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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one
3    * or more contributor license agreements.  See the NOTICE file
4    * distributed with this work for additional information
5    * regarding copyright ownership.  The ASF licenses this file
6    * to you under the Apache License, Version 2.0 (the
7    * "License"); you may not use this file except in compliance
8    * with the License.  You may obtain a copy of the License at
9    *
10   *   https://www.apache.org/licenses/LICENSE-2.0
11   *
12   * Unless required by applicable law or agreed to in writing,
13   * software distributed under the License is distributed on an
14   * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15   * KIND, either express or implied.  See the License for the
16   * specific language governing permissions and limitations
17   * under the License.
18   */
19  package org.apache.commons.compress.harmony.unpack200.bytecode.forms;
20  
21  import java.util.Arrays;
22  import java.util.HashMap;
23  import java.util.Map;
24  
25  import org.apache.commons.compress.harmony.pack200.Pack200Exception;
26  import org.apache.commons.compress.harmony.unpack200.bytecode.ByteCode;
27  import org.apache.commons.compress.harmony.unpack200.bytecode.CodeAttribute;
28  import org.apache.commons.compress.harmony.unpack200.bytecode.OperandManager;
29  
30  /**
31   * Abstract byte code form.
32   */
33  public abstract class ByteCodeForm {
34  
35      protected static final boolean WIDENED = true;
36  
37      protected static final ByteCodeForm[] byteCodeArray = new ByteCodeForm[256];
38      protected static final Map<String, ByteCodeForm> byteCodesByName = new HashMap<>(256);
39      static {
40          byteCodeArray[0] = new NoArgumentForm(0, "nop");
41          byteCodeArray[1] = new NoArgumentForm(1, "aconst_null");
42          byteCodeArray[2] = new NoArgumentForm(2, "iconst_m1");
43          byteCodeArray[3] = new NoArgumentForm(3, "iconst_0");
44          byteCodeArray[4] = new NoArgumentForm(4, "iconst_1");
45          byteCodeArray[5] = new NoArgumentForm(5, "iconst_2");
46          byteCodeArray[6] = new NoArgumentForm(6, "iconst_3");
47          byteCodeArray[7] = new NoArgumentForm(7, "iconst_4");
48          byteCodeArray[8] = new NoArgumentForm(8, "iconst_5");
49          byteCodeArray[9] = new NoArgumentForm(9, "lconst_0");
50          byteCodeArray[10] = new NoArgumentForm(10, "lconst_1");
51          byteCodeArray[11] = new NoArgumentForm(11, "fconst_0");
52          byteCodeArray[12] = new NoArgumentForm(12, "fconst_1");
53          byteCodeArray[13] = new NoArgumentForm(13, "fconst_2");
54          byteCodeArray[14] = new NoArgumentForm(14, "dconst_0");
55          byteCodeArray[15] = new NoArgumentForm(15, "dconst_1");
56          byteCodeArray[16] = new ByteForm(16, "bipush", new int[] { 16, -1 });
57          byteCodeArray[17] = new ShortForm(17, "sipush", new int[] { 17, -1, -1 });
58          byteCodeArray[18] = new StringRefForm(18, "ldc", new int[] { 18, -1 });
59          byteCodeArray[19] = new StringRefForm(19, "ldc_w", new int[] { 19, -1, -1 }, WIDENED);
60          byteCodeArray[20] = new LongForm(20, "ldc2_w", new int[] { 20, -1, -1 });
61          byteCodeArray[21] = new LocalForm(21, "iload", new int[] { 21, -1 });
62          byteCodeArray[22] = new LocalForm(22, "lload", new int[] { 22, -1 });
63          byteCodeArray[23] = new LocalForm(23, "fload", new int[] { 23, -1 });
64          byteCodeArray[24] = new LocalForm(24, "dload", new int[] { 24, -1 });
65          byteCodeArray[25] = new LocalForm(25, "aload", new int[] { 25, -1 });
66          byteCodeArray[26] = new NoArgumentForm(26, "iload_0");
67          byteCodeArray[27] = new NoArgumentForm(27, "iload_1");
