JDK8/Java8源码在线阅读
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* 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).
*
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* 2 along with this work; if not, write to the Free Software Foundation,
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*
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package java.lang.invoke;
import sun.invoke.util.Wrapper;
import java.lang.ref.WeakReference;
import java.lang.ref.Reference;
import java.lang.ref.ReferenceQueue;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Objects;
import java.util.concurrent.ConcurrentMap;
import java.util.concurrent.ConcurrentHashMap;
import sun.invoke.util.BytecodeDescriptor;
import static java.lang.invoke.MethodHandleStatics.*;
import sun.invoke.util.VerifyType;
/**
* A method type represents the arguments and return type accepted and
* returned by a method handle, or the arguments and return type passed
* and expected by a method handle caller. Method types must be properly
* matched between a method handle and all its callers,
* and the JVM's operations enforce this matching at, specifically
* during calls to {@link MethodHandle#invokeExact MethodHandle.invokeExact}
* and {@link MethodHandle#invoke MethodHandle.invoke}, and during execution
* of {@code invokedynamic} instructions.
* <p>
* The structure is a return type accompanied by any number of parameter types.
* The types (primitive, {@code void}, and reference) are represented by {@link Class} objects.
* (For ease of exposition, we treat {@code void} as if it were a type.
* In fact, it denotes the absence of a return type.)
* <p>
* All instances of {@code MethodType} are immutable.
* Two instances are completely interchangeable if they compare equal.
* Equality depends on pairwise correspondence of the return and parameter types and on nothing else.
* <p>
* This type can be created only by factory methods.
* All factory methods may cache values, though caching is not guaranteed.
* Some factory methods are static, while others are virtual methods which
* modify precursor method types, e.g., by changing a selected parameter.
* <p>
* Factory methods which operate on groups of parameter types
* are systematically presented in two versions, so that both Java arrays and
* Java lists can be used to work with groups of parameter types.
* The query methods {@code parameterArray} and {@code parameterList}
* also provide a choice between arrays and lists.
* <p>
* {@code MethodType} objects are sometimes derived from bytecode instructions
* such as {@code invokedynamic}, specifically from the type descriptor strings associated
* with the instructions in a class file's constant pool.
* <p>
* Like classes and strings, method types can also be represented directly
* in a class file's constant pool as constants.
* A method type may be loaded by an {@code ldc} instruction which refers
* to a suitable {@code CONSTANT_MethodType} constant pool entry.
* The entry refers to a {@code CONSTANT_Utf8} spelling for the descriptor string.
* (For full details on method type constants,
* see sections 4.4.8 and 5.4.3.5 of the Java Virtual Machine Specification.)
* <p>
* When the JVM materializes a {@code MethodType} from a descriptor string,
* all classes named in the descriptor must be accessible, and will be loaded.
* (But the classes need not be initialized, as is the case with a {@code CONSTANT_Class}.)
* This loading may occur at any time before the {@code MethodType} object is first derived.
* @author John Rose, JSR 292 EG
*/
public final
class MethodType implements java.io.Serializable {
private static final long serialVersionUID = 292L; // {rtype, {ptype...}}
// The rtype and ptypes fields define the structural identity of the method type:
private final Class<?> rtype;
private final Class<?>[] ptypes;
// The remaining fields are caches of various sorts:
private @Stable MethodTypeForm form; // erased form, plus cached data about primitives
private @Stable MethodType wrapAlt; // alternative wrapped/unwrapped version
private @Stable Invokers invokers; // cache of handy higher-order adapters
private @Stable String methodDescriptor; // cache for toMethodDescriptorString
/**
* Check the given parameters for validity and store them into the final fields.
*/
private MethodType(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
checkRtype(rtype);
checkPtypes(ptypes);
this.rtype = rtype;
// defensively copy the array passed in by the user
this.ptypes = trusted ? ptypes : Arrays.copyOf(ptypes, ptypes.length);
}
/**
* Construct a temporary unchecked instance of MethodType for use only as a key to the intern table.
* Does not check the given parameters for validity, and must be discarded after it is used as a searching key.
* The parameters are reversed for this constructor, so that is is not accidentally used.
*/
private MethodType(Class<?>[] ptypes, Class<?> rtype) {
this.rtype = rtype;
this.ptypes = ptypes;
}
/*trusted*/ MethodTypeForm form() { return form; }
/*trusted*/ Class<?> rtype() { return rtype; }
/*trusted*/ Class<?>[] ptypes() { return ptypes; }
void setForm(MethodTypeForm f) { form = f; }
/** This number, mandated by the JVM spec as 255,
* is the maximum number of <em>slots</em>
* that any Java method can receive in its argument list.
* It limits both JVM signatures and method type objects.
* The longest possible invocation will look like
* {@code staticMethod(arg1, arg2, ..., arg255)} or
* {@code x.virtualMethod(arg1, arg2, ..., arg254)}.
*/
/*non-public*/ static final int MAX_JVM_ARITY = 255; // this is mandated by the JVM spec.
/** This number is the maximum arity of a method handle, 254.
