Refactor BootstrapMethods attribute reading into function

Author: Matthias Güdemann

src/java_bytecode/java_bytecode_parser.cpp

@@ -136,6 +136,7 @@ class java_bytecode_parsert:public parsert
   void parse_local_variable_type_table(methodt &method);
   optionalt<lambda_method_handlet>
   parse_method_handle(const class method_handle_infot &entry);
+  void read_bootstrapmethods_entry(classt &);
 
   void skip_bytes(std::size_t bytes)
   {
@@ -1595,117 +1596,7 @@ void java_bytecode_parsert::rclass_attribute(classt &parsed_class)
 
     // mark as read in parsed class
     parsed_class.attribute_bootstrapmethods_read = true;
-    u2 num_bootstrap_methods = read_u2();
-    for(size_t i = 0; i < num_bootstrap_methods; i++)
-    {
-      u2 bootstrap_methodhandle_ref = read_u2();
-      const pool_entryt &entry = pool_entry(bootstrap_methodhandle_ref);
-
-      method_handle_infot method_handle{entry};
-
-      u2 num_bootstrap_arguments = read_u2();
-      debug() << "INFO: parse BootstrapMethod handle "
-              << num_bootstrap_arguments << " #args" << eom;
-
-        // try parsing bootstrap method handle
-      if(num_bootstrap_arguments >= 3)
-      {
-        // each entry contains a MethodHandle structure
-        // u2 tag
-        // u2 reference kind which must be in the range from 1 to 9
-        // u2 reference index into the constant pool
-        //
-        // reference kinds use the following
-        // 1 to 4 must point to a CONSTANT_Fieldref structure
-        // 5 or 8 must point to a CONSTANT_Methodref structure
-        // 6 or 7 must point to a CONSTANT_Methodref or
-        // CONSTANT_InterfaceMethodref structure, if the class file version
-        // number is 52.0 or above, to a CONSTANT_Methodref only in the case
-        // of less than 52.0
-        // 9 must point to a CONSTANT_InterfaceMethodref structure
-
-        // the index must point to a CONSTANT_String
-        //                           CONSTANT_Class
-        //                           CONSTANT_Integer
-        //                           CONSTANT_Long
-        //                           CONSTANT_Float
-        //                           CONSTANT_Double
-        //                           CONSTANT_MethodHandle
-        //                           CONSTANT_MethodType
-
-        // We read the three arguments here to see whether they correspond to
-        // our hypotheses for this being a lambda function entry.
-
-        u2 argument_index1 = read_u2();
-        u2 argument_index2 = read_u2();
-        u2 argument_index3 = read_u2();
-
-        // The additional arguments for the altmetafactory call are skipped,
-        // as they are currently not used. We verify though that they are of
-        // CONSTANT_Integer type, cases where this does not hold will be
-        // analyzed further.
-        bool recognized = true;
-        for(size_t i = 3; i < num_bootstrap_arguments; i++)
-        {
-          u2 skipped_argument = read_u2();
-          recognized |= pool_entry(skipped_argument).tag == CONSTANT_Integer;
-        }
-        if(!recognized)
-        {
-          debug() << "format of BootstrapMethods entry not recognized" << eom;
-          return;
-        }
-
-        const pool_entryt &interface_type_argument =
-          pool_entry(argument_index1);
-        const pool_entryt &method_handle_argument =
-          pool_entry(argument_index2);
-        const pool_entryt &method_type_argument = pool_entry(argument_index3);
-
-        if(
-          !(interface_type_argument.tag == CONSTANT_MethodType &&
-            method_handle_argument.tag == CONSTANT_MethodHandle &&
-            method_type_argument.tag == CONSTANT_MethodType))
-          return;
-
-        debug() << "INFO: parse lambda handle" << eom;
-        optionalt<lambda_method_handlet> lambda_method_handle =
-          parse_method_handle(method_handle_infot{method_handle_argument});
-
-        if(
-          lambda_method_handle.has_value() &&
-          lambda_method_handle->handle_type !=
-            method_handle_typet::LAMBDA_METHOD_HANDLE)
-        {
-          error() << "ERROR: could not parse lambda function method handle"
-                  << eom;
-        }
-        else
-        {
-          lambda_method_handle->interface_type =
-            pool_entry(interface_type_argument.ref1).s;
-          lambda_method_handle->method_type =
-            pool_entry(method_type_argument.ref1).s;
-          debug() << "lambda function reference "
-                  << id2string(lambda_method_handle->lambda_method_name)
-                  << " in class \"" << parsed_class.name << "\""
-                  << "\n  interface type is "
-                  << id2string(pool_entry(interface_type_argument.ref1).s)
-                  << "\n  method type is "
-                  << id2string(pool_entry(method_type_argument.ref1).s)
-                  << eom;
-          parsed_class.lambda_method_handle_map[{parsed_class.name, i}] =
-            *lambda_method_handle;
-        }
-      }
-      else
-      {
-        // skip bytes to align for next entry
-        for(size_t i = 0; i < num_bootstrap_arguments; i++)
-          read_u2();
-        error() << "ERROR: num_bootstrap_arguments must be at least 3" << eom;
-      }
-    }
+    read_bootstrapmethods_entry(parsed_class);
   }
   else
     skip_bytes(attribute_length);
@@ -1879,3 +1770,119 @@ java_bytecode_parsert::parse_method_handle(const method_handle_infot &entry)
 
