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package sun.tools.asm;
import sun.tools.java.*;
import java.io.IOException;
import java.io.DataOutputStream;
This class is used to assemble the local variable table.
WARNING: The contents of this source file are not part of any
supported API. Code that depends on them does so at its own risk:
they are subject to change or removal without notice.
Author: Arthur van Hoff
/**
* This class is used to assemble the local variable table.
*
* WARNING: The contents of this source file are not part of any
* supported API. Code that depends on them does so at its own risk:
* they are subject to change or removal without notice.
*
* @author Arthur van Hoff
*/
final
class LocalVariableTable {
LocalVariable locals[] = new LocalVariable[8];
int len;
Define a new local variable. Merge entries where possible.
/**
* Define a new local variable. Merge entries where possible.
*/
void define(MemberDefinition field, int slot, int from, int to) {
if (from >= to) {
return;
}
for (int i = 0 ; i < len ; i++) {
if ((locals[i].field == field) && (locals[i].slot == slot) &&
(from <= locals[i].to) && (to >= locals[i].from)) {
locals[i].from = Math.min(locals[i].from, from);
locals[i].to = Math.max(locals[i].to, to);
return;
}
}
if (len == locals.length) {
LocalVariable newlocals[] = new LocalVariable[len * 2];
System.arraycopy(locals, 0, newlocals, 0, len);
locals = newlocals;
}
locals[len++] = new LocalVariable(field, slot, from, to);
}
Trim overlapping local ranges. Java forbids shadowing of
locals in nested scopes, but non-nested scopes may still declare
locals with the same name. Because local variable ranges are
computed using flow analysis as part of assembly, it isn't
possible to simply make sure variable ranges end where the
enclosing lexical scope ends. This method makes sure that
variables with the same name don't overlap, giving priority to
fields with higher slot numbers that should have appeared later
in the source.
/**
* Trim overlapping local ranges. Java forbids shadowing of
* locals in nested scopes, but non-nested scopes may still declare
* locals with the same name. Because local variable ranges are
* computed using flow analysis as part of assembly, it isn't
* possible to simply make sure variable ranges end where the
* enclosing lexical scope ends. This method makes sure that
* variables with the same name don't overlap, giving priority to
* fields with higher slot numbers that should have appeared later
* in the source.
*/
private void trim_ranges() {
for (int i=0; i<len; i++) {
for (int j=i+1; j<len; j++) {
if ((locals[i].field.getName()==locals[j].field.getName())
&& (locals[i].from <= locals[j].to)
&& (locals[i].to >= locals[j].from)) {
// At this point we know that both ranges are
// the same name and there is also overlap or they abut
if (locals[i].slot < locals[j].slot) {
if (locals[i].from < locals[j].from) {
locals[i].to = Math.min(locals[i].to, locals[j].from);
} else {
// We've detected two local variables with the
// same name, and the one with the greater slot
// number starts before the other. This order
// reversal may happen with locals with the same
// name declared in both a try body and an
// associated catch clause. This is rare, and
// we give up.
}
} else if (locals[i].slot > locals[j].slot) {
if (locals[i].from > locals[j].from) {
locals[j].to = Math.min(locals[j].to, locals[i].from);
} else {
// Same situation as above; just give up.
}
} else {
// This case can happen if there are two variables
// with the same name and slot numbers, and ranges
// that abut. AFAIK the only way this can occur
// is with multiple static initializers. Punt.
}
}
}
}
}
Write out the data.
/**
* Write out the data.
*/
void write(Environment env, DataOutputStream out, ConstantPool tab) throws IOException {
trim_ranges();
out.writeShort(len);
for (int i = 0 ; i < len ; i++) {
//System.out.println("pc=" + locals[i].from + ", len=" + (locals[i].to - locals[i].from) + ", nm=" + locals[i].field.getName() + ", slot=" + locals[i].slot);
out.writeShort(locals[i].from);
out.writeShort(locals[i].to - locals[i].from);
out.writeShort(tab.index(locals[i].field.getName().toString()));
out.writeShort(tab.index(locals[i].field.getType().getTypeSignature()));
out.writeShort(locals[i].slot);
}
}
}