JDK8/Java8源码在线阅读
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* accompanied this code).
*
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package java.lang.invoke;
import sun.invoke.util.Wrapper;
import java.lang.ref.SoftReference;
import static java.lang.invoke.MethodHandleStatics.*;
/**
* Shared information for a group of method types, which differ
* only by reference types, and therefore share a common erasure
* and wrapping.
* <p>
* For an empirical discussion of the structure of method types,
* see <a href="http://groups.google.com/group/jvm-languages/browse_thread/thread/ac9308ae74da9b7e/">
* the thread "Avoiding Boxing" on jvm-languages</a>.
* There are approximately 2000 distinct erased method types in the JDK.
* There are a little over 10 times that number of unerased types.
* No more than half of these are likely to be loaded at once.
* @author John Rose
*/
final class MethodTypeForm {
final int[] argToSlotTable, slotToArgTable;
final long argCounts; // packed slot & value counts
final long primCounts; // packed prim & double counts
final MethodType erasedType; // the canonical erasure
final MethodType basicType; // the canonical erasure, with primitives simplified
// Cached adapter information:
@Stable final SoftReference<MethodHandle>[] methodHandles;
// Indexes into methodHandles:
static final int
MH_BASIC_INV = 0, // cached instance of MH.invokeBasic
MH_NF_INV = 1, // cached helper for LF.NamedFunction
MH_UNINIT_CS = 2, // uninitialized call site
MH_LIMIT = 3;
// Cached lambda form information, for basic types only:
final @Stable SoftReference<LambdaForm>[] lambdaForms;
// Indexes into lambdaForms:
static final int
LF_INVVIRTUAL = 0, // DMH invokeVirtual
LF_INVSTATIC = 1,
LF_INVSPECIAL = 2,
LF_NEWINVSPECIAL = 3,
LF_INVINTERFACE = 4,
LF_INVSTATIC_INIT = 5, // DMH invokeStatic with <clinit> barrier
LF_INTERPRET = 6, // LF interpreter
LF_REBIND = 7, // BoundMethodHandle
LF_DELEGATE = 8, // DelegatingMethodHandle
LF_DELEGATE_BLOCK_INLINING = 9, // Counting DelegatingMethodHandle w/ @DontInline
LF_EX_LINKER = 10, // invokeExact_MT (for invokehandle)
LF_EX_INVOKER = 11, // MHs.invokeExact
LF_GEN_LINKER = 12, // generic invoke_MT (for invokehandle)
LF_GEN_INVOKER = 13, // generic MHs.invoke
LF_CS_LINKER = 14, // linkToCallSite_CS
LF_MH_LINKER = 15, // linkToCallSite_MH
LF_GWC = 16, // guardWithCatch (catchException)
LF_GWT = 17, // guardWithTest
LF_LIMIT = 18;
/** Return the type corresponding uniquely (1-1) to this MT-form.
* It might have any primitive returns or arguments, but will have no references except Object.
*/
public MethodType erasedType() {
return erasedType;
}
/** Return the basic type derived from the erased type of this MT-form.
* A basic type is erased (all references Object) and also has all primitive
* types (except int, long, float, double, void) normalized to int.
* Such basic types correspond to low-level JVM calling sequences.
*/
public MethodType basicType() {
return basicType;
}
private boolean assertIsBasicType() {
// primitives must be flattened also
assert(erasedType == basicType)
: "erasedType: " + erasedType + " != basicType: " + basicType;
return true;
}
public MethodHandle cachedMethodHandle(int which) {
assert(assertIsBasicType());
SoftReference<MethodHandle> entry = methodHandles[which];
return (entry != null) ? entry.get() : null;
}
synchronized public MethodHandle setCachedMethodHandle(int which, MethodHandle mh) {
// Simulate a CAS, to avoid racy duplication of results.
SoftReference<MethodHandle> entry = methodHandles[which];
if (entry != null) {
MethodHandle prev = entry.get();
if (prev != null) {
return prev;
}
}
methodHandles[which] = new SoftReference<>(mh);
return mh;
}
public LambdaForm cachedLambdaForm(int which) {
assert(assertIsBasicType());
SoftReference<LambdaForm> entry = lambdaForms[which];
return (entry != null) ? entry.get() : null;
}
synchronized public LambdaForm setCachedLambdaForm(int which, LambdaForm form) {
// Simulate a CAS, to avoid racy duplication of results.
