1 /*
  2  * Copyright (c) 2007, 2026, Oracle and/or its affiliates. All rights reserved.
  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  4  *
  5  * This code is free software; you can redistribute it and/or modify it
  6  * under the terms of the GNU General Public License version 2 only, as
  7  * published by the Free Software Foundation.  Oracle designates this
  8  * particular file as subject to the "Classpath" exception as provided
  9  * by Oracle in the LICENSE file that accompanied this code.
 10  *
 11  * This code is distributed in the hope that it will be useful, but WITHOUT
 12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 14  * version 2 for more details (a copy is included in the LICENSE file that
 15  * accompanied this code).
 16  *
 17  * You should have received a copy of the GNU General Public License version
 18  * 2 along with this work; if not, write to the Free Software Foundation,
 19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 20  *
 21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 22  * or visit www.oracle.com if you need additional information or have any
 23  * questions.
 24  */
 25 
 26 package com.sun.tools.javap;
 27 
 28 import java.lang.classfile.AccessFlags;
 29 import java.lang.classfile.Attributes;
 30 import java.lang.classfile.ClassFile;
 31 import java.lang.classfile.ClassHierarchyResolver;
 32 import java.lang.classfile.ClassModel;
 33 import java.lang.classfile.ClassSignature;
 34 import java.lang.classfile.FieldModel;
 35 import java.lang.classfile.MethodModel;
 36 import java.lang.classfile.MethodSignature;
 37 import java.lang.classfile.Signature;
 38 import java.lang.classfile.attribute.CodeAttribute;
 39 import java.lang.classfile.attribute.SignatureAttribute;
 40 import java.lang.classfile.constantpool.ClassEntry;
 41 import java.lang.classfile.constantpool.ConstantValueEntry;
 42 import java.lang.classfile.constantpool.PoolEntry;
 43 import java.lang.constant.ClassDesc;
 44 import java.lang.reflect.AccessFlag;
 45 import java.lang.reflect.ClassFileFormatVersion;
 46 import java.lang.reflect.Modifier;
 47 import java.net.URI;
 48 import java.text.DateFormat;
 49 import java.util.ArrayList;
 50 import java.util.Collection;
 51 import java.util.Date;
 52 import java.util.EnumSet;
 53 import java.util.LinkedHashSet;
 54 import java.util.List;
 55 import java.util.Locale;
 56 import java.util.Set;
 57 
 58 import static java.lang.classfile.ClassFile.*;
 59 
 60 /*
 61  *  The main javap class to write the contents of a class file as text.
 62  *
 63  *  <p><b>This is NOT part of any supported API.
 64  *  If you write code that depends on this, you do so at your own risk.
 65  *  This code and its internal interfaces are subject to change or
 66  *  deletion without notice.</b>
 67  */
 68 public class ClassWriter extends BasicWriter {
 69     static ClassWriter instance(Context context) {
 70         ClassWriter instance = context.get(ClassWriter.class);
 71         if (instance == null)
 72             instance = new ClassWriter(context);
 73         return instance;
 74     }
 75 
 76     protected ClassWriter(Context context) {
 77         super(context);
 78         context.put(ClassWriter.class, this);
 79         options = Options.instance(context);
 80         attrWriter = AttributeWriter.instance(context);
 81         codeWriter = CodeWriter.instance(context);
 82         constantWriter = ConstantWriter.instance(context);
 83         sigPrinter = new SignaturePrinter(options.verbose);
 84     }
 85 
 86     void setDigest(String name, byte[] digest) {
 87         this.digestName = name;
 88         this.digest = digest;
 89     }
 90 
 91     void setFile(URI uri) {
 92         this.uri = uri;
 93     }
 94 
 95     void setFileSize(int size) {
 96         this.size = size;
 97     }
 98 
 99     void setLastModified(long lastModified) {
100         this.lastModified = lastModified;
101     }
102 
103     protected ClassModel getClassModel() {
104         return classModel;
105     }
106 
107     protected void setClassFile(ClassModel cm) {
108         classModel = cm;
109     }
110 
111     protected MethodModel getMethod() {
112         return method;
113     }
114 
115     protected void setMethod(MethodModel m) {
116         method = m;
117     }
118 
119     protected ClassFileFormatVersion cffv() {
120         var major = classModel.majorVersion();
121         if (major < JAVA_1_VERSION || major > ClassFile.latestMajorVersion())
122             // something not representable by CFFV, let's fall back
123             return ClassFileFormatVersion.latest();
124         if (major >= JAVA_12_VERSION && classModel.minorVersion() != 0) {
125             // preview versions aren't explicitly supported, but latest is good enough for now
