byte expected,
byte x) {
return compareAndExchangeByte(o, offset, expected, x) == expected;
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetByte(Object o, long offset,
byte expected,
byte x) {
return compareAndSetByte(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetByteAcquire(Object o, long offset,
byte expected,
byte x) {
return weakCompareAndSetByte(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetByteRelease(Object o, long offset,
byte expected,
byte x) {
return weakCompareAndSetByte(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetBytePlain(Object o, long offset,
byte expected,
byte x) {
return weakCompareAndSetByte(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final byte compareAndExchangeByteAcquire(Object o, long offset,
byte expected,
byte x) {
return compareAndExchangeByte(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final byte compareAndExchangeByteRelease(Object o, long offset,
byte expected,
byte x) {
return compareAndExchangeByte(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final short compareAndExchangeShort(Object o, long offset,
short expected,
short x) {
if ((offset & 3) == 3) {
throw new IllegalArgumentException("Update spans the word, not supported");
}
long wordOffset = offset & ~3;
int shift = (int) (offset & 3) << 3;
if (BE) {
shift = 16 - shift;
}
int mask = 0xFFFF << shift;
int maskedExpected = (expected & 0xFFFF) << shift;
int maskedX = (x & 0xFFFF) << shift;
int fullWord;
do {
fullWord = getIntVolatile(o, wordOffset);
if ((fullWord & mask) != maskedExpected) {
return (short) ((fullWord & mask) >> shift);
}
} while (!weakCompareAndSetInt(o, wordOffset,
fullWord, (fullWord & ~mask) | maskedX));
return expected;
}
@HotSpotIntrinsicCandidate
public final boolean compareAndSetShort(Object o, long offset,
short expected,
short x) {
return compareAndExchangeShort(o, offset, expected, x) == expected;
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetShort(Object o, long offset,
short expected,
short x) {
return compareAndSetShort(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetShortAcquire(Object o, long offset,
short expected,
short x) {
return weakCompareAndSetShort(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetShortRelease(Object o, long offset,
short expected,
short x) {
return weakCompareAndSetShort(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetShortPlain(Object o, long offset,
short expected,
short x) {
return weakCompareAndSetShort(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final short compareAndExchangeShortAcquire(Object o, long offset,
short expected,
short x) {
return compareAndExchangeShort(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final short compareAndExchangeShortRelease(Object o, long offset,
short expected,
short x) {
return compareAndExchangeShort(o, offset, expected, x);
}
@ForceInline
private char s2c(short s) {
return (char) s;
}
@ForceInline
private short c2s(char s) {
return (short) s;
}
@ForceInline
public final boolean compareAndSetChar(Object o, long offset,
char expected,
char x) {
return compareAndSetShort(o, offset, c2s(expected), c2s(x));
}
@ForceInline
public final char compareAndExchangeChar(Object o, long offset,
char expected,
char x) {
return s2c(compareAndExchangeShort(o, offset, c2s(expected), c2s(x)));
}
@ForceInline
public final char compareAndExchangeCharAcquire(Object o, long offset,
char expected,
char x) {
return s2c(compareAndExchangeShortAcquire(o, offset, c2s(expected), c2s(x)));
}
@ForceInline
public final char compareAndExchangeCharRelease(Object o, long offset,
char expected,
char x) {
return s2c(compareAndExchangeShortRelease(o, offset, c2s(expected), c2s(x)));
}
@ForceInline
public final boolean weakCompareAndSetChar(Object o, long offset,
char expected,
char x) {
return weakCompareAndSetShort(o, offset, c2s(expected), c2s(x));
}
@ForceInline
public final boolean weakCompareAndSetCharAcquire(Object o, long offset,
char expected,
char x) {
return weakCompareAndSetShortAcquire(o, offset, c2s(expected), c2s(x));
}
@ForceInline
public final boolean weakCompareAndSetCharRelease(Object o, long offset,
char expected,
char x) {
return weakCompareAndSetShortRelease(o, offset, c2s(expected), c2s(x));
}
@ForceInline
public final boolean weakCompareAndSetCharPlain(Object o, long offset,
char expected,
char x) {
return weakCompareAndSetShortPlain(o, offset, c2s(expected), c2s(x));
}
/**
* The JVM converts integral values to boolean values using two
* different conventions, byte testing against zero and truncation
* to least-significant bit.