SoftReference<LambdaForm> entry = lambdaForms[which];
if (entry != null) {
LambdaForm prev = entry.get();
if (prev != null) {
return prev;
}
}
lambdaForms[which] = new SoftReference<>(form);
return form;
}
/**
* Build an MTF for a given type, which must have all references erased to Object.
* This MTF will stand for that type and all un-erased variations.
* Eagerly compute some basic properties of the type, common to all variations.
*/
@SuppressWarnings({"rawtypes", "unchecked"})
protected MethodTypeForm(MethodType erasedType) {
this.erasedType = erasedType;
Class<?>[] ptypes = erasedType.ptypes();
int ptypeCount = ptypes.length;
int pslotCount = ptypeCount; // temp. estimate
int rtypeCount = 1; // temp. estimate
int rslotCount = 1; // temp. estimate
int[] argToSlotTab = null, slotToArgTab = null;
// Walk the argument types, looking for primitives.
int pac = 0, lac = 0, prc = 0, lrc = 0;
Class<?>[] epts = ptypes;
Class<?>[] bpts = epts;
for (int i = 0; i < epts.length; i++) {
Class<?> pt = epts[i];
if (pt != Object.class) {
++pac;
Wrapper w = Wrapper.forPrimitiveType(pt);
if (w.isDoubleWord()) ++lac;
if (w.isSubwordOrInt() && pt != int.class) {
if (bpts == epts)
bpts = bpts.clone();
bpts[i] = int.class;
}
}
}
pslotCount += lac; // #slots = #args + #longs
Class<?> rt = erasedType.returnType();
Class<?> bt = rt;
if (rt != Object.class) {
++prc; // even void.class counts as a prim here
Wrapper w = Wrapper.forPrimitiveType(rt);
if (w.isDoubleWord()) ++lrc;
if (w.isSubwordOrInt() && rt != int.class)
bt = int.class;
// adjust #slots, #args
if (rt == void.class)
rtypeCount = rslotCount = 0;
else
rslotCount += lrc;
}
if (epts == bpts && bt == rt) {
this.basicType = erasedType;
} else {
this.basicType = MethodType.makeImpl(bt, bpts, true);
// fill in rest of data from the basic type:
MethodTypeForm that = this.basicType.form();
assert(this != that);
this.primCounts = that.primCounts;
this.argCounts = that.argCounts;
this.argToSlotTable = that.argToSlotTable;
this.slotToArgTable = that.slotToArgTable;
this.methodHandles = null;
this.lambdaForms = null;
return;
}
if (lac != 0) {
int slot = ptypeCount + lac;
slotToArgTab = new int[slot+1];
argToSlotTab = new int[1+ptypeCount];
argToSlotTab[0] = slot; // argument "-1" is past end of slots
for (int i = 0; i < epts.length; i++) {
Class<?> pt = epts[i];
Wrapper w = Wrapper.forBasicType(pt);
if (w.isDoubleWord()) --slot;
--slot;
slotToArgTab[slot] = i+1; // "+1" see argSlotToParameter note
argToSlotTab[1+i] = slot;
}
assert(slot == 0); // filled the table
} else if (pac != 0) {
// have primitives but no long primitives; share slot counts with generic
assert(ptypeCount == pslotCount);
MethodTypeForm that = MethodType.genericMethodType(ptypeCount).form();
assert(this != that);
slotToArgTab = that.slotToArgTable;
argToSlotTab = that.argToSlotTable;
} else {
int slot = ptypeCount; // first arg is deepest in stack
slotToArgTab = new int[slot+1];
argToSlotTab = new int[1+ptypeCount];
argToSlotTab[0] = slot; // argument "-1" is past end of slots
for (int i = 0; i < ptypeCount; i++) {
--slot;
slotToArgTab[slot] = i+1; // "+1" see argSlotToParameter note
argToSlotTab[1+i] = slot;
}
}
this.primCounts = pack(lrc, prc, lac, pac);
this.argCounts = pack(rslotCount, rtypeCount, pslotCount, ptypeCount);
this.argToSlotTable = argToSlotTab;
this.slotToArgTable = slotToArgTab;
if (pslotCount >= 256) throw newIllegalArgumentException("too many arguments");
// Initialize caches, but only for basic types
assert(basicType == erasedType);
this.lambdaForms = new SoftReference[LF_LIMIT];
this.methodHandles = new SoftReference[MH_LIMIT];
}
private static long pack(int a, int b, int c, int d) {
assert(((a|b|c|d) & ~0xFFFF) == 0);
