[glib/th/g-ptr-array-set-null-terminated: 2/2] array: add support for %NULL termination in GPtrArray
- From: Thomas Haller <thaller src gnome org>
- To: commits-list gnome org
- Cc:
- Subject: [glib/th/g-ptr-array-set-null-terminated: 2/2] array: add support for %NULL termination in GPtrArray
- Date: Tue, 19 Jan 2021 13:06:09 +0000 (UTC)
commit 0c1c8efb0c3a009e972bd4a9c09cd6591757ca8a
Author: Thomas Haller <thaller redhat com>
Date: Wed May 6 19:35:37 2020 +0200
array: add support for %NULL termination in GPtrArray
GArray supports a "zero_terminated" flag, but GPtrArray doesn't.
This is odd, because especially for a pointer array it makes sense
to have a %NULL sentinel. This would be for example useful to track
or construct a strv array with a GPtrArray.
As workaround for this missing feature you could use a GArray instead
(ugly) or to explicitly add the %NULL element. However the latter increases
the "len" of the array, which can be problematic if you want to still use
the GPtrArray for other purposes.
Add API for marking a GPtrArray as %NULL terminated. In that case, the
API will ensure that there is always a valid %NULL sentinel after the
array. Note that the API does not enforce that a %NULL terminated API
actually has any data allocated. That means, even with a %NULL terminated
array, pdata can still be %NULL (only if len is zero).
Add g_ptr_array_new_null_terminated() constructor. The null-terminated flag
cannot be cleared. Once the GPtrArray is flagged to be %NULL terminated, it
sticks. The purpose is that once a user checks whether a GPtrArray instance
is safe to be treated as a %NULL terminated array, the decision does
not need to be re-evaluated.
Also add a g_ptr_array_is_null_terminated(). That is useful because it
allows you to check whether a GPtrArray created by somebody else is safe
to use as a %NULL terminated array. Since there is no API to make an
array not %NULL terminated anymore, this is not error prone.
The new flag is tracked as a guint8 in GRealPtrArray. On common 64 bit
architectures this does not increase the size of the struct as it fits
in an existing hole. Note that this is not a bitfield because it's
probably more efficient to access the entire guint8. However, there is
still a 3 bytes hole (on common 32 and 64 architectures), so if we need
to add more flags in the future, we still have space for 24 bits,
despite the new flag not being a bitfield.
The biggest downside of the patch is the runtime overhead that most
operations now need to check whether %NULL termination is requested.
https://gitlab.gnome.org/GNOME/glib/-/issues/353
docs/reference/glib/glib-sections.txt | 2 +
glib/garray.c | 184 ++++++++++++++++++++++++++++------
glib/garray.h | 7 ++
glib/tests/array-test.c | 64 ++++++++++--
4 files changed, 220 insertions(+), 37 deletions(-)
---
diff --git a/docs/reference/glib/glib-sections.txt b/docs/reference/glib/glib-sections.txt
index eed764893..3a7e3428a 100644
--- a/docs/reference/glib/glib-sections.txt
+++ b/docs/reference/glib/glib-sections.txt
@@ -2928,7 +2928,9 @@ g_ptr_array_sized_new
g_ptr_array_new_with_free_func
g_ptr_array_copy
g_ptr_array_new_full
+g_ptr_array_new_null_terminated
g_ptr_array_set_free_func
+g_ptr_array_is_null_terminated
g_ptr_array_ref
g_ptr_array_unref
g_ptr_array_add
diff --git a/glib/garray.c b/glib/garray.c
index 215788b39..79a70c5f9 100644
--- a/glib/garray.c
+++ b/glib/garray.c
@@ -1058,6 +1058,7 @@ struct _GRealPtrArray
guint len;
