Added check for a type being a valid formed Java array

Essentially serves to programatically document what is expected of a
Java array type when represented in GOTO.

Author: thk123

src/java_bytecode/java_types.cpp

@@ -314,3 +314,50 @@ symbol_typet java_classname(const std::string &id)
 
   return symbol_type;
 }
+
+/// Programmatic documentation of the structure of a Java array (of either
+/// primitives or references) type.
+/// A Java array is represented in GOTO in the following way:
+/// A struct component with a tag like java::array[type] where type is either
+/// a primitive like int, or reference.
+/// The struct has precisely three components:
+/// 1. \@java.lang.Object: of type struct {java.lang.Object} containing the base
+///   class data
+/// 2. length: of type Java integer - the length of the array
+/// 3. data: of type pointer to either pointer to a primitive type, or pointer
+///   to pointer to empty (i.e. a void**) pointing to the contents of the array
+/// \param type: A type that might represent a Java array
+/// \return True if it is a Java array type, false otherwise
+bool is_valid_java_array(const struct_typet &type)
+{
+  bool correct_num_components=type.components().size()==3;
+  if(!correct_num_components)
+    return false;
+
+  // First component, the base class (Object) data
+  const struct_union_typet::componentt base_class_component=
+    type.components()[0];
+
+  bool base_component_valid=true;
+  base_component_valid&=base_class_component.get_name()=="@java.lang.Object";
+  base_component_valid&=base_class_component.type().id()==ID_struct;
+  base_component_valid&=
+    base_class_component.type().get_string(ID_tag)=="java.lang.Object";
+
+  bool length_component_valid=true;
+  const struct_union_typet::componentt length_component=
+    type.components()[1];
+  length_component_valid&=length_component.get_name()=="length";
+  length_component_valid&=length_component.type()==java_int_type();
+
+  bool data_component_valid=true;
+  const struct_union_typet::componentt data_component=
+    type.components()[2];
+  data_component_valid&=data_component.get_name()=="data";
+  data_component_valid&=data_component.type().id()==ID_pointer;
+
+  return correct_num_components &&
+    base_component_valid &&
+    length_component_valid &&
+    data_component_valid;
+}

src/java_bytecode/java_types.h

@@ -74,4 +74,6 @@ exprt java_bytecode_promotion(const exprt &);
 
 bool is_java_array_tag(const irep_idt& tag);
 
+bool is_valid_java_array(const struct_typet &type);
+
 #endif // CPROVER_JAVA_BYTECODE_JAVA_TYPES_H