68          byteCodeArray[28] = new NoArgumentForm(28, "iload_2");
69          byteCodeArray[29] = new NoArgumentForm(29, "iload_3");
70          byteCodeArray[30] = new NoArgumentForm(30, "lload_0");
71          byteCodeArray[31] = new NoArgumentForm(31, "lload_1");
72          byteCodeArray[32] = new NoArgumentForm(32, "lload_2");
73          byteCodeArray[33] = new NoArgumentForm(33, "lload_3");
74          byteCodeArray[34] = new NoArgumentForm(34, "fload_0");
75          byteCodeArray[35] = new NoArgumentForm(35, "fload_1");
76          byteCodeArray[36] = new NoArgumentForm(36, "fload_2");
77          byteCodeArray[37] = new NoArgumentForm(37, "fload_3");
78          byteCodeArray[38] = new NoArgumentForm(38, "dload_0");
79          byteCodeArray[39] = new NoArgumentForm(39, "dload_1");
80          byteCodeArray[40] = new NoArgumentForm(40, "dload_2");
81          byteCodeArray[41] = new NoArgumentForm(41, "dload_3");
82          byteCodeArray[42] = new NoArgumentForm(42, "aload_0");
83          byteCodeArray[43] = new NoArgumentForm(43, "aload_1");
84          byteCodeArray[44] = new NoArgumentForm(44, "aload_2");
85          byteCodeArray[45] = new NoArgumentForm(45, "aload_3");
86          byteCodeArray[46] = new NoArgumentForm(46, "iaload");
87          byteCodeArray[47] = new NoArgumentForm(47, "laload");
88          byteCodeArray[48] = new NoArgumentForm(48, "faload");
89          byteCodeArray[49] = new NoArgumentForm(49, "daload");
90          byteCodeArray[50] = new NoArgumentForm(50, "aaload");
91          byteCodeArray[51] = new NoArgumentForm(51, "baload");
92          byteCodeArray[52] = new NoArgumentForm(52, "caload");
93          byteCodeArray[53] = new NoArgumentForm(53, "saload");
94          byteCodeArray[54] = new LocalForm(54, "istore", new int[] { 54, -1 });
95          byteCodeArray[55] = new LocalForm(55, "lstore", new int[] { 55, -1 });
96          byteCodeArray[56] = new LocalForm(56, "fstore", new int[] { 56, -1 });
97          byteCodeArray[57] = new LocalForm(57, "dstore", new int[] { 57, -1 });
98          byteCodeArray[58] = new LocalForm(58, "astore", new int[] { 58, -1 });
99          byteCodeArray[59] = new NoArgumentForm(59, "istore_0");
100         byteCodeArray[60] = new NoArgumentForm(60, "istore_1");
101         byteCodeArray[61] = new NoArgumentForm(61, "istore_2");
102         byteCodeArray[62] = new NoArgumentForm(62, "istore_3");
103         byteCodeArray[63] = new NoArgumentForm(63, "lstore_0");
104         byteCodeArray[64] = new NoArgumentForm(64, "lstore_1");
105         byteCodeArray[65] = new NoArgumentForm(65, "lstore_2");
106         byteCodeArray[66] = new NoArgumentForm(66, "lstore_3");
107         byteCodeArray[67] = new NoArgumentForm(67, "fstore_0");
108         byteCodeArray[68] = new NoArgumentForm(68, "fstore_1");
109         byteCodeArray[69] = new NoArgumentForm(69, "fstore_2");
110         byteCodeArray[70] = new NoArgumentForm(70, "fstore_3");
111         byteCodeArray[71] = new NoArgumentForm(71, "dstore_0");
112         byteCodeArray[72] = new NoArgumentForm(72, "dstore_1");
113         byteCodeArray[73] = new NoArgumentForm(73, "dstore_2");
114         byteCodeArray[74] = new NoArgumentForm(74, "dstore_3");
115         byteCodeArray[75] = new NoArgumentForm(75, "astore_0");
116         byteCodeArray[76] = new NoArgumentForm(76, "astore_1");
117         byteCodeArray[77] = new NoArgumentForm(77, "astore_2");
118         byteCodeArray[78] = new NoArgumentForm(78, "astore_3");
119         byteCodeArray[79] = new NoArgumentForm(79, "iastore");
120         byteCodeArray[80] = new NoArgumentForm(80, "lastore");
121         byteCodeArray[81] = new NoArgumentForm(81, "fastore");
122         byteCodeArray[82] = new NoArgumentForm(82, "dastore");
