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
__go_can_convert_to_interface(const struct __go_type_descriptor * to_descriptor,const struct __go_type_descriptor * from_descriptor)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 }
79