* It is derived from the absolute JVM-imposed arity by subtracting one,
* which is the slot occupied by the method handle itself at the
* beginning of the argument list used to invoke the method handle.
* The longest possible invocation will look like
* {@code mh.invoke(arg1, arg2, ..., arg254)}.
*/
// Issue: Should we allow MH.invokeWithArguments to go to the full 255?
/*non-public*/ static final int MAX_MH_ARITY = MAX_JVM_ARITY-1; // deduct one for mh receiver
/** This number is the maximum arity of a method handle invoker, 253.
* It is derived from the absolute JVM-imposed arity by subtracting two,
* which are the slots occupied by invoke method handle, and the
* target method handle, which are both at the beginning of the argument
* list used to invoke the target method handle.
* The longest possible invocation will look like
* {@code invokermh.invoke(targetmh, arg1, arg2, ..., arg253)}.
*/
/*non-public*/ static final int MAX_MH_INVOKER_ARITY = MAX_MH_ARITY-1; // deduct one more for invoker
private static void checkRtype(Class<?> rtype) {
Objects.requireNonNull(rtype);
}
private static void checkPtype(Class<?> ptype) {
Objects.requireNonNull(ptype);
if (ptype == void.class)
throw newIllegalArgumentException("parameter type cannot be void");
}
/** Return number of extra slots (count of long/double args). */
private static int checkPtypes(Class<?>[] ptypes) {
int slots = 0;
for (Class<?> ptype : ptypes) {
checkPtype(ptype);
if (ptype == double.class || ptype == long.class) {
slots++;
}
}
checkSlotCount(ptypes.length + slots);
return slots;
}
static void checkSlotCount(int count) {
assert((MAX_JVM_ARITY & (MAX_JVM_ARITY+1)) == 0);
// MAX_JVM_ARITY must be power of 2 minus 1 for following code trick to work:
if ((count & MAX_JVM_ARITY) != count)
throw newIllegalArgumentException("bad parameter count "+count);
}
private static IndexOutOfBoundsException newIndexOutOfBoundsException(Object num) {
if (num instanceof Integer) num = "bad index: "+num;
return new IndexOutOfBoundsException(num.toString());
}
static final ConcurrentWeakInternSet<MethodType> internTable = new ConcurrentWeakInternSet<>();
static final Class<?>[] NO_PTYPES = {};
/**
* Finds or creates an instance of the given method type.
* @param rtype the return type
* @param ptypes the parameter types
* @return a method type with the given components
* @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
* @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
*/
public static
MethodType methodType(Class<?> rtype, Class<?>[] ptypes) {
return makeImpl(rtype, ptypes, false);
}
/**
* Finds or creates a method type with the given components.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* @param rtype the return type
* @param ptypes the parameter types
* @return a method type with the given components
* @throws NullPointerException if {@code rtype} or {@code ptypes} or any element of {@code ptypes} is null
* @throws IllegalArgumentException if any element of {@code ptypes} is {@code void.class}
*/
public static
MethodType methodType(Class<?> rtype, List<Class<?>> ptypes) {
boolean notrust = false; // random List impl. could return evil ptypes array
return makeImpl(rtype, listToArray(ptypes), notrust);
}
private static Class<?>[] listToArray(List<Class<?>> ptypes) {
// sanity check the size before the toArray call, since size might be huge
checkSlotCount(ptypes.size());
return ptypes.toArray(NO_PTYPES);
}
/**
* Finds or creates a method type with the given components.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* The leading parameter type is prepended to the remaining array.
* @param rtype the return type
* @param ptype0 the first parameter type
* @param ptypes the remaining parameter types
* @return a method type with the given components
* @throws NullPointerException if {@code rtype} or {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is null
* @throws IllegalArgumentException if {@code ptype0} or {@code ptypes} or any element of {@code ptypes} is {@code void.class}
*/
public static
MethodType methodType(Class<?> rtype, Class<?> ptype0, Class<?>... ptypes) {
Class<?>[] ptypes1 = new Class<?>[1+ptypes.length];
ptypes1[0] = ptype0;
System.arraycopy(ptypes, 0, ptypes1, 1, ptypes.length);
return makeImpl(rtype, ptypes1, true);
}
/**
* Finds or creates a method type with the given components.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* The resulting method has no parameter types.
* @param rtype the return type
* @return a method type with the given return value
* @throws NullPointerException if {@code rtype} is null
*/
public static
MethodType methodType(Class<?> rtype) {
return makeImpl(rtype, NO_PTYPES, true);
}
/**
* Finds or creates a method type with the given components.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* The resulting method has the single given parameter type.
* @param rtype the return type
* @param ptype0 the parameter type
* @return a method type with the given return value and parameter type
* @throws NullPointerException if {@code rtype} or {@code ptype0} is null
* @throws IllegalArgumentException if {@code ptype0} is {@code void.class}
*/
public static
MethodType methodType(Class<?> rtype, Class<?> ptype0) {
return makeImpl(rtype, new Class<?>[]{ ptype0 }, true);
}
/**
* Finds or creates a method type with the given components.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* The resulting method has the same parameter types as {@code ptypes},
* and the specified return type.
