content: /*
   * Copyright (c) 1999, 2021, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package openjdk.tools.javac.jvm;
  
  import java.io.*;
  import java.util.LinkedHashMap;
  import java.util.Map;
  import java.util.Set;
  import java.util.LinkedHashSet;
  import java.util.function.ToIntFunction;
  
  import jdkx.tools.JavaFileManager;
  import jdkx.tools.FileObject;
  import jdkx.tools.JavaFileManager.Location;
  import jdkx.tools.JavaFileObject;
  
  import openjdk.tools.javac.code.*;
  import openjdk.tools.javac.code.Attribute.RetentionPolicy;
  import openjdk.tools.javac.code.Directive.*;
  import openjdk.tools.javac.code.Source.Feature;
  import openjdk.tools.javac.code.Symbol.*;
  import openjdk.tools.javac.code.Type.*;
  import openjdk.tools.javac.code.Types.SignatureGenerator.InvalidSignatureException;
  import openjdk.tools.javac.comp.Check;
  import openjdk.tools.javac.file.PathFileObject;
  import openjdk.tools.javac.jvm.PoolConstant.LoadableConstant;
  import openjdk.tools.javac.jvm.PoolConstant.Dynamic.BsmKey;
  import openjdk.tools.javac.resources.CompilerProperties.Errors;
  import openjdk.tools.javac.resources.CompilerProperties.Fragments;
  import openjdk.tools.javac.util.*;
  import openjdk.tools.javac.util.List;
  
  import static openjdk.tools.javac.code.Flags.*;
  import static openjdk.tools.javac.code.Kinds.Kind.*;
  import static openjdk.tools.javac.code.Scope.LookupKind.NON_RECURSIVE;
  import static openjdk.tools.javac.code.TypeTag.*;
  import static openjdk.tools.javac.main.Option.*;
  
  import static jdkx.tools.StandardLocation.CLASS_OUTPUT;
  
  /** This class provides operations to map an internal symbol table graph
   *  rooted in a ClassSymbol into a classfile.
   *
   *  <p><b>This is NOT part of any supported API.
   *  If you write code that depends on this, you do so at your own risk.
   *  This code and its internal interfaces are subject to change or
   *  deletion without notice.</b>
   */
  public class ClassWriter extends ClassFile {
      protected static final Context.Key<ClassWriter> classWriterKey = new Context.Key<>();
  
      private final Symtab syms;
  
      private final Options options;
  
      /** Switch: verbose output.
       */
      private boolean verbose;
  
      /** Switch: emit source file attribute.
       */
      private boolean emitSourceFile;
  
      /** Switch: generate CharacterRangeTable attribute.
       */
      private boolean genCrt;
  
      /** Switch: describe the generated stackmap.
       */
      private boolean debugstackmap;
  
      /** Preview language level.
       */
      private Preview preview;
  
      /**
       * Target class version.
       */
      private Target target;
  
      /**
       * Source language version.
       */
      private Source source;
  
      /** Type utilities. */
      private Types types;
  
      private Check check;
  
      /**
       * If true, class files will be written in module-specific subdirectories
       * of the CLASS_OUTPUT location.
       */
      public boolean multiModuleMode;
  
      private List<ToIntFunction<Symbol>> extraAttributeHooks = List.nil();
  
      /** The initial sizes of the data and constant pool buffers.
       *  Sizes are increased when buffers get full.
       */
      static final int DATA_BUF_SIZE = 0x0fff0;
      static final int CLASS_BUF_SIZE = 0x1fff0;
  
      /** An output buffer for member info.
       */
      public ByteBuffer databuf = new ByteBuffer(DATA_BUF_SIZE);
  
      /** An output buffer for the constant pool.
       */
      ByteBuffer poolbuf = new ByteBuffer(CLASS_BUF_SIZE);
  
      /** The constant pool writer.
       */
      final PoolWriter poolWriter;
  
      /** The log to use for verbose output.
       */
      private final Log log;
  
      /** The name table. */
      private final Names names;
  
      /** Access to files. */
      private final JavaFileManager fileManager;
  
      /** The tags and constants used in compressed stackmap. */
      static final int SAME_FRAME_SIZE = 64;
      static final int SAME_LOCALS_1_STACK_ITEM_EXTENDED = 247;
      static final int SAME_FRAME_EXTENDED = 251;
      static final int FULL_FRAME = 255;
      static final int MAX_LOCAL_LENGTH_DIFF = 4;
  
      /** Get the ClassWriter instance for this context. */
      public static ClassWriter instance(Context context) {
          ClassWriter instance = context.get(classWriterKey);
          if (instance == null)
              instance = new ClassWriter(context);
          return instance;
      }
  
      /** Construct a class writer, given an options table.
       */
      protected ClassWriter(Context context) {
          context.put(classWriterKey, this);
  
          log = Log.instance(context);
          names = Names.instance(context);
          syms = Symtab.instance(context);
          options = Options.instance(context);
          preview = Preview.instance(context);
          target = Target.instance(context);
          source = Source.instance(context);
          types = Types.instance(context);
          check = Check.instance(context);
          fileManager = context.get(JavaFileManager.class);
          poolWriter = Gen.instance(context).poolWriter;
  
          verbose        = options.isSet(VERBOSE);
          genCrt         = options.isSet(XJCOV);
          debugstackmap = options.isSet("debug.stackmap");
  
          emitSourceFile = options.isUnset(G_CUSTOM) ||
                              options.isSet(G_CUSTOM, "source");
  
          String modifierFlags = options.get("debug.dumpmodifiers");
          if (modifierFlags != null) {
              dumpClassModifiers = modifierFlags.indexOf('c') != -1;
              dumpFieldModifiers = modifierFlags.indexOf('f') != -1;
              dumpInnerClassModifiers = modifierFlags.indexOf('i') != -1;
              dumpMethodModifiers = modifierFlags.indexOf('m') != -1;
          }
      }
  
      public void addExtraAttributes(ToIntFunction<Symbol> addExtraAttributes) {
          extraAttributeHooks = extraAttributeHooks.prepend(addExtraAttributes);
      }
  
  /******************************************************************
   * Diagnostics: dump generated class names and modifiers
   ******************************************************************/
  
      /** Value of option 'dumpmodifiers' is a string
       *  indicating which modifiers should be dumped for debugging:
       *    'c' -- classes
       *    'f' -- fields
       *    'i' -- innerclass attributes
       *    'm' -- methods
       *  For example, to dump everything:
       *    javac -XDdumpmodifiers=cifm MyProg.java
       */
      private boolean dumpClassModifiers; // -XDdumpmodifiers=c
      private boolean dumpFieldModifiers; // -XDdumpmodifiers=f
      private boolean dumpInnerClassModifiers; // -XDdumpmodifiers=i
      private boolean dumpMethodModifiers; // -XDdumpmodifiers=m
  
  
      /** Return flags as a string, separated by " ".
       */
      public static String flagNames(long flags) {
          StringBuilder sbuf = new StringBuilder();
          int i = 0;
          long f = flags & StandardFlags;
          while (f != 0) {
              if ((f & 1) != 0) {
                  sbuf.append(" ");
                  sbuf.append(flagName[i]);
              }
              f = f >> 1;
              i++;
          }
          return sbuf.toString();
      }
      //where
          private static final String[] flagName = {
              "PUBLIC", "PRIVATE", "PROTECTED", "STATIC", "FINAL",
              "SUPER", "VOLATILE", "TRANSIENT", "NATIVE", "INTERFACE",
              "ABSTRACT", "STRICTFP"};
  
  /******************************************************************
   * Output routines
   ******************************************************************/
  
      /** Write a character into given byte buffer;
       *  byte buffer will not be grown.
       */
      void putChar(ByteBuffer buf, int op, int x) {
          buf.elems[op  ] = (byte)((x >>  8) & 0xFF);
          buf.elems[op+1] = (byte)((x      ) & 0xFF);
      }
  
