jdk.internal.jvmci.meta

Interface ConstantReflectionProvider

All Known Implementing Classes:

HotSpotConstantReflectionProvider, HotSpotGraalConstantReflectionProvider, TruffleConstantReflectionProvider

public interface ConstantReflectionProvider

Reflection operations on values represented as constants. All methods in this interface require the VM to access the actual object encapsulated in object constants. This access is not always possible, depending on kind of VM and the state that the VM is in. Therefore, all methods can return null at any time, to indicate that the result is not available at this point. The caller is responsible to check for null results and handle them properly, e.g., not perform an optimization.

Method Summary

Modifier and Type	Method and Description
ResolvedJavaType	asJavaType(Constant constant) Returns the ResolvedJavaType for a Class object (or any other object regarded as a class by the VM) encapsulated in the given constant.
JavaConstant	boxPrimitive(JavaConstant source) Converts the given primitive constant to a boxed object constant, according to the Java boxing rules.
Boolean	constantEquals(Constant x, Constant y) Compares two constants for equality.
JavaConstant	forString(String value) Gets a string as a JavaConstant.
MemoryAccessProvider	getMemoryAccessProvider() Gets raw memory access.
MethodHandleAccessProvider	getMethodHandleAccess() Gets access to the internals of MethodHandle.
JavaConstant	readArrayElement(JavaConstant array, int index) Reads a value from the given array at the given index.
Integer	readArrayLength(JavaConstant array) Returns the length of the array constant.
JavaConstant	readConstantArrayElement(JavaConstant array, int index) Reads a value from the given array at the given index if it is a stable array.
JavaConstant	readConstantArrayElementForOffset(JavaConstant array, long offset) Reads a value from the given array at the given offset if it is a stable array.
JavaConstant	readConstantFieldValue(JavaField field, JavaConstant receiver) Gets the constant value of this field.
JavaConstant	readFieldValue(JavaField field, JavaConstant receiver) Gets the current value of this field for a given object, if available.
JavaConstant	readStableFieldValue(JavaField field, JavaConstant receiver, boolean isDefaultStable) Gets the current value of this field for a given object, if available.
JavaConstant	unboxPrimitive(JavaConstant source) Converts the given object constant to a primitive constant, according to the Java unboxing rules.

Method Detail

constantEquals

Boolean constantEquals(Constant x,
                       Constant y)

Compares two constants for equality. The equality relationship is symmetric. Returns true if the two constants represent the same run time value, false if they are different. Returns null if the constants cannot be compared at this point.

readArrayLength

Integer readArrayLength(JavaConstant array)

Returns the length of the array constant. Returns null if the constant is not an array, or if the array length is not available at this point.

readArrayElement

JavaConstant readArrayElement(JavaConstant array,
                              int index)

Reads a value from the given array at the given index. Returns null if the constant is not an array, if the index is out of bounds, or if the value is not available at this point.

readConstantArrayElement

JavaConstant readConstantArrayElement(JavaConstant array,
                                      int index)

Reads a value from the given array at the given index if it is a stable array. Returns null if the constant is not a stable array, if it is a default value, if the index is out of bounds, or if the value is not available at this point.

readConstantArrayElementForOffset

JavaConstant readConstantArrayElementForOffset(JavaConstant array,
                                               long offset)

Reads a value from the given array at the given offset if it is a stable array. The offset will be decoded relative to the platform addressing into an index into the array. Returns null if the constant is not a stable array, if it is a default value, if the offset is out of bounds, or if the value is not available at this point.

readConstantFieldValue

JavaConstant readConstantFieldValue(JavaField field,
                                    JavaConstant receiver)

Gets the constant value of this field. Note that a static final field may not be considered constant if its declaring class is not yet initialized or if it is a well known field that can be updated via other means (e.g., System.setOut(java.io.PrintStream)).

Parameters:

receiver - object from which this field's value is to be read. This value is ignored if this field is static.

Returns:

the constant value of this field or null if this field is not considered constant by the runtime

readFieldValue

JavaConstant readFieldValue(JavaField field,
                            JavaConstant receiver)

Gets the current value of this field for a given object, if available. There is no guarantee that the same value will be returned by this method for a field unless the field is considered to be constant by the runtime.

Parameters:

receiver - object from which this field's value is to be read. This value is ignored if this field is static.

Returns:

the value of this field or null if the value is not available (e.g., because the field holder is not yet initialized).

readStableFieldValue

JavaConstant readStableFieldValue(JavaField field,
                                  JavaConstant receiver,
                                  boolean isDefaultStable)

Gets the current value of this field for a given object, if available. Like readFieldValue(JavaField, JavaConstant) but treats array fields as stable. There is no guarantee that the same value will be returned by this method for a field unless the field is considered to be constant by the runtime.

Parameters:

receiver - object from which this field's value is to be read. This value is ignored if this field is static.

isDefaultStable - if true, default values are considered stable

Returns:

the value of this field or null if the value is not available (e.g., because the field holder is not yet initialized).

boxPrimitive

JavaConstant boxPrimitive(JavaConstant source)

Converts the given primitive constant to a boxed object constant, according to the Java boxing rules. Returns null if the source is is not a primitive constant, or the boxed value is not available at this point.

unboxPrimitive

JavaConstant unboxPrimitive(JavaConstant source)

Converts the given object constant to a primitive constant, according to the Java unboxing rules. Returns null if the source is is not an object constant that can be unboxed, or the unboxed value is not available at this point.

forString

JavaConstant forString(String value)

Gets a string as a JavaConstant.

asJavaType

ResolvedJavaType asJavaType(Constant constant)

Returns the ResolvedJavaType for a Class object (or any other object regarded as a class by the VM) encapsulated in the given constant. Returns null if the constant does not encapsulate a class, or if the type is not available at this point.

getMethodHandleAccess

MethodHandleAccessProvider getMethodHandleAccess()

Gets access to the internals of MethodHandle.

getMemoryAccessProvider

MemoryAccessProvider getMemoryAccessProvider()

Gets raw memory access.