79  * String, MethodType, String, Object...)} using the advanced forms of capturing
  80  * the constant arguments. The advanced strategy can produce marginally better
  81  * invocation bytecode, at the expense of exploding the number of shapes of
  82  * string concatenation methods present at runtime, because those shapes would
  83  * include constant static arguments as well.
  84  *
  85  * @author Aleksey Shipilev
  86  * @author Remi Forax
  87  * @author Peter Levart
  88  *
  89  * @apiNote
  90  * <p>There is a JVM limit (classfile structural constraint): no method
  91  * can call with more than 255 slots. This limits the number of static and
  92  * dynamic arguments one can pass to bootstrap method. Since there are potential
  93  * concatenation strategies that use {@code MethodHandle} combinators, we need
  94  * to reserve a few empty slots on the parameter lists to to capture the
  95  * temporal results. This is why bootstrap methods in this factory do not accept
  96  * more than 200 argument slots. Users requiring more than 200 argument slots in
  97  * concatenation are expected to split the large concatenation in smaller
  98  * expressions.


  99  */
 100 public final class StringConcatFactory {
 101 
 102     /**
 103      * Tag used to demarcate an ordinary argument.
 104      */
 105     private static final char TAG_ARG = '\u0001';
 106 
 107     /**
 108      * Tag used to demarcate a constant.
 109      */
 110     private static final char TAG_CONST = '\u0002';
 111 
 112     /**
 113      * Maximum number of argument slots in String Concat call.
 114      *
 115      * While the maximum number of argument slots that indy call can handle is 253,
 116      * we do not use all those slots, to let the strategies with MethodHandle
 117      * combinators to use some arguments.
 118      */

  79  * String, MethodType, String, Object...)} using the advanced forms of capturing
  80  * the constant arguments. The advanced strategy can produce marginally better
  81  * invocation bytecode, at the expense of exploding the number of shapes of
  82  * string concatenation methods present at runtime, because those shapes would
  83  * include constant static arguments as well.
  84  *
  85  * @author Aleksey Shipilev
  86  * @author Remi Forax
  87  * @author Peter Levart
  88  *
  89  * @apiNote
  90  * <p>There is a JVM limit (classfile structural constraint): no method
  91  * can call with more than 255 slots. This limits the number of static and
  92  * dynamic arguments one can pass to bootstrap method. Since there are potential
  93  * concatenation strategies that use {@code MethodHandle} combinators, we need
  94  * to reserve a few empty slots on the parameter lists to to capture the
  95  * temporal results. This is why bootstrap methods in this factory do not accept
  96  * more than 200 argument slots. Users requiring more than 200 argument slots in
  97  * concatenation are expected to split the large concatenation in smaller
  98  * expressions.
  99  *
 100  * @since 9
 101  */
 102 public final class StringConcatFactory {
 103 
 104     /**
 105      * Tag used to demarcate an ordinary argument.
 106      */
 107     private static final char TAG_ARG = '\u0001';
 108 
 109     /**
 110      * Tag used to demarcate a constant.
 111      */
 112     private static final char TAG_CONST = '\u0002';
 113 
 114     /**
 115      * Maximum number of argument slots in String Concat call.
 116      *
 117      * While the maximum number of argument slots that indy call can handle is 253,
 118      * we do not use all those slots, to let the strategies with MethodHandle
 119      * combinators to use some arguments.
 120      */