*
* The JNI documents specify that, at least for returning
* values from native methods, a Java boolean value is converted
* to the value-set 0..1 by first truncating to a byte (0..255 or
* maybe -128..127) and then testing against zero. Thus, Java
* booleans in non-Java data structures are by convention
* represented as 8-bit containers containing either zero (for
* false) or any non-zero value (for true).
*
* Java booleans in the heap are also stored in bytes, but are
* strongly normalized to the value-set 0..1 (i.e., they are
* truncated to the least-significant bit).
*
* The main reason for having different conventions for
* conversion is performance: Truncation to the least-significant
* bit can be usually implemented with fewer (machine)
* instructions than byte testing against zero.
*
* A number of Unsafe methods load boolean values from the heap
* as bytes. Unsafe converts those values according to the JNI
* rules (i.e, using the "testing against zero" convention). The
* method {@code byte2bool} implements that conversion.
*
* @param b the byte to be converted to boolean
* @return the result of the conversion
*/
@ForceInline
private boolean byte2bool(byte b) {
return b != 0;
}
/**
* Convert a boolean value to a byte. The return value is strongly
* normalized to the value-set 0..1 (i.e., the value is truncated
* to the least-significant bit). See {@link #byte2bool(byte)} for
* more details on conversion conventions.
*
* @param b the boolean to be converted to byte (and then normalized)
* @return the result of the conversion
*/
@ForceInline
private byte bool2byte(boolean b) {
return b ? (byte)1 : (byte)0;
}
@ForceInline
public final boolean compareAndSetBoolean(Object o, long offset,
boolean expected,
boolean x) {
return compareAndSetByte(o, offset, bool2byte(expected), bool2byte(x));
}
@ForceInline
public final boolean compareAndExchangeBoolean(Object o, long offset,
boolean expected,
boolean x) {
return byte2bool(compareAndExchangeByte(o, offset, bool2byte(expected), bool2byte(x)));
}
@ForceInline
public final boolean compareAndExchangeBooleanAcquire(Object o, long offset,
boolean expected,
boolean x) {
return byte2bool(compareAndExchangeByteAcquire(o, offset, bool2byte(expected), bool2byte(x)));
}
@ForceInline
public final boolean compareAndExchangeBooleanRelease(Object o, long offset,
boolean expected,
boolean x) {
return byte2bool(compareAndExchangeByteRelease(o, offset, bool2byte(expected), bool2byte(x)));
}
@ForceInline
public final boolean weakCompareAndSetBoolean(Object o, long offset,
boolean expected,
boolean x) {
return weakCompareAndSetByte(o, offset, bool2byte(expected), bool2byte(x));
}
@ForceInline
public final boolean weakCompareAndSetBooleanAcquire(Object o, long offset,
boolean expected,
boolean x) {
return weakCompareAndSetByteAcquire(o, offset, bool2byte(expected), bool2byte(x));
}
@ForceInline
public final boolean weakCompareAndSetBooleanRelease(Object o, long offset,
boolean expected,
boolean x) {
return weakCompareAndSetByteRelease(o, offset, bool2byte(expected), bool2byte(x));
}
@ForceInline
public final boolean weakCompareAndSetBooleanPlain(Object o, long offset,
boolean expected,
boolean x) {
return weakCompareAndSetBytePlain(o, offset, bool2byte(expected), bool2byte(x));
}
/**
* Atomically updates Java variable to {@code x} if it is currently
* holding {@code expected}.
*
* This operation has memory semantics of a {@code volatile} read
* and write. Corresponds to C11 atomic_compare_exchange_strong.