* @param rtype the return type
* @param ptypes the method type which supplies the parameter types
* @return a method type with the given components
* @throws NullPointerException if {@code rtype} or {@code ptypes} is null
*/
public static
MethodType methodType(Class<?> rtype, MethodType ptypes) {
return makeImpl(rtype, ptypes.ptypes, true);
}
/**
* Sole factory method to find or create an interned method type.
* @param rtype desired return type
* @param ptypes desired parameter types
* @param trusted whether the ptypes can be used without cloning
* @return the unique method type of the desired structure
*/
/*trusted*/ static
MethodType makeImpl(Class<?> rtype, Class<?>[] ptypes, boolean trusted) {
MethodType mt = internTable.get(new MethodType(ptypes, rtype));
if (mt != null)
return mt;
if (ptypes.length == 0) {
ptypes = NO_PTYPES; trusted = true;
}
mt = new MethodType(rtype, ptypes, trusted);
// promote the object to the Real Thing, and reprobe
mt.form = MethodTypeForm.findForm(mt);
return internTable.add(mt);
}
private static final MethodType[] objectOnlyTypes = new MethodType[20];
/**
* Finds or creates a method type whose components are {@code Object} with an optional trailing {@code Object[]} array.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* All parameters and the return type will be {@code Object},
* except the final array parameter if any, which will be {@code Object[]}.
* @param objectArgCount number of parameters (excluding the final array parameter if any)
* @param finalArray whether there will be a trailing array parameter, of type {@code Object[]}
* @return a generally applicable method type, for all calls of the given fixed argument count and a collected array of further arguments
* @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255 (or 254, if {@code finalArray} is true)
* @see #genericMethodType(int)
*/
public static
MethodType genericMethodType(int objectArgCount, boolean finalArray) {
MethodType mt;
checkSlotCount(objectArgCount);
int ivarargs = (!finalArray ? 0 : 1);
int ootIndex = objectArgCount*2 + ivarargs;
if (ootIndex < objectOnlyTypes.length) {
mt = objectOnlyTypes[ootIndex];
if (mt != null) return mt;
}
Class<?>[] ptypes = new Class<?>[objectArgCount + ivarargs];
Arrays.fill(ptypes, Object.class);
if (ivarargs != 0) ptypes[objectArgCount] = Object[].class;
mt = makeImpl(Object.class, ptypes, true);
if (ootIndex < objectOnlyTypes.length) {
objectOnlyTypes[ootIndex] = mt; // cache it here also!
}
return mt;
}
/**
* Finds or creates a method type whose components are all {@code Object}.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* All parameters and the return type will be Object.
* @param objectArgCount number of parameters
* @return a generally applicable method type, for all calls of the given argument count
* @throws IllegalArgumentException if {@code objectArgCount} is negative or greater than 255
* @see #genericMethodType(int, boolean)
*/
public static
MethodType genericMethodType(int objectArgCount) {
return genericMethodType(objectArgCount, false);
}
/**
* Finds or creates a method type with a single different parameter type.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* @param num the index (zero-based) of the parameter type to change
* @param nptype a new parameter type to replace the old one with
* @return the same type, except with the selected parameter changed
* @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
* @throws IllegalArgumentException if {@code nptype} is {@code void.class}
* @throws NullPointerException if {@code nptype} is null
*/
public MethodType changeParameterType(int num, Class<?> nptype) {
if (parameterType(num) == nptype) return this;
checkPtype(nptype);
Class<?>[] nptypes = ptypes.clone();
nptypes[num] = nptype;
return makeImpl(rtype, nptypes, true);
}
/**
* Finds or creates a method type with additional parameter types.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* @param num the position (zero-based) of the inserted parameter type(s)
* @param ptypesToInsert zero or more new parameter types to insert into the parameter list
* @return the same type, except with the selected parameter(s) inserted
* @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
* @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
* or if the resulting method type would have more than 255 parameter slots
* @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
*/
public MethodType insertParameterTypes(int num, Class<?>... ptypesToInsert) {
int len = ptypes.length;
if (num < 0 || num > len)
throw newIndexOutOfBoundsException(num);
int ins = checkPtypes(ptypesToInsert);
checkSlotCount(parameterSlotCount() + ptypesToInsert.length + ins);
int ilen = ptypesToInsert.length;
if (ilen == 0) return this;
Class<?>[] nptypes = Arrays.copyOfRange(ptypes, 0, len+ilen);
System.arraycopy(nptypes, num, nptypes, num+ilen, len-num);
System.arraycopy(ptypesToInsert, 0, nptypes, num, ilen);
return makeImpl(rtype, nptypes, true);
}
/**
* Finds or creates a method type with additional parameter types.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
* @return the same type, except with the selected parameter(s) appended
* @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
* or if the resulting method type would have more than 255 parameter slots
* @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
*/
public MethodType appendParameterTypes(Class<?>... ptypesToInsert) {
return insertParameterTypes(parameterCount(), ptypesToInsert);
}
/**
* Finds or creates a method type with additional parameter types.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* @param num the position (zero-based) of the inserted parameter type(s)
* @param ptypesToInsert zero or more new parameter types to insert into the parameter list
* @return the same type, except with the selected parameter(s) inserted
* @throws IndexOutOfBoundsException if {@code num} is negative or greater than {@code parameterCount()}
* @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
* or if the resulting method type would have more than 255 parameter slots
* @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
*/
