JDK8/Java8源码在线阅读
/*
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* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
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*
* 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,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package java.lang.invoke;
import java.lang.invoke.MethodHandles.Lookup;
import java.lang.reflect.Field;
import static java.lang.invoke.MethodHandleNatives.Constants.*;
import static java.lang.invoke.MethodHandleStatics.*;
import static java.lang.invoke.MethodHandles.Lookup.IMPL_LOOKUP;
/**
* The JVM interface for the method handles package is all here.
* This is an interface internal and private to an implementation of JSR 292.
* <em>This class is not part of the JSR 292 standard.</em>
* @author jrose
*/
class MethodHandleNatives {
private MethodHandleNatives() { } // static only
/// MemberName support
static native void init(MemberName self, Object ref);
static native void expand(MemberName self);
static native MemberName resolve(MemberName self, Class<?> caller) throws LinkageError;
static native int getMembers(Class<?> defc, String matchName, String matchSig,
int matchFlags, Class<?> caller, int skip, MemberName[] results);
/// Field layout queries parallel to sun.misc.Unsafe:
static native long objectFieldOffset(MemberName self); // e.g., returns vmindex
static native long staticFieldOffset(MemberName self); // e.g., returns vmindex
static native Object staticFieldBase(MemberName self); // e.g., returns clazz
static native Object getMemberVMInfo(MemberName self); // returns {vmindex,vmtarget}
/// MethodHandle support
/** Fetch MH-related JVM parameter.
* which=0 retrieves MethodHandlePushLimit
* which=1 retrieves stack slot push size (in address units)
*/
static native int getConstant(int which);
static final boolean COUNT_GWT;
/// CallSite support
/** Tell the JVM that we need to change the target of a CallSite. */
static native void setCallSiteTargetNormal(CallSite site, MethodHandle target);
static native void setCallSiteTargetVolatile(CallSite site, MethodHandle target);
private static native void registerNatives();
static {
registerNatives();
COUNT_GWT = getConstant(Constants.GC_COUNT_GWT) != 0;
// The JVM calls MethodHandleNatives.<clinit>. Cascade the <clinit> calls as needed:
MethodHandleImpl.initStatics();
}
// All compile-time constants go here.
// There is an opportunity to check them against the JVM's idea of them.
static class Constants {
Constants() { } // static only
// MethodHandleImpl
static final int // for getConstant
GC_COUNT_GWT = 4,
GC_LAMBDA_SUPPORT = 5;
// MemberName
// The JVM uses values of -2 and above for vtable indexes.
// Field values are simple positive offsets.
// Ref: src/share/vm/oops/methodOop.hpp
// This value is negative enough to avoid such numbers,
// but not too negative.
static final int
MN_IS_METHOD = 0x00010000, // method (not constructor)
MN_IS_CONSTRUCTOR = 0x00020000, // constructor
MN_IS_FIELD = 0x00040000, // field
MN_IS_TYPE = 0x00080000, // nested type
MN_CALLER_SENSITIVE = 0x00100000, // @CallerSensitive annotation detected
MN_REFERENCE_KIND_SHIFT = 24, // refKind
MN_REFERENCE_KIND_MASK = 0x0F000000 >> MN_REFERENCE_KIND_SHIFT,
// The SEARCH_* bits are not for MN.flags but for the matchFlags argument of MHN.getMembers:
MN_SEARCH_SUPERCLASSES = 0x00100000,
MN_SEARCH_INTERFACES = 0x00200000;
/**
* Basic types as encoded in the JVM. These code values are not
* intended for use outside this class. They are used as part of
* a private interface between the JVM and this class.
*/
static final int
T_BOOLEAN = 4,
T_CHAR = 5,
T_FLOAT = 6,
T_DOUBLE = 7,
T_BYTE = 8,
T_SHORT = 9,
T_INT = 10,
T_LONG = 11,
T_OBJECT = 12,
//T_ARRAY = 13
T_VOID = 14,
//T_ADDRESS = 15
T_ILLEGAL = 99;
/**
* Constant pool entry types.