123         byteCodeArray[83] = new NoArgumentForm(83, "aastore");
124         byteCodeArray[84] = new NoArgumentForm(84, "bastore");
125         byteCodeArray[85] = new NoArgumentForm(85, "castore");
126         byteCodeArray[86] = new NoArgumentForm(86, "sastore");
127         byteCodeArray[87] = new NoArgumentForm(87, "pop");
128         byteCodeArray[88] = new NoArgumentForm(88, "pop2");
129         byteCodeArray[89] = new NoArgumentForm(89, "dup");
130         byteCodeArray[90] = new NoArgumentForm(90, "dup_x1");
131         byteCodeArray[91] = new NoArgumentForm(91, "dup_x2");
132         byteCodeArray[92] = new NoArgumentForm(92, "dup2");
133         byteCodeArray[93] = new NoArgumentForm(93, "dup2_x1");
134         byteCodeArray[94] = new NoArgumentForm(94, "dup2_x2");
135         byteCodeArray[95] = new NoArgumentForm(95, "swap");
136         byteCodeArray[96] = new NoArgumentForm(96, "iadd");
137         byteCodeArray[97] = new NoArgumentForm(97, "ladd");
138         byteCodeArray[98] = new NoArgumentForm(98, "fadd");
139         byteCodeArray[99] = new NoArgumentForm(99, "dadd");
140         byteCodeArray[100] = new NoArgumentForm(100, "isub");
141         byteCodeArray[101] = new NoArgumentForm(101, "lsub");
142         byteCodeArray[102] = new NoArgumentForm(102, "fsub");
143         byteCodeArray[103] = new NoArgumentForm(103, "dsub");
144         byteCodeArray[104] = new NoArgumentForm(104, "imul");
145         byteCodeArray[105] = new NoArgumentForm(105, "lmul");
146         byteCodeArray[106] = new NoArgumentForm(106, "fmul");
147         byteCodeArray[107] = new NoArgumentForm(107, "dmul");
148         byteCodeArray[108] = new NoArgumentForm(108, "idiv");
149         byteCodeArray[109] = new NoArgumentForm(109, "ldiv");
150         byteCodeArray[110] = new NoArgumentForm(110, "fdiv");
151         byteCodeArray[111] = new NoArgumentForm(111, "ddiv");
152         byteCodeArray[112] = new NoArgumentForm(112, "irem");
153         byteCodeArray[113] = new NoArgumentForm(113, "lrem");
154         byteCodeArray[114] = new NoArgumentForm(114, "frem");
155         byteCodeArray[115] = new NoArgumentForm(115, "drem");
156         byteCodeArray[116] = new NoArgumentForm(116, "");
157         byteCodeArray[117] = new NoArgumentForm(117, "lneg");
158         byteCodeArray[118] = new NoArgumentForm(118, "fneg");
159         byteCodeArray[119] = new NoArgumentForm(119, "dneg");
160         byteCodeArray[120] = new NoArgumentForm(120, "ishl");
161         byteCodeArray[121] = new NoArgumentForm(121, "lshl");
162         byteCodeArray[122] = new NoArgumentForm(122, "ishr");
163         byteCodeArray[123] = new NoArgumentForm(123, "lshr");
164         byteCodeArray[124] = new NoArgumentForm(124, "iushr");
165         byteCodeArray[125] = new NoArgumentForm(125, "lushr");
166         byteCodeArray[126] = new NoArgumentForm(126, "iand");
167         byteCodeArray[127] = new NoArgumentForm(127, "land");
168         byteCodeArray[128] = new NoArgumentForm(128, "ior");
169         byteCodeArray[129] = new NoArgumentForm(129, "lor");
170         byteCodeArray[130] = new NoArgumentForm(130, "ixor");
171         byteCodeArray[131] = new NoArgumentForm(131, "lxor");
172         byteCodeArray[132] = new IincForm(132, "iinc", new int[] { 132, -1, -1 });
173         byteCodeArray[133] = new NoArgumentForm(133, "i2l");
174         byteCodeArray[134] = new NoArgumentForm(134, "i2f");
175         byteCodeArray[135] = new NoArgumentForm(135, "i2d");
176         byteCodeArray[136] = new NoArgumentForm(136, "l2i");
177         byteCodeArray[137] = new NoArgumentForm(137, "l2f");
178         byteCodeArray[138] = new NoArgumentForm(138, "l2d");
179         byteCodeArray[139] = new NoArgumentForm(139, "f2i");