      /** Write an integer into given byte buffer;
       *  byte buffer will not be grown.
       */
      void putInt(ByteBuffer buf, int adr, int x) {
          buf.elems[adr  ] = (byte)((x >> 24) & 0xFF);
          buf.elems[adr+1] = (byte)((x >> 16) & 0xFF);
          buf.elems[adr+2] = (byte)((x >>  8) & 0xFF);
          buf.elems[adr+3] = (byte)((x      ) & 0xFF);
      }
  
  /******************************************************************
   * Writing the Constant Pool
   ******************************************************************/
  
      /** Thrown when the constant pool is over full.
       */
      public static class PoolOverflow extends RuntimeException {
          private static final long serialVersionUID = 0;
          public PoolOverflow() {}
      }
      public static class StringOverflow extends RuntimeException {
          private static final long serialVersionUID = 0;
          public final String value;
          public StringOverflow(String s) {
              value = s;
          }
      }
  
  /******************************************************************
   * Writing Attributes
   ******************************************************************/
  
      /** Write header for an attribute to data buffer and return
       *  position past attribute length index.
       */
      public int writeAttr(Name attrName) {
          int index = poolWriter.putName(attrName);
          databuf.appendChar(index);
          databuf.appendInt(0);
          return databuf.length;
      }
  
      /** Fill in attribute length.
       */
      public void endAttr(int index) {
          putInt(databuf, index - 4, databuf.length - index);
      }
  
      /** Leave space for attribute count and return index for
       *  number of attributes field.
       */
      int beginAttrs() {
          databuf.appendChar(0);
          return databuf.length;
      }
  
      /** Fill in number of attributes.
       */
      void endAttrs(int index, int count) {
          putChar(databuf, index - 2, count);
      }
  
      /** Write the EnclosingMethod attribute if needed.
       *  Returns the number of attributes written (0 or 1).
       */
      int writeEnclosingMethodAttribute(ClassSymbol c) {
          return writeEnclosingMethodAttribute(names.EnclosingMethod, c);
      }
  
      /** Write the EnclosingMethod attribute with a specified name.
       *  Returns the number of attributes written (0 or 1).
       */
      protected int writeEnclosingMethodAttribute(Name attributeName, ClassSymbol c) {
          if (c.owner.kind != MTH && // neither a local class
              c.name != names.empty) // nor anonymous
              return 0;
  
          int alenIdx = writeAttr(attributeName);
          ClassSymbol enclClass = c.owner.enclClass();
          MethodSymbol enclMethod =
              (c.owner.type == null // local to init block
               || c.owner.kind != MTH) // or member init
              ? null
              : ((MethodSymbol)c.owner).originalEnclosingMethod();
          databuf.appendChar(poolWriter.putClass(enclClass));
          databuf.appendChar(enclMethod == null ? 0 : poolWriter.putNameAndType(enclMethod));
          endAttr(alenIdx);
          return 1;
      }
  
      /** Write flag attributes; return number of attributes written.
       */
      int writeFlagAttrs(long flags) {
          int acount = 0;
          if ((flags & DEPRECATED) != 0) {
              int alenIdx = writeAttr(names.Deprecated);
              endAttr(alenIdx);
              acount++;
          }
          return acount;
      }
  
      /** Write member (field or method) attributes;
       *  return number of attributes written.
       */
      int writeMemberAttrs(Symbol sym, boolean isRecordComponent) {
          int acount = 0;
          if (!isRecordComponent) {
              acount = writeFlagAttrs(sym.flags());
          }
          long flags = sym.flags();
          if ((flags & (SYNTHETIC | BRIDGE)) != SYNTHETIC &&
              (flags & ANONCONSTR) == 0 &&
              (!types.isSameType(sym.type, sym.erasure(types)) ||
               poolWriter.signatureGen.hasTypeVar(sym.type.getThrownTypes()))) {
              // note that a local class with captured variables
              // will get a signature attribute
              int alenIdx = writeAttr(names.Signature);
              databuf.appendChar(poolWriter.putSignature(sym));
              endAttr(alenIdx);
              acount++;
          }
          acount += writeJavaAnnotations(sym.getRawAttributes());
          acount += writeExtraJavaAnnotations(sym.getRawAttributes());
          acount += writeTypeAnnotations(sym.getRawTypeAttributes(), false);
          acount += writeExtraTypeAnnotations(sym.getRawTypeAttributes());
          return acount;
      }
  
      /**Allows subclasses to write additional member attributes
       *
       * @return the number of attributes written
       */
      protected int writeExtraMemberAttributes(Symbol sym) {
          return 0;
      }
  
      /**
       * Write method parameter names attribute.
       */
      int writeMethodParametersAttr(MethodSymbol m) {
          MethodType ty = m.externalType(types).asMethodType();
          final int allparams = ty.argtypes.size();
          if (m.params != null && allparams != 0) {
              final int attrIndex = writeAttr(names.MethodParameters);
              databuf.appendByte(allparams);
              // Write extra parameters first
              for (VarSymbol s : m.extraParams) {
                  final int flags =
                      ((int) s.flags() & (FINAL | SYNTHETIC | MANDATED)) |
                      ((int) m.flags() & SYNTHETIC);
                  databuf.appendChar(poolWriter.putName(s.name));
                  databuf.appendChar(flags);
              }
              // Now write the real parameters
              for (VarSymbol s : m.params) {
                  final int flags =
                      ((int) s.flags() & (FINAL | SYNTHETIC | MANDATED)) |
                      ((int) m.flags() & SYNTHETIC);
                  databuf.appendChar(poolWriter.putName(s.name));
                  databuf.appendChar(flags);
              }
              // Now write the captured locals
              for (VarSymbol s : m.capturedLocals) {
                  final int flags =
                      ((int) s.flags() & (FINAL | SYNTHETIC | MANDATED)) |
                      ((int) m.flags() & SYNTHETIC);
                  databuf.appendChar(poolWriter.putName(s.name));
                  databuf.appendChar(flags);
              }
              endAttr(attrIndex);
              return 1;
          } else
              return 0;
      }
  
      private void writeParamAnnotations(List<VarSymbol> params,
                                         RetentionPolicy retention) {
          databuf.appendByte(params.length());
          for (VarSymbol s : params) {
              ListBuffer<Attribute.Compound> buf = new ListBuffer<>();
              for (Attribute.Compound a : s.getRawAttributes())
                  if (types.getRetention(a) == retention)
                      buf.append(a);
              databuf.appendChar(buf.length());
              for (Attribute.Compound a : buf)
                  writeCompoundAttribute(a);
          }
  
      }
  
      private void writeParamAnnotations(MethodSymbol m,
                                         RetentionPolicy retention) {
          databuf.appendByte(m.params.length());
          writeParamAnnotations(m.params, retention);
      }
  
      /** Write method parameter annotations;
       *  return number of attributes written.
       */
      int writeParameterAttrs(List<VarSymbol> vars) {
          boolean hasVisible = false;
          boolean hasInvisible = false;
          if (vars != null) {
              for (VarSymbol s : vars) {
                  for (Attribute.Compound a : s.getRawAttributes()) {
                      switch (types.getRetention(a)) {
                      case CLASS: hasInvisible = true; break;
                      case RUNTIME: hasVisible = true; break;
                      default: // /* fail soft */ throw new AssertionError(vis);
                      }
                  }
              }
          }
  
          int attrCount = 0;
          if (hasVisible) {
              int attrIndex = writeAttr(names.RuntimeVisibleParameterAnnotations);
              writeParamAnnotations(vars, RetentionPolicy.RUNTIME);
              endAttr(attrIndex);
              attrCount++;
          }
          if (hasInvisible) {
              int attrIndex = writeAttr(names.RuntimeInvisibleParameterAnnotations);
              writeParamAnnotations(vars, RetentionPolicy.CLASS);
              endAttr(attrIndex);
              attrCount++;
          }
          return attrCount;
      }
  
