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glib-aux: add nm_g_array_index() macro and improve nm_g_array_index_p() macros

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Add nm_g_array_index() as a replacement for g_array_index(). The value
of nm_g_array_index(), nm_g_array_index_p(), nm_g_array_first() and
nm_g_array_last() is that they add nm_assert() checks for valid
parameters.

nm_g_array_{first,last}() now returns an lvalue and not a pointer.
As such, they are just shorthands for nm_g_array_index() at index
0 and len-1, respectively.

`nm_g_array_index_p(arr, Type, idx)` is almost the same as
`&nm_g_array_index(arr, Type, idx)`. The only difference (and why the
former variant exists), is that nm_g_array_index_p() allows to get a
pointer one after the end.

This means, this is correct and valid to do:

   // arr->len might be zero
   arr = nm_g_array_index_p(arr, Type, 0);
   for (i = 0; i < arr->len; i++, arr++)
       ...

   ptr = nm_g_array_index_p(arr, Type, 0);
   end = nm_g_array_index_p(arr, Type, arr->len);
   for (; ptr < end; ptr++)
       ...

This would not be valid to do with nm_g_array_{index,first,last}().

Also fix supporting "const GArray *arr" parameter. Of course, the function
casts the constness away. Technically, that matches the fact that arr->data
is also not a const pointer. In practice, we might want to propagate the
constness of the container to the constness of the element lookup. While
doable, that is not implemented.
This commit is contained in:
Thomas Haller 2022-09-08 11:52:49 +02:00
parent 2c8dcbeaf9
commit 07b32d5d22
No known key found for this signature in database
GPG key ID: 29C2366E4DFC5728
3 changed files with 85 additions and 34 deletions
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2
src/core/nm-core-utils.c
View file

@ -3022,7 +3022,7 @@ nmtst_utils_host_id_pop(void)
&host_id_static,
h,
nmtst_host_id_stack->len == 0u ? nmtst_host_id_static_0
: nm_g_array_last(nmtst_host_id_stack, HostIdData)))
: &nm_g_array_last(nmtst_host_id_stack, HostIdData)))
g_assert_not_reached();
}

84
src/libnm-glib-aux/nm-shared-utils.h
View file

@ -1866,43 +1866,61 @@ nm_g_array_unref(GArray *arr)
g_array_unref(arr);
}
#define nm_g_array_first(arr, Type) \
({ \
GArray *const _arr = (arr); \
\
nm_assert(_arr); \
nm_assert(sizeof(Type) == g_array_get_element_size(_arr)); \
nm_assert(_arr->len > 0); \
\
&g_array_index(arr, Type, 0); \
})
#define nm_g_array_last(arr, Type) \
({ \
GArray *const _arr = (arr); \
\
nm_assert(_arr); \
nm_assert(sizeof(Type) == g_array_get_element_size(_arr)); \
nm_assert(_arr->len > 0); \
\
&g_array_index(arr, Type, _arr->len - 1u); \
})
/* Similar to g_array_index(). The differences are
* - this does nm_assert() checks that the arguments are valid.
* - returns a pointer to the element. */
#define nm_g_array_index_p(arr, Type, idx) \
({ \
GArray *const _arr_55 = (arr); \
const guint _idx_55 = (idx); \
\
nm_assert(_arr_55); \
nm_assert(sizeof(Type) == g_array_get_element_size(_arr_55)); \
nm_assert(_idx_55 < _arr_55->len); \
\
&g_array_index(_arr_55, Type, _idx_55); \
* - returns a pointer to the element.
* - it asserts that @idx is <= arr->len. That is, it allows
* to get a pointer after the data, of course, you are not
* allowed to dereference in that case. */
#define nm_g_array_index_p(arr, Type, idx) \
({ \
const GArray *const _arr_55 = (arr); \
const guint _idx_55 = (idx); \
\
nm_assert(_arr_55); \
nm_assert(sizeof(Type) == g_array_get_element_size((GArray *) _arr_55)); \
nm_assert(_idx_55 <= _arr_55->len); \
\
/* If arr->len is zero, arr->data might be NULL. The macro
* allows to access at index [arr->len] (one past the data).
* We need to take care of undefined behavior, but (NULL + 0)
* should work mostly fine for us. */ \
((Type *) ((gpointer) _arr_55->data)) + (_idx_55); \
})
/* Very similar to g_array_index().
* - nm_assert() that arguments are valid.
* - returns an lvalue to the element.
* - similar to nm_g_array_index_p(), but dereferences the pointer.
* - one difference to nm_g_array_index_p() is that it @idx MUST be
* smaller than arr->len (unlike nm_g_array_index_p() which allows
* access one element past the buffer. */
#define nm_g_array_index(arr, Type, idx) \
(*({ \
const GArray *const _arr_55 = (arr); \
const guint _idx_55 = (idx); \
\
nm_assert(_arr_55); \
nm_assert(sizeof(Type) == g_array_get_element_size((GArray *) _arr_55)); \
nm_assert(_idx_55 < _arr_55->len); \
\
&g_array_index((GArray *) _arr_55, Type, _idx_55); \
}))
#define nm_g_array_first(arr, Type) nm_g_array_index(arr, Type, 0)
/* Same as g_array_index(arr, Type, arr->len-1). */
#define nm_g_array_last(arr, Type) \
(*({ \
const GArray *const _arr = (arr); \
\
nm_assert(_arr); \
nm_assert(sizeof(Type) == g_array_get_element_size((GArray *) _arr)); \
nm_assert(_arr->len > 0); \
\
&g_array_index((GArray *) arr, Type, _arr->len - 1u); \
}))
#define nm_g_array_append_new(arr, Type) \
({ \
GArray *const _arr = (arr); \