*
* @return {@code true} if successful
*/
@ForceInline
public final boolean compareAndSetFloat(Object o, long offset,
float expected,
float x) {
return compareAndSetInt(o, offset,
Float.floatToRawIntBits(expected),
Float.floatToRawIntBits(x));
}
@ForceInline
public final float compareAndExchangeFloat(Object o, long offset,
float expected,
float x) {
int w = compareAndExchangeInt(o, offset,
Float.floatToRawIntBits(expected),
Float.floatToRawIntBits(x));
return Float.intBitsToFloat(w);
}
@ForceInline
public final float compareAndExchangeFloatAcquire(Object o, long offset,
float expected,
float x) {
int w = compareAndExchangeIntAcquire(o, offset,
Float.floatToRawIntBits(expected),
Float.floatToRawIntBits(x));
return Float.intBitsToFloat(w);
}
@ForceInline
public final float compareAndExchangeFloatRelease(Object o, long offset,
float expected,
float x) {
int w = compareAndExchangeIntRelease(o, offset,
Float.floatToRawIntBits(expected),
Float.floatToRawIntBits(x));
return Float.intBitsToFloat(w);
}
@ForceInline
public final boolean weakCompareAndSetFloatPlain(Object o, long offset,
float expected,
float x) {
return weakCompareAndSetIntPlain(o, offset,
Float.floatToRawIntBits(expected),
Float.floatToRawIntBits(x));
}
@ForceInline
public final boolean weakCompareAndSetFloatAcquire(Object o, long offset,
float expected,
float x) {
return weakCompareAndSetIntAcquire(o, offset,
Float.floatToRawIntBits(expected),
Float.floatToRawIntBits(x));
}
@ForceInline
public final boolean weakCompareAndSetFloatRelease(Object o, long offset,
float expected,
float x) {
return weakCompareAndSetIntRelease(o, offset,
Float.floatToRawIntBits(expected),
Float.floatToRawIntBits(x));
}
@ForceInline
public final boolean weakCompareAndSetFloat(Object o, long offset,
float expected,
float x) {
return weakCompareAndSetInt(o, offset,
Float.floatToRawIntBits(expected),
Float.floatToRawIntBits(x));
}
/**
* Atomically updates Java variable to {@code x} if it is currently
* holding {@code expected}.
*
* This operation has memory semantics of a {@code volatile} read
* and write. Corresponds to C11 atomic_compare_exchange_strong.
*
* @return {@code true} if successful
*/
@ForceInline
public final boolean compareAndSetDouble(Object o, long offset,
double expected,
double x) {
return compareAndSetLong(o, offset,
Double.doubleToRawLongBits(expected),
Double.doubleToRawLongBits(x));
}
@ForceInline
public final double compareAndExchangeDouble(Object o, long offset,
double expected,
double x) {
long w = compareAndExchangeLong(o, offset,
Double.doubleToRawLongBits(expected),
Double.doubleToRawLongBits(x));
return Double.longBitsToDouble(w);
}
@ForceInline
public final double compareAndExchangeDoubleAcquire(Object o, long offset,
double expected,
double x) {
long w = compareAndExchangeLongAcquire(o, offset,
Double.doubleToRawLongBits(expected),
Double.doubleToRawLongBits(x));
return Double.longBitsToDouble(w);
}
@ForceInline
public final double compareAndExchangeDoubleRelease(Object o, long offset,
double expected,
double x) {
long w = compareAndExchangeLongRelease(o, offset,
Double.doubleToRawLongBits(expected),
Double.doubleToRawLongBits(x));
return Double.longBitsToDouble(w);
}
@ForceInline
public final boolean weakCompareAndSetDoublePlain(Object o, long offset,
double expected,
double x) {
return weakCompareAndSetLongPlain(o, offset,
Double.doubleToRawLongBits(expected),
Double.doubleToRawLongBits(x));
}
@ForceInline
public final boolean weakCompareAndSetDoubleAcquire(Object o, long offset,
double expected,
double x) {
return weakCompareAndSetLongAcquire(o, offset,
Double.doubleToRawLongBits(expected),
Double.doubleToRawLongBits(x));
}
@ForceInline
public final boolean weakCompareAndSetDoubleRelease(Object o, long offset,
double expected,
double x) {
return weakCompareAndSetLongRelease(o, offset,
Double.doubleToRawLongBits(expected),
Double.doubleToRawLongBits(x));
}
@ForceInline
public final boolean weakCompareAndSetDouble(Object o, long offset,
double expected,
double x) {
return weakCompareAndSetLong(o, offset,
Double.doubleToRawLongBits(expected),
Double.doubleToRawLongBits(x));
}
/**
* Atomically updates Java variable to {@code x} if it is currently
* holding {@code expected}.
*
* This operation has memory semantics of a {@code volatile} read
* and write. Corresponds to C11 atomic_compare_exchange_strong.