      /**Allows subclasses to write additional parameter attributes
       *
       * @return the number of attributes written
       */
      protected int writeExtraParameterAttributes(MethodSymbol m) {
          return 0;
      }
  /**********************************************************************
   * Writing Java-language annotations (aka metadata, attributes)
   **********************************************************************/
  
      /** Write Java-language annotations; return number of JVM
       *  attributes written (zero or one).
       */
      int writeJavaAnnotations(List<Attribute.Compound> attrs) {
          if (attrs.isEmpty()) return 0;
          ListBuffer<Attribute.Compound> visibles = new ListBuffer<>();
          ListBuffer<Attribute.Compound> invisibles = new ListBuffer<>();
          for (Attribute.Compound a : attrs) {
              switch (types.getRetention(a)) {
              case CLASS: invisibles.append(a); break;
              case RUNTIME: visibles.append(a); break;
              default: // /* fail soft */ throw new AssertionError(vis);
              }
          }
  
          int attrCount = 0;
          if (visibles.length() != 0) {
              int attrIndex = writeAttr(names.RuntimeVisibleAnnotations);
              databuf.appendChar(visibles.length());
              for (Attribute.Compound a : visibles)
                  writeCompoundAttribute(a);
              endAttr(attrIndex);
              attrCount++;
          }
          if (invisibles.length() != 0) {
              int attrIndex = writeAttr(names.RuntimeInvisibleAnnotations);
              databuf.appendChar(invisibles.length());
              for (Attribute.Compound a : invisibles)
                  writeCompoundAttribute(a);
              endAttr(attrIndex);
              attrCount++;
          }
          return attrCount;
      }
  
      /**Allows subclasses to write additional Java-language annotations
       *
       * @return the number of JVM attributes written
       */
      protected int writeExtraJavaAnnotations(List<Attribute.Compound> attrs) {
          return 0;
      }
  
      int writeTypeAnnotations(List<Attribute.TypeCompound> typeAnnos, boolean inCode) {
          if (typeAnnos.isEmpty()) return 0;
  
          ListBuffer<Attribute.TypeCompound> visibles = new ListBuffer<>();
          ListBuffer<Attribute.TypeCompound> invisibles = new ListBuffer<>();
  
          for (Attribute.TypeCompound tc : typeAnnos) {
              if (tc.hasUnknownPosition()) {
                  boolean fixed = tc.tryFixPosition();
  
                  // Could we fix it?
                  if (!fixed) {
                      // This happens for nested types like @A Outer. @B Inner.
                      // For method parameters we get the annotation twice! Once with
                      // a valid position, once unknown.
                      // TODO: find a cleaner solution.
                      PrintWriter pw = log.getWriter(Log.WriterKind.ERROR);
                      pw.println("ClassWriter: Position UNKNOWN in type annotation: " + tc);
                      continue;
                  }
              }
  
              if (tc.position.type.isLocal() != inCode)
                  continue;
              if (!tc.position.emitToClassfile())
                  continue;
              switch (types.getRetention(tc)) {
              case SOURCE: break;
              case CLASS: invisibles.append(tc); break;
              case RUNTIME: visibles.append(tc); break;
              default: // /* fail soft */ throw new AssertionError(vis);
              }
          }
  
          int attrCount = 0;
          if (visibles.length() != 0) {
              int attrIndex = writeAttr(names.RuntimeVisibleTypeAnnotations);
              databuf.appendChar(visibles.length());
              for (Attribute.TypeCompound p : visibles)
                  writeTypeAnnotation(p);
              endAttr(attrIndex);
              attrCount++;
          }
  
          if (invisibles.length() != 0) {
              int attrIndex = writeAttr(names.RuntimeInvisibleTypeAnnotations);
              databuf.appendChar(invisibles.length());
              for (Attribute.TypeCompound p : invisibles)
                  writeTypeAnnotation(p);
              endAttr(attrIndex);
              attrCount++;
          }
  
          return attrCount;
      }
  
      /**Allows subclasses to write additional type annotations
       *
       * @return the number of JVM attributes written
       */
      protected int writeExtraTypeAnnotations(List<Attribute.TypeCompound> attrs) {
          return 0;
      }
  
      /** A visitor to write an attribute including its leading
       *  single-character marker.
       */
      class AttributeWriter implements Attribute.Visitor {
          public void visitConstant(Attribute.Constant _value) {
              if (_value.type.getTag() == CLASS) {
                  Assert.check(_value.value instanceof String);
                  String s = (String)_value.value;
                  databuf.appendByte('s');
                  databuf.appendChar(poolWriter.putName(names.fromString(s)));
              } else {
                  switch (_value.type.getTag()) {
                      case BYTE:
                          databuf.appendByte('B');
                          break;
                      case CHAR:
                          databuf.appendByte('C');
                          break;
                      case SHORT:
                          databuf.appendByte('S');
                          break;
                      case INT:
                          databuf.appendByte('I');
                          break;
                      case LONG:
                          databuf.appendByte('J');
                          break;
                      case FLOAT:
                          databuf.appendByte('F');
                          break;
                      case DOUBLE:
                          databuf.appendByte('D');
                          break;
                      case BOOLEAN:
                          databuf.appendByte('Z');
                          break;
                      default:
                          throw new AssertionError(_value.type);
                  }
                  databuf.appendChar(poolWriter.putConstant(_value.value));
              }
          }
          public void visitEnum(Attribute.Enum e) {
              databuf.appendByte('e');
              databuf.appendChar(poolWriter.putDescriptor(e.value.type));
              databuf.appendChar(poolWriter.putName(e.value.name));
          }
          public void visitClass(Attribute.Class clazz) {
              databuf.appendByte('c');
              databuf.appendChar(poolWriter.putDescriptor(clazz.classType));
          }
          public void visitCompound(Attribute.Compound compound) {
              databuf.appendByte('@');
              writeCompoundAttribute(compound);
          }
          public void visitError(Attribute.Error x) {
              throw new AssertionError(x);
          }
          public void visitArray(Attribute.Array array) {
              databuf.appendByte('[');
              int count = array.values.length;
              for (Attribute a : array.values) {
                  if (a instanceof Attribute.Error) count--;
              }
              databuf.appendChar(count);
              for (Attribute a : array.values) {
                  if (a instanceof Attribute.Error) continue;
                  a.accept(this);
              }
          }
      }
      AttributeWriter awriter = new AttributeWriter();
  
      /** Write a compound attribute excluding the '@' marker. */
      void writeCompoundAttribute(Attribute.Compound c) {
          databuf.appendChar(poolWriter.putDescriptor(c.type));
          databuf.appendChar(c.values.length());
          for (Pair<Symbol.MethodSymbol,Attribute> p : c.values) {
              databuf.appendChar(poolWriter.putName(p.fst.name));
              p.snd.accept(awriter);
          }
      }
  
      protected void writeTypeAnnotation(Attribute.TypeCompound c) {
          writePosition(c.position);
          writeCompoundAttribute(c);
      }
  