126             return ClassFileFormatVersion.latest();
127         }
128         return ClassFileFormatVersion.fromMajor(major);
129     }
130 
131     public boolean write(ClassModel cm) {
132         errorReported = false;
133         setClassFile(cm);
134 
135         if (options.sysInfo || options.verbose) {
136             if (uri != null) {
137                 if (uri.getScheme().equals("file"))
138                     println("Classfile " + uri.getPath());
139                 else
140                     println("Classfile " + uri);
141             }
142             indent(+1);
143             if (lastModified != -1) {
144                 Date lm = new Date(lastModified);
145                 DateFormat df = DateFormat.getDateInstance();
146                 if (size > 0) {
147                     println("Last modified " + df.format(lm) + "; size " + size
148                             + " bytes");
149                 } else {
150                     println("Last modified " + df.format(lm));
151                 }
152             } else if (size > 0) {
153                 println("Size " + size + " bytes");
154             }
155             if (digestName != null && digest != null) {
156                 StringBuilder sb = new StringBuilder();
157                 for (byte b: digest)
158                     sb.append(String.format("%02x", b));
159                 println(digestName + " checksum " + sb);
160             }
161         }
162 
163         cm.findAttribute(Attributes.sourceFile()).ifPresent(sfa ->
164             println("Compiled from \"" + sfa.sourceFile().stringValue() + "\""));
165 
166         if (options.sysInfo || options.verbose) {
167             indent(-1);
168         }
169 
170         writeModifiers(getClassModifiers(cm.flags()));
171 
172         if ((classModel.flags().flagsMask() & ACC_MODULE) != 0) {
173             var attr = classModel.findAttribute(Attributes.module());
174             if (attr.isPresent()) {
175                 var modAttr = attr.get();
176                 if ((modAttr.moduleFlagsMask() & ACC_OPEN) != 0) {
177                     print("open ");
178                 }
179                 print("module ");
180                 print(() -> modAttr.moduleName().name().stringValue());
181                 if (modAttr.moduleVersion().isPresent()) {
182                     print("@");
183                     print(() -> modAttr.moduleVersion().get().stringValue());
184                 }
185             } else {
186                 // fallback for malformed class files
187                 print("class ");
188                 print(() -> getJavaName(classModel.thisClass().asInternalName()));
189             }
190         } else {
191             if ((classModel.flags().flagsMask() & ACC_INTERFACE) == 0)
192                 print("class ");
193             else
194                 print("interface ");
195 
196             print(() -> getJavaName(classModel.thisClass().asInternalName()));
197         }
198 
199         try {
200             var sigAttr = classModel.findAttribute(Attributes.signature()).orElse(null);
201             if (sigAttr == null) {
202                 // use info from class file header
203                 if ((classModel.flags().flagsMask() & ACC_INTERFACE) == 0
204                         && classModel.superclass().isPresent()) {
205                     String sn = getJavaName(classModel.superclass().get().asInternalName());
206                     if (!sn.equals("java.lang.Object")) {
207                         print(" extends ");
208                         print(sn);
209                     }
210                 }
211                 var interfaces = classModel.interfaces();
212                 for (int i = 0; i < interfaces.size(); i++) {
213                     print(i == 0 ? ((classModel.flags().flagsMask() & ACC_INTERFACE) == 0
214                             ? " implements " : " extends ") : ",");
215                     print(getJavaName(interfaces.get(i).asInternalName()));
216                 }
217             } else {
218                 var t = sigAttr.asClassSignature();
219                 print(sigPrinter.print(t, (classModel.flags().flagsMask() & ACC_INTERFACE) != 0));
220             }
221         } catch (IllegalArgumentException e) {
222             report(e);
223         }
224 
225         if (options.verbose) {
226             println();
227             indent(+1);
228             println("minor version: " + classModel.minorVersion());
229             println("major version: " + classModel.majorVersion());
230             writeList(String.format("flags: (0x%04x) ", cm.flags().flagsMask()),
231                     getClassFlags(cm.flags()), "\n");
232             print("this_class: #");print(() -> classModel.thisClass().index());
233             tab();
