8148775: Spec for j.l.ProcessBuilder.Redirect.DISCARD need to be improved
Reviewed-by: martin
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* accompanied this code).
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package java.lang;
import jdk.internal.misc.JavaLangInvokeAccess;
import jdk.internal.misc.SharedSecrets;
import static java.lang.StackWalker.Option.*;
import java.lang.StackWalker.StackFrame;
import java.util.Optional;
import java.util.OptionalInt;
class StackFrameInfo implements StackFrame {
private final static JavaLangInvokeAccess jlInvokeAccess =
SharedSecrets.getJavaLangInvokeAccess();
// -XX:+MemberNameInStackFrame will initialize MemberName and all other fields;
// otherwise, VM will set the hidden fields (injected by the VM).
// -XX:+MemberNameInStackFrame is temporary to enable performance measurement
//
// Footprint improvement: MemberName::clazz and MemberName::name
// can replace StackFrameInfo::declaringClass and StackFrameInfo::methodName
// Currently VM sets StackFrameInfo::methodName instead of expanding MemberName::name
final StackWalker walker;
final Class<?> declaringClass;
final Object memberName;
final int bci;
// methodName, fileName, and lineNumber will be lazily set by the VM
// when first requested.
private String methodName;
private String fileName = null; // default for unavailable filename
private int lineNumber = -1; // default for unavailable lineNumber
/*
* Create StackFrameInfo for StackFrameTraverser and LiveStackFrameTraverser
* to use
*/
StackFrameInfo(StackWalker walker) {
this.walker = walker;
this.declaringClass = null;
this.bci = -1;
this.memberName = jlInvokeAccess.newMemberName();
}
@Override
public String getClassName() {
return declaringClass.getName();
}
@Override
public Class<?> getDeclaringClass() {
walker.ensureAccessEnabled(RETAIN_CLASS_REFERENCE);
return declaringClass;
}
// Call the VM to set methodName, lineNumber, and fileName
private synchronized void ensureMethodInfoInitialized() {
if (methodName == null) {
setMethodInfo();
}
}
@Override
public String getMethodName() {
ensureMethodInfoInitialized();
return methodName;
}
@Override
public Optional<String> getFileName() {
ensureMethodInfoInitialized();
return fileName != null ? Optional.of(fileName) : Optional.empty();
}
@Override
public OptionalInt getLineNumber() {
ensureMethodInfoInitialized();
return lineNumber > 0 ? OptionalInt.of(lineNumber) : OptionalInt.empty();
}
@Override
public boolean isNativeMethod() {
ensureMethodInfoInitialized();
return lineNumber == -2;
}
@Override
public String toString() {
ensureMethodInfoInitialized();
// similar format as StackTraceElement::toString
if (isNativeMethod()) {
return getClassName() + "." + getMethodName() + "(Native Method)";
} else {
// avoid allocating Optional objects
return getClassName() + "." + getMethodName() +
"(" + (fileName != null ? fileName : "Unknown Source") +
(lineNumber > 0 ? ":" + lineNumber : " bci:" + bci) + ")";
}
}
/**
* Lazily initialize method name, file name, line number
*/
private native void setMethodInfo();
/**
* Fill in source file name and line number of the given StackFrame array.
*/
static native void fillInStackFrames(int startIndex,
Object[] stackframes,
int fromIndex, int toIndex);
}