180         byteCodeArray[140] = new NoArgumentForm(140, "f2l");
181         byteCodeArray[141] = new NoArgumentForm(141, "f2d");
182         byteCodeArray[142] = new NoArgumentForm(142, "d2i");
183         byteCodeArray[143] = new NoArgumentForm(143, "d2l");
184         byteCodeArray[144] = new NoArgumentForm(144, "d2f");
185         byteCodeArray[145] = new NoArgumentForm(145, "i2b");
186         byteCodeArray[146] = new NoArgumentForm(146, "i2c");
187         byteCodeArray[147] = new NoArgumentForm(147, "i2s");
188         byteCodeArray[148] = new NoArgumentForm(148, "lcmp");
189         byteCodeArray[149] = new NoArgumentForm(149, "fcmpl");
190         byteCodeArray[150] = new NoArgumentForm(150, "fcmpg");
191         byteCodeArray[151] = new NoArgumentForm(151, "dcmpl");
192         byteCodeArray[152] = new NoArgumentForm(152, "dcmpg");
193         byteCodeArray[153] = new LabelForm(153, "ifeq", new int[] { 153, -1, -1 });
194         byteCodeArray[154] = new LabelForm(154, "ifne", new int[] { 154, -1, -1 });
195         byteCodeArray[155] = new LabelForm(155, "iflt", new int[] { 155, -1, -1 });
196         byteCodeArray[156] = new LabelForm(156, "ifge", new int[] { 156, -1, -1 });
197         byteCodeArray[157] = new LabelForm(157, "ifgt", new int[] { 157, -1, -1 });
198         byteCodeArray[158] = new LabelForm(158, "ifle", new int[] { 158, -1, -1 });
199         byteCodeArray[159] = new LabelForm(159, "if_icmpeq", new int[] { 159, -1, -1 });
200         byteCodeArray[160] = new LabelForm(160, "if_icmpne", new int[] { 160, -1, -1 });
201         byteCodeArray[161] = new LabelForm(161, "if_icmplt", new int[] { 161, -1, -1 });
202         byteCodeArray[162] = new LabelForm(162, "if_icmpge", new int[] { 162, -1, -1 });
203         byteCodeArray[163] = new LabelForm(163, "if_icmpgt", new int[] { 163, -1, -1 });
204         byteCodeArray[164] = new LabelForm(164, "if_icmple", new int[] { 164, -1, -1 });
205         byteCodeArray[165] = new LabelForm(165, "if_acmpeq", new int[] { 165, -1, -1 });
206         byteCodeArray[166] = new LabelForm(166, "if_acmpne", new int[] { 166, -1, -1 });
207         byteCodeArray[167] = new LabelForm(167, "goto", new int[] { 167, -1, -1 });
208         byteCodeArray[168] = new LabelForm(168, "jsr", new int[] { 168, -1, -1 });
209         byteCodeArray[169] = new LocalForm(169, "ret", new int[] { 169, -1 });
210         byteCodeArray[170] = new TableSwitchForm(170, "tableswitch");
211         byteCodeArray[171] = new LookupSwitchForm(171, "lookupswitch");
212         byteCodeArray[172] = new NoArgumentForm(172, "ireturn");
213         byteCodeArray[173] = new NoArgumentForm(173, "lreturn");
214         byteCodeArray[174] = new NoArgumentForm(174, "freturn");
215         byteCodeArray[175] = new NoArgumentForm(175, "dreturn");
216         byteCodeArray[176] = new NoArgumentForm(176, "areturn");
217         byteCodeArray[177] = new NoArgumentForm(177, "return");
218         byteCodeArray[178] = new FieldRefForm(178, "getstatic", new int[] { 178, -1, -1 });
219         byteCodeArray[179] = new FieldRefForm(179, "putstatic", new int[] { 179, -1, -1 });
220         byteCodeArray[180] = new FieldRefForm(180, "getfield", new int[] { 180, -1, -1 });
221         byteCodeArray[181] = new FieldRefForm(181, "putfield", new int[] { 181, -1, -1 });
222         byteCodeArray[182] = new MethodRefForm(182, "invokevirtual", new int[] { 182, -1, -1 });
223         byteCodeArray[183] = new MethodRefForm(183, "invokespecial", new int[] { 183, -1, -1 });
224         byteCodeArray[184] = new MethodRefForm(184, "invokestatic", new int[] { 184, -1, -1 });
225         byteCodeArray[185] = new IMethodRefForm(185, "invokeinterface", new int[] { 185, -1, -1, /* count */-1, 0 });