234             print(() -> "// " + classModel.thisClass().asInternalName());
235             println();
236             print("super_class: #");print(() -> classModel.superclass()
237                     .map(ClassEntry::index).orElse(0));
238             try {
239                 if (classModel.superclass().isPresent()) {
240                     tab();
241                     print(() -> "// " + classModel.superclass().get().asInternalName());
242                 }
243             } catch (IllegalArgumentException e) {
244                 report(e);
245             }
246             println();
247             print("interfaces: ");print(() -> classModel.interfaces().size());
248             print(", fields: " + classModel.fields().size());
249             print(", methods: " + classModel.methods().size());
250             println(", attributes: " + classModel.attributes().size());
251             indent(-1);
252             constantWriter.writeConstantPool();
253         } else {
254             print(" ");
255         }
256 
257         println("{");
258         indent(+1);
259         if ((cm.flags().flagsMask() & ACC_MODULE) != 0 && !options.verbose) {
260             writeDirectives();
261         }
262         writeFields();
263         writeMethods();
264         indent(-1);
265         println("}");
266 
267         if (options.verbose) {
268             attrWriter.write(classModel.attributes(), cffv());
269         }
270 
271         if (options.verify) {
272             var vErrors = VERIFIER.verify(classModel);
273             if (!vErrors.isEmpty()) {
274                 println();
275                 for (var ve : vErrors) {
276                     println(ve.getMessage());
277                 }
278                 errorReported = true;
279             }
280         }
281         return !errorReported;
282     }
283     // where
284 
285     private static final ClassFile VERIFIER = ClassFile.of(ClassHierarchyResolverOption.of(
286             ClassHierarchyResolver.defaultResolver().orElse(new ClassHierarchyResolver() {
287                 @Override
288                 public ClassHierarchyInfo getClassInfo(ClassDesc classDesc) {
289                     // mark all unresolved classes as interfaces to exclude them from assignability verification
290                     return ClassHierarchyInfo.ofInterface();
291                 }
292             })));
293 
294     final SignaturePrinter sigPrinter;
295 
296     public static record SignaturePrinter(boolean verbose) {
297 
298         public String print(ClassSignature cs, boolean isInterface) {
299             var sb = new StringBuilder();
300             print(sb, cs.typeParameters());
301             if (isInterface) {
302                 String sep = " extends ";
303                 for (var is : cs.superinterfaceSignatures()) {
304                     sb.append(sep);
305                     print(sb, is);
306                     sep = ", ";
307                 }
308             } else {
309                 if (cs.superclassSignature() != null
310                         && (verbose || !isObject(cs.superclassSignature()))) {
311                     sb.append(" extends ");
312                     print(sb, cs.superclassSignature());
313                 }
314                 String sep = " implements ";
315                 for (var is : cs.superinterfaceSignatures()) {
316                     sb.append(sep);
317                     print(sb, is);
318                     sep = ", ";
319                 }
320             }
321             return sb.toString();
322         }
323 
324         public String print(Signature sig) {
325             var sb = new StringBuilder();
326             print(sb, sig);
327             return sb.toString();
328         }
329 
330         public String printTypeParams(List<Signature.TypeParam> tps) {
331             var sb = new StringBuilder();
332             print(sb, tps);
333             return sb.toString();
334         }
335 
336         public String printList(String prefix, List<? extends Signature> args,
337                 String postfix) {
338             var sb = new StringBuilder();
339             sb.append(prefix);
340             String sep = "";
341             for (var arg : args) {
342                 sb.append(sep);
343                 print(sb, arg);
344                 sep = ", ";
345             }
346             return sb.append(postfix).toString();
347         }
348 
349         private boolean isObject(Signature sig) {
350             return (sig instanceof Signature.ClassTypeSig cts)
351                     && cts.outerType().isEmpty()
352                     && cts.className().equals("java/lang/Object")
353                     && (cts.typeArgs().isEmpty());
354         }
355 