*
* @return {@code true} if successful
*/
@HotSpotIntrinsicCandidate
public final native boolean compareAndSetLong(Object o, long offset,
long expected,
long x);
@HotSpotIntrinsicCandidate
public final native long compareAndExchangeLong(Object o, long offset,
long expected,
long x);
@HotSpotIntrinsicCandidate
public final long compareAndExchangeLongAcquire(Object o, long offset,
long expected,
long x) {
return compareAndExchangeLong(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final long compareAndExchangeLongRelease(Object o, long offset,
long expected,
long x) {
return compareAndExchangeLong(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetLongPlain(Object o, long offset,
long expected,
long x) {
return compareAndSetLong(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetLongAcquire(Object o, long offset,
long expected,
long x) {
return compareAndSetLong(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetLongRelease(Object o, long offset,
long expected,
long x) {
return compareAndSetLong(o, offset, expected, x);
}
@HotSpotIntrinsicCandidate
public final boolean weakCompareAndSetLong(Object o, long offset,
long expected,
long x) {
return compareAndSetLong(o, offset, expected, x);
}
/**
* Fetches a reference value from a given Java variable, with volatile
* load semantics. Otherwise identical to {@link #getObject(Object, long)}
*/
@HotSpotIntrinsicCandidate
public native Object getObjectVolatile(Object o, long offset);
/**
* Global lock for atomic and volatile strength access to any value of
* a value type. This is a temporary workaround until better localized
* atomic access mechanisms are supported for value types.
*/
private static final Object valueLock = new Object();
public final
*
* The specification of this method is the same as {@link
* #getLong(Object, long)} except that the offset does not need to
* have been obtained from {@link #objectFieldOffset} on the
* {@link java.lang.reflect.Field} of some Java field. The value
* in memory is raw data, and need not correspond to any Java
* variable. Unless The read will be atomic with respect to the largest power
* of two that divides the GCD of the offset and the storage size.
* For example, getLongUnaligned will make atomic reads of 2-, 4-,
* or 8-byte storage units if the offset is zero mod 2, 4, or 8,
* respectively. There are no other guarantees of atomicity.
*
* 8-byte atomicity is only guaranteed on platforms on which
* support atomic accesses to longs.
*
* @param o Java heap object in which the value resides, if any, else
* null
* @param offset The offset in bytes from the start of the object
* @return the value fetched from the indicated object
* @throws RuntimeException No defined exceptions are thrown, not even
* {@link NullPointerException}
* @since 9
*/
@HotSpotIntrinsicCandidate
public final long getLongUnaligned(Object o, long offset) {
if ((offset & 7) == 0) {
return getLong(o, offset);
} else if ((offset & 3) == 0) {
return makeLong(getInt(o, offset),
getInt(o, offset + 4));
} else if ((offset & 1) == 0) {
return makeLong(getShort(o, offset),
getShort(o, offset + 2),
getShort(o, offset + 4),
getShort(o, offset + 6));
} else {
return makeLong(getByte(o, offset),
getByte(o, offset + 1),
getByte(o, offset + 2),
getByte(o, offset + 3),
getByte(o, offset + 4),
getByte(o, offset + 5),
getByte(o, offset + 6),
getByte(o, offset + 7));
}
}
/**
* As {@link #getLongUnaligned(Object, long)} but with an
* additional argument which specifies the endianness of the value
* as stored in memory.