226         byteCodeArray[186] = new NoArgumentForm(186, "xxxunusedxxx");
227         byteCodeArray[187] = new NewClassRefForm(187, "new", new int[] { 187, -1, -1 });
228         byteCodeArray[188] = new ByteForm(188, "newarray", new int[] { 188, -1 });
229         byteCodeArray[189] = new ClassRefForm(189, "anewarray", new int[] { 189, -1, -1 });
230         byteCodeArray[190] = new NoArgumentForm(190, "arraylength");
231         byteCodeArray[191] = new NoArgumentForm(191, "athrow");
232         byteCodeArray[192] = new ClassRefForm(192, "checkcast", new int[] { 192, -1, -1 });
233         byteCodeArray[193] = new ClassRefForm(193, "instanceof", new int[] { 193, -1, -1 });
234         byteCodeArray[194] = new NoArgumentForm(194, "monitorenter");
235         byteCodeArray[195] = new NoArgumentForm(195, "monitorexit");
236         byteCodeArray[196] = new WideForm(196, "wide");
237         byteCodeArray[197] = new MultiANewArrayForm(197, "multianewarray", new int[] { 197, -1, -1, -1 });
238         byteCodeArray[198] = new LabelForm(198, "ifnull", new int[] { 198, -1, -1 });
239         byteCodeArray[199] = new LabelForm(199, "ifnonnull", new int[] { 199, -1, -1 });
240         byteCodeArray[200] = new LabelForm(200, "goto_w", new int[] { 200, -1, -1, -1, -1 }, WIDENED);
241         byteCodeArray[201] = new LabelForm(201, "jsr_w", new int[] { 201, -1, -1, -1, -1 }, WIDENED);
242 
243         // Extra ones defined by pack200
244         byteCodeArray[202] = new ThisFieldRefForm(202, "getstatic_this", new int[] { 178, -1, -1 });
245         byteCodeArray[203] = new ThisFieldRefForm(203, "putstatic_this", new int[] { 179, -1, -1 });
246         byteCodeArray[204] = new ThisFieldRefForm(204, "getfield_this", new int[] { 180, -1, -1 });
247         byteCodeArray[205] = new ThisFieldRefForm(205, "putfield_this", new int[] { 181, -1, -1 });
248         byteCodeArray[206] = new ThisMethodRefForm(206, "invokevirtual_this", new int[] { 182, -1, -1 });
249         byteCodeArray[207] = new ThisMethodRefForm(207, "invokespecial_this", new int[] { 183, -1, -1 });
250         byteCodeArray[208] = new ThisMethodRefForm(208, "invokestatic_this", new int[] { 184, -1, -1 });
251         byteCodeArray[209] = new ThisFieldRefForm(209, "aload_0_getstatic_this", new int[] { 42, 178, -1, -1 });
252         byteCodeArray[210] = new ThisFieldRefForm(210, "aload_0_putstatic_this", new int[] { 42, 179, -1, -1 });
253         byteCodeArray[211] = new ThisFieldRefForm(211, "aload_0_getfield_this", new int[] { 42, 180, -1, -1 });
254         byteCodeArray[212] = new ThisFieldRefForm(212, "aload_0_putfield_this", new int[] { 42, 181, -1, -1 });
255         byteCodeArray[213] = new ThisMethodRefForm(213, "aload_0_invokevirtual_this", new int[] { 42, 182, -1, -1 });
256         byteCodeArray[214] = new ThisMethodRefForm(214, "aload_0_invokespecial_this", new int[] { 42, 183, -1, -1 });
257         byteCodeArray[215] = new ThisMethodRefForm(215, "aload_0_invokestatic_this", new int[] { 42, 184, -1, -1 });
258         byteCodeArray[216] = new SuperFieldRefForm(216, "getstatic_super", new int[] { 178, -1, -1 });
259         byteCodeArray[217] = new SuperFieldRefForm(217, "putstatic_super", new int[] { 179, -1, -1 });
260         byteCodeArray[218] = new SuperFieldRefForm(218, "getfield_super", new int[] { 180, -1, -1 });
261         byteCodeArray[219] = new SuperFieldRefForm(219, "putfield_super", new int[] { 181, -1, -1 });
262         byteCodeArray[220] = new SuperMethodRefForm(220, "invokevirtual_super", new int[] { 182, -1, -1 });
263         byteCodeArray[221] = new SuperMethodRefForm(221, "invokespecial_super", new int[] { 183, -1, -1 });
264         byteCodeArray[222] = new SuperMethodRefForm(222, "invokestatic_super", new int[] { 184, -1, -1 });