356         private void print(StringBuilder sb, List<Signature.TypeParam> tps) {
357             if (!tps.isEmpty()) {
358                 sb.append('<');
359                 String sep = "";
360                 for (var tp : tps) {
361                     sb.append(sep).append(tp.identifier());
362                     sep = " extends ";
363                     if (tp.classBound().isPresent()
364                             && (verbose || !isObject(tp.classBound().get()))) {
365                         sb.append(sep);
366                         print(sb, tp.classBound().get());
367                         sep = " & ";
368                     }
369                     for (var bound: tp.interfaceBounds()) {
370                         sb.append(sep);
371                         print(sb, bound);
372                         sep = " & ";
373                     }
374                     sep = ", ";
375                 }
376                 sb.append('>');
377             }
378         }
379 
380         private void print(StringBuilder sb, Signature sig) {
381             if (sig instanceof Signature.BaseTypeSig bts) {
382                     sb.append(ClassDesc.ofDescriptor("" + bts.baseType()).displayName());
383             } else if (sig instanceof Signature.ClassTypeSig cts) {
384                 if (cts.outerType().isPresent()) {
385                     print(sb, cts.outerType().get());
386                     sb.append(".");
387                 }
388                 sb.append(getJavaName(cts.className()));
389                 if (!cts.typeArgs().isEmpty()) {
390                     String sep = "";
391                     sb.append('<');
392                     for (var ta : cts.typeArgs()) {
393                         sb.append(sep);
394                         print(sb, ta);
395                         sep = ", ";
396                     }
397                     sb.append('>');
398                 }
399             } else if (sig instanceof Signature.TypeVarSig tvs) {
400                 sb.append(tvs.identifier());
401             } else if (sig instanceof Signature.ArrayTypeSig ats) {
402                 print(sb, ats.componentSignature());
403                 sb.append("[]");
404             }
405         }
406 
407         private void print(StringBuilder sb, Signature.TypeArg ta) {
408             switch (ta) {
409                 case Signature.TypeArg.Unbounded _ -> sb.append('?');
410                 case Signature.TypeArg.Bounded bta -> {
411                     switch (bta.wildcardIndicator()) {
412                         case NONE -> print(sb, bta.boundType());
413                         case EXTENDS -> {
414                             sb.append("? extends ");
415                             print(sb, bta.boundType());
416                         }
417                         case SUPER -> {
418                             sb.append("? super ");
419                             print(sb, bta.boundType());
420                         }
421                     }
422                 }
423             }
424         }
425     }
426 
427     protected void writeFields() {
428         for (var f: classModel.fields()) {
429             writeField(f);
430         }
431     }
432 
433     protected void writeField(FieldModel f) {
434         if (!options.checkAccess(f.flags().flagsMask()))
435             return;
436 
437         var flags = f.flags();
438         writeModifiers(getModifiers(flagsReportUnknown(flags, cffv())));
439         print(() -> sigPrinter.print(
440                 f.findAttribute(Attributes.signature())
441                         .map(SignatureAttribute::asTypeSignature)
442                         .orElseGet(() -> Signature.of(f.fieldTypeSymbol()))));
443         print(" ");
444         print(() -> f.fieldName().stringValue());
445         if (options.showConstants) {
446             var a = f.findAttribute(Attributes.constantValue());
447             if (a.isPresent()) {
448                 print(" = ");
449                 var cv = a.get();
450                 print(() -> getConstantValue(f.fieldTypeSymbol(), cv.constant()));
451             }
452         }
453         print(";");
454         println();
455 
456         indent(+1);
457 
458         boolean showBlank = false;
459 
460         if (options.showDescriptors) {
461             print("descriptor: ");println(() -> f.fieldType().stringValue());
462         }
463 
464         if (options.verbose)
465             writeList(String.format("flags: (0x%04x) ", flags.flagsMask()),
466                     flagsReportUnknown(flags, cffv()).stream().map(fl -> "ACC_" + fl.name()).toList(),
467                     "\n");
468 
469         if (options.showAllAttrs) {
470             attrWriter.write(f.attributes(), cffv());
471             showBlank = true;
472         }
473 
