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package jdk.internal.misc;
A class used to expose details of the underlying hardware that
configure the operation of class Unsafe. This class is
package-private as the only intended client is class Unsafe.
All fields in this class must be static final constants.
Since: 13 Implementation Note:
The JVM injects hardware-specific values into all the static fields
of this class during JVM initialization. The static initialization
block is executed when the class is initialized then JVM injection
updates the fields with the correct constants. The static block
is required to prevent the fields from being considered constant
variables, so the field values will be not be compiled directly into
any class that uses them.
/**
* A class used to expose details of the underlying hardware that
* configure the operation of class Unsafe. This class is
* package-private as the only intended client is class Unsafe.
* All fields in this class must be static final constants.
*
* @since 13
*
* @implNote
*
* The JVM injects hardware-specific values into all the static fields
* of this class during JVM initialization. The static initialization
* block is executed when the class is initialized then JVM injection
* updates the fields with the correct constants. The static block
* is required to prevent the fields from being considered constant
* variables, so the field values will be not be compiled directly into
* any class that uses them.
*/
final class UnsafeConstants {
This constructor is private because the class is not meant to
be instantiated.
/**
* This constructor is private because the class is not meant to
* be instantiated.
*/
private UnsafeConstants() {}
The size in bytes of a native pointer, as stored via 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. Implementation Note:
The actual value for this field is injected by the JVM.
/**
* 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.
*
* @implNote
* The actual value for this field is injected by the JVM.
*/
static final int ADDRESS_SIZE0;
The size in bytes of a native memory page (whatever that is).
This value will always be a power of two.
Implementation Note:
The actual value for this field is injected by the JVM.
/**
* The size in bytes of a native memory page (whatever that is).
* This value will always be a power of two.
*
* @implNote
* The actual value for this field is injected by the JVM.
*/
static final int PAGE_SIZE;
Flag whose value is true if and only if the native endianness
of this platform is big.
Implementation Note:
The actual value for this field is injected by the JVM.
/**
* Flag whose value is true if and only if the native endianness
* of this platform is big.
*
* @implNote
* The actual value for this field is injected by the JVM.
*/
static final boolean BIG_ENDIAN;
Flag whose value is true if and only if the platform can
perform unaligned accesses
Implementation Note:
The actual value for this field is injected by the JVM.
/**
* Flag whose value is true if and only if the platform can
* perform unaligned accesses
*
* @implNote
* The actual value for this field is injected by the JVM.
*/
static final boolean UNALIGNED_ACCESS;
The size of an L1 data cache line which will be either a power
of two or zero.
A non-zero value indicates that writeback to memory is
enabled for the current processor. The value defines the
natural alignment and size of any data cache line committed to
memory by a single writeback operation. If data cache line
writeback is not enabled for the current hardware the field
will have value 0.
Implementation Note:
The actual value for this field is injected by the JVM.
/**
* The size of an L1 data cache line which will be either a power
* of two or zero.
*
* <p>A non-zero value indicates that writeback to memory is
* enabled for the current processor. The value defines the
* natural alignment and size of any data cache line committed to
* memory by a single writeback operation. If data cache line
* writeback is not enabled for the current hardware the field
* will have value 0.
*
* @implNote
* The actual value for this field is injected by the JVM.
*/
static final int DATA_CACHE_LINE_FLUSH_SIZE;
static {
ADDRESS_SIZE0 = 0;
PAGE_SIZE = 0;
BIG_ENDIAN = false;
UNALIGNED_ACCESS = false;
DATA_CACHE_LINE_FLUSH_SIZE = 0;
}
}