* * {@code LiveStackFrame} represents a frame storing data and partial results. * Each frame has its own array of local variables (JVMS section 2.6.1), * its own operand stack (JVMS section 2.6.2) for a method invocation. * * @jvms 2.6 Frames */ /* package-private */ interface LiveStackFrame extends StackFrame { /** * Return the monitors held by this stack frame. This method returns * an empty array if no monitor is held by this stack frame. * * @return the monitors held by this stack frames */ public Object[] getMonitors(); /** * Gets the local variable array of this stack frame. * *
A single local variable can hold a value of type boolean, byte, char, * short, int, float, reference or returnAddress. A pair of local variables * can hold a value of type long or double (JVMS section 2.6.1). Primitive * locals are represented in the returned array as {@code PrimitiveSlot}s, * with longs and doubles occupying a pair of consecutive * {@code PrimitiveSlot}s. * *
The current VM implementation does not provide specific type * information for primitive locals. This method simply returns the raw * contents of the VM's primitive locals on a best-effort basis, without * indicating a specific type. * *
The returned array may contain null entries for local variables that * are not live. * * @implNote *
The specific subclass of {@code PrimitiveSlot} will reflect the * underlying architecture, and will be either {@code PrimitiveSlot32} or * {@code PrimitiveSlot64}. * *
How a long or double value is stored in the pair of * {@code PrimitiveSlot}s can vary based on the underlying architecture and * VM implementation. On 32-bit architectures, long/double values are split * between the two {@code PrimitiveSlot32}s. * On 64-bit architectures, the entire value may be stored in one of the * {@code PrimitiveSlot64}s, with the other {@code PrimitiveSlot64} being * unused. * *
The contents of the unused, high-order portion of a * {@code PrimitiveSlot64} (when storing a primitive other than a long or * double) is unspecified. In particular, the unused bits are not * necessarily zeroed out. * * @return the local variable array of this stack frame. */ public Object[] getLocals(); /** * Gets the operand stack of this stack frame. * *
* The 0-th element of the returned array represents the top of the operand stack. * This method returns an empty array if the operand stack is empty. * *
Each entry on the operand stack can hold a value of any Java Virtual * Machine Type. * For a value of primitive type, the element in the returned array is * a {@link PrimitiveSlot} object; otherwise, the element is the {@code Object} * on the operand stack. * * @return the operand stack of this stack frame. */ public Object[] getStack(); /** * UNSUPPORTED This interface is intended to be package-private * or moved to an internal package.
*
* Represents a local variable or an entry on the operand stack whose value is
* of primitive type.
*/
public abstract class PrimitiveSlot {
/**
* Constructor.
*/
PrimitiveSlot() {}
/**
* Returns the size, in bytes, of the slot.
*/
public abstract int size();
/**
* Returns the int value if this primitive value is of size 4
* @return the int value if this primitive value is of size 4
*
* @throws UnsupportedOperationException if this primitive value is not
* of size 4.
*/
public int intValue() {
throw new UnsupportedOperationException("this " + size() + "-byte primitive");
}
/**
* Returns the long value if this primitive value is of size 8
* @return the long value if this primitive value is of size 8
*
* @throws UnsupportedOperationException if this primitive value is not
* of size 8.
*/
public long longValue() {
throw new UnsupportedOperationException("this " + size() + "-byte primitive");
}
}
/**
* Gets {@code StackWalker} that can get locals and operands.
*
* @throws SecurityException if the security manager is present and
* denies access to {@code RuntimePermission("liveStackFrames")}
*/
public static StackWalker getStackWalker() {
return getStackWalker(EnumSet.noneOf(StackWalker.Option.class));
}
/**
* Gets a {@code StackWalker} instance with the given options specifying
* the stack frame information it can access, and which will traverse at most
* the given {@code maxDepth} number of stack frames. If no option is
* specified, this {@code StackWalker} obtains the method name and
* the class name with all
* {@linkplain StackWalker.Option#SHOW_HIDDEN_FRAMES hidden frames} skipped.
* The returned {@code StackWalker} can get locals and operands.
*
* @param options stack walk {@link StackWalker.Option options}
*
* @throws SecurityException if the security manager is present and
* it denies access to {@code RuntimePermission("liveStackFrames")};
* or if the given {@code options} contains
* {@link StackWalker.Option#RETAIN_CLASS_REFERENCE Option.RETAIN_CLASS_REFERENCE}
* and it denies access to {@code RuntimePermission("getStackWalkerWithClassReference")}.
*/
public static StackWalker getStackWalker(Set