guint alloc;
gatomicrefcount ref_count;
+ guint8 null_terminated; /* always either 0 or 1, so it can be added to array lengths */
GDestroyNotify element_free_func;
};
@@ -1077,9 +1078,17 @@ struct _GRealPtrArray
static void g_ptr_array_maybe_expand (GRealPtrArray *array,
guint len);
+static void
+ptr_array_null_terminate (GRealPtrArray *rarray)
+{
+ if (G_UNLIKELY (rarray->null_terminated))
+ rarray->pdata[rarray->len] = NULL;
+}
+
static GPtrArray *
ptr_array_new (guint reserved_size,
- GDestroyNotify element_free_func)
+ GDestroyNotify element_free_func,
+ gboolean null_terminated)
{
GRealPtrArray *array;
@@ -1088,12 +1097,25 @@ ptr_array_new (guint reserved_size,
array->pdata = NULL;
array->len = 0;
array->alloc = 0;
+ array->null_terminated = null_terminated ? 1 : 0;
array->element_free_func = element_free_func;
g_atomic_ref_count_init (&array->ref_count);
if (reserved_size != 0)
- g_ptr_array_maybe_expand (array, reserved_size);
+ {
+ if (G_LIKELY (reserved_size < G_MAXUINT) &&
+ null_terminated)
+ reserved_size++;
+ g_ptr_array_maybe_expand (array, reserved_size);
+ if (null_terminated)
+ {
+ /* don't use ptr_array_null_terminate(). It helps the compiler
+ * to see when @null_terminated is false and thereby inline
+ * ptr_array_new() and possibly remove the code entirely. */
+ array->pdata[0] = NULL;
+ }
+ }
return (GPtrArray *) array;
}
@@ -1108,7 +1130,7 @@ ptr_array_new (guint reserved_size,
GPtrArray *
g_ptr_array_new (void)
{
- return ptr_array_new (0, NULL);
+ return ptr_array_new (0, NULL, FALSE);
}
/**
@@ -1202,7 +1224,8 @@ g_ptr_array_steal (GPtrArray *array,
* pointing to) are copied to the new #GPtrArray.
*
* The copy of @array will have the same #GDestroyNotify for its elements as
- * @array.
+ * @array. The copy will also be %NULL terminated if (and only if) the source
+ * array is.
*
* Returns: (transfer full): a deep copy of the initial #GPtrArray.
*
@@ -1213,27 +1236,39 @@ g_ptr_array_copy (GPtrArray *array,
GCopyFunc func,
gpointer user_data)
{
+ GRealPtrArray *rarray = (GRealPtrArray *) array;
GPtrArray *new_array;
g_return_val_if_fail (array != NULL, NULL);
- new_array = ptr_array_new (array->len,
- ((GRealPtrArray *) array)->element_free_func);
+ new_array = ptr_array_new (0,
+ rarray->element_free_func,
+ rarray->null_terminated);
- if (func != NULL)
+ if (rarray->alloc > 0)
{
- guint i;
+ g_ptr_array_maybe_expand ((GRealPtrArray *) new_array, array->len + rarray->null_terminated);
- for (i = 0; i < array->len; i++)
- new_array->pdata[i] = func (array->pdata[i], user_data);
- }
- else if (array->len > 0)
- {
- memcpy (new_array->pdata, array->pdata,
- array->len * sizeof (*array->pdata));
- }
+ if (array->len > 0)
+ {
+ if (func != NULL)
+ {
+ guint i;
- new_array->len = array->len;
+ for (i = 0; i < array->len; i++)
+ new_array->pdata[i] = func (array->pdata[i], user_data);
+ }
+ else
+ {
+ memcpy (new_array->pdata, array->pdata,
+ array->len * sizeof (*array->pdata));
+ }
+
+ new_array->len = array->len;
+ }
+
+ ptr_array_null_terminate (rarray);
+ }
return new_array;
}
@@ -1252,7 +1287,7 @@ g_ptr_array_copy (GPtrArray *array,
GPtrArray *
g_ptr_array_sized_new (guint reserved_size)
{
- return ptr_array_new (reserved_size, NULL);
+ return ptr_array_new (reserved_size, NULL, FALSE);
}
/**
@@ -1296,14 +1331,14 @@ g_array_copy (GArray *array)
* either via g_ptr_array_unref(), when g_ptr_array_free() is called with
* @free_segment set to %TRUE or when removing elements.