*/
static final byte
CONSTANT_Utf8 = 1,
CONSTANT_Integer = 3,
CONSTANT_Float = 4,
CONSTANT_Long = 5,
CONSTANT_Double = 6,
CONSTANT_Class = 7,
CONSTANT_String = 8,
CONSTANT_Fieldref = 9,
CONSTANT_Methodref = 10,
CONSTANT_InterfaceMethodref = 11,
CONSTANT_NameAndType = 12,
CONSTANT_MethodHandle = 15, // JSR 292
CONSTANT_MethodType = 16, // JSR 292
CONSTANT_InvokeDynamic = 18,
CONSTANT_LIMIT = 19; // Limit to tags found in classfiles
/**
* Access modifier flags.
*/
static final char
ACC_PUBLIC = 0x0001,
ACC_PRIVATE = 0x0002,
ACC_PROTECTED = 0x0004,
ACC_STATIC = 0x0008,
ACC_FINAL = 0x0010,
ACC_SYNCHRONIZED = 0x0020,
ACC_VOLATILE = 0x0040,
ACC_TRANSIENT = 0x0080,
ACC_NATIVE = 0x0100,
ACC_INTERFACE = 0x0200,
ACC_ABSTRACT = 0x0400,
ACC_STRICT = 0x0800,
ACC_SYNTHETIC = 0x1000,
ACC_ANNOTATION = 0x2000,
ACC_ENUM = 0x4000,
// aliases:
ACC_SUPER = ACC_SYNCHRONIZED,
ACC_BRIDGE = ACC_VOLATILE,
ACC_VARARGS = ACC_TRANSIENT;
/**
* Constant pool reference-kind codes, as used by CONSTANT_MethodHandle CP entries.
*/
static final byte
REF_NONE = 0, // null value
REF_getField = 1,
REF_getStatic = 2,
REF_putField = 3,
REF_putStatic = 4,
REF_invokeVirtual = 5,
REF_invokeStatic = 6,
REF_invokeSpecial = 7,
REF_newInvokeSpecial = 8,
REF_invokeInterface = 9,
REF_LIMIT = 10;
}
static boolean refKindIsValid(int refKind) {
return (refKind > REF_NONE && refKind < REF_LIMIT);
}
static boolean refKindIsField(byte refKind) {
assert(refKindIsValid(refKind));
return (refKind <= REF_putStatic);
}
static boolean refKindIsGetter(byte refKind) {
assert(refKindIsValid(refKind));
return (refKind <= REF_getStatic);
}
static boolean refKindIsSetter(byte refKind) {
return refKindIsField(refKind) && !refKindIsGetter(refKind);
}
static boolean refKindIsMethod(byte refKind) {
return !refKindIsField(refKind) && (refKind != REF_newInvokeSpecial);
}
static boolean refKindIsConstructor(byte refKind) {
return (refKind == REF_newInvokeSpecial);
}
static boolean refKindHasReceiver(byte refKind) {
assert(refKindIsValid(refKind));
return (refKind & 1) != 0;
}
static boolean refKindIsStatic(byte refKind) {
return !refKindHasReceiver(refKind) && (refKind != REF_newInvokeSpecial);
}
static boolean refKindDoesDispatch(byte refKind) {
assert(refKindIsValid(refKind));
return (refKind == REF_invokeVirtual ||
refKind == REF_invokeInterface);
}
static {
final int HR_MASK = ((1 << REF_getField) |
(1 << REF_putField) |
(1 << REF_invokeVirtual) |
(1 << REF_invokeSpecial) |
(1 << REF_invokeInterface)
);
for (byte refKind = REF_NONE+1; refKind < REF_LIMIT; refKind++) {
assert(refKindHasReceiver(refKind) == (((1<<refKind) & HR_MASK) != 0)) : refKind;
}
}
static String refKindName(byte refKind) {
assert(refKindIsValid(refKind));
switch (refKind) {
case REF_getField: return "getField";
case REF_getStatic: return "getStatic";
case REF_putField: return "putField";
case REF_putStatic: return "putStatic";
case REF_invokeVirtual: return "invokeVirtual";
case REF_invokeStatic: return "invokeStatic";
case REF_invokeSpecial: return "invokeSpecial";
case REF_newInvokeSpecial: return "newInvokeSpecial";
case REF_invokeInterface: return "invokeInterface";
default: return "REF_???";
}
}
private static native int getNamedCon(int which, Object[] name);
static boolean verifyConstants() {
Object[] box = { null };
for (int i = 0; ; i++) {
box[0] = null;
int vmval = getNamedCon(i, box);
if (box[0] == null) break;
String name = (String) box[0];
try {
Field con = Constants.class.getDeclaredField(name);
int jval = con.getInt(null);
if (jval == vmval) continue;
String err = (name+": JVM has "+vmval+" while Java has "+jval);
if (name.equals("CONV_OP_LIMIT")) {
System.err.println("warning: "+err);
continue;
}
throw new InternalError(err);
} catch (NoSuchFieldException | IllegalAccessException ex) {
String err = (name+": JVM has "+vmval+" which Java does not define");
// ignore exotic ops the JVM cares about; we just wont issue them
//System.err.println("warning: "+err);
continue;
}
}
return true;
}
static {
assert(verifyConstants());
}
// Up-calls from the JVM.