      void writePosition(TypeAnnotationPosition p) {
          databuf.appendByte(p.type.targetTypeValue()); // TargetType tag is a byte
          switch (p.type) {
          // instanceof
          case INSTANCEOF:
          // new expression
          case NEW:
          // constructor/method reference receiver
          case CONSTRUCTOR_REFERENCE:
          case METHOD_REFERENCE:
              databuf.appendChar(p.offset);
              break;
          // local variable
          case LOCAL_VARIABLE:
          // resource variable
          case RESOURCE_VARIABLE:
              databuf.appendChar(p.lvarOffset.length);  // for table length
              for (int i = 0; i < p.lvarOffset.length; ++i) {
                  databuf.appendChar(p.lvarOffset[i]);
                  databuf.appendChar(p.lvarLength[i]);
                  databuf.appendChar(p.lvarIndex[i]);
              }
              break;
          // exception parameter
          case EXCEPTION_PARAMETER:
              databuf.appendChar(p.getExceptionIndex());
              break;
          // method receiver
          case METHOD_RECEIVER:
              // Do nothing
              break;
          // type parameter
          case CLASS_TYPE_PARAMETER:
          case METHOD_TYPE_PARAMETER:
              databuf.appendByte(p.parameter_index);
              break;
          // type parameter bound
          case CLASS_TYPE_PARAMETER_BOUND:
          case METHOD_TYPE_PARAMETER_BOUND:
              databuf.appendByte(p.parameter_index);
              databuf.appendByte(p.bound_index);
              break;
          // class extends or implements clause
          case CLASS_EXTENDS:
              databuf.appendChar(p.type_index);
              break;
          // throws
          case THROWS:
              databuf.appendChar(p.type_index);
              break;
          // method parameter
          case METHOD_FORMAL_PARAMETER:
              databuf.appendByte(p.parameter_index);
              break;
          // type cast
          case CAST:
          // method/constructor/reference type argument
          case CONSTRUCTOR_INVOCATION_TYPE_ARGUMENT:
          case METHOD_INVOCATION_TYPE_ARGUMENT:
          case CONSTRUCTOR_REFERENCE_TYPE_ARGUMENT:
          case METHOD_REFERENCE_TYPE_ARGUMENT:
              databuf.appendChar(p.offset);
              databuf.appendByte(p.type_index);
              break;
          // We don't need to worry about these
          case METHOD_RETURN:
          case FIELD:
              break;
          case UNKNOWN:
              throw new AssertionError("jvm.ClassWriter: UNKNOWN target type should never occur!");
          default:
              throw new AssertionError("jvm.ClassWriter: Unknown target type for position: " + p);
          }
  
          { // Append location data for generics/arrays.
              databuf.appendByte(p.location.size());
              java.util.List<Integer> loc = TypeAnnotationPosition.getBinaryFromTypePath(p.location);
              for (int i : loc)
                  databuf.appendByte((byte)i);
          }
      }
  
  /**********************************************************************
   * Writing module attributes
   **********************************************************************/
  
      /** Write the Module attribute if needed.
       *  Returns the number of attributes written (0 or 1).
       */
      int writeModuleAttribute(ClassSymbol c) {
          ModuleSymbol m = (ModuleSymbol) c.owner;
  
          int alenIdx = writeAttr(names.Module);
  
          databuf.appendChar(poolWriter.putModule(m));
          databuf.appendChar(ModuleFlags.value(m.flags)); // module_flags
          databuf.appendChar(m.version != null ? poolWriter.putName(m.version) : 0);
  
          ListBuffer<RequiresDirective> requires = new ListBuffer<>();
          for (RequiresDirective r: m.requires) {
              if (!r.flags.contains(RequiresFlag.EXTRA))
                  requires.add(r);
          }
          databuf.appendChar(requires.size());
          for (RequiresDirective r: requires) {
              databuf.appendChar(poolWriter.putModule(r.module));
              databuf.appendChar(RequiresFlag.value(r.flags));
              databuf.appendChar(r.module.version != null ? poolWriter.putName(r.module.version) : 0);
          }
  
          List<ExportsDirective> exports = m.exports;
          databuf.appendChar(exports.size());
          for (ExportsDirective e: exports) {
              databuf.appendChar(poolWriter.putPackage(e.packge));
              databuf.appendChar(ExportsFlag.value(e.flags));
              if (e.modules == null) {
                  databuf.appendChar(0);
              } else {
                  databuf.appendChar(e.modules.size());
                  for (ModuleSymbol msym: e.modules) {
                      databuf.appendChar(poolWriter.putModule(msym));
                  }
              }
          }
  
          List<OpensDirective> opens = m.opens;
          databuf.appendChar(opens.size());
          for (OpensDirective o: opens) {
              databuf.appendChar(poolWriter.putPackage(o.packge));
              databuf.appendChar(OpensFlag.value(o.flags));
              if (o.modules == null) {
                  databuf.appendChar(0);
              } else {
                  databuf.appendChar(o.modules.size());
                  for (ModuleSymbol msym: o.modules) {
                      databuf.appendChar(poolWriter.putModule(msym));
                  }
              }
          }
  
          List<UsesDirective> uses = m.uses;
          databuf.appendChar(uses.size());
          for (UsesDirective s: uses) {
              databuf.appendChar(poolWriter.putClass(s.service));
          }
  
          // temporary fix to merge repeated provides clause for same service;
          // eventually this should be disallowed when analyzing the module,
          // so that each service type only appears once.
          Map<ClassSymbol, Set<ClassSymbol>> mergedProvides = new LinkedHashMap<>();
          for (ProvidesDirective p : m.provides) {
              mergedProvides.computeIfAbsent(p.service, s -> new LinkedHashSet<>()).addAll(p.impls);
          }
          databuf.appendChar(mergedProvides.size());
          mergedProvides.forEach((srvc, impls) -> {
              databuf.appendChar(poolWriter.putClass(srvc));
              databuf.appendChar(impls.size());
              impls.forEach(impl -> databuf.appendChar(poolWriter.putClass(impl)));
          });
  
          endAttr(alenIdx);
          return 1;
      }
  
  /**********************************************************************
   * Writing Objects
   **********************************************************************/
  
      /** Write "inner classes" attribute.
       */
      void writeInnerClasses() {
          int alenIdx = writeAttr(names.InnerClasses);
          databuf.appendChar(poolWriter.innerClasses.size());
          for (ClassSymbol inner : poolWriter.innerClasses) {
              inner.markAbstractIfNeeded(types);
              char flags = (char) adjustFlags(inner.flags_field);
              if ((flags & INTERFACE) != 0) flags |= ABSTRACT; // Interfaces are always ABSTRACT
              flags &= ~STRICTFP; //inner classes should not have the strictfp flag set.
              if (dumpInnerClassModifiers) {
                  PrintWriter pw = log.getWriter(Log.WriterKind.ERROR);
                  pw.println("INNERCLASS  " + inner.name);
                  pw.println("---" + flagNames(flags));
              }
              databuf.appendChar(poolWriter.putClass(inner));
              databuf.appendChar(
                  inner.owner.kind == TYP && !inner.name.isEmpty() ? poolWriter.putClass((ClassSymbol)inner.owner) : 0);
              databuf.appendChar(
                  !inner.name.isEmpty() ? poolWriter.putName(inner.name) : 0);
              databuf.appendChar(flags);
          }
          endAttr(alenIdx);
      }
  
      int writeRecordAttribute(ClassSymbol csym) {
          int alenIdx = writeAttr(names.Record);
          Scope s = csym.members();
          databuf.appendChar(csym.getRecordComponents().size());
          for (VarSymbol v: csym.getRecordComponents()) {
              //databuf.appendChar(poolWriter.putMember(v.accessor.head.snd));
              databuf.appendChar(poolWriter.putName(v.name));
              databuf.appendChar(poolWriter.putDescriptor(v));
              int acountIdx = beginAttrs();
              int acount = 0;
              acount += writeMemberAttrs(v, true);
              endAttrs(acountIdx, acount);
          }
          endAttr(alenIdx);
          return 1;
      }
  
      /**
       * Write NestMembers attribute (if needed)
       */
      int writeNestMembersIfNeeded(ClassSymbol csym) {
          ListBuffer<ClassSymbol> nested = new ListBuffer<>();
          listNested(csym, nested);
          Set<ClassSymbol> nestedUnique = new LinkedHashSet<>(nested);
          if (csym.owner.kind == PCK && !nestedUnique.isEmpty()) {
              int alenIdx = writeAttr(names.NestMembers);
              databuf.appendChar(nestedUnique.size());
              for (ClassSymbol s : nestedUnique) {
                  databuf.appendChar(poolWriter.putClass(s));
              }
              endAttr(alenIdx);
              return 1;
          }
          return 0;
      }
  