long hw = ((a << 16) | b), lw = ((c << 16) | d);
return (hw << 32) | lw;
}
private static char unpack(long packed, int word) { // word==0 => return a, ==3 => return d
assert(word <= 3);
return (char)(packed >> ((3-word) * 16));
}
public int parameterCount() { // # outgoing values
return unpack(argCounts, 3);
}
public int parameterSlotCount() { // # outgoing interpreter slots
return unpack(argCounts, 2);
}
public int returnCount() { // = 0 (V), or 1
return unpack(argCounts, 1);
}
public int returnSlotCount() { // = 0 (V), 2 (J/D), or 1
return unpack(argCounts, 0);
}
public int primitiveParameterCount() {
return unpack(primCounts, 3);
}
public int longPrimitiveParameterCount() {
return unpack(primCounts, 2);
}
public int primitiveReturnCount() { // = 0 (obj), or 1
return unpack(primCounts, 1);
}
public int longPrimitiveReturnCount() { // = 1 (J/D), or 0
return unpack(primCounts, 0);
}
public boolean hasPrimitives() {
return primCounts != 0;
}
public boolean hasNonVoidPrimitives() {
if (primCounts == 0) return false;
if (primitiveParameterCount() != 0) return true;
return (primitiveReturnCount() != 0 && returnCount() != 0);
}
public boolean hasLongPrimitives() {
return (longPrimitiveParameterCount() | longPrimitiveReturnCount()) != 0;
}
public int parameterToArgSlot(int i) {
return argToSlotTable[1+i];
}
public int argSlotToParameter(int argSlot) {
// Note: Empty slots are represented by zero in this table.
// Valid arguments slots contain incremented entries, so as to be non-zero.
// We return -1 the caller to mean an empty slot.
return slotToArgTable[argSlot] - 1;
}
static MethodTypeForm findForm(MethodType mt) {
MethodType erased = canonicalize(mt, ERASE, ERASE);
if (erased == null) {
// It is already erased. Make a new MethodTypeForm.
return new MethodTypeForm(mt);
} else {
// Share the MethodTypeForm with the erased version.
return erased.form();
}
}
/** Codes for {@link #canonicalize(java.lang.Class, int)}.
* ERASE means change every reference to {@code Object}.
* WRAP means convert primitives (including {@code void} to their
* corresponding wrapper types. UNWRAP means the reverse of WRAP.
* INTS means convert all non-void primitive types to int or long,
* according to size. LONGS means convert all non-void primitives
* to long, regardless of size. RAW_RETURN means convert a type
* (assumed to be a return type) to int if it is smaller than an int,
* or if it is void.
*/
public static final int NO_CHANGE = 0, ERASE = 1, WRAP = 2, UNWRAP = 3, INTS = 4, LONGS = 5, RAW_RETURN = 6;
/** Canonicalize the types in the given method type.
* If any types change, intern the new type, and return it.
* Otherwise return null.
*/
public static MethodType canonicalize(MethodType mt, int howRet, int howArgs) {
Class<?>[] ptypes = mt.ptypes();
Class<?>[] ptc = MethodTypeForm.canonicalizeAll(ptypes, howArgs);
Class<?> rtype = mt.returnType();
Class<?> rtc = MethodTypeForm.canonicalize(rtype, howRet);
if (ptc == null && rtc == null) {
// It is already canonical.
return null;
}
// Find the erased version of the method type:
if (rtc == null) rtc = rtype;
if (ptc == null) ptc = ptypes;
return MethodType.makeImpl(rtc, ptc, true);
}
/** Canonicalize the given return or param type.
* Return null if the type is already canonicalized.
*/
static Class<?> canonicalize(Class<?> t, int how) {
Class<?> ct;
if (t == Object.class) {
// no change, ever
} else if (!t.isPrimitive()) {
switch (how) {
case UNWRAP:
ct = Wrapper.asPrimitiveType(t);
if (ct != t) return ct;
break;
case RAW_RETURN:
case ERASE:
return Object.class;
}
} else if (t == void.class) {
// no change, usually
switch (how) {
case RAW_RETURN:
return int.class;
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