1 /* go-convert-interface.c -- convert interfaces for Go.
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. */
11 #include "go-string.h"
13 #include "interface.h"
15 /* This is called when converting one interface type into another
16 interface type. LHS_DESCRIPTOR is the type descriptor of the
17 resulting interface. RHS_DESCRIPTOR is the type descriptor of the
18 object being converted. This builds and returns a new interface
19 method table. If any method in the LHS_DESCRIPTOR interface is not
20 implemented by the object, the conversion fails. If the conversion
21 fails, then if MAY_FAIL is true this returns NULL; otherwise, it
25 __go_convert_interface_2 (const struct __go_type_descriptor *lhs_descriptor,
26 const struct __go_type_descriptor *rhs_descriptor,
29 const struct __go_interface_type *lhs_interface;
31 const struct __go_interface_method* lhs_methods;
33 const struct __go_uncommon_type *rhs_uncommon;
35 const struct __go_method *p_rhs_method;
38 if (rhs_descriptor == NULL)
40 /* A nil value always converts to nil. */
44 __go_assert (lhs_descriptor->__code == GO_INTERFACE);
45 lhs_interface = (const struct __go_interface_type *) lhs_descriptor;
46 lhs_method_count = lhs_interface->__methods.__count;
47 lhs_methods = ((const struct __go_interface_method *)
48 lhs_interface->__methods.__values);
50 /* This should not be called for an empty interface. */
51 __go_assert (lhs_method_count > 0);
53 rhs_uncommon = rhs_descriptor->__uncommon;
54 if (rhs_uncommon == NULL || rhs_uncommon->__methods.__count == 0)
56 struct __go_empty_interface panic_arg;
61 runtime_newTypeAssertionError (NULL, rhs_descriptor->__reflection,
62 lhs_descriptor->__reflection,
63 lhs_methods[0].__name,
65 __go_panic (panic_arg);
68 rhs_method_count = rhs_uncommon->__methods.__count;
69 p_rhs_method = ((const struct __go_method *)
70 rhs_uncommon->__methods.__values);
74 for (i = 0; i < lhs_method_count; ++i)
76 const struct __go_interface_method *p_lhs_method;
78 p_lhs_method = &lhs_methods[i];
80 while (rhs_method_count > 0
81 && (!__go_ptr_strings_equal (p_lhs_method->__name,
83 || !__go_ptr_strings_equal (p_lhs_method->__pkg_path,
84 p_rhs_method->__pkg_path)))
90 if (rhs_method_count == 0
91 || !__go_type_descriptors_equal (p_lhs_method->__type,
92 p_rhs_method->__mtype))
94 struct __go_empty_interface panic_arg;
102 runtime_newTypeAssertionError (NULL, rhs_descriptor->__reflection,
103 lhs_descriptor->__reflection,
104 p_lhs_method->__name, &panic_arg);
105 __go_panic (panic_arg);
110 methods = (const void **) __go_alloc ((lhs_method_count + 1)
113 /* The first field in the method table is always the type of
115 methods[0] = rhs_descriptor;
118 methods[i + 1] = p_rhs_method->__function;
124 /* This is called by the compiler to convert a value from one
125 interface type to another. */
128 __go_convert_interface (const struct __go_type_descriptor *lhs_descriptor,
129 const struct __go_type_descriptor *rhs_descriptor)
131 return __go_convert_interface_2 (lhs_descriptor, rhs_descriptor, 0);