265         byteCodeArray[223] = new SuperFieldRefForm(223, "aload_0_getstatic_super", new int[] { 42, 178, -1, -1 });
266         byteCodeArray[224] = new SuperFieldRefForm(224, "aload_0_putstatic_super", new int[] { 42, 179, -1, -1 });
267         byteCodeArray[225] = new SuperFieldRefForm(225, "aload_0_getfield_super", new int[] { 42, 180, -1, -1 });
268         byteCodeArray[226] = new SuperFieldRefForm(226, "aload_0_putfield_super", new int[] { 42, 181, -1, -1 });
269         byteCodeArray[227] = new SuperMethodRefForm(227, "aload_0_invokevirtual_super", new int[] { 42, 182, -1, -1 });
270         byteCodeArray[228] = new SuperMethodRefForm(228, "aload_0_invokespecial_super", new int[] { 42, 183, -1, -1 });
271         byteCodeArray[229] = new SuperMethodRefForm(229, "aload_0_invokestatic_super", new int[] { 42, 184, -1, -1 });
272         byteCodeArray[230] = new ThisInitMethodRefForm(230, "invokespecial_this_init", new int[] { 183, -1, -1 });
273         byteCodeArray[231] = new SuperInitMethodRefForm(231, "invokespecial_super_init", new int[] { 183, -1, -1 });
274         byteCodeArray[232] = new NewInitMethodRefForm(232, "invokespecial_new_init", new int[] { 183, -1, -1 });
275         byteCodeArray[233] = new NarrowClassRefForm(233, "cldc", new int[] { 18, -1 });
276         byteCodeArray[234] = new IntRefForm(234, "ildc", new int[] { 18, -1 });
277         byteCodeArray[235] = new FloatRefForm(235, "fldc", new int[] { 18, -1 });
278         byteCodeArray[236] = new NarrowClassRefForm(236, "cldc_w", new int[] { 19, -1, -1 }, WIDENED);
279         byteCodeArray[237] = new IntRefForm(237, "ildc_w", new int[] { 19, -1, -1 }, WIDENED);
280         byteCodeArray[238] = new FloatRefForm(238, "fldc_w", new int[] { 19, -1, -1 }, WIDENED);
281         byteCodeArray[239] = new DoubleForm(239, "dldc2_w", new int[] { 20, -1, -1 });
282 
283         // Reserved bytecodes
284         byteCodeArray[254] = new NoArgumentForm(254, "impdep1");
285         byteCodeArray[255] = new NoArgumentForm(255, "impdep2");
286 
287         // Bytecodes that aren't defined in the spec but are useful when
288         // unpacking (all must be >255)
289         // maybe wide versions of the others? etc.
290 
291         // Put all the bytecodes in a HashMap so we can
292         // get them by either name or number
293         for (final ByteCodeForm byteCode : byteCodeArray) {
294             if (byteCode != null) {
295                 byteCodesByName.put(byteCode.getName(), byteCode);
296             }
297         }
298     }
299 
300     /**
301      * Gets a ByteCodeForm.
302      *
303      * @param opcode opcode index.
304      * @return the matching ByteCodeForm at the given opcode.
305      */
306     public static ByteCodeForm get(final int opcode) {
307         return byteCodeArray[opcode];
308     }
309 
310     private final int opcode;
311     private final String name;
312     private final int[] rewrite;
313     private int firstOperandIndex;
314 
315     private int operandLength;
316 
317     /**
318      * Constructs a new instance with the specified opcode and name. Assume no rewrite.
319      *
320      * @param opcode index corresponding to the opcode's value.
321      * @param name   printable name of the opcode.
322      */
323     public ByteCodeForm(final int opcode, final String name) {
324         this(opcode, name, new int[] { opcode });
325     }
326 
327     /**
328      * Constructs a new instance with the specified opcode, name, operandType and rewrite.
329      *
330      * @param opcode  index corresponding to the opcode's value.
331      * @param name    String printable name of the opcode.
332      * @param rewrite Operand positions (which will later be rewritten in ByteCodes) are indicated by -1.
