1 cananian 1.2.2.2 // InSwitch.java, created Sun Sep 13 22:49:21 1998 by cananian
2 cananian 1.2 // Copyright (C) 1998 C. Scott Ananian <cananian@alumni.princeton.edu>
3 cananian 1.2 // Licensed under the terms of the GNU GPL; see COPYING for details.
4 cananian 1.1 package harpoon.IR.Bytecode;
5 cananian 1.1
6 cananian 1.1 import harpoon.Util.Util;
7 cananian 1.1
8 cananian 1.1 /**
9 cananian 1.1 * <code>InSwitch</code> is used for the <code>tableswitch</code> and
10 cananian 1.1 * <code>lookupswitch</code> java bytecode instructions.
11 cananian 1.1 * It is a control-transfer instruction. It should have exactly
12 cananian 1.1 * one predecessor. The first successor will be the default
13 cananian 1.1 * target; each subsequent successor corresponds to a <code>case</code>
14 cananian 1.1 * of the switch statement; the match key can be looked up using the
15 cananian 1.1 * <code>key</code> method.
16 cananian 1.1 *
17 cananian 1.1 * @author C. Scott Ananian <cananian@alumni.princeton.edu>
18 cananian 1.3 * @version $Id: InSwitch.java,v 1.3 2002/02/25 21:04:17 cananian Exp $
19 cananian 1.1 * @see Instr
20 cananian 1.1 */
21 cananian 1.1 public class InSwitch extends InCti {
22 cananian 1.2.2.1 final int keys[];
23 cananian 1.1
24 cananian 1.1 /** Constructor. Creates an <code>InSwitch</code> from a chunk of
25 cananian 1.1 * bytecode starting at the given pc.
26 cananian 1.1 * @exception Error if the opcode at <code>code[pc]</code> doesn't
27 cananian 1.1 * correspond to a <code>tableswitch</code> or
28 cananian 1.1 * <code>lookupswitch</code>.
29 cananian 1.1 */
30 cananian 1.1 public InSwitch(String sourcefile, int linenumber, byte[] code, int pc) {
31 cananian 1.1 super(sourcefile, linenumber, code, pc);
32 cananian 1.1 int pad = 3-(pc%4);
33 cananian 1.1 if (code[pc]==Op.LOOKUPSWITCH) {
34 cananian 1.1 int npairs = s4(code, pc+pad+5);
35 cananian 1.1 if (npairs<0) throw new Error("Invalid npairs in lookupswitch.");
36 cananian 1.1 keys = new int[npairs+1];
37 cananian 1.1 // keys[0] is invalid; the first succ. is the default branch target.
38 cananian 1.1 for (int i=0; i<npairs; i++)
39 cananian 1.1 keys[i+1] = s4(code,pc+pad+9+(8*i));
40 cananian 1.1 } else if (code[pc]==Op.TABLESWITCH) {
41 cananian 1.1 int low = s4(code, pc+pad+5);
42 cananian 1.1 int high= s4(code, pc+pad+9);
43 cananian 1.1 int npairs=high-low+1;
44 cananian 1.1 if (low>high) throw new Error("Invalid low/high in tableswitch.");
45 cananian 1.1 keys = new int[npairs+1];
46 cananian 1.1 // again, keys[0] is invalid. No key for default target.
47 cananian 1.1 for (int i=0; i<npairs; i++)
48 cananian 1.1 keys[i+1]=low+i;
49 cananian 1.1 } else throw new Error("InSwitch constructor given invalid opcode.");
50 cananian 1.1 }
51 cananian 1.1 /**
52 cananian 1.1 * Returns the case key corresponding to the given branch target index.<p>
53 cananian 1.1 * <code>InSwitch.key(n)</code> corresponds to
54 cananian 1.1 * <code>InSwitch.next()[n]</code> for
55 cananian 1.1 * <code>0<n<InSwitch.next().length</code>.
56 cananian 1.1 * @exception Error if the default target or
57 cananian 1.1 * an instruction not corresponding to a target is given.
58 cananian 1.1 */
59 cananian 1.1 public int key(int index) {
60 cananian 1.1 if (index<0) throw new Error("Invalid key lookup index.");
61 cananian 1.1 if (index==0) throw new Error("No key for default target.");
62 cananian 1.1 return keys[index];
63 cananian 1.1 }
64 cananian 1.1 /** Return human-readable instruction string. */
65 cananian 1.1 public String toString() {
66 cananian 1.1 StringBuffer sb = new StringBuffer(Op.toString(opcode));
67 cananian 1.1 Instr[] targets = next();
68 cananian 1.1 sb.append(" { default: goto #"); sb.append(targets[0].getID());
69 cananian 1.1 for (int i=1; i<targets.length; i++)
70 cananian 1.1 sb.append("; case "+keys[i]+": goto #"+targets[i].getID());
71 cananian 1.1 sb.append(" }");
72 cananian 1.1 return sb.toString();
73 cananian 1.1 }
74 cananian 1.1
75 cananian 1.1 // utility.
76 cananian 1.1 /** Make signed 4-bit int from four bytes. */
77 cananian 1.1 int s4(byte[] code, int pc) {
78 cananian 1.1 return
79 cananian 1.1 ( u1(code,pc) << 24) |
80 cananian 1.1 ( u1(code,pc+1) << 16) |
81 cananian 1.1 ( u1(code,pc+2) << 8) |
82 cananian 1.1 ( u1(code,pc+3) << 0);
83 cananian 1.1 }
84 cananian 1.1 /** Make integer from <i>unsigned</i> byte. */
85 cananian 1.1 int u1(byte[] code, int pc) { return ((int)code[pc])&0xFF; }
86 cananian 1.1 }
87 cananian 1.1
88 cananian 1.1 // set emacs indentation style.
89 cananian 1.1 // Local Variables:
90 cananian 1.1 // c-basic-offset:2
91 cananian 1.1 // End: