scala.tools.asm.Handler Maven / Gradle / Ivy
// ASM: a very small and fast Java bytecode manipulation framework
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package scala.tools.asm;
/**
* Information about an exception handler. Corresponds to an element of the exception_table array of
* a Code attribute, as defined in the Java Virtual Machine Specification (JVMS). Handler instances
* can be chained together, with their {@link #nextHandler} field, to describe a full JVMS
* exception_table array.
*
* @see JVMS
* 4.7.3
* @author Eric Bruneton
*/
final class Handler {
/**
* The start_pc field of this JVMS exception_table entry. Corresponds to the beginning of the
* exception handler's scope (inclusive).
*/
final Label startPc;
/**
* The end_pc field of this JVMS exception_table entry. Corresponds to the end of the exception
* handler's scope (exclusive).
*/
final Label endPc;
/**
* The handler_pc field of this JVMS exception_table entry. Corresponding to the beginning of the
* exception handler's code.
*/
final Label handlerPc;
/**
* The catch_type field of this JVMS exception_table entry. This is the constant pool index of the
* internal name of the type of exceptions handled by this handler, or 0 to catch any exceptions.
*/
final int catchType;
/**
* The internal name of the type of exceptions handled by this handler, or {@literal null} to
* catch any exceptions.
*/
final String catchTypeDescriptor;
/** The next exception handler. */
Handler nextHandler;
/**
* Constructs a new Handler.
*
* @param startPc the start_pc field of this JVMS exception_table entry.
* @param endPc the end_pc field of this JVMS exception_table entry.
* @param handlerPc the handler_pc field of this JVMS exception_table entry.
* @param catchType The catch_type field of this JVMS exception_table entry.
* @param catchTypeDescriptor The internal name of the type of exceptions handled by this handler,
* or {@literal null} to catch any exceptions.
*/
Handler(
final Label startPc,
final Label endPc,
final Label handlerPc,
final int catchType,
final String catchTypeDescriptor) {
this.startPc = startPc;
this.endPc = endPc;
this.handlerPc = handlerPc;
this.catchType = catchType;
this.catchTypeDescriptor = catchTypeDescriptor;
}
/**
* Constructs a new Handler from the given one, with a different scope.
*
* @param handler an existing Handler.
* @param startPc the start_pc field of this JVMS exception_table entry.
* @param endPc the end_pc field of this JVMS exception_table entry.
*/
Handler(final Handler handler, final Label startPc, final Label endPc) {
this(startPc, endPc, handler.handlerPc, handler.catchType, handler.catchTypeDescriptor);
this.nextHandler = handler.nextHandler;
}
/**
* Removes the range between start and end from the Handler list that begins with the given
* element.
*
* @param firstHandler the beginning of a Handler list. May be {@literal null}.
* @param start the start of the range to be removed.
* @param end the end of the range to be removed. Maybe {@literal null}.
* @return the exception handler list with the start-end range removed.
*/
static Handler removeRange(final Handler firstHandler, final Label start, final Label end) {
if (firstHandler == null) {
return null;
} else {
firstHandler.nextHandler = removeRange(firstHandler.nextHandler, start, end);
}
int handlerStart = firstHandler.startPc.bytecodeOffset;
int handlerEnd = firstHandler.endPc.bytecodeOffset;
int rangeStart = start.bytecodeOffset;
int rangeEnd = end == null ? Integer.MAX_VALUE : end.bytecodeOffset;
// Return early if [handlerStart,handlerEnd[ and [rangeStart,rangeEnd[ don't intersect.
if (rangeStart >= handlerEnd || rangeEnd <= handlerStart) {
return firstHandler;
}
if (rangeStart <= handlerStart) {
if (rangeEnd >= handlerEnd) {
// If [handlerStart,handlerEnd[ is included in [rangeStart,rangeEnd[, remove firstHandler.
return firstHandler.nextHandler;
} else {
// [handlerStart,handlerEnd[ - [rangeStart,rangeEnd[ = [rangeEnd,handlerEnd[
return new Handler(firstHandler, end, firstHandler.endPc);
}
} else if (rangeEnd >= handlerEnd) {
// [handlerStart,handlerEnd[ - [rangeStart,rangeEnd[ = [handlerStart,rangeStart[
return new Handler(firstHandler, firstHandler.startPc, start);
} else {
// [handlerStart,handlerEnd[ - [rangeStart,rangeEnd[ =
// [handlerStart,rangeStart[ + [rangeEnd,handerEnd[
firstHandler.nextHandler = new Handler(firstHandler, end, firstHandler.endPc);
return new Handler(firstHandler, firstHandler.startPc, start);
}
}
/**
* Returns the number of elements of the Handler list that begins with the given element.
*
* @param firstHandler the beginning of a Handler list. May be {@literal null}.
* @return the number of elements of the Handler list that begins with 'handler'.
*/
static int getExceptionTableLength(final Handler firstHandler) {
int length = 0;
Handler handler = firstHandler;
while (handler != null) {
length++;
handler = handler.nextHandler;
}
return length;
}
/**
* Returns the size in bytes of the JVMS exception_table corresponding to the Handler list that
* begins with the given element. This includes the exception_table_length field.
*
* @param firstHandler the beginning of a Handler list. May be {@literal null}.
* @return the size in bytes of the exception_table_length and exception_table structures.
*/
static int getExceptionTableSize(final Handler firstHandler) {
return 2 + 8 * getExceptionTableLength(firstHandler);
}
/**
* Puts the JVMS exception_table corresponding to the Handler list that begins with the given
* element. This includes the exception_table_length field.
*
* @param firstHandler the beginning of a Handler list. May be {@literal null}.
* @param output where the exception_table_length and exception_table structures must be put.
*/
static void putExceptionTable(final Handler firstHandler, final ByteVector output) {
output.putShort(getExceptionTableLength(firstHandler));
Handler handler = firstHandler;
while (handler != null) {
output
.putShort(handler.startPc.bytecodeOffset)
.putShort(handler.endPc.bytecodeOffset)
.putShort(handler.handlerPc.bytecodeOffset)
.putShort(handler.catchType);
handler = handler.nextHandler;
}
}
}
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