33
src/libnm-glib-aux/tests/test-shared-general.c
View file

@ -2218,6 +2218,38 @@ test_inet_utils(void)
/*****************************************************************************/
static void
test_garray(void)
{
gs_unref_array GArray *arr = NULL;
int v;
arr = g_array_new(FALSE, FALSE, sizeof(int));
g_assert(nm_g_array_index_p(arr, int, 0) == (gpointer) arr->data);
v = 1;
g_array_append_val(arr, v);
g_assert(nm_g_array_index_p(arr, int, 0) == (gpointer) arr->data);
g_assert(nm_g_array_index_p(arr, int, 1) == ((int *) ((gpointer) arr->data)) + 1);
g_assert(&nm_g_array_index(arr, int, 0) == (gpointer) arr->data);
g_assert(&nm_g_array_first(arr, int) == (gpointer) arr->data);
g_assert(&nm_g_array_last(arr, int) == (gpointer) arr->data);
g_assert(nm_g_array_index(arr, int, 0) == 1);
v = 2;
g_array_append_val(arr, v);
g_assert(nm_g_array_index_p(arr, int, 0) == (gpointer) arr->data);
g_assert(nm_g_array_index_p(arr, int, 1) == ((int *) ((gpointer) arr->data)) + 1);
g_assert(nm_g_array_index_p(arr, int, 2) == ((int *) ((gpointer) arr->data)) + 2);
g_assert(&nm_g_array_index(arr, int, 0) == (gpointer) arr->data);
g_assert(&nm_g_array_first(arr, int) == (gpointer) arr->data);
g_assert(&nm_g_array_last(arr, int) == ((int *) ((gpointer) arr->data)) + 1);
g_assert(nm_g_array_index(arr, int, 0) == 1);
g_assert(nm_g_array_index(arr, int, 1) == 2);
}
/*****************************************************************************/
NMTST_DEFINE();
int
@ -2263,6 +2295,7 @@ main(int argc, char **argv)
g_test_add_func("/general/test_path_simplify", test_path_simplify);
g_test_add_func("/general/test_hostname_is_valid", test_hostname_is_valid);
g_test_add_func("/general/test_inet_utils", test_inet_utils);
g_test_add_func("/general/test_garray", test_garray);
return g_test_run();
}