java.lang.constant.DynamicConstantDesc Maven / Gradle / Ivy
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package java.lang.constant;
import java.lang.Enum.EnumDesc;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.lang.invoke.VarHandle.VarHandleDesc;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.function.Function;
import java.util.stream.Stream;
import static java.lang.constant.ConstantDescs.CD_Class;
import static java.lang.constant.ConstantDescs.CD_VarHandle;
import static java.lang.constant.ConstantDescs.DEFAULT_NAME;
import static java.lang.constant.ConstantUtils.EMPTY_CONSTANTDESC;
import static java.lang.constant.ConstantUtils.validateMemberName;
import static java.util.Objects.requireNonNull;
import static java.util.stream.Collectors.joining;
/**
* A nominal descriptor for a
* dynamic constant (one described in the constant pool with
* {@code Constant_Dynamic_info}.)
*
* Concrete subtypes of {@linkplain DynamicConstantDesc} should be immutable
* and their behavior should not rely on object identity.
*
* @param the type of the dynamic constant
*
* @since 12
*/
public abstract non-sealed class DynamicConstantDesc
implements ConstantDesc {
private final DirectMethodHandleDesc bootstrapMethod;
private final ConstantDesc[] bootstrapArgs;
private final String constantName;
private final ClassDesc constantType;
/**
* Creates a nominal descriptor for a dynamic constant.
*
* @param bootstrapMethod a {@link DirectMethodHandleDesc} describing the
* bootstrap method for the constant
* @param constantName The unqualified name that would appear in the {@code NameAndType}
* operand of the {@code LDC} for this constant
* @param constantType a {@link ClassDesc} describing the type
* that would appear in the {@code NameAndType} operand
* of the {@code LDC} for this constant
* @param bootstrapArgs {@link ConstantDesc}s describing the static arguments
* to the bootstrap, that would appear in the
* {@code BootstrapMethods} attribute
* @throws NullPointerException if any argument is null
* @throws IllegalArgumentException if the {@code name} has the incorrect
* format
* @jvms 4.2.2 Unqualified Names
*/
protected DynamicConstantDesc(DirectMethodHandleDesc bootstrapMethod,
String constantName,
ClassDesc constantType,
ConstantDesc... bootstrapArgs) {
this.bootstrapMethod = requireNonNull(bootstrapMethod);
this.constantName = validateMemberName(requireNonNull(constantName), true);
this.constantType = requireNonNull(constantType);
this.bootstrapArgs = requireNonNull(bootstrapArgs).clone();
if (constantName.length() == 0)
throw new IllegalArgumentException("Illegal invocation name: " + constantName);
}
/**
* Returns a nominal descriptor for a dynamic constant, transforming it into
* a more specific type if the constant bootstrap is a well-known one and a
* more specific nominal descriptor type (e.g., ClassDesc) is available.
*
* Classes whose {@link Constable#describeConstable()} method produce
* a {@linkplain DynamicConstantDesc} with a well-known bootstrap including
* {@link Class} (for instances describing primitive types), {@link Enum},
* and {@link VarHandle}.
*
*
Bytecode-reading APIs that process the constant pool and wish to expose
* entries as {@link ConstantDesc} to their callers should generally use this
* method in preference to {@link #ofNamed(DirectMethodHandleDesc, String, ClassDesc, ConstantDesc...)}
* because this may result in a more specific type that can be provided to
* callers.
*
* @param the type of the dynamic constant
* @param bootstrapMethod a {@link DirectMethodHandleDesc} describing the
* bootstrap method for the constant
* @param constantName The unqualified name that would appear in the {@code NameAndType}
* operand of the {@code LDC} for this constant
* @param constantType a {@link ClassDesc} describing the type
* that would appear in the {@code NameAndType} operand
* of the {@code LDC} for this constant
* @param bootstrapArgs {@link ConstantDesc}s describing the static arguments
* to the bootstrap, that would appear in the
* {@code BootstrapMethods} attribute
* @return the nominal descriptor
* @throws NullPointerException if any argument is null
* @throws IllegalArgumentException if the {@code name} has the incorrect
* format
* @jvms 4.2.2 Unqualified Names
*/
// Do not call this method from the static initialization of java.lang.constant.ConstantDescs
// since that can lead to potential deadlock during multi-threaded concurrent execution
public static ConstantDesc ofCanonical(DirectMethodHandleDesc bootstrapMethod,
String constantName,
ClassDesc constantType,
ConstantDesc[] bootstrapArgs) {
return DynamicConstantDesc.ofNamed(bootstrapMethod, constantName, constantType, bootstrapArgs)
.tryCanonicalize();
}
/**
* Returns a nominal descriptor for a dynamic constant.