public MethodType insertParameterTypes(int num, List<Class<?>> ptypesToInsert) {
return insertParameterTypes(num, listToArray(ptypesToInsert));
}
/**
* Finds or creates a method type with additional parameter types.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* @param ptypesToInsert zero or more new parameter types to insert after the end of the parameter list
* @return the same type, except with the selected parameter(s) appended
* @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
* or if the resulting method type would have more than 255 parameter slots
* @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
*/
public MethodType appendParameterTypes(List<Class<?>> ptypesToInsert) {
return insertParameterTypes(parameterCount(), ptypesToInsert);
}
/**
* Finds or creates a method type with modified parameter types.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* @param start the position (zero-based) of the first replaced parameter type(s)
* @param end the position (zero-based) after the last replaced parameter type(s)
* @param ptypesToInsert zero or more new parameter types to insert into the parameter list
* @return the same type, except with the selected parameter(s) replaced
* @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
* or if {@code end} is negative or greater than {@code parameterCount()}
* or if {@code start} is greater than {@code end}
* @throws IllegalArgumentException if any element of {@code ptypesToInsert} is {@code void.class}
* or if the resulting method type would have more than 255 parameter slots
* @throws NullPointerException if {@code ptypesToInsert} or any of its elements is null
*/
/*non-public*/ MethodType replaceParameterTypes(int start, int end, Class<?>... ptypesToInsert) {
if (start == end)
return insertParameterTypes(start, ptypesToInsert);
int len = ptypes.length;
if (!(0 <= start && start <= end && end <= len))
throw newIndexOutOfBoundsException("start="+start+" end="+end);
int ilen = ptypesToInsert.length;
if (ilen == 0)
return dropParameterTypes(start, end);
return dropParameterTypes(start, end).insertParameterTypes(start, ptypesToInsert);
}
/** Replace the last arrayLength parameter types with the component type of arrayType.
* @param arrayType any array type
* @param arrayLength the number of parameter types to change
* @return the resulting type
*/
/*non-public*/ MethodType asSpreaderType(Class<?> arrayType, int arrayLength) {
assert(parameterCount() >= arrayLength);
int spreadPos = ptypes.length - arrayLength;
if (arrayLength == 0) return this; // nothing to change
if (arrayType == Object[].class) {
if (isGeneric()) return this; // nothing to change
if (spreadPos == 0) {
// no leading arguments to preserve; go generic
MethodType res = genericMethodType(arrayLength);
if (rtype != Object.class) {
res = res.changeReturnType(rtype);
}
return res;
}
}
Class<?> elemType = arrayType.getComponentType();
assert(elemType != null);
for (int i = spreadPos; i < ptypes.length; i++) {
if (ptypes[i] != elemType) {
Class<?>[] fixedPtypes = ptypes.clone();
Arrays.fill(fixedPtypes, i, ptypes.length, elemType);
return methodType(rtype, fixedPtypes);
}
}
return this; // arguments check out; no change
}
/** Return the leading parameter type, which must exist and be a reference.
* @return the leading parameter type, after error checks
*/
/*non-public*/ Class<?> leadingReferenceParameter() {
Class<?> ptype;
if (ptypes.length == 0 ||
(ptype = ptypes[0]).isPrimitive())
throw newIllegalArgumentException("no leading reference parameter");
return ptype;
}
/** Delete the last parameter type and replace it with arrayLength copies of the component type of arrayType.
* @param arrayType any array type
* @param arrayLength the number of parameter types to insert
* @return the resulting type
*/
/*non-public*/ MethodType asCollectorType(Class<?> arrayType, int arrayLength) {
assert(parameterCount() >= 1);
assert(lastParameterType().isAssignableFrom(arrayType));
MethodType res;
if (arrayType == Object[].class) {
res = genericMethodType(arrayLength);
if (rtype != Object.class) {
res = res.changeReturnType(rtype);
}
} else {
Class<?> elemType = arrayType.getComponentType();
assert(elemType != null);
res = methodType(rtype, Collections.nCopies(arrayLength, elemType));
}
if (ptypes.length == 1) {
return res;
} else {
return res.insertParameterTypes(0, parameterList().subList(0, ptypes.length-1));
}
}
/**
* Finds or creates a method type with some parameter types omitted.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* @param start the index (zero-based) of the first parameter type to remove
* @param end the index (greater than {@code start}) of the first parameter type after not to remove
* @return the same type, except with the selected parameter(s) removed
* @throws IndexOutOfBoundsException if {@code start} is negative or greater than {@code parameterCount()}
* or if {@code end} is negative or greater than {@code parameterCount()}
* or if {@code start} is greater than {@code end}
*/
public MethodType dropParameterTypes(int start, int end) {
int len = ptypes.length;
if (!(0 <= start && start <= end && end <= len))
throw newIndexOutOfBoundsException("start="+start+" end="+end);
if (start == end) return this;
Class<?>[] nptypes;
if (start == 0) {
if (end == len) {
// drop all parameters
nptypes = NO_PTYPES;
} else {
// drop initial parameter(s)
nptypes = Arrays.copyOfRange(ptypes, end, len);
}
} else {
if (end == len) {
// drop trailing parameter(s)
nptypes = Arrays.copyOfRange(ptypes, 0, start);
} else {
int tail = len - end;
nptypes = Arrays.copyOfRange(ptypes, 0, start + tail);
System.arraycopy(ptypes, end, nptypes, start, tail);
}
}
return makeImpl(rtype, nptypes, true);
}
/**
* Finds or creates a method type with a different return type.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* @param nrtype a return parameter type to replace the old one with
* @return the same type, except with the return type change
* @throws NullPointerException if {@code nrtype} is null
*/
public MethodType changeReturnType(Class<?> nrtype) {
if (returnType() == nrtype) return this;
return makeImpl(nrtype, ptypes, true);
}
/**
* Reports if this type contains a primitive argument or return value.