      /**
       * Write NestHost attribute (if needed)
       */
      int writeNestHostIfNeeded(ClassSymbol csym) {
          if (csym.owner.kind != PCK) {
              int alenIdx = writeAttr(names.NestHost);
              databuf.appendChar(poolWriter.putClass(csym.outermostClass()));
              endAttr(alenIdx);
              return 1;
          }
          return 0;
      }
  
      private void listNested(Symbol sym, ListBuffer<ClassSymbol> seen) {
          if (sym.kind != TYP) return;
          ClassSymbol csym = (ClassSymbol)sym;
          if (csym.owner.kind != PCK) {
              seen.add(csym);
          }
          if (csym.members() != null) {
              for (Symbol s : sym.members().getSymbols()) {
                  listNested(s, seen);
              }
          }
          if (csym.trans_local != null) {
              for (Symbol s : csym.trans_local) {
                  listNested(s, seen);
              }
          }
      }
  
      /** Write "PermittedSubclasses" attribute.
       */
      int writePermittedSubclassesIfNeeded(ClassSymbol csym) {
          if (csym.permitted.nonEmpty()) {
              int alenIdx = writeAttr(names.PermittedSubclasses);
              databuf.appendChar(csym.permitted.size());
              for (Symbol c : csym.permitted) {
                  databuf.appendChar(poolWriter.putClass((ClassSymbol) c));
              }
              endAttr(alenIdx);
              return 1;
          }
          return 0;
      }
  
      /** Write "bootstrapMethods" attribute.
       */
      void writeBootstrapMethods() {
          int alenIdx = writeAttr(names.BootstrapMethods);
          databuf.appendChar(poolWriter.bootstrapMethods.size());
          for (BsmKey bsmKey : poolWriter.bootstrapMethods.keySet()) {
              //write BSM handle
              databuf.appendChar(poolWriter.putConstant(bsmKey.bsm));
              LoadableConstant[] uniqueArgs = bsmKey.staticArgs;
              //write static args length
              databuf.appendChar(uniqueArgs.length);
              //write static args array
              for (LoadableConstant arg : uniqueArgs) {
                  databuf.appendChar(poolWriter.putConstant(arg));
              }
          }
          endAttr(alenIdx);
      }
  
      /** Write field symbol, entering all references into constant pool.
       */
      void writeField(VarSymbol v) {
          int flags = adjustFlags(v.flags());
          databuf.appendChar(flags);
          if (dumpFieldModifiers) {
              PrintWriter pw = log.getWriter(Log.WriterKind.ERROR);
              pw.println("FIELD  " + v.name);
              pw.println("---" + flagNames(v.flags()));
          }
          databuf.appendChar(poolWriter.putName(v.name));
          databuf.appendChar(poolWriter.putDescriptor(v));
          int acountIdx = beginAttrs();
          int acount = 0;
          if (v.getConstValue() != null) {
              int alenIdx = writeAttr(names.ConstantValue);
              databuf.appendChar(poolWriter.putConstant(v.getConstValue()));
              endAttr(alenIdx);
              acount++;
          }
          acount += writeMemberAttrs(v, false);
  		acount += writeExtraAttributes(v);
          acount += writeExtraMemberAttributes(v);
          endAttrs(acountIdx, acount);
      }
  
      /** Write method symbol, entering all references into constant pool.
       */
      void writeMethod(MethodSymbol m) {
          int flags = adjustFlags(m.flags());
          databuf.appendChar(flags);
          if (dumpMethodModifiers) {
              PrintWriter pw = log.getWriter(Log.WriterKind.ERROR);
              pw.println("METHOD  " + m.name);
              pw.println("---" + flagNames(m.flags()));
          }
          databuf.appendChar(poolWriter.putName(m.name));
          databuf.appendChar(poolWriter.putDescriptor(m));
          int acountIdx = beginAttrs();
          int acount = 0;
          if (m.code != null) {
              int alenIdx = writeAttr(names.Code);
              writeCode(m.code);
              endAttr(alenIdx);
              acount++;
          }
          List<Type> thrown = m.erasure(types).getThrownTypes();
          if (thrown.nonEmpty()) {
              int alenIdx = writeAttr(names.Exceptions);
              databuf.appendChar(thrown.length());
              for (List<Type> l = thrown; l.nonEmpty(); l = l.tail)
                  databuf.appendChar(poolWriter.putClass(l.head));
              endAttr(alenIdx);
              acount++;
          }
          if (m.defaultValue != null) {
              int alenIdx = writeAttr(names.AnnotationDefault);
              m.defaultValue.accept(awriter);
              endAttr(alenIdx);
              acount++;
          }
          if (target.hasMethodParameters() && (options.isSet(PARAMETERS) || m.isConstructor() && (m.flags_field & RECORD) != 0)) {
              if (!m.isLambdaMethod()) // Per JDK-8138729, do not emit parameters table for lambda bodies.
                  acount += writeMethodParametersAttr(m);
          }
          acount += writeMemberAttrs(m, false);
          acount += writeExtraMemberAttributes(m);
          if (!m.isLambdaMethod()) {
              acount += writeParameterAttrs(m.params);
              acount += writeExtraParameterAttributes(m);
          }
  		acount += writeExtraAttributes(m);
          endAttrs(acountIdx, acount);
          m.code = null; // to conserve space
      }
  
      /** Write code attribute of method.
       */
      void writeCode(Code code) {
          databuf.appendChar(code.max_stack);
          databuf.appendChar(code.max_locals);
          databuf.appendInt(code.cp);
          databuf.appendBytes(code.code, 0, code.cp);
          databuf.appendChar(code.catchInfo.length());
          for (List<char[]> l = code.catchInfo.toList();
               l.nonEmpty();
               l = l.tail) {
              for (int i = 0; i < l.head.length; i++)
                  databuf.appendChar(l.head[i]);
          }
          int acountIdx = beginAttrs();
          int acount = 0;
  
          if (code.lineInfo.nonEmpty()) {
              int alenIdx = writeAttr(names.LineNumberTable);
              databuf.appendChar(code.lineInfo.length());
              for (List<char[]> l = code.lineInfo.reverse();
                   l.nonEmpty();
                   l = l.tail)
                  for (int i = 0; i < l.head.length; i++)
                      databuf.appendChar(l.head[i]);
              endAttr(alenIdx);
              acount++;
          }
  
          if (genCrt && (code.crt != null)) {
              CRTable crt = code.crt;
              int alenIdx = writeAttr(names.CharacterRangeTable);
              int crtIdx = beginAttrs();
              int crtEntries = crt.writeCRT(databuf, code.lineMap, log);
              endAttrs(crtIdx, crtEntries);
              endAttr(alenIdx);
              acount++;
          }
  