*
* @param the type of the dynamic constant
* @param bootstrapMethod a {@link DirectMethodHandleDesc} describing the
* bootstrap method for the constant
* @param constantName The unqualified name that would appear in the {@code NameAndType}
* operand of the {@code LDC} for this constant
* @param constantType a {@link ClassDesc} describing the type
* that would appear in the {@code NameAndType} operand
* of the {@code LDC} for this constant
* @param bootstrapArgs {@link ConstantDesc}s describing the static arguments
* to the bootstrap, that would appear in the
* {@code BootstrapMethods} attribute
* @return the nominal descriptor
* @throws NullPointerException if any argument is null
* @throws IllegalArgumentException if the {@code name} has the incorrect
* format
* @jvms 4.2.2 Unqualified Names
*/
public static DynamicConstantDesc ofNamed(DirectMethodHandleDesc bootstrapMethod,
String constantName,
ClassDesc constantType,
ConstantDesc... bootstrapArgs) {
return new AnonymousDynamicConstantDesc<>(bootstrapMethod, constantName, constantType, bootstrapArgs);
}
/**
* Returns a nominal descriptor for a dynamic constant whose name parameter
* is {@link ConstantDescs#DEFAULT_NAME}, and whose type parameter is always
* the same as the bootstrap method return type.
*
* @param the type of the dynamic constant
* @param bootstrapMethod a {@link DirectMethodHandleDesc} describing the
* bootstrap method for the constant
* @param bootstrapArgs {@link ConstantDesc}s describing the static arguments
* to the bootstrap, that would appear in the
* {@code BootstrapMethods} attribute
* @return the nominal descriptor
* @throws NullPointerException if any argument is null
* @jvms 4.2.2 Unqualified Names
*/
public static DynamicConstantDesc of(DirectMethodHandleDesc bootstrapMethod,
ConstantDesc... bootstrapArgs) {
return ofNamed(bootstrapMethod, DEFAULT_NAME, bootstrapMethod.invocationType().returnType(), bootstrapArgs);
}
/**
* Returns a nominal descriptor for a dynamic constant whose bootstrap has
* no static arguments, whose name parameter is {@link ConstantDescs#DEFAULT_NAME},
* and whose type parameter is always the same as the bootstrap method return type.
*
* @param the type of the dynamic constant
* @param bootstrapMethod a {@link DirectMethodHandleDesc} describing the
* bootstrap method for the constant
* @return the nominal descriptor
* @throws NullPointerException if any argument is null
*/
public static DynamicConstantDesc of(DirectMethodHandleDesc bootstrapMethod) {
return of(bootstrapMethod, EMPTY_CONSTANTDESC);
}
/**
* Returns the name that would appear in the {@code NameAndType} operand
* of the {@code LDC} for this constant.
*
* @return the constant name
*/
public String constantName() {
return constantName;
}
/**
* Returns a {@link ClassDesc} describing the type that would appear in the
* {@code NameAndType} operand of the {@code LDC} for this constant.
*
* @return the constant type
*/
public ClassDesc constantType() {
return constantType;
}
/**
* Returns a {@link MethodHandleDesc} describing the bootstrap method for
* this constant.
*
* @return the bootstrap method
*/
public DirectMethodHandleDesc bootstrapMethod() {
return bootstrapMethod;
}
/**
* Returns the bootstrap arguments for this constant.
*
* @return the bootstrap arguments
*/
public ConstantDesc[] bootstrapArgs() {
return bootstrapArgs.clone();
}
/**
* Returns the bootstrap arguments for this constant as an immutable {@link List}.
*
* @return a {@link List} of the bootstrap arguments
*/
public List bootstrapArgsList() {
return List.of(bootstrapArgs);
}
@SuppressWarnings("unchecked")
public T resolveConstantDesc(MethodHandles.Lookup lookup) throws ReflectiveOperationException {
try {
MethodHandle bsm = (MethodHandle) bootstrapMethod.resolveConstantDesc(lookup);
if (bsm.type().parameterCount() < 2 ||
!MethodHandles.Lookup.class.isAssignableFrom(bsm.type().parameterType(0))) {
throw new BootstrapMethodError(
"Invalid bootstrap method declared for resolving a dynamic constant: " + bootstrapMethod);
}
Object[] bsmArgs = new Object[3 + bootstrapArgs.length];
bsmArgs[0] = lookup;
bsmArgs[1] = constantName;
bsmArgs[2] = constantType.resolveConstantDesc(lookup);
for (int i = 0; i < bootstrapArgs.length; i++)
bsmArgs[3 + i] = bootstrapArgs[i].resolveConstantDesc(lookup);
return (T) bsm.invokeWithArguments(bsmArgs);
} catch (Error e) {
throw e;
} catch (Throwable t) {
throw new BootstrapMethodError(t);