* The return type {@code void} counts as a primitive.
* @return true if any of the types are primitives
*/
public boolean hasPrimitives() {
return form.hasPrimitives();
}
/**
* Reports if this type contains a wrapper argument or return value.
* Wrappers are types which box primitive values, such as {@link Integer}.
* The reference type {@code java.lang.Void} counts as a wrapper,
* if it occurs as a return type.
* @return true if any of the types are wrappers
*/
public boolean hasWrappers() {
return unwrap() != this;
}
/**
* Erases all reference types to {@code Object}.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* All primitive types (including {@code void}) will remain unchanged.
* @return a version of the original type with all reference types replaced
*/
public MethodType erase() {
return form.erasedType();
}
/**
* Erases all reference types to {@code Object}, and all subword types to {@code int}.
* This is the reduced type polymorphism used by private methods
* such as {@link MethodHandle#invokeBasic invokeBasic}.
* @return a version of the original type with all reference and subword types replaced
*/
/*non-public*/ MethodType basicType() {
return form.basicType();
}
/**
* @return a version of the original type with MethodHandle prepended as the first argument
*/
/*non-public*/ MethodType invokerType() {
return insertParameterTypes(0, MethodHandle.class);
}
/**
* Converts all types, both reference and primitive, to {@code Object}.
* Convenience method for {@link #genericMethodType(int) genericMethodType}.
* The expression {@code type.wrap().erase()} produces the same value
* as {@code type.generic()}.
* @return a version of the original type with all types replaced
*/
public MethodType generic() {
return genericMethodType(parameterCount());
}
/*non-public*/ boolean isGeneric() {
return this == erase() && !hasPrimitives();
}
/**
* Converts all primitive types to their corresponding wrapper types.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* All reference types (including wrapper types) will remain unchanged.
* A {@code void} return type is changed to the type {@code java.lang.Void}.
* The expression {@code type.wrap().erase()} produces the same value
* as {@code type.generic()}.
* @return a version of the original type with all primitive types replaced
*/
public MethodType wrap() {
return hasPrimitives() ? wrapWithPrims(this) : this;
}
/**
* Converts all wrapper types to their corresponding primitive types.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* All primitive types (including {@code void}) will remain unchanged.
* A return type of {@code java.lang.Void} is changed to {@code void}.
* @return a version of the original type with all wrapper types replaced
*/
public MethodType unwrap() {
MethodType noprims = !hasPrimitives() ? this : wrapWithPrims(this);
return unwrapWithNoPrims(noprims);
}
private static MethodType wrapWithPrims(MethodType pt) {
assert(pt.hasPrimitives());
MethodType wt = pt.wrapAlt;
if (wt == null) {
// fill in lazily
wt = MethodTypeForm.canonicalize(pt, MethodTypeForm.WRAP, MethodTypeForm.WRAP);
assert(wt != null);
pt.wrapAlt = wt;
}
return wt;
}
private static MethodType unwrapWithNoPrims(MethodType wt) {
assert(!wt.hasPrimitives());
MethodType uwt = wt.wrapAlt;
if (uwt == null) {
// fill in lazily
uwt = MethodTypeForm.canonicalize(wt, MethodTypeForm.UNWRAP, MethodTypeForm.UNWRAP);
if (uwt == null)
uwt = wt; // type has no wrappers or prims at all
wt.wrapAlt = uwt;
}
return uwt;
}
/**
* Returns the parameter type at the specified index, within this method type.
* @param num the index (zero-based) of the desired parameter type
* @return the selected parameter type
* @throws IndexOutOfBoundsException if {@code num} is not a valid index into {@code parameterArray()}
*/
public Class<?> parameterType(int num) {
return ptypes[num];
}
/**
* Returns the number of parameter types in this method type.
* @return the number of parameter types
*/
public int parameterCount() {
return ptypes.length;
}
/**
* Returns the return type of this method type.
* @return the return type
*/
public Class<?> returnType() {
return rtype;
}
/**
* Presents the parameter types as a list (a convenience method).
