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glib-aux: add nm_g_array_first_p() and fix nm_g_array_index_p() with NULL array

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nm_g_array_first_p() is a convenient helper to get the pointer to
the first index. But this one should also accept that the array is NULL,
has array->data as NULL or is empty.
This commit is contained in:
Thomas Haller 2022-12-01 16:04:02 +01:00
parent afac3d8102
commit cfc6e63403
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GPG key ID: 29C2366E4DFC5728
1 changed files with 23 additions and 15 deletions
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38
src/libnm-glib-aux/nm-shared-utils.h
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@ -1869,6 +1869,8 @@ char *nm_utils_g_slist_strlist_join(const GSList *a, const char *separator);
static inline gpointer
nm_g_array_data(const GArray *arr)
{
/* You may want to use nm_g_array_first_p() instead, which can assert
* for the expected type. */
return arr ? arr->data : NULL;
}
@ -1890,21 +1892,25 @@ nm_g_array_unref(GArray *arr)
* - 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); \
* allowed to dereference in that case.
* - in particular, unlike nm_g_array_index(), you are allowed to call this
* with "arr" NULL (for index zero) or with "arr->data" NULL
* (for index zero). In that case, NULL is returned.
*
* When accessing index zero, then this returns NULL if-and-only-if
* "arr" is NULL or "arr->data" is NULL. In all other cases, this
* returns the pointer &((Type*) arr->data)[idx]. Note that the pointer
* may not be followed, if "idx" is equal to "arr->len". */
#define nm_g_array_index_p(arr, Type, idx) \
({ \
const GArray *const _arr_55 = (arr); \
const guint _idx_55 = (idx); \
\
nm_assert(_arr_55 || _idx_55 == 0); \
nm_assert(_idx_55 <= (_arr_55 ? _arr_55->len : 0u)); \
nm_assert(!_arr_55 || sizeof(Type) == g_array_get_element_size((GArray *) _arr_55)); \
\
((_arr_55 && _arr_55->data) ? &(((Type *) ((gpointer) _arr_55->data))[_idx_55]) : NULL); \
})
/* Very similar to g_array_index().
@ -1928,6 +1934,8 @@ nm_g_array_unref(GArray *arr)
#define nm_g_array_first(arr, Type) nm_g_array_index(arr, Type, 0)
#define nm_g_array_first_p(arr, Type) nm_g_array_index_p(arr, Type, 0)
/* Same as g_array_index(arr, Type, arr->len-1). */
#define nm_g_array_last(arr, Type) \
(*({ \