          // counter for number of generic local variables
          if (code.varDebugInfo && code.varBufferSize > 0) {
              int nGenericVars = 0;
              int alenIdx = writeAttr(names.LocalVariableTable);
              databuf.appendChar(code.getLVTSize());
              for (int i=0; i<code.varBufferSize; i++) {
                  Code.LocalVar var = code.varBuffer[i];
  
                  for (Code.LocalVar.Range r: var.aliveRanges) {
                      // write variable info
                      Assert.check(r.start_pc >= 0
                              && r.start_pc <= code.cp);
                      databuf.appendChar(r.start_pc);
                      Assert.check(r.length > 0
                              && (r.start_pc + r.length) <= code.cp);
                      databuf.appendChar(r.length);
                      VarSymbol sym = var.sym;
                      databuf.appendChar(poolWriter.putName(sym.name));
                      databuf.appendChar(poolWriter.putDescriptor(sym));
                      databuf.appendChar(var.reg);
                      if (needsLocalVariableTypeEntry(var.sym.type)) {
                          nGenericVars++;
                      }
                  }
              }
              endAttr(alenIdx);
              acount++;
  
              if (nGenericVars > 0) {
                  alenIdx = writeAttr(names.LocalVariableTypeTable);
                  databuf.appendChar(nGenericVars);
                  int count = 0;
  
                  for (int i=0; i<code.varBufferSize; i++) {
                      Code.LocalVar var = code.varBuffer[i];
                      VarSymbol sym = var.sym;
                      if (!needsLocalVariableTypeEntry(sym.type))
                          continue;
                      for (Code.LocalVar.Range r : var.aliveRanges) {
                          // write variable info
                          databuf.appendChar(r.start_pc);
                          databuf.appendChar(r.length);
                          databuf.appendChar(poolWriter.putName(sym.name));
                          databuf.appendChar(poolWriter.putSignature(sym));
                          databuf.appendChar(var.reg);
                          count++;
                      }
                  }
                  Assert.check(count == nGenericVars);
                  endAttr(alenIdx);
                  acount++;
              }
          }
  
          if (code.stackMapBufferSize > 0) {
              if (debugstackmap) System.out.println("Stack map for " + code.meth);
              int alenIdx = writeAttr(code.stackMap.getAttributeName(names));
              writeStackMap(code);
              endAttr(alenIdx);
              acount++;
          }
  
          acount += writeTypeAnnotations(code.meth.getRawTypeAttributes(), true);
  
          endAttrs(acountIdx, acount);
      }
      //where
      private boolean needsLocalVariableTypeEntry(Type t) {
          //a local variable needs a type-entry if its type T is generic
          //(i.e. |T| != T) and if it's not an non-denotable type (non-denotable
          // types are not supported in signature attribute grammar!)
          return !types.isSameType(t, types.erasure(t)) &&
                  check.checkDenotable(t);
      }
  
      void writeStackMap(Code code) {
          int nframes = code.stackMapBufferSize;
          if (debugstackmap) System.out.println(" nframes = " + nframes);
          databuf.appendChar(nframes);
  
          switch (code.stackMap) {
          case CLDC:
              for (int i=0; i<nframes; i++) {
                  if (debugstackmap) System.out.print("  " + i + ":");
                  Code.StackMapFrame frame = code.stackMapBuffer[i];
  
                  // output PC
                  if (debugstackmap) System.out.print(" pc=" + frame.pc);
                  databuf.appendChar(frame.pc);
  
                  // output locals
                  int localCount = 0;
                  for (int j=0; j<frame.locals.length;
                       j += Code.width(frame.locals[j])) {
                      localCount++;
                  }
                  if (debugstackmap) System.out.print(" nlocals=" +
                                                      localCount);
                  databuf.appendChar(localCount);
                  for (int j=0; j<frame.locals.length;
                       j += Code.width(frame.locals[j])) {
                      if (debugstackmap) System.out.print(" local[" + j + "]=");
                      writeStackMapType(frame.locals[j]);
                  }
  
                  // output stack
                  int stackCount = 0;
                  for (int j=0; j<frame.stack.length;
                       j += Code.width(frame.stack[j])) {
                      stackCount++;
                  }
                  if (debugstackmap) System.out.print(" nstack=" +
                                                      stackCount);
                  databuf.appendChar(stackCount);
                  for (int j=0; j<frame.stack.length;
                       j += Code.width(frame.stack[j])) {
                      if (debugstackmap) System.out.print(" stack[" + j + "]=");
                      writeStackMapType(frame.stack[j]);
                  }
                  if (debugstackmap) System.out.println();
              }
              break;
          case JSR202: {
              Assert.checkNull(code.stackMapBuffer);
              for (int i=0; i<nframes; i++) {
                  if (debugstackmap) System.out.print("  " + i + ":");
                  StackMapTableFrame frame = code.stackMapTableBuffer[i];
                  frame.write(this);
                  if (debugstackmap) System.out.println();
              }
              break;
          }
          default:
              throw new AssertionError("Unexpected stackmap format value");
          }
      }
  
          //where
          void writeStackMapType(Type t) {
              if (t == null) {
                  if (debugstackmap) System.out.print("empty");
                  databuf.appendByte(0);
              }
              else switch(t.getTag()) {
              case BYTE:
              case CHAR:
              case SHORT:
              case INT:
              case BOOLEAN:
                  if (debugstackmap) System.out.print("int");
                  databuf.appendByte(1);
                  break;
              case FLOAT:
                  if (debugstackmap) System.out.print("float");
                  databuf.appendByte(2);
                  break;
              case DOUBLE:
                  if (debugstackmap) System.out.print("double");
                  databuf.appendByte(3);
                  break;
              case LONG:
                  if (debugstackmap) System.out.print("long");
                  databuf.appendByte(4);
                  break;
              case BOT: // null
                  if (debugstackmap) System.out.print("null");
                  databuf.appendByte(5);
                  break;
              case ERROR:
                  t = syms.objectType;
              case CLASS:
              case ARRAY:
              case TYPEVAR:
                  if (debugstackmap) System.out.print("object(" + types.erasure(t).tsym + ")");
                  databuf.appendByte(7);
                  databuf.appendChar(poolWriter.putClass(types.erasure(t)));
                  break;
              case UNINITIALIZED_THIS:
                  if (debugstackmap) System.out.print("uninit_this");
                  databuf.appendByte(6);
                  break;
              case UNINITIALIZED_OBJECT:
                  { UninitializedType uninitType = (UninitializedType)t;
                  databuf.appendByte(8);
                  if (debugstackmap) System.out.print("uninit_object@" + uninitType.offset);
                  databuf.appendChar(uninitType.offset);
                  }
                  break;
              default:
                  throw new AssertionError();
              }
          }
  
      /** An entry in the JSR202 StackMapTable */
      abstract static class StackMapTableFrame {
          abstract int getFrameType();
  
          void write(ClassWriter writer) {
              int frameType = getFrameType();
              writer.databuf.appendByte(frameType);
              if (writer.debugstackmap) System.out.print(" frame_type=" + frameType);
          }
  
          static class SameFrame extends StackMapTableFrame {
              final int offsetDelta;
              SameFrame(int offsetDelta) {
                  this.offsetDelta = offsetDelta;
              }
              int getFrameType() {
                  return (offsetDelta < SAME_FRAME_SIZE) ? offsetDelta : SAME_FRAME_EXTENDED;
              }
              @Override
              void write(ClassWriter writer) {
                  super.write(writer);
                  if (getFrameType() == SAME_FRAME_EXTENDED) {
                      writer.databuf.appendChar(offsetDelta);
                      if (writer.debugstackmap){
                          System.out.print(" offset_delta=" + offsetDelta);
                      }
                  }
              }
          }
  
          static class SameLocals1StackItemFrame extends StackMapTableFrame {
              final int offsetDelta;
              final Type stack;
              SameLocals1StackItemFrame(int offsetDelta, Type stack) {
                  this.offsetDelta = offsetDelta;
                  this.stack = stack;
              }
              int getFrameType() {
                  return (offsetDelta < SAME_FRAME_SIZE) ?
                         (SAME_FRAME_SIZE + offsetDelta) :
                         SAME_LOCALS_1_STACK_ITEM_EXTENDED;
              }
              @Override
              void write(ClassWriter writer) {
                  super.write(writer);
                  if (getFrameType() == SAME_LOCALS_1_STACK_ITEM_EXTENDED) {
                      writer.databuf.appendChar(offsetDelta);
                      if (writer.debugstackmap) {
                          System.out.print(" offset_delta=" + offsetDelta);
                      }
                  }
                  if (writer.debugstackmap) {
                      System.out.print(" stack[" + 0 + "]=");
                  }
                  writer.writeStackMapType(stack);
              }
          }
  