// These must NOT be public.
/**
* The JVM is linking an invokedynamic instruction. Create a reified call site for it.
*/
static MemberName linkCallSite(Object callerObj,
Object bootstrapMethodObj,
Object nameObj, Object typeObj,
Object staticArguments,
Object[] appendixResult) {
MethodHandle bootstrapMethod = (MethodHandle)bootstrapMethodObj;
Class<?> caller = (Class<?>)callerObj;
String name = nameObj.toString().intern();
MethodType type = (MethodType)typeObj;
if (!TRACE_METHOD_LINKAGE)
return linkCallSiteImpl(caller, bootstrapMethod, name, type,
staticArguments, appendixResult);
return linkCallSiteTracing(caller, bootstrapMethod, name, type,
staticArguments, appendixResult);
}
static MemberName linkCallSiteImpl(Class<?> caller,
MethodHandle bootstrapMethod,
String name, MethodType type,
Object staticArguments,
Object[] appendixResult) {
CallSite callSite = CallSite.makeSite(bootstrapMethod,
name,
type,
staticArguments,
caller);
if (callSite instanceof ConstantCallSite) {
appendixResult[0] = callSite.dynamicInvoker();
return Invokers.linkToTargetMethod(type);
} else {
appendixResult[0] = callSite;
return Invokers.linkToCallSiteMethod(type);
}
}
// Tracing logic:
static MemberName linkCallSiteTracing(Class<?> caller,
MethodHandle bootstrapMethod,
String name, MethodType type,
Object staticArguments,
Object[] appendixResult) {
Object bsmReference = bootstrapMethod.internalMemberName();
if (bsmReference == null) bsmReference = bootstrapMethod;
Object staticArglist = (staticArguments instanceof Object[] ?
java.util.Arrays.asList((Object[]) staticArguments) :
staticArguments);
System.out.println("linkCallSite "+caller.getName()+" "+
bsmReference+" "+
name+type+"/"+staticArglist);
try {
MemberName res = linkCallSiteImpl(caller, bootstrapMethod, name, type,
staticArguments, appendixResult);
System.out.println("linkCallSite => "+res+" + "+appendixResult[0]);
return res;
} catch (Throwable ex) {
System.out.println("linkCallSite => throw "+ex);
throw ex;
}
}
/**
* The JVM wants a pointer to a MethodType. Oblige it by finding or creating one.
*/
static MethodType findMethodHandleType(Class<?> rtype, Class<?>[] ptypes) {
return MethodType.makeImpl(rtype, ptypes, true);
}
/**
* The JVM wants to link a call site that requires a dynamic type check.
* Name is a type-checking invoker, invokeExact or invoke.
* Return a JVM method (MemberName) to handle the invoking.
* The method assumes the following arguments on the stack:
* 0: the method handle being invoked
* 1-N: the arguments to the method handle invocation
* N+1: an optional, implicitly added argument (typically the given MethodType)
* <p>
* The nominal method at such a call site is an instance of
* a signature-polymorphic method (see @PolymorphicSignature).
* Such method instances are user-visible entities which are
* "split" from the generic placeholder method in {@code MethodHandle}.
* (Note that the placeholder method is not identical with any of
* its instances. If invoked reflectively, is guaranteed to throw an
* {@code UnsupportedOperationException}.)
* If the signature-polymorphic method instance is ever reified,
* it appears as a "copy" of the original placeholder
* (a native final member of {@code MethodHandle}) except
* that its type descriptor has shape required by the instance,
* and the method instance is <em>not</em> varargs.
* The method instance is also marked synthetic, since the
* method (by definition) does not appear in Java source code.
