libgo/runtime/go-can-convert-interface.c

   1 /* go-can-convert-interface.c -- can we convert to an interface?
   2
   3    Copyright 2009 The Go Authors. All rights reserved.
   4    Use of this source code is governed by a BSD-style
   5    license that can be found in the LICENSE file.  */
   6
   7 #include "go-assert.h"
   8 #include "go-type.h"
   9 #include "interface.h"
  10
  11 /* Return whether we can convert from the type in FROM_DESCRIPTOR to
  12    the interface in TO_DESCRIPTOR.  This is used for type
  13    switches.  */
  14
  15 _Bool
  16 __go_can_convert_to_interface (
  17     const struct __go_type_descriptor *to_descriptor,
  18     const struct __go_type_descriptor *from_descriptor)
  19 {
  20   const struct __go_interface_type *to_interface;
  21   int to_method_count;
  22   const struct __go_interface_method *to_method;
  23   const struct __go_uncommon_type *from_uncommon;
  24   int from_method_count;
  25   const struct __go_method *from_method;
  26   int i;
  27
  28   /* In a type switch FROM_DESCRIPTOR can be NULL.  */
  29   if (from_descriptor == NULL)
  30     return 0;
  31
  32   __go_assert (to_descriptor->__code == GO_INTERFACE);
  33   to_interface = (const struct __go_interface_type *) to_descriptor;
  34   to_method_count = to_interface->__methods.__count;
  35   to_method = ((const struct __go_interface_method *)
  36                to_interface->__methods.__values);
  37
  38   from_uncommon = from_descriptor->__uncommon;
  39   if (from_uncommon == NULL)
  40     {
  41       from_method_count = 0;
  42       from_method = NULL;
  43     }
  44   else
  45     {
  46       from_method_count = from_uncommon->__methods.__count;
  47       from_method = ((const struct __go_method *)
  48                      from_uncommon->__methods.__values);
  49     }
  50
  51   for (i = 0; i < to_method_count; ++i)
  52     {
  53       while (from_method_count > 0
  54              && (!__go_ptr_strings_equal (from_method->__name,
  55                                           to_method->__name)
  56                  || !__go_ptr_strings_equal (from_method->__pkg_path,
  57                                              to_method->__pkg_path)))
  58         {
  59           ++from_method;
  60           --from_method_count;
  61         }
  62
  63       if (from_method_count == 0)
  64         return 0;
  65
  66       if (!__go_type_descriptors_equal (from_method->__mtype,
  67                                         to_method->__type))
  68         return 0;
  69
  70       ++to_method;
  71       ++from_method;
  72       --from_method_count;
  73     }
  74
  75   return 1;
  76 }