474         indent(-1);
475 
476         if (showBlank || options.showDisassembled || options.showLineAndLocalVariableTables)
477             println();
478     }
479 
480     protected void writeMethods() {
481         for (MethodModel m: classModel.methods())
482             writeMethod(m);
483         setPendingNewline(false);
484     }
485 
486     private static final int DEFAULT_ALLOWED_MAJOR_VERSION = 52;
487     private static final int DEFAULT_ALLOWED_MINOR_VERSION = 0;
488 
489     protected void writeMethod(MethodModel m) {
490         if (!options.checkAccess(m.flags().flagsMask()))
491             return;
492 
493         method = m;
494 
495         int flags = m.flags().flagsMask();
496 
497         var modifiers = getModifiers(flagsReportUnknown(m.flags(), cffv()));
498 
499         String name = "???";
500         try {
501             name = m.methodName().stringValue();
502         } catch (IllegalArgumentException e) {
503             report(e);
504         }
505 
506         if ((classModel.flags().flagsMask() & ACC_INTERFACE) != 0 &&
507                 ((flags & ACC_ABSTRACT) == 0) && !name.equals("<clinit>")) {
508             if (classModel.majorVersion() > DEFAULT_ALLOWED_MAJOR_VERSION ||
509                     (classModel.majorVersion() == DEFAULT_ALLOWED_MAJOR_VERSION
510                     && classModel.minorVersion() >= DEFAULT_ALLOWED_MINOR_VERSION)) {
511                 if ((flags & (ACC_STATIC | ACC_PRIVATE)) == 0) {
512                     modifiers.add("default");
513                 }
514             }
515         }
516         writeModifiers(modifiers);
517 
518         try {
519             var sigAttr = m.findAttribute(Attributes.signature());
520             MethodSignature d;
521             if (sigAttr.isEmpty()) {
522                 d = MethodSignature.parseFrom(m.methodType().stringValue());
523             } else {
524                 d = sigAttr.get().asMethodSignature();
525             }
526 
527             if (!d.typeParameters().isEmpty()) {
528                 print(sigPrinter.printTypeParams(d.typeParameters()) + " ");
529             }
530             switch (name) {
531                 case "<init>":
532                     print(getJavaName(classModel.thisClass().asInternalName()));
533                     print(getJavaParameterTypes(d, flags));
534                     break;
535                 case "<clinit>":
536                     print("{}");
537                     break;
538                 default:
539                     print(getJavaName(sigPrinter.print(d.result())));
540                     print(" ");
541                     print(name);
542                     print(getJavaParameterTypes(d, flags));
543                     break;
544             }
545 
546             var e_attr = m.findAttribute(Attributes.exceptions());
547             // if there are generic exceptions, there must be erased exceptions
548             if (e_attr.isPresent()) {
549                 var exceptions = e_attr.get();
550                 print(" throws ");
551                 if (d != null && !d.throwableSignatures().isEmpty()) { // use generic list if available
552                     print(() -> sigPrinter.printList("", d.throwableSignatures(), ""));
553                 } else {
554                     var exNames = exceptions.exceptions();
555                     for (int i = 0; i < exNames.size(); i++) {
556                         if (i > 0)
557                             print(", ");
558                         int ii = i;
559                         print(() -> getJavaName(exNames.get(ii).asInternalName()));
560                     }
561                 }
562             }
563         } catch (IllegalArgumentException e) {
564             report(e);
565         }
566 
567         println(";");
568 
569         indent(+1);
570 
571         if (options.showDescriptors) {
572             print("descriptor: ");println(() -> m.methodType().stringValue());
573         }
574 
575         if (options.verbose) {
576             StringBuilder sb = new StringBuilder();
577             String sep = "";
578             sb.append(String.format("flags: (0x%04x) ", flags));
579             for (var f : flagsReportUnknown(m.flags(), cffv())) {
580                 sb.append(sep).append("ACC_").append(f.name());
581                 sep = ", ";
582             }
583             println(sb.toString());
584         }
585 
586         var code = (CodeAttribute)m.code().orElse(null);
587 
588         if (options.showAllAttrs) {
589             attrWriter.write(m.attributes(), cffv());
590         } else if (code != null && options.showDisassembled) {
591             codeWriter.writeMinimal(code);
592         }
593 
594         indent(-1);
595 
596         // set pendingNewline to write a newline before the next method (if any)