*
* @param o Java heap object in which the variable resides
* @param offset The offset in bytes from the start of the object
* @param bigEndian The endianness of the value
* @return the value fetched from the indicated object
* @since 9
*/
public final long getLongUnaligned(Object o, long offset, boolean bigEndian) {
return convEndian(bigEndian, getLongUnaligned(o, offset));
}
/** @see #getLongUnaligned(Object, long) */
@HotSpotIntrinsicCandidate
public final int getIntUnaligned(Object o, long offset) {
if ((offset & 3) == 0) {
return getInt(o, offset);
} else if ((offset & 1) == 0) {
return makeInt(getShort(o, offset),
getShort(o, offset + 2));
} else {
return makeInt(getByte(o, offset),
getByte(o, offset + 1),
getByte(o, offset + 2),
getByte(o, offset + 3));
}
}
/** @see #getLongUnaligned(Object, long, boolean) */
public final int getIntUnaligned(Object o, long offset, boolean bigEndian) {
return convEndian(bigEndian, getIntUnaligned(o, offset));
}
/** @see #getLongUnaligned(Object, long) */
@HotSpotIntrinsicCandidate
public final short getShortUnaligned(Object o, long offset) {
if ((offset & 1) == 0) {
return getShort(o, offset);
} else {
return makeShort(getByte(o, offset),
getByte(o, offset + 1));
}
}
/** @see #getLongUnaligned(Object, long, boolean) */
public final short getShortUnaligned(Object o, long offset, boolean bigEndian) {
return convEndian(bigEndian, getShortUnaligned(o, offset));
}
/** @see #getLongUnaligned(Object, long) */
@HotSpotIntrinsicCandidate
public final char getCharUnaligned(Object o, long offset) {
if ((offset & 1) == 0) {
return getChar(o, offset);
} else {
return (char)makeShort(getByte(o, offset),
getByte(o, offset + 1));
}
}
/** @see #getLongUnaligned(Object, long, boolean) */
public final char getCharUnaligned(Object o, long offset, boolean bigEndian) {
return convEndian(bigEndian, getCharUnaligned(o, offset));
}
/**
* Stores a value at some byte offset into a given Java object.
*
* The specification of this method is the same as {@link
* #getLong(Object, long)} except that the offset does not need to
* have been obtained from {@link #objectFieldOffset} on the
* {@link java.lang.reflect.Field} of some Java field. The value
* in memory is raw data, and need not correspond to any Java
* variable. The endianness of the value in memory is the
* endianness of the native platform.
*
* The write will be atomic with respect to the largest power of
* two that divides the GCD of the offset and the storage size.
* For example, putLongUnaligned will make atomic writes of 2-, 4-,
* or 8-byte storage units if the offset is zero mod 2, 4, or 8,
* respectively. There are no other guarantees of atomicity.
*
* 8-byte atomicity is only guaranteed on platforms on which
* support atomic accesses to longs.
*
* @param o Java heap object in which the value resides, if any, else
* null
* @param offset The offset in bytes from the start of the object
* @param x the value to store
* @throws RuntimeException No defined exceptions are thrown, not even
* {@link NullPointerException}
* @since 9
*/
@HotSpotIntrinsicCandidate
public final void putLongUnaligned(Object o, long offset, long x) {
if ((offset & 7) == 0) {
putLong(o, offset, x);
} else if ((offset & 3) == 0) {
putLongParts(o, offset,
(int)(x >> 0),
(int)(x >>> 32));
} else if ((offset & 1) == 0) {
putLongParts(o, offset,
(short)(x >>> 0),
(short)(x >>> 16),
(short)(x >>> 32),
(short)(x >>> 48));
} else {
putLongParts(o, offset,
(byte)(x >>> 0),
(byte)(x >>> 8),
(byte)(x >>> 16),
(byte)(x >>> 24),
(byte)(x >>> 32),
(byte)(x >>> 40),
(byte)(x >>> 48),
(byte)(x >>> 56));
}
}
/**
* As {@link #putLongUnaligned(Object, long, long)} but with an additional
* argument which specifies the endianness of the value as stored in memory.