          static class ChopFrame extends StackMapTableFrame {
              final int frameType;
              final int offsetDelta;
              ChopFrame(int frameType, int offsetDelta) {
                  this.frameType = frameType;
                  this.offsetDelta = offsetDelta;
              }
              int getFrameType() { return frameType; }
              @Override
              void write(ClassWriter writer) {
                  super.write(writer);
                  writer.databuf.appendChar(offsetDelta);
                  if (writer.debugstackmap) {
                      System.out.print(" offset_delta=" + offsetDelta);
                  }
              }
          }
  
          static class AppendFrame extends StackMapTableFrame {
              final int frameType;
              final int offsetDelta;
              final Type[] locals;
              AppendFrame(int frameType, int offsetDelta, Type[] locals) {
                  this.frameType = frameType;
                  this.offsetDelta = offsetDelta;
                  this.locals = locals;
              }
              int getFrameType() { return frameType; }
              @Override
              void write(ClassWriter writer) {
                  super.write(writer);
                  writer.databuf.appendChar(offsetDelta);
                  if (writer.debugstackmap) {
                      System.out.print(" offset_delta=" + offsetDelta);
                  }
                  for (int i=0; i<locals.length; i++) {
                       if (writer.debugstackmap) System.out.print(" locals[" + i + "]=");
                       writer.writeStackMapType(locals[i]);
                  }
              }
          }
  
          static class FullFrame extends StackMapTableFrame {
              final int offsetDelta;
              final Type[] locals;
              final Type[] stack;
              FullFrame(int offsetDelta, Type[] locals, Type[] stack) {
                  this.offsetDelta = offsetDelta;
                  this.locals = locals;
                  this.stack = stack;
              }
              int getFrameType() { return FULL_FRAME; }
              @Override
              void write(ClassWriter writer) {
                  super.write(writer);
                  writer.databuf.appendChar(offsetDelta);
                  writer.databuf.appendChar(locals.length);
                  if (writer.debugstackmap) {
                      System.out.print(" offset_delta=" + offsetDelta);
                      System.out.print(" nlocals=" + locals.length);
                  }
                  for (int i=0; i<locals.length; i++) {
                      if (writer.debugstackmap) System.out.print(" locals[" + i + "]=");
                      writer.writeStackMapType(locals[i]);
                  }
  
                  writer.databuf.appendChar(stack.length);
                  if (writer.debugstackmap) { System.out.print(" nstack=" + stack.length); }
                  for (int i=0; i<stack.length; i++) {
                      if (writer.debugstackmap) System.out.print(" stack[" + i + "]=");
                      writer.writeStackMapType(stack[i]);
                  }
              }
          }
  
         /** Compare this frame with the previous frame and produce
          *  an entry of compressed stack map frame. */
          static StackMapTableFrame getInstance(Code.StackMapFrame this_frame,
                                                int prev_pc,
                                                Type[] prev_locals,
                                                Types types) {
              Type[] locals = this_frame.locals;
              Type[] stack = this_frame.stack;
              int offset_delta = this_frame.pc - prev_pc - 1;
              if (stack.length == 1) {
                  if (locals.length == prev_locals.length
                      && compare(prev_locals, locals, types) == 0) {
                      return new SameLocals1StackItemFrame(offset_delta, stack[0]);
                  }
              } else if (stack.length == 0) {
                  int diff_length = compare(prev_locals, locals, types);
                  if (diff_length == 0) {
                      return new SameFrame(offset_delta);
                  } else if (-MAX_LOCAL_LENGTH_DIFF < diff_length && diff_length < 0) {
                      // APPEND
                      Type[] local_diff = new Type[-diff_length];
                      for (int i=prev_locals.length, j=0; i<locals.length; i++,j++) {
                          local_diff[j] = locals[i];
                      }
                      return new AppendFrame(SAME_FRAME_EXTENDED - diff_length,
                                             offset_delta,
                                             local_diff);
                  } else if (0 < diff_length && diff_length < MAX_LOCAL_LENGTH_DIFF) {
                      // CHOP
                      return new ChopFrame(SAME_FRAME_EXTENDED - diff_length,
                                           offset_delta);
                  }
              }
              // FULL_FRAME
              return new FullFrame(offset_delta, locals, stack);
          }
  
          static boolean isInt(Type t) {
              return (t.getTag().isStrictSubRangeOf(INT)  || t.hasTag(BOOLEAN));
          }
  
          static boolean isSameType(Type t1, Type t2, Types types) {
              if (t1 == null) { return t2 == null; }
              if (t2 == null) { return false; }
  
              if (isInt(t1) && isInt(t2)) { return true; }
  
              if (t1.hasTag(UNINITIALIZED_THIS)) {
                  return t2.hasTag(UNINITIALIZED_THIS);
              } else if (t1.hasTag(UNINITIALIZED_OBJECT)) {
                  if (t2.hasTag(UNINITIALIZED_OBJECT)) {
                      return ((UninitializedType)t1).offset == ((UninitializedType)t2).offset;
                  } else {
                      return false;
                  }
              } else if (t2.hasTag(UNINITIALIZED_THIS) || t2.hasTag(UNINITIALIZED_OBJECT)) {
                  return false;
              }
  
              return types.isSameType(t1, t2);
          }
  
          static int compare(Type[] arr1, Type[] arr2, Types types) {
              int diff_length = arr1.length - arr2.length;
              if (diff_length > MAX_LOCAL_LENGTH_DIFF || diff_length < -MAX_LOCAL_LENGTH_DIFF) {
                  return Integer.MAX_VALUE;
              }
              int len = (diff_length > 0) ? arr2.length : arr1.length;
              for (int i=0; i<len; i++) {
                  if (!isSameType(arr1[i], arr2[i], types)) {
                      return Integer.MAX_VALUE;
                  }
              }
              return diff_length;
          }
      }
  
      void writeFields(Scope s) {
          // process them in reverse sibling order;
          // i.e., process them in declaration order.
          List<VarSymbol> vars = List.nil();
          for (Symbol sym : s.getSymbols(NON_RECURSIVE)) {
              if (sym.kind == VAR) vars = vars.prepend((VarSymbol)sym);
          }
          while (vars.nonEmpty()) {
              writeField(vars.head);
              vars = vars.tail;
          }
      }
  
      void writeMethods(Scope s) {
          List<MethodSymbol> methods = List.nil();
          for (Symbol sym : s.getSymbols(NON_RECURSIVE)) {
              if (sym.kind == MTH && (sym.flags() & HYPOTHETICAL) == 0)
                  methods = methods.prepend((MethodSymbol)sym);
          }
          while (methods.nonEmpty()) {
              writeMethod(methods.head);
              methods = methods.tail;
          }
      }
  
      /** Emit a class file for a given class.
       *  @param c      The class from which a class file is generated.
       */
      public JavaFileObject writeClass(ClassSymbol c)
          throws IOException, PoolOverflow, StringOverflow
      {
          String name = (c.owner.kind == MDL ? c.name : c.flatname).toString();
          Location outLocn;
          if (multiModuleMode) {
              ModuleSymbol msym = c.owner.kind == MDL ? (ModuleSymbol) c.owner : c.packge().modle;
              outLocn = fileManager.getLocationForModule(CLASS_OUTPUT, msym.name.toString());
          } else {
              outLocn = CLASS_OUTPUT;
          }
          if (outLocn == null) {
              return null;
          }
          JavaFileObject outFile
              = fileManager.getJavaFileForOutput(outLocn,
                                                 name,
                                                 JavaFileObject.Kind.CLASS,
                                                 c.sourcefile);
          OutputStream out = outFile.openOutputStream();
          try {
              writeClassFile(out, c);
              if (verbose)
                  log.printVerbose("wrote.file", outFile.getName());
              out.close();
              out = null;
          } catch (InvalidSignatureException ex) {
              log.error(Errors.CannotGenerateClass(c, Fragments.IllegalSignature(c, ex.type())));
          } finally {
              if (out != null) {
                  // if we are propagating an exception, delete the file
                  out.close();
                  outFile.delete();
                  outFile = null;
              }
          }
          return outFile; // may be null if write failed
      }
  