}
}
private ConstantDesc tryCanonicalize() {
Function, ConstantDesc> f = CanonicalMapHolder.CANONICAL_MAP.get(bootstrapMethod);
if (f != null) {
try {
return f.apply(this);
}
catch (Throwable t) {
return this;
}
}
return this;
}
private static ConstantDesc canonicalizeNull(DynamicConstantDesc desc) {
if (desc.bootstrapArgs.length != 0)
return desc;
return ConstantDescs.NULL;
}
private static ConstantDesc canonicalizeEnum(DynamicConstantDesc desc) {
if (desc.bootstrapArgs.length != 0
|| desc.constantName == null)
return desc;
return EnumDesc.of(desc.constantType, desc.constantName);
}
private static ConstantDesc canonicalizePrimitiveClass(DynamicConstantDesc desc) {
if (desc.bootstrapArgs.length != 0
|| !desc.constantType().equals(CD_Class)
|| desc.constantName == null)
return desc;
return ClassDesc.ofDescriptor(desc.constantName);
}
private static ConstantDesc canonicalizeStaticFieldVarHandle(DynamicConstantDesc desc) {
if (desc.bootstrapArgs.length != 2
|| !desc.constantType().equals(CD_VarHandle))
return desc;
return VarHandleDesc.ofStaticField((ClassDesc) desc.bootstrapArgs[0],
desc.constantName,
(ClassDesc) desc.bootstrapArgs[1]);
}
private static ConstantDesc canonicalizeFieldVarHandle(DynamicConstantDesc desc) {
if (desc.bootstrapArgs.length != 2
|| !desc.constantType().equals(CD_VarHandle))
return desc;
return VarHandleDesc.ofField((ClassDesc) desc.bootstrapArgs[0],
desc.constantName,
(ClassDesc) desc.bootstrapArgs[1]);
}
private static ConstantDesc canonicalizeArrayVarHandle(DynamicConstantDesc desc) {
if (desc.bootstrapArgs.length != 1
|| !desc.constantType().equals(CD_VarHandle))
return desc;
return VarHandleDesc.ofArray((ClassDesc) desc.bootstrapArgs[0]);
}
// @@@ To eventually support in canonicalization: DCR with BSM=MHR_METHODHANDLEDESC_ASTYPE becomes AsTypeMHDesc
/**
* Compares the specified object with this descriptor for equality. Returns
* {@code true} if and only if the specified object is also a
* {@linkplain DynamicConstantDesc}, and both descriptors have equal
* bootstrap methods, bootstrap argument lists, constant name, and
* constant type.
*
* @param o the {@code DynamicConstantDesc} to compare to this
* {@code DynamicConstantDesc}
* @return {@code true} if the specified {@code DynamicConstantDesc}
* is equal to this {@code DynamicConstantDesc}.
*
*/
@Override
public final boolean equals(Object o) {
if (this == o) return true;
return (o instanceof DynamicConstantDesc desc)
&& Objects.equals(bootstrapMethod, desc.bootstrapMethod)
&& Arrays.equals(bootstrapArgs, desc.bootstrapArgs)
&& Objects.equals(constantName, desc.constantName)
&& Objects.equals(constantType, desc.constantType);
}
@Override
public final int hashCode() {
int result = Objects.hash(bootstrapMethod, constantName, constantType);
result = 31 * result + Arrays.hashCode(bootstrapArgs);
return result;
}
/**
* Returns a compact textual description of this constant description,
* including the bootstrap method, the constant name and type, and
* the static bootstrap arguments.
*
* @return A compact textual description of this call site descriptor
*/
@Override
public String toString() {
return String.format("DynamicConstantDesc[%s::%s(%s%s)%s]",
bootstrapMethod.owner().displayName(),
bootstrapMethod.methodName(),
constantName.equals(ConstantDescs.DEFAULT_NAME) ? "" : constantName + "/",
Stream.of(bootstrapArgs).map(Object::toString).collect(joining(",")),
constantType.displayName());
}
private static class AnonymousDynamicConstantDesc extends DynamicConstantDesc {
AnonymousDynamicConstantDesc(DirectMethodHandleDesc bootstrapMethod, String constantName, ClassDesc constantType, ConstantDesc... bootstrapArgs) {
super(bootstrapMethod, constantName, constantType, bootstrapArgs);
}
}
private static final class CanonicalMapHolder {
static final Map, ConstantDesc>> CANONICAL_MAP =
Map.ofEntries(
Map.entry(ConstantDescs.BSM_PRIMITIVE_CLASS, DynamicConstantDesc::canonicalizePrimitiveClass),
Map.entry(ConstantDescs.BSM_ENUM_CONSTANT, DynamicConstantDesc::canonicalizeEnum),
Map.entry(ConstantDescs.BSM_NULL_CONSTANT, DynamicConstantDesc::canonicalizeNull),
Map.entry(ConstantDescs.BSM_VARHANDLE_STATIC_FIELD, DynamicConstantDesc::canonicalizeStaticFieldVarHandle),
Map.entry(ConstantDescs.BSM_VARHANDLE_FIELD, DynamicConstantDesc::canonicalizeFieldVarHandle),
Map.entry(ConstantDescs.BSM_VARHANDLE_ARRAY, DynamicConstantDesc::canonicalizeArrayVarHandle));
}
}