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/* go-convert-interface.c -- convert interfaces for Go.
Copyright 2009 The Go Authors. All rights reserved.
Use of this source code is governed by a BSD-style
license that can be found in the LICENSE file. */
#include "runtime.h"
#include "go-alloc.h"
#include "go-assert.h"
#include "go-panic.h"
#include "go-string.h"
#include "go-type.h"
#include "interface.h"
/* This is called when converting one interface type into another
interface type. LHS_DESCRIPTOR is the type descriptor of the
resulting interface. RHS_DESCRIPTOR is the type descriptor of the
object being converted. This builds and returns a new interface
method table. If any method in the LHS_DESCRIPTOR interface is not
implemented by the object, the conversion fails. If the conversion
fails, then if MAY_FAIL is true this returns NULL; otherwise, it
panics. */
void *
__go_convert_interface_2 (const struct __go_type_descriptor *lhs_descriptor,
const struct __go_type_descriptor *rhs_descriptor,
_Bool may_fail)
{
const struct __go_interface_type *lhs_interface;
int lhs_method_count;
const struct __go_interface_method* lhs_methods;
const void **methods;
const struct __go_uncommon_type *rhs_uncommon;
int rhs_method_count;
const struct __go_method *p_rhs_method;
int i;
if (rhs_descriptor == NULL)
{
/* A nil value always converts to nil. */
return NULL;
}
__go_assert (lhs_descriptor->__code == GO_INTERFACE);
lhs_interface = (const struct __go_interface_type *) lhs_descriptor;
lhs_method_count = lhs_interface->__methods.__count;
lhs_methods = ((const struct __go_interface_method *)
lhs_interface->__methods.__values);
/* This should not be called for an empty interface. */
__go_assert (lhs_method_count > 0);
rhs_uncommon = rhs_descriptor->__uncommon;
if (rhs_uncommon == NULL || rhs_uncommon->__methods.__count == 0)
{
struct __go_empty_interface panic_arg;
if (may_fail)
return NULL;
runtime_newTypeAssertionError (NULL, rhs_descriptor->__reflection,
lhs_descriptor->__reflection,
lhs_methods[0].__name,
&panic_arg);
__go_panic (panic_arg);
}
rhs_method_count = rhs_uncommon->__methods.__count;
p_rhs_method = ((const struct __go_method *)
rhs_uncommon->__methods.__values);
methods = NULL;
for (i = 0; i < lhs_method_count; ++i)
{
const struct __go_interface_method *p_lhs_method;
p_lhs_method = &lhs_methods[i];
while (rhs_method_count > 0
&& (!__go_ptr_strings_equal (p_lhs_method->__name,
p_rhs_method->__name)
|| !__go_ptr_strings_equal (p_lhs_method->__pkg_path,
p_rhs_method->__pkg_path)))
{
++p_rhs_method;
--rhs_method_count;
}
if (rhs_method_count == 0
|| !__go_type_descriptors_equal (p_lhs_method->__type,
p_rhs_method->__mtype))
{
struct __go_empty_interface panic_arg;
if (methods != NULL)
__go_free (methods);
if (may_fail)
return NULL;
runtime_newTypeAssertionError (NULL, rhs_descriptor->__reflection,
lhs_descriptor->__reflection,
p_lhs_method->__name, &panic_arg);
__go_panic (panic_arg);
}
if (methods == NULL)
{
methods = (const void **) __go_alloc ((lhs_method_count + 1)
* sizeof (void *));
/* The first field in the method table is always the type of
the object. */
methods[0] = rhs_descriptor;
}
methods[i + 1] = p_rhs_method->__function;
}
return methods;
}
/* This is called by the compiler to convert a value from one
interface type to another. */
void *
__go_convert_interface (const struct __go_type_descriptor *lhs_descriptor,
const struct __go_type_descriptor *rhs_descriptor)
{
return __go_convert_interface_2 (lhs_descriptor, rhs_descriptor, 0);
}
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