Add code_typet::get_parameter_indices

This is simply the opposite of the existing get_parameter_indentifiers,
useful for mapping from parameter identifier to its argument or parameter
index.

Author: smowton

src/util/std_types.h

@@ -890,6 +890,26 @@ class code_typet:public typet
       result.push_back(it->get_identifier());
     return result;
   }
+
+  typedef
+    std::unordered_map<irep_idt, std::size_t, irep_id_hash> parameter_indicest;
+
+  /// Get a map from parameter name to its index
+  parameter_indicest parameter_indices() const
+  {
+    parameter_indicest parameter_indices;
+    const parameterst &p = parameters();
+    parameter_indices.reserve(p.size());
+    std::size_t index = 0;
+    for(const auto &p : parameters())
+    {
+      const irep_idt &id = p.get_identifier();
+      if(!id.empty())
+        parameter_indices.insert({ id, index });
+      ++index;
+    }
+    return parameter_indices;
+  }
 };
 
 /*! \brief Cast a generic typet to a \ref code_typet

unit/Makefile

@@ -35,6 +35,7 @@ SRC += unit_tests.cpp \
        util/expr_cast/expr_cast.cpp \
        util/expr_iterator.cpp \
        util/message.cpp \
+       util/parameter_indices.cpp \
        util/simplify_expr.cpp \
        util/symbol_table.cpp \
        catch_example.cpp \

unit/util/ParameterIndicesTest.class

@@ -0,0 +1,8 @@
+
+public class ParameterIndicesTest {
+
+  public void f(ParameterIndicesTest param1, int param2) {}
+
+  public static void g(float param1, ParameterIndicesTest param2) {}
+
+}

unit/util/ParameterIndicesTest.java

@@ -0,0 +1,33 @@
+/*******************************************************************\
+
+ Module: Parameter indices test
+
+ Author: Diffblue Limited. All rights reserved.
+
+\*******************************************************************/
+
+#include <testing-utils/catch.hpp>
+#include <testing-utils/load_java_class.h>
+#include <util/std_types.h>
+
+void check_consistency(const symbolt &symbol)
+{
+  const auto &code_type = to_code_type(symbol.type);
+  auto parameter_ids = code_type.parameter_identifiers();
+  auto parameter_indices = code_type.parameter_indices();
+
+  REQUIRE(parameter_ids.size() == parameter_indices.size());
+  for(std::size_t i = 0; i < parameter_ids.size(); ++i)
+    REQUIRE(parameter_indices.at(parameter_ids.at(i)) == i);
+}
+
+TEST_CASE("Parmeter indices consistency", "[core][util][parameter_indices]")
+{
+  symbol_tablet symbol_table = load_java_class("ParameterIndicesTest", "util/");
+  check_consistency(
+    symbol_table.lookup_ref(
+      "java::ParameterIndicesTest.f:(LParameterIndicesTest;I)V"));
+  check_consistency(
+    symbol_table.lookup_ref(
+      "java::ParameterIndicesTest.g:(FLParameterIndicesTest;)V"));
+}