* The list will be immutable.
* @return the parameter types (as an immutable list)
*/
public List<Class<?>> parameterList() {
return Collections.unmodifiableList(Arrays.asList(ptypes.clone()));
}
/*non-public*/ Class<?> lastParameterType() {
int len = ptypes.length;
return len == 0 ? void.class : ptypes[len-1];
}
/**
* Presents the parameter types as an array (a convenience method).
* Changes to the array will not result in changes to the type.
* @return the parameter types (as a fresh copy if necessary)
*/
public Class<?>[] parameterArray() {
return ptypes.clone();
}
/**
* Compares the specified object with this type for equality.
* That is, it returns <tt>true</tt> if and only if the specified object
* is also a method type with exactly the same parameters and return type.
* @param x object to compare
* @see Object#equals(Object)
*/
@Override
public boolean equals(Object x) {
return this == x || x instanceof MethodType && equals((MethodType)x);
}
private boolean equals(MethodType that) {
return this.rtype == that.rtype
&& Arrays.equals(this.ptypes, that.ptypes);
}
/**
* Returns the hash code value for this method type.
* It is defined to be the same as the hashcode of a List
* whose elements are the return type followed by the
* parameter types.
* @return the hash code value for this method type
* @see Object#hashCode()
* @see #equals(Object)
* @see List#hashCode()
*/
@Override
public int hashCode() {
int hashCode = 31 + rtype.hashCode();
for (Class<?> ptype : ptypes)
hashCode = 31*hashCode + ptype.hashCode();
return hashCode;
}
/**
* Returns a string representation of the method type,
* of the form {@code "(PT0,PT1...)RT"}.
* The string representation of a method type is a
* parenthesis enclosed, comma separated list of type names,
* followed immediately by the return type.
* <p>
* Each type is represented by its
* {@link java.lang.Class#getSimpleName simple name}.
*/
@Override
public String toString() {
StringBuilder sb = new StringBuilder();
sb.append("(");
for (int i = 0; i < ptypes.length; i++) {
if (i > 0) sb.append(",");
sb.append(ptypes[i].getSimpleName());
}
sb.append(")");
sb.append(rtype.getSimpleName());
return sb.toString();
}
/** True if the old return type can always be viewed (w/o casting) under new return type,
* and the new parameters can be viewed (w/o casting) under the old parameter types.
*/
/*non-public*/
boolean isViewableAs(MethodType newType, boolean keepInterfaces) {
if (!VerifyType.isNullConversion(returnType(), newType.returnType(), keepInterfaces))
return false;
return parametersAreViewableAs(newType, keepInterfaces);
}
/** True if the new parameters can be viewed (w/o casting) under the old parameter types. */
/*non-public*/
boolean parametersAreViewableAs(MethodType newType, boolean keepInterfaces) {
if (form == newType.form && form.erasedType == this)
return true; // my reference parameters are all Object
if (ptypes == newType.ptypes)
return true;
int argc = parameterCount();
if (argc != newType.parameterCount())
return false;
for (int i = 0; i < argc; i++) {
if (!VerifyType.isNullConversion(newType.parameterType(i), parameterType(i), keepInterfaces))
return false;
}
return true;
}
/*non-public*/
boolean isConvertibleTo(MethodType newType) {
MethodTypeForm oldForm = this.form();
MethodTypeForm newForm = newType.form();
if (oldForm == newForm)
// same parameter count, same primitive/object mix
return true;
if (!canConvert(returnType(), newType.returnType()))
return false;
Class<?>[] srcTypes = newType.ptypes;
Class<?>[] dstTypes = ptypes;
if (srcTypes == dstTypes)
return true;
int argc;
if ((argc = srcTypes.length) != dstTypes.length)
return false;
if (argc <= 1) {
if (argc == 1 && !canConvert(srcTypes[0], dstTypes[0]))
return false;
return true;
}
if ((oldForm.primitiveParameterCount() == 0 && oldForm.erasedType == this) ||
(newForm.primitiveParameterCount() == 0 && newForm.erasedType == newType)) {
// Somewhat complicated test to avoid a loop of 2 or more trips.
// If either type has only Object parameters, we know we can convert.
assert(canConvertParameters(srcTypes, dstTypes));
return true;
}
return canConvertParameters(srcTypes, dstTypes);
}
/** Returns true if MHs.explicitCastArguments produces the same result as MH.asType.
* If the type conversion is impossible for either, the result should be false.
*/
/*non-public*/
boolean explicitCastEquivalentToAsType(MethodType newType) {
if (this == newType) return true;
if (!explicitCastEquivalentToAsType(rtype, newType.rtype)) {
return false;
}
Class<?>[] srcTypes = newType.ptypes;
Class<?>[] dstTypes = ptypes;
if (dstTypes == srcTypes) {
return true;
}
assert(dstTypes.length == srcTypes.length);
for (int i = 0; i < dstTypes.length; i++) {
if (!explicitCastEquivalentToAsType(srcTypes[i], dstTypes[i])) {
return false;
}
}
return true;
}
/** Reports true if the src can be converted to the dst, by both asType and MHs.eCE,
* and with the same effect.
