7.4.2 ParameterTable Attribute

The ParameterTable attribute represents the BML related information about the method parameters. The structure of the attribute is as follows:

     ParameterTable_attribute {
       u2 attribute_name_index;
       u4 attribute_length;
       u2 parameters_count;
       {
         u2 name_index;
         u2 access_flags;
         u4 BML_flags;
         u2 index;
       } parameters[parameters_count];
     }

The meaning of the fields is as follows:

• attribute_name_index - index in the constant pool of the attribute name (org.bmlspecs.ParameterTable)
• attribute_length - length in bytes of the whole structure
• parameters_count - the number of parameters of the method. It must be equal to the number of parameters in the method's type description.
• parameters - the table of parameter descriptions, where each element is a structure containing one field:
  • name_index - the index in the first or the second constant pool where the parameter's name is stored as a CONSTANT_Utf8_info element
  • access_flags - the JVM flags that are set for the given parameter. The only allowed flag is ACC_FINAL. All other flags must be cleared.
  • BML_flags - the BML flags that are set for the given parameter. The allowed flags are BML_NON_NULL, BML_NULLABLE, BML_PEER, BML_REP, BML_READONLY. All other flags must be cleared. Only one of BML_NON_NULL, BML_NULLABLE can be set. Only one of BML_PEER, BML_REP, BML_READONLY can be set.
  • index - the index by which the parameter is referenced in the BML expressions and the code of this method

Note that for methods where the Code attribute (see Code Attribute) contains a LocalVariableTable attribute (see LocalVariableTable Attribute) the parameter names can already be stored in this table. In this case the two names must be equal. However, for methods without the Code attribute (because they are declared in an interface, abstract or native) the parameter's name is only stored in this attribute.

The index field in each parameter description must correspond to the index by which this parameter is referenced in the code (if it is present) and BML expressions in the method specification and other formulas in the method's code. Note that if there are long integer or double float parameters in the list, the value of the index does not have to be equal to the position of the parameter in the method's signature.

The order of parameters is not specified and not all of them must be described in the table, but any parameter must be described at most once.