* <p>
* The JVM is allowed to reify this method as instance metadata.
* For example, {@code invokeBasic} is always reified.
* But the JVM may instead call {@code linkMethod}.
* If the result is an * ordered pair of a {@code (method, appendix)},
* the method gets all the arguments (0..N inclusive)
* plus the appendix (N+1), and uses the appendix to complete the call.
* In this way, one reusable method (called a "linker method")
* can perform the function of any number of polymorphic instance
* methods.
* <p>
* Linker methods are allowed to be weakly typed, with any or
* all references rewritten to {@code Object} and any primitives
* (except {@code long}/{@code float}/{@code double})
* rewritten to {@code int}.
* A linker method is trusted to return a strongly typed result,
* according to the specific method type descriptor of the
* signature-polymorphic instance it is emulating.
* This can involve (as necessary) a dynamic check using
* data extracted from the appendix argument.
* <p>
* The JVM does not inspect the appendix, other than to pass
* it verbatim to the linker method at every call.
* This means that the JDK runtime has wide latitude
* for choosing the shape of each linker method and its
* corresponding appendix.
* Linker methods should be generated from {@code LambdaForm}s
* so that they do not become visible on stack traces.
* <p>
* The {@code linkMethod} call is free to omit the appendix
* (returning null) and instead emulate the required function
* completely in the linker method.
* As a corner case, if N==255, no appendix is possible.
* In this case, the method returned must be custom-generated to
* to perform any needed type checking.
* <p>
* If the JVM does not reify a method at a call site, but instead
* calls {@code linkMethod}, the corresponding call represented
* in the bytecodes may mention a valid method which is not
* representable with a {@code MemberName}.
* Therefore, use cases for {@code linkMethod} tend to correspond to
* special cases in reflective code such as {@code findVirtual}
* or {@code revealDirect}.
*/
static MemberName linkMethod(Class<?> callerClass, int refKind,
Class<?> defc, String name, Object type,
Object[] appendixResult) {
if (!TRACE_METHOD_LINKAGE)
return linkMethodImpl(callerClass, refKind, defc, name, type, appendixResult);
return linkMethodTracing(callerClass, refKind, defc, name, type, appendixResult);
}
static MemberName linkMethodImpl(Class<?> callerClass, int refKind,
Class<?> defc, String name, Object type,
Object[] appendixResult) {
try {
if (defc == MethodHandle.class && refKind == REF_invokeVirtual) {
return Invokers.methodHandleInvokeLinkerMethod(name, fixMethodType(callerClass, type), appendixResult);
}
} catch (Throwable ex) {
if (ex instanceof LinkageError)
throw (LinkageError) ex;
else
throw new LinkageError(ex.getMessage(), ex);
}
throw new LinkageError("no such method "+defc.getName()+"."+name+type);
}
private static MethodType fixMethodType(Class<?> callerClass, Object type) {
if (type instanceof MethodType)
return (MethodType) type;
else
return MethodType.fromMethodDescriptorString((String)type, callerClass.getClassLoader());
}
// Tracing logic:
static MemberName linkMethodTracing(Class<?> callerClass, int refKind,
Class<?> defc, String name, Object type,
Object[] appendixResult) {
System.out.println("linkMethod "+defc.getName()+"."+
name+type+"/"+Integer.toHexString(refKind));
try {
MemberName res = linkMethodImpl(callerClass, refKind, defc, name, type, appendixResult);
System.out.println("linkMethod => "+res+" + "+appendixResult[0]);
return res;
} catch (Throwable ex) {
System.out.println("linkMethod => throw "+ex);
throw ex;
}
}
/**
* The JVM is resolving a CONSTANT_MethodHandle CP entry. And it wants our help.
* It will make an up-call to this method. (Do not change the name or signature.)
* The type argument is a Class for field requests and a MethodType for non-fields.
* <p>
* Recent versions of the JVM may also pass a resolved MemberName for the type.
* In that case, the name is ignored and may be null.
*/
static MethodHandle linkMethodHandleConstant(Class<?> callerClass, int refKind,
Class<?> defc, String name, Object type) {
try {
Lookup lookup = IMPL_LOOKUP.in(callerClass);
assert(refKindIsValid(refKind));
return lookup.linkMethodHandleConstant((byte) refKind, defc, name, type);
} catch (IllegalAccessException ex) {
Throwable cause = ex.getCause();
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