333      */
334     public ByteCodeForm(final int opcode, final String name, final int[] rewrite) {
335         this.opcode = opcode;
336         this.name = name;
337         this.rewrite = rewrite;
338         calculateOperandPosition();
339     }
340 
341     protected void calculateOperandPosition() {
342         firstOperandIndex = -1;
343         operandLength = -1;
344 
345         // Find the first negative number in the rewrite array
346         int iterationIndex = 0;
347         while (iterationIndex < rewrite.length) {
348             if (rewrite[iterationIndex] < 0) {
349                 // Found the first opcode to substitute
350                 firstOperandIndex = iterationIndex;
351                 iterationIndex = rewrite.length;
352             } else {
353                 iterationIndex++;
354             }
355         }
356 
357         if (firstOperandIndex == -1) {
358             // Nothing more to do since the opcode has no operands
359             return;
360         }
361 
362         // Find the last negative number in the rewrite array
363         int lastOperandIndex = -1;
364         iterationIndex = firstOperandIndex;
365         while (iterationIndex < rewrite.length) {
366             if (rewrite[iterationIndex] < 0) {
367                 lastOperandIndex = iterationIndex;
368             }
369             iterationIndex++;
370         }
371 
372         // Now we have the first index and the last index.
373         final int difference = lastOperandIndex - firstOperandIndex;
374 
375         // If last < first, something is wrong.
376         if (difference < 0) {
377             throw new Error("Logic error: not finding rewrite operands correctly");
378         }
379         operandLength = difference + 1;
380     }
381 
382     public int firstOperandIndex() {
383         return firstOperandIndex;
384     }
385 
386     /**
387      * The ByteCodeForm knows how to fix up a bytecode if it needs to be fixed up because it holds a Label bytecode.
388      *
389      * @param byteCode      a ByteCode to be fixed up
390      * @param codeAttribute a CodeAttribute used to determine how the ByteCode should be fixed up.
391      */
392     public void fixUpByteCodeTargets(final ByteCode byteCode, final CodeAttribute codeAttribute) {
393         // Most ByteCodeForms don't have any fixing up to do.
394     }
395 
396     /**
397      * Gets the name.
398      *
399      * @return the name.
400      */
401     public String getName() {
402         return name;
403     }
404 
405     /**
406      * Gets the opcode.
407      *
408      * @return the opcode.
409      */
410     public int getOpcode() {
411         return opcode;
412     }
413 
414     /**
415      * Gets the rewrite array.
416      *
417      * @return the rewrite array.
418      */
419     public int[] getRewrite() {
420         return rewrite;
421     }
422 
423     /**
424      * Gets a copy of the rewrite array.
425      *
426      * @return a copy of the rewrite array.
427      */
428     public int[] getRewriteCopy() {
429         return Arrays.copyOf(rewrite, rewrite.length);
430     }
431 
432     /**
433      * This method will answer true if the receiver is a multi-bytecode instruction (such as aload0_putfield_super); otherwise, it will answer false.
434      *
435      * @return boolean true if multibytecode, false otherwise
436      */
437     public boolean hasMultipleByteCodes() {
438         // Currently, all multi-bytecode instructions
439         // begin with aload_0, so this is how we test.
440         if (rewrite.length > 1 && rewrite[0] == 42) {
441             // If there's an instruction (not a negative
442             // number, which is an operand) after the
443             // aload_0, it's a multibytecode instruction.
444             return rewrite[1] > 0;
445         }
446         return false;
447     }
448 
449     /**
450      * Tests whether this instance has an operand.
451      *
452      * @return whether this instance has an operand.
453      */
454     public boolean hasNoOperand() {
455         return false;
456     }
457 
458     public boolean nestedMustStartClassPool() {
459         return false;
460     }
461 
462     /**
463      * Gets the operand length.
464      *
465      * @return the operand length.
466      */
467     public int operandLength() {
468         return operandLength;
469     }
470 
471     /**
472      * Sets the rewrite of the byteCode.
473      *
474      * @param byteCode       ByteCode to be updated (!)
475      * @param operandManager OperandTable from which to draw info
476      * @param codeLength     Length of bytes (excluding this bytecode) from the beginning of the method. Used in calculating padding for some variable-length
477      *                       bytecodes (such as lookupswitch, tableswitch).
478      * @throws Pack200Exception if a type is not supported or an index not in the range [0, {@link Integer#MAX_VALUE}].
479      */
480     public abstract void setByteCodeOperands(ByteCode byteCode, OperandManager operandManager, int codeLength) throws Pack200Exception;
481 
482     @Override
483     public String toString() {
484         return this.getClass().getName() + "(" + getName() + ")";
485     }
486 }