   return {};
 }
+
+/// Read all entries of the `BootstrapMethods` attribute of a class file.
+/// \param parsed_class: the class representation of the class file that is
+/// currently parsed
+void java_bytecode_parsert::read_bootstrapmethods_entry(
+  classt &parsed_class)
+{
+  u2 num_bootstrap_methods = read_u2();
+  for(size_t i = 0; i < num_bootstrap_methods; i++)
+  {
+    u2 bootstrap_methodhandle_ref = read_u2();
+    const pool_entryt &entry = pool_entry(bootstrap_methodhandle_ref);
+
+    method_handle_infot method_handle{entry};
+
+    u2 num_bootstrap_arguments = read_u2();
+    debug() << "INFO: parse BootstrapMethod handle "
+            << num_bootstrap_arguments << " #args" << eom;
+
+    // try parsing bootstrap method handle
+    if(num_bootstrap_arguments >= 3)
+    {
+      // each entry contains a MethodHandle structure
+      // u2 tag
+      // u2 reference kind which must be in the range from 1 to 9
+      // u2 reference index into the constant pool
+      //
+      // reference kinds use the following
+      // 1 to 4 must point to a CONSTANT_Fieldref structure
+      // 5 or 8 must point to a CONSTANT_Methodref structure
+      // 6 or 7 must point to a CONSTANT_Methodref or
+      // CONSTANT_InterfaceMethodref structure, if the class file version
+      // number is 52.0 or above, to a CONSTANT_Methodref only in the case
+      // of less than 52.0
+      // 9 must point to a CONSTANT_InterfaceMethodref structure
+
+      // the index must point to a CONSTANT_String
+      //                           CONSTANT_Class
+      //                           CONSTANT_Integer
+      //                           CONSTANT_Long
+      //                           CONSTANT_Float
+      //                           CONSTANT_Double
+      //                           CONSTANT_MethodHandle
+      //                           CONSTANT_MethodType
+
+      // We read the three arguments here to see whether they correspond to
+      // our hypotheses for this being a lambda function entry.
+
+      u2 argument_index1 = read_u2();
+      u2 argument_index2 = read_u2();
+      u2 argument_index3 = read_u2();
+
+      // The additional arguments for the altmetafactory call are skipped,
+      // as they are currently not used. We verify though that they are of
+      // CONSTANT_Integer type, cases where this does not hold will be
+      // analyzed further.
+      bool recognized = true;
+      for(size_t i = 3; i < num_bootstrap_arguments; i++)
+      {
+        u2 skipped_argument = read_u2();
+        recognized &= pool_entry(skipped_argument).tag == CONSTANT_Integer;
+      }
+      if(!recognized)
+      {
+        debug() << "format of BootstrapMethods entry not recognized" << eom;
+        return;
+      }
+
+      const pool_entryt &interface_type_argument = pool_entry(argument_index1);
+      const pool_entryt &method_handle_argument = pool_entry(argument_index2);
+      const pool_entryt &method_type_argument = pool_entry(argument_index3);
+
+      if(
+        !(interface_type_argument.tag == CONSTANT_MethodType &&
+          method_handle_argument.tag == CONSTANT_MethodHandle &&
+          method_type_argument.tag == CONSTANT_MethodType))
+        return;
+
+      debug() << "INFO: parse lambda handle" << eom;
+      optionalt<lambda_method_handlet> lambda_method_handle =
+        parse_method_handle(method_handle_infot{method_handle_argument});
+
+      if(
+        lambda_method_handle.has_value() &&
+        lambda_method_handle->handle_type !=
+          method_handle_typet::LAMBDA_METHOD_HANDLE)
+      {
+        error() << "ERROR: could not parse lambda function method handle"
+                << eom;
+      }
+      else
+      {
+        lambda_method_handle->interface_type =
+          pool_entry(interface_type_argument.ref1).s;
+        lambda_method_handle->method_type =
+          pool_entry(method_type_argument.ref1).s;
+        debug() << "lambda function reference "
+                << id2string(lambda_method_handle->lambda_method_name)
+                << " in class \"" << parsed_class.name << "\""
+                << "\n  interface type is "
+                << id2string(pool_entry(interface_type_argument.ref1).s)
+                << "\n  method type is "
+                << id2string(pool_entry(method_type_argument.ref1).s) << eom;
+        parsed_class.lambda_method_handle_map[{parsed_class.name, i}] =
+          *lambda_method_handle;
+      }
+    }
+    else
+    {
+      // skip bytes to align for next entry
+      for(size_t i = 0; i < num_bootstrap_arguments; i++)
+        read_u2();
+      error() << "ERROR: num_bootstrap_arguments must be at least 3" << eom;
+    }
+  }
+}