* MHs.eCA has the following "upgrades" to MH.asType:
* 1. interfaces are unchecked (that is, treated as if aliased to Object)
* Therefore, {@code Object->CharSequence} is possible in both cases but has different semantics
* 2. the full matrix of primitive-to-primitive conversions is supported
* Narrowing like {@code long->byte} and basic-typing like {@code boolean->int}
* are not supported by asType, but anything supported by asType is equivalent
* with MHs.eCE.
* 3a. unboxing conversions can be followed by the full matrix of primitive conversions
* 3b. unboxing of null is permitted (creates a zero primitive value)
* Other than interfaces, reference-to-reference conversions are the same.
* Boxing primitives to references is the same for both operators.
*/
private static boolean explicitCastEquivalentToAsType(Class<?> src, Class<?> dst) {
if (src == dst || dst == Object.class || dst == void.class) return true;
if (src.isPrimitive()) {
// Could be a prim/prim conversion, where casting is a strict superset.
// Or a boxing conversion, which is always to an exact wrapper class.
return canConvert(src, dst);
} else if (dst.isPrimitive()) {
// Unboxing behavior is different between MHs.eCA & MH.asType (see 3b).
return false;
} else {
// R->R always works, but we have to avoid a check-cast to an interface.
return !dst.isInterface() || dst.isAssignableFrom(src);
}
}
private boolean canConvertParameters(Class<?>[] srcTypes, Class<?>[] dstTypes) {
for (int i = 0; i < srcTypes.length; i++) {
if (!canConvert(srcTypes[i], dstTypes[i])) {
return false;
}
}
return true;
}
/*non-public*/
static boolean canConvert(Class<?> src, Class<?> dst) {
// short-circuit a few cases:
if (src == dst || src == Object.class || dst == Object.class) return true;
// the remainder of this logic is documented in MethodHandle.asType
if (src.isPrimitive()) {
// can force void to an explicit null, a la reflect.Method.invoke
// can also force void to a primitive zero, by analogy
if (src == void.class) return true; //or !dst.isPrimitive()?
Wrapper sw = Wrapper.forPrimitiveType(src);
if (dst.isPrimitive()) {
// P->P must widen
return Wrapper.forPrimitiveType(dst).isConvertibleFrom(sw);
} else {
// P->R must box and widen
return dst.isAssignableFrom(sw.wrapperType());
}
} else if (dst.isPrimitive()) {
// any value can be dropped
if (dst == void.class) return true;
Wrapper dw = Wrapper.forPrimitiveType(dst);
// R->P must be able to unbox (from a dynamically chosen type) and widen
// For example:
// Byte/Number/Comparable/Object -> dw:Byte -> byte.
// Character/Comparable/Object -> dw:Character -> char
// Boolean/Comparable/Object -> dw:Boolean -> boolean
// This means that dw must be cast-compatible with src.
if (src.isAssignableFrom(dw.wrapperType())) {
return true;
}
// The above does not work if the source reference is strongly typed
// to a wrapper whose primitive must be widened. For example:
// Byte -> unbox:byte -> short/int/long/float/double
// Character -> unbox:char -> int/long/float/double
if (Wrapper.isWrapperType(src) &&
dw.isConvertibleFrom(Wrapper.forWrapperType(src))) {
// can unbox from src and then widen to dst
return true;
}
// We have already covered cases which arise due to runtime unboxing
// of a reference type which covers several wrapper types:
// Object -> cast:Integer -> unbox:int -> long/float/double
// Serializable -> cast:Byte -> unbox:byte -> byte/short/int/long/float/double
// An marginal case is Number -> dw:Character -> char, which would be OK if there were a
// subclass of Number which wraps a value that can convert to char.
// Since there is none, we don't need an extra check here to cover char or boolean.
return false;
} else {
// R->R always works, since null is always valid dynamically
return true;
}
}
/// Queries which have to do with the bytecode architecture
/** Reports the number of JVM stack slots required to invoke a method
* of this type. Note that (for historical reasons) the JVM requires
* a second stack slot to pass long and double arguments.
* So this method returns {@link #parameterCount() parameterCount} plus the
* number of long and double parameters (if any).
* <p>
* This method is included for the benefit of applications that must
* generate bytecodes that process method handles and invokedynamic.
* @return the number of JVM stack slots for this type's parameters
*/
/*non-public*/ int parameterSlotCount() {
return form.parameterSlotCount();
}
/*non-public*/ Invokers invokers() {
Invokers inv = invokers;
if (inv != null) return inv;
invokers = inv = new Invokers(this);
return inv;
}
/** Reports the number of JVM stack slots which carry all parameters including and after
* the given position, which must be in the range of 0 to
* {@code parameterCount} inclusive. Successive parameters are
* more shallowly stacked, and parameters are indexed in the bytecodes
* according to their trailing edge. Thus, to obtain the depth
* in the outgoing call stack of parameter {@code N}, obtain
* the {@code parameterSlotDepth} of its trailing edge
* at position {@code N+1}.