* @param o Java heap object in which the value resides
* @param offset The offset in bytes from the start of the object
* @param x the value to store
* @param bigEndian The endianness of the value
* @throws RuntimeException No defined exceptions are thrown, not even
* {@link NullPointerException}
* @since 9
*/
public final void putLongUnaligned(Object o, long offset, long x, boolean bigEndian) {
putLongUnaligned(o, offset, convEndian(bigEndian, x));
}
/** @see #putLongUnaligned(Object, long, long) */
@HotSpotIntrinsicCandidate
public final void putIntUnaligned(Object o, long offset, int x) {
if ((offset & 3) == 0) {
putInt(o, offset, x);
} else if ((offset & 1) == 0) {
putIntParts(o, offset,
(short)(x >> 0),
(short)(x >>> 16));
} else {
putIntParts(o, offset,
(byte)(x >>> 0),
(byte)(x >>> 8),
(byte)(x >>> 16),
(byte)(x >>> 24));
}
}
/** @see #putLongUnaligned(Object, long, long, boolean) */
public final void putIntUnaligned(Object o, long offset, int x, boolean bigEndian) {
putIntUnaligned(o, offset, convEndian(bigEndian, x));
}
/** @see #putLongUnaligned(Object, long, long) */
@HotSpotIntrinsicCandidate
public final void putShortUnaligned(Object o, long offset, short x) {
if ((offset & 1) == 0) {
putShort(o, offset, x);
} else {
putShortParts(o, offset,
(byte)(x >>> 0),
(byte)(x >>> 8));
}
}
/** @see #putLongUnaligned(Object, long, long, boolean) */
public final void putShortUnaligned(Object o, long offset, short x, boolean bigEndian) {
putShortUnaligned(o, offset, convEndian(bigEndian, x));
}
/** @see #putLongUnaligned(Object, long, long) */
@HotSpotIntrinsicCandidate
public final void putCharUnaligned(Object o, long offset, char x) {
putShortUnaligned(o, offset, (short)x);
}
/** @see #putLongUnaligned(Object, long, long, boolean) */
public final void putCharUnaligned(Object o, long offset, char x, boolean bigEndian) {
putCharUnaligned(o, offset, convEndian(bigEndian, x));
}
// JVM interface methods
// BE is true iff the native endianness of this platform is big.
private static final boolean BE = theUnsafe.isBigEndian0();
// unalignedAccess is true iff this platform can perform unaligned accesses.
private static final boolean unalignedAccess = theUnsafe.unalignedAccess0();
private static int pickPos(int top, int pos) { return BE ? top - pos : pos; }
// These methods construct integers from bytes. The byte ordering
// is the native endianness of this platform.
private static long makeLong(byte i0, byte i1, byte i2, byte i3, byte i4, byte i5, byte i6, byte i7) {
return ((toUnsignedLong(i0) << pickPos(56, 0))
| (toUnsignedLong(i1) << pickPos(56, 8))
| (toUnsignedLong(i2) << pickPos(56, 16))
| (toUnsignedLong(i3) << pickPos(56, 24))
| (toUnsignedLong(i4) << pickPos(56, 32))
| (toUnsignedLong(i5) << pickPos(56, 40))
| (toUnsignedLong(i6) << pickPos(56, 48))
| (toUnsignedLong(i7) << pickPos(56, 56)));
}
private static long makeLong(short i0, short i1, short i2, short i3) {
return ((toUnsignedLong(i0) << pickPos(48, 0))
| (toUnsignedLong(i1) << pickPos(48, 16))
| (toUnsignedLong(i2) << pickPos(48, 32))
| (toUnsignedLong(i3) << pickPos(48, 48)));
}
private static long makeLong(int i0, int i1) {
return (toUnsignedLong(i0) << pickPos(32, 0))
| (toUnsignedLong(i1) << pickPos(32, 32));
}
private static int makeInt(short i0, short i1) {
return (toUnsignedInt(i0) << pickPos(16, 0))
| (toUnsignedInt(i1) << pickPos(16, 16));
}
private static int makeInt(byte i0, byte i1, byte i2, byte i3) {
return ((toUnsignedInt(i0) << pickPos(24, 0))
| (toUnsignedInt(i1) << pickPos(24, 8))
| (toUnsignedInt(i2) << pickPos(24, 16))
| (toUnsignedInt(i3) << pickPos(24, 24)));
}
private static short makeShort(byte i0, byte i1) {
return (short)((toUnsignedInt(i0) << pickPos(8, 0))
| (toUnsignedInt(i1) << pickPos(8, 8)));
}
private static byte pick(byte le, byte be) { return BE ? be : le; }
private static short pick(short le, short be) { return BE ? be : le; }
private static int pick(int le, int be) { return BE ? be : le; }
// These methods write integers to memory from smaller parts
// provided by their caller. The ordering in which these parts
// are written is the native endianness of this platform.