      /** Write class `c' to outstream `out'.
       */
      public void writeClassFile(OutputStream out, ClassSymbol c)
          throws IOException, PoolOverflow, StringOverflow {
          Assert.check((c.flags() & COMPOUND) == 0);
          databuf.reset();
          poolbuf.reset();
  
          Type supertype = types.supertype(c.type);
          List<Type> interfaces = types.interfaces(c.type);
          List<Type> typarams = c.type.getTypeArguments();
  
          int flags;
          if (c.owner.kind == MDL) {
              flags = ACC_MODULE;
          } else {
              flags = adjustFlags(c.flags() & ~DEFAULT);
              if ((flags & PROTECTED) != 0) flags |= PUBLIC;
              flags = flags & ClassFlags & ~STRICTFP;
              if ((flags & INTERFACE) == 0) flags |= ACC_SUPER;
          }
  
          if (dumpClassModifiers) {
              PrintWriter pw = log.getWriter(Log.WriterKind.ERROR);
              pw.println();
              pw.println("CLASSFILE  " + c.getQualifiedName());
              pw.println("---" + flagNames(flags));
          }
          databuf.appendChar(flags);
  
          if (c.owner.kind == MDL) {
              PackageSymbol unnamed = ((ModuleSymbol) c.owner).unnamedPackage;
              databuf.appendChar(poolWriter.putClass(new ClassSymbol(0, names.module_info, unnamed)));
          } else {
              databuf.appendChar(poolWriter.putClass(c));
          }
          databuf.appendChar(supertype.hasTag(CLASS) ? poolWriter.putClass((ClassSymbol)supertype.tsym) : 0);
          databuf.appendChar(interfaces.length());
          for (List<Type> l = interfaces; l.nonEmpty(); l = l.tail)
              databuf.appendChar(poolWriter.putClass((ClassSymbol)l.head.tsym));
          int fieldsCount = 0;
          int methodsCount = 0;
          for (Symbol sym : c.members().getSymbols(NON_RECURSIVE)) {
              switch (sym.kind) {
              case VAR: fieldsCount++; break;
              case MTH: if ((sym.flags() & HYPOTHETICAL) == 0) methodsCount++;
                        break;
              case TYP: poolWriter.enterInner((ClassSymbol)sym); break;
              default : Assert.error();
              }
          }
  
          if (c.trans_local != null) {
              for (ClassSymbol local : c.trans_local) {
                  poolWriter.enterInner(local);
              }
          }
  
          databuf.appendChar(fieldsCount);
          writeFields(c.members());
          databuf.appendChar(methodsCount);
          writeMethods(c.members());
  
          int acountIdx = beginAttrs();
          int acount = 0;
  
          boolean sigReq =
              typarams.length() != 0 || supertype.allparams().length() != 0;
          for (List<Type> l = interfaces; !sigReq && l.nonEmpty(); l = l.tail)
              sigReq = l.head.allparams().length() != 0;
          if (sigReq) {
              int alenIdx = writeAttr(names.Signature);
              databuf.appendChar(poolWriter.putSignature(c));
              endAttr(alenIdx);
              acount++;
          }
  
          if (c.sourcefile != null && emitSourceFile) {
              int alenIdx = writeAttr(names.SourceFile);
              // WHM 6/29/1999: Strip file path prefix.  We do it here at
              // the last possible moment because the sourcefile may be used
              // elsewhere in error diagnostics. Fixes 4241573.
              String simpleName = PathFileObject.getSimpleName(c.sourcefile);
              databuf.appendChar(poolWriter.putName(names.fromString(simpleName)));
              endAttr(alenIdx);
              acount++;
          }
  
          if (genCrt) {
              // Append SourceID attribute
              int alenIdx = writeAttr(names.SourceID);
              databuf.appendChar(poolWriter.putName(names.fromString(Long.toString(getLastModified(c.sourcefile)))));
              endAttr(alenIdx);
              acount++;
              // Append CompilationID attribute
              alenIdx = writeAttr(names.CompilationID);
              databuf.appendChar(poolWriter.putName(names.fromString(Long.toString(System.currentTimeMillis()))));
              endAttr(alenIdx);
              acount++;
          }
  
          acount += writeFlagAttrs(c.flags());
          acount += writeJavaAnnotations(c.getRawAttributes());
          acount += writeExtraJavaAnnotations(c.getRawAttributes());
          acount += writeTypeAnnotations(c.getRawTypeAttributes(), false);
          acount += writeExtraTypeAnnotations(c.getRawTypeAttributes());
          acount += writeEnclosingMethodAttribute(c);
          if (c.owner.kind == MDL) {
              acount += writeModuleAttribute(c);
              acount += writeFlagAttrs(c.owner.flags() & ~DEPRECATED);
          }
          acount += writeExtraClassAttributes(c);
          acount += writeExtraAttributes(c);
  
          poolbuf.appendInt(JAVA_MAGIC);
          if (preview.isEnabled() && preview.usesPreview(c.sourcefile)) {
              poolbuf.appendChar(ClassFile.PREVIEW_MINOR_VERSION);
          } else {
              poolbuf.appendChar(target.minorVersion);
          }
          poolbuf.appendChar(target.majorVersion);
  
          if (c.owner.kind != MDL) {
              if (target.hasNestmateAccess()) {
                  acount += writeNestMembersIfNeeded(c);
                  acount += writeNestHostIfNeeded(c);
              }
          }
  
          if (c.isRecord()) {
              acount += writeRecordAttribute(c);
          }
  
          if (target.hasSealedClasses()) {
              acount += writePermittedSubclassesIfNeeded(c);
          }
  
          if (!poolWriter.bootstrapMethods.isEmpty()) {
              writeBootstrapMethods();
              acount++;
          }
  
          if (!poolWriter.innerClasses.isEmpty()) {
              writeInnerClasses();
              acount++;
          }
  
          endAttrs(acountIdx, acount);
  
          out.write(poolbuf.elems, 0, poolbuf.length);
  
          poolWriter.writePool(out);
          poolWriter.reset(); // to save space
  
          out.write(databuf.elems, 0, databuf.length);
      }
  
       /**Allows subclasses to write additional class attributes
        *
        * @return the number of attributes written
        */
      protected int writeExtraClassAttributes(ClassSymbol c) {
          return 0;
      }
  
      /**Allows friends to write additional attributes
       *
       * @return the number of attributes written
       */
      protected int writeExtraAttributes(Symbol sym) {
          int i = 0;
          for (ToIntFunction<Symbol> hook : extraAttributeHooks) {
              i += hook.applyAsInt(sym);
          }
          return i;
      }
  
      int adjustFlags(final long flags) {
          int result = (int)flags;
  
          // Elide strictfp bit in class files
          if (target.obsoleteAccStrict())
              result &= ~STRICTFP;
  
          if ((flags & BRIDGE) != 0)
              result |= ACC_BRIDGE;
          if ((flags & VARARGS) != 0)
              result |= ACC_VARARGS;
          if ((flags & DEFAULT) != 0)
              result &= ~ABSTRACT;
          return result;
      }
  
      long getLastModified(FileObject filename) {
          long mod = 0;
          try {
              mod = filename.getLastModified();
          } catch (SecurityException e) {
              throw new AssertionError("CRT: couldn't get source file modification date: " + e.getMessage());
          }
          return mod;
      }
  }
  