597         // if a separator is desired
598         setPendingNewline(
599                 options.showDisassembled ||
600                 options.showAllAttrs ||
601                 options.showDescriptors ||
602                 options.showLineAndLocalVariableTables ||
603                 options.verbose);
604     }
605 
606     void writeModifiers(Collection<String> items) {
607         for (Object item: items) {
608             print(item);
609             print(" ");
610         }
611     }
612 
613     public static final int ACC_TRANSITIVE = 0x0020;
614     public static final int ACC_STATIC_PHASE = 0x0040;
615 
616     void writeDirectives() {
617         var attr = classModel.findAttribute(Attributes.module());
618         if (attr.isEmpty())
619             return;
620 
621         var m = attr.get();
622         for (var entry: m.requires()) {
623             print("requires");
624             if ((entry.requiresFlagsMask() & ACC_STATIC_PHASE) != 0)
625                 print(" static");
626             if ((entry.requiresFlagsMask() & ACC_TRANSITIVE) != 0)
627                 print(" transitive");
628             print(" ");
629             String mname;
630             print(entry.requires().name().stringValue());
631             println(";");
632         }
633 
634         for (var entry: m.exports()) {
635             print("exports");
636             print(" ");
637             print(entry.exportedPackage().name().stringValue().replace('/', '.'));
638             boolean first = true;
639             for (var mod: entry.exportsTo()) {
640                 if (first) {
641                     println(" to");
642                     indent(+1);
643                     first = false;
644                 } else {
645                     println(",");
646                 }
647                 print(mod.name().stringValue());
648             }
649             println(";");
650             if (!first)
651                 indent(-1);
652         }
653 
654         for (var entry: m.opens()) {
655             print("opens");
656             print(" ");
657             print(entry.openedPackage().name().stringValue().replace('/', '.'));
658             boolean first = true;
659             for (var mod: entry.opensTo()) {
660                 if (first) {
661                     println(" to");
662                     indent(+1);
663                     first = false;
664                 } else {
665                     println(",");
666                 }
667                 print(mod.name().stringValue());
668             }
669             println(";");
670             if (!first)
671                 indent(-1);
672         }
673 
674         for (var entry: m.uses()) {
675             print("uses ");
676             print(entry.asInternalName().replace('/', '.'));
677             println(";");
678         }
679 
680         for (var entry: m.provides()) {
681             print("provides  ");
682             print(entry.provides().asInternalName().replace('/', '.'));
683             boolean first = true;
684             for (var ce: entry.providesWith()) {
685                 if (first) {
686                     println(" with");
687                     indent(+1);
688                     first = false;
689                 } else {
690                     println(",");
691                 }
692                 print(ce.asInternalName().replace('/', '.'));
693             }
694             println(";");
695             if (!first)
696                 indent(-1);
697         }
698     }
699 
700     void writeList(String prefix, Collection<?> items, String suffix) {
701         print(prefix);
702         String sep = "";
703         for (Object item: items) {
704             print(sep);
705             print(item);
706             sep = ", ";
707         }
708         print(suffix);
709     }
710 
711     void writeListIfNotEmpty(String prefix, List<?> items, String suffix) {
712         if (items != null && items.size() > 0)
713             writeList(prefix, items, suffix);
714     }
715 
716     String adjustVarargs(int flags, String params) {
717         if ((flags & ACC_VARARGS) != 0) {
718             int i = params.lastIndexOf("[]");
719             if (i > 0)
720                 return params.substring(0, i) + "..." + params.substring(i+2);
721         }
722 
723         return params;
724     }
725 
726     String getJavaParameterTypes(MethodSignature d, int flags) {
727         return getJavaName(adjustVarargs(flags,
728                 sigPrinter.printList("(", d.arguments(), ")")));
729     }
730 
731     static String getJavaName(String name) {
732         return name.replace('/', '.');
733     }
734 
735     /**
736      * Get the value of an entry in the constant pool as a Java constant.
