github.com/llvm-mirror/llgo@v0.0.0-20190322182713-bf6f0a60fce1/third_party/gofrontend/libgo/runtime/go-can-convert-interface.c (about)

     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  }