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 "runtime.h"
   8 #include "go-assert.h"
   9 #include "go-string.h"
  10 #include "go-type.h"
  11 #include "interface.h"
  12
  13 /* Return whether we can convert from the type in FROM_DESCRIPTOR to
  14    the interface in TO_DESCRIPTOR.  This is used for type
  15    switches.  */
  16
  17 _Bool
  18 __go_can_convert_to_interface (
  19     const struct __go_type_descriptor *to_descriptor,
  20     const struct __go_type_descriptor *from_descriptor)
  21 {
  22   const struct __go_interface_type *to_interface;
  23   int to_method_count;
  24   const struct __go_interface_method *to_method;
  25   const struct __go_uncommon_type *from_uncommon;
  26   int from_method_count;
  27   const struct __go_method *from_method;
  28   int i;
  29
  30   /* In a type switch FROM_DESCRIPTOR can be NULL.  */
  31   if (from_descriptor == NULL)
  32     return 0;
  33
  34   __go_assert ((to_descriptor->__code & GO_CODE_MASK) == GO_INTERFACE);
  35   to_interface = (const struct __go_interface_type *) to_descriptor;
  36   to_method_count = to_interface->__methods.__count;
  37   to_method = ((const struct __go_interface_method *)
  38                to_interface->__methods.__values);
  39
  40   from_uncommon = from_descriptor->__uncommon;
  41   if (from_uncommon == NULL)
  42     {
  43       from_method_count = 0;
  44       from_method = NULL;
  45     }
  46   else
  47     {
  48       from_method_count = from_uncommon->__methods.__count;
  49       from_method = ((const struct __go_method *)
  50                      from_uncommon->__methods.__values);
  51     }
  52
  53   for (i = 0; i < to_method_count; ++i)
  54     {
  55       while (from_method_count > 0
  56              && (!__go_ptr_strings_equal (from_method->__name,
  57                                           to_method->__name)
  58                  || !__go_ptr_strings_equal (from_method->__pkg_path,
  59                                              to_method->__pkg_path)))
  60         {
  61           ++from_method;
  62           --from_method_count;
  63         }
  64
  65       if (from_method_count == 0)
  66         return 0;
  67
  68       if (!__go_type_descriptors_equal (from_method->__mtype,
  69                                         to_method->__type))
  70         return 0;
  71
  72       ++to_method;
  73       ++from_method;
  74       --from_method_count;
  75     }
  76
  77   return 1;
  78 }