737      * Characters and booleans are represented by CONSTANT_Intgere entries.
738      * Character and string values are processed to escape characters outside
739      * the basic printable ASCII set.
740      * @param d the descriptor, giving the expected type of the constant
741      * @param index the index of the value in the constant pool
742      * @return a printable string containing the value of the constant.
743      */
744     String getConstantValue(ClassDesc d, ConstantValueEntry cpInfo) {
745         switch (cpInfo.tag()) {
746             case PoolEntry.TAG_INTEGER: {
747                 var val = (Integer)cpInfo.constantValue();
748                 switch (d.descriptorString()) {
749                     case "C":
750                         // character
751                         return getConstantCharValue((char)val.intValue());
752                     case "Z":
753                         // boolean
754                         return String.valueOf(val == 1);
755                     default:
756                         // other: assume integer
757                         return String.valueOf(val);
758                 }
759             }
760             case PoolEntry.TAG_STRING:
761                 return getConstantStringValue(cpInfo.constantValue().toString());
762             default:
763                 return constantWriter.stringValue(cpInfo);
764         }
765     }
766 
767     private String getConstantCharValue(char c) {
768         StringBuilder sb = new StringBuilder();
769         sb.append('\'');
770         sb.append(esc(c, '\''));
771         sb.append('\'');
772         return sb.toString();
773     }
774 
775     private String getConstantStringValue(String s) {
776         StringBuilder sb = new StringBuilder();
777         sb.append("\"");
778         for (int i = 0; i < s.length(); i++) {
779             sb.append(esc(s.charAt(i), '"'));
780         }
781         sb.append("\"");
782         return sb.toString();
783     }
784 
785     private String esc(char c, char quote) {
786         if (32 <= c && c <= 126 && c != quote && c != '\\')
787             return String.valueOf(c);
788         else switch (c) {
789             case '\b': return "\\b";
790             case '\n': return "\\n";
791             case '\t': return "\\t";
792             case '\f': return "\\f";
793             case '\r': return "\\r";
794             case '\\': return "\\\\";
795             case '\'': return "\\'";
796             case '\"': return "\\\"";
797             default:   return String.format("\\u%04x", (int) c);
798         }
799     }
800 
801     private Set<String> getClassModifiers(AccessFlags flags) {
802         var flagSet = flagsReportUnknown(flags, cffv());
803         Set<AccessFlag> set;
804         if (flagSet.contains(AccessFlag.INTERFACE)) {
805             set = EnumSet.copyOf(flagSet);
806             set.remove(AccessFlag.ABSTRACT);
807         } else {
808             set = flagSet;
809         }
810         return getModifiers(set);
811     }
812 
813     private static Set<String> getModifiers(Set<AccessFlag> flags) {
814         Set<String> s = new LinkedHashSet<>();
815         for (var f : flags)
816             if (f.sourceModifier()) s.add(f == AccessFlag.STRICT ? "strictfp" : f.name().toLowerCase(Locale.ROOT));
817         return s;
818     }
819 
820     private Set<String> getClassFlags(AccessFlags flags) {
821         return getFlags(flags.flagsMask(), flagsReportUnknown(flags, cffv()));
822     }
823 
824     private static Set<String> getFlags(int mask, Set<AccessFlag> flags) {
825         Set<String> s = new LinkedHashSet<>();
826         for (var f: flags) {
827             s.add("ACC_" + f.name());
828             mask = mask & ~f.mask();
829         }
830         while (mask != 0) {
831             int bit = Integer.highestOneBit(mask);
832             s.add("0x" + Integer.toHexString(bit));
833             mask = mask & ~bit;
834         }
835         return s;
836     }
837 
838     private final Options options;
839     private final AttributeWriter attrWriter;
840     private final CodeWriter codeWriter;
841     private final ConstantWriter constantWriter;
842     private ClassModel classModel;
843     private URI uri;
844     private long lastModified;
845     private String digestName;
846     private byte[] digest;
847     private int size;
848     private MethodModel method;
849 }