* <p>
* Parameters of type {@code long} and {@code double} occupy
* two stack slots (for historical reasons) and all others occupy one.
* Therefore, the number returned is the number of arguments
* <em>including</em> and <em>after</em> the given parameter,
* <em>plus</em> the number of long or double arguments
* at or after after the argument for the given parameter.
* <p>
* This method is included for the benefit of applications that must
* generate bytecodes that process method handles and invokedynamic.
* @param num an index (zero-based, inclusive) within the parameter types
* @return the index of the (shallowest) JVM stack slot transmitting the
* given parameter
* @throws IllegalArgumentException if {@code num} is negative or greater than {@code parameterCount()}
*/
/*non-public*/ int parameterSlotDepth(int num) {
if (num < 0 || num > ptypes.length)
parameterType(num); // force a range check
return form.parameterToArgSlot(num-1);
}
/** Reports the number of JVM stack slots required to receive a return value
* from a method of this type.
* If the {@link #returnType() return type} is void, it will be zero,
* else if the return type is long or double, it will be two, else one.
* <p>
* This method is included for the benefit of applications that must
* generate bytecodes that process method handles and invokedynamic.
* @return the number of JVM stack slots (0, 1, or 2) for this type's return value
* Will be removed for PFD.
*/
/*non-public*/ int returnSlotCount() {
return form.returnSlotCount();
}
/**
* Finds or creates an instance of a method type, given the spelling of its bytecode descriptor.
* Convenience method for {@link #methodType(java.lang.Class, java.lang.Class[]) methodType}.
* Any class or interface name embedded in the descriptor string
* will be resolved by calling {@link ClassLoader#loadClass(java.lang.String)}
* on the given loader (or if it is null, on the system class loader).
* <p>
* Note that it is possible to encounter method types which cannot be
* constructed by this method, because their component types are
* not all reachable from a common class loader.
* <p>
* This method is included for the benefit of applications that must
* generate bytecodes that process method handles and {@code invokedynamic}.
* @param descriptor a bytecode-level type descriptor string "(T...)T"
* @param loader the class loader in which to look up the types
* @return a method type matching the bytecode-level type descriptor
* @throws NullPointerException if the string is null
* @throws IllegalArgumentException if the string is not well-formed
* @throws TypeNotPresentException if a named type cannot be found
*/
public static MethodType fromMethodDescriptorString(String descriptor, ClassLoader loader)
throws IllegalArgumentException, TypeNotPresentException
{
if (!descriptor.startsWith("(") || // also generates NPE if needed
descriptor.indexOf(')') < 0 ||
descriptor.indexOf('.') >= 0)
throw newIllegalArgumentException("not a method descriptor: "+descriptor);
List<Class<?>> types = BytecodeDescriptor.parseMethod(descriptor, loader);
Class<?> rtype = types.remove(types.size() - 1);
checkSlotCount(types.size());
Class<?>[] ptypes = listToArray(types);
return makeImpl(rtype, ptypes, true);
}
/**
* Produces a bytecode descriptor representation of the method type.
* <p>
* Note that this is not a strict inverse of {@link #fromMethodDescriptorString fromMethodDescriptorString}.
* Two distinct classes which share a common name but have different class loaders
* will appear identical when viewed within descriptor strings.
* <p>
* This method is included for the benefit of applications that must
* generate bytecodes that process method handles and {@code invokedynamic}.
* {@link #fromMethodDescriptorString(java.lang.String, java.lang.ClassLoader) fromMethodDescriptorString},
* because the latter requires a suitable class loader argument.
* @return the bytecode type descriptor representation
*/
public String toMethodDescriptorString() {
String desc = methodDescriptor;
if (desc == null) {
desc = BytecodeDescriptor.unparse(this);
methodDescriptor = desc;
}
return desc;
}
/*non-public*/ static String toFieldDescriptorString(Class<?> cls) {
return BytecodeDescriptor.unparse(cls);
}
/// Serialization.
/**
* There are no serializable fields for {@code MethodType}.
*/
private static final java.io.ObjectStreamField[] serialPersistentFields = { };
/**
* Save the {@code MethodType} instance to a stream.
*
* @serialData
* For portability, the serialized format does not refer to named fields.
* Instead, the return type and parameter type arrays are written directly
* from the {@code writeObject} method, using two calls to {@code s.writeObject}
* as follows:
* <blockquote><pre>{@code
s.writeObject(this.returnType());
s.writeObject(this.parameterArray());
* }</pre></blockquote>
* <p>
* The deserialized field values are checked as if they were
* provided to the factory method {@link #methodType(Class,Class[]) methodType}.
* For example, null values, or {@code void} parameter types,
* will lead to exceptions during deserialization.
* @param s the stream to write the object to
* @throws java.io.IOException if there is a problem writing the object
*/
private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException {
s.defaultWriteObject(); // requires serialPersistentFields to be an empty array
s.writeObject(returnType());
s.writeObject(parameterArray());
}
/**
* Reconstitute the {@code MethodType} instance from a stream (that is,
* deserialize it).
* This instance is a scratch object with bogus final fields.
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