private void putLongParts(Object o, long offset, byte i0, byte i1, byte i2, byte i3, byte i4, byte i5, byte i6, byte i7) {
putByte(o, offset + 0, pick(i0, i7));
putByte(o, offset + 1, pick(i1, i6));
putByte(o, offset + 2, pick(i2, i5));
putByte(o, offset + 3, pick(i3, i4));
putByte(o, offset + 4, pick(i4, i3));
putByte(o, offset + 5, pick(i5, i2));
putByte(o, offset + 6, pick(i6, i1));
putByte(o, offset + 7, pick(i7, i0));
}
private void putLongParts(Object o, long offset, short i0, short i1, short i2, short i3) {
putShort(o, offset + 0, pick(i0, i3));
putShort(o, offset + 2, pick(i1, i2));
putShort(o, offset + 4, pick(i2, i1));
putShort(o, offset + 6, pick(i3, i0));
}
private void putLongParts(Object o, long offset, int i0, int i1) {
putInt(o, offset + 0, pick(i0, i1));
putInt(o, offset + 4, pick(i1, i0));
}
private void putIntParts(Object o, long offset, short i0, short i1) {
putShort(o, offset + 0, pick(i0, i1));
putShort(o, offset + 2, pick(i1, i0));
}
private void putIntParts(Object o, long offset, byte i0, byte i1, byte i2, byte i3) {
putByte(o, offset + 0, pick(i0, i3));
putByte(o, offset + 1, pick(i1, i2));
putByte(o, offset + 2, pick(i2, i1));
putByte(o, offset + 3, pick(i3, i0));
}
private void putShortParts(Object o, long offset, byte i0, byte i1) {
putByte(o, offset + 0, pick(i0, i1));
putByte(o, offset + 1, pick(i1, i0));
}
// Zero-extend an integer
private static int toUnsignedInt(byte n) { return n & 0xff; }
private static int toUnsignedInt(short n) { return n & 0xffff; }
private static long toUnsignedLong(byte n) { return n & 0xffl; }
private static long toUnsignedLong(short n) { return n & 0xffffl; }
private static long toUnsignedLong(int n) { return n & 0xffffffffl; }
// Maybe byte-reverse an integer
private static char convEndian(boolean big, char n) { return big == BE ? n : Character.reverseBytes(n); }
private static short convEndian(boolean big, short n) { return big == BE ? n : Short.reverseBytes(n) ; }
private static int convEndian(boolean big, int n) { return big == BE ? n : Integer.reverseBytes(n) ; }
private static long convEndian(boolean big, long n) { return big == BE ? n : Long.reverseBytes(n) ; }
private native long allocateMemory0(long bytes);
private native long reallocateMemory0(long address, long bytes);
private native void freeMemory0(long address);
private native void setMemory0(Object o, long offset, long bytes, byte value);
@HotSpotIntrinsicCandidate
private native void copyMemory0(Object srcBase, long srcOffset, Object destBase, long destOffset, long bytes);
private native void copySwapMemory0(Object srcBase, long srcOffset, Object destBase, long destOffset, long bytes, long elemSize);
private native long objectFieldOffset0(Field f);
private native long objectFieldOffset1(Class> c, String name);
private native long staticFieldOffset0(Field f);
private native Object staticFieldBase0(Field f);
private native boolean shouldBeInitialized0(Class> c);
private native void ensureClassInitialized0(Class> c);
private native int arrayBaseOffset0(Class> arrayClass);
private native int arrayIndexScale0(Class> arrayClass);
private native int addressSize0();
private native Class> defineAnonymousClass0(Class> hostClass, byte[] data, Object[] cpPatches);
private native int getLoadAverage0(double[] loadavg, int nelems);
private native boolean unalignedAccess0();
private native boolean isBigEndian0();
}
*
* @param hostClass context for linkage, access control, protection domain, and class loader
* @param data bytes of a class file
* @param cpPatches where non-null entries exist, they replace corresponding CP entries in data
*/
public Class> defineAnonymousClass(Class> hostClass, byte[] data, Object[] cpPatches) {
if (hostClass == null || data == null) {
throw new NullPointerException();
}
if (hostClass.isArray() || hostClass.isPrimitive()) {
throw new IllegalArgumentException();
}
return defineAnonymousClass0(hostClass, data, cpPatches);
}
/**
* Allocates an instance but does not run any constructor.
* Initializes the class if it has not yet been.
*/
@HotSpotIntrinsicCandidate
public native Object allocateInstance(Class> cls)
throws InstantiationException;
/**
* Allocates an array of a given type, but does not do zeroing.
* o
at the given offset, or (if o
is
* null) from the memory address whose numerical value is the
* given offset. o
is null, the value accessed
* must be entirely within the allocated object. The endianness
* of the value in memory is the endianness of the native platform.
*
*