*
- * Returns: A new #GPtrArray
+ * Returns: (transfer full): A new #GPtrArray
*
* Since: 2.22
*/
GPtrArray *
g_ptr_array_new_with_free_func (GDestroyNotify element_free_func)
{
- return ptr_array_new (0, element_free_func);
+ return ptr_array_new (0, element_free_func, FALSE);
}
/**
@@ -1320,7 +1355,7 @@ g_ptr_array_new_with_free_func (GDestroyNotify element_free_func)
* g_ptr_array_unref(), when g_ptr_array_free() is called with
* @free_segment set to %TRUE or when removing elements.
*
- * Returns: A new #GPtrArray
+ * Returns: (transfer full): A new #GPtrArray
*
* Since: 2.30
*/
@@ -1328,7 +1363,45 @@ GPtrArray *
g_ptr_array_new_full (guint reserved_size,
GDestroyNotify element_free_func)
{
- return ptr_array_new (reserved_size, element_free_func);
+ return ptr_array_new (reserved_size, element_free_func, FALSE);
+}
+
+/**
+ * g_ptr_array_new_null_terminated:
+ * @reserved_size: number of pointers preallocated.
+ * If @null_terminated is %TRUE, the actually allocated
+ * buffer size is @reserved_size plus 1, unless @reserved_size
+ * is zero, in which case no initial buffer gets allocated.
+ * @element_free_func: (nullable): A function to free elements with
+ * destroy @array or %NULL
+ * @null_terminated: whether to make the array as %NULL terminated.
+ *
+ * Like g_ptr_array_new_full() but also allows to set the array to
+ * be %NULL terminated. A %NULL terminated pointer array has an
+ * additional %NULL pointer after the last element, beyond the
+ * current length.
+ *
+ * #GPtrArray created by other constructors are not automatically %NULL
+ * terminated.
+ *
+ * Note that if the @array's length is zero and currently no
+ * data array is allocated, then pdata will still be %NULL.
+ * %GPtrArray will only %NULL terminate pdata, if an actual
+ * array is allocated. It does not guarantee that an array
+ * is always allocated. In other words, if the length is zero,
+ * then pdata may either point to a %NULL terminated array of length
+ * zero or be %NULL.
+ *
+ * Returns: (transfer full): A new #GPtrArray
+ *
+ * Since: 2.68
+ */
+GPtrArray *
+g_ptr_array_new_null_terminated (guint reserved_size,
+ GDestroyNotify element_free_func,
+ gboolean null_terminated)
+{
+ return ptr_array_new (reserved_size, element_free_func, null_terminated);
}
/**
@@ -1354,6 +1427,22 @@ g_ptr_array_set_free_func (GPtrArray *array,
rarray->element_free_func = element_free_func;
}
+/**
+ * g_ptr_array_is_null_terminated:
+ * @array: the #GPtrArray
+ *
+ * Returns: %TRUE if the array is made to be %NULL terminated.
+ *
+ * Since: 2.68
+ */
+gboolean
+g_ptr_array_is_null_terminated (GPtrArray *array)
+{
+ g_return_val_if_fail (array, FALSE);
+
+ return ((GRealPtrArray *) array)->null_terminated;
+}
+
/**
* g_ptr_array_ref:
* @array: a #GPtrArray
@@ -1417,6 +1506,10 @@ g_ptr_array_unref (GPtrArray *array)
* be freed separately if @free_seg is %TRUE and no #GDestroyNotify
* function has been set for @array.
*
+ * Note that if the array is %NULL terminated and @free_seg is %FALSE
+ * and the pdata is %NULL (and the length is zero), the this function
+ * will return %NULL too and not allocate an empty %NULL terminated buffer.
+ *
* This function is not thread-safe. If using a #GPtrArray from multiple
* threads, use only the atomic g_ptr_array_ref() and g_ptr_array_unref()
* functions.
@@ -1499,6 +1592,7 @@ g_ptr_array_maybe_expand (GRealPtrArray *array,
if ((array->len + len) > array->alloc)
{
guint old_alloc = array->alloc;
+
array->alloc = g_nearest_pow (array->len + len);
array->alloc = MAX (array->alloc, MIN_ARRAY_SIZE);
array->pdata = g_realloc (array->pdata, sizeof (gpointer) * array->alloc);
@@ -1534,7 +1628,13 @@ g_ptr_array_set_size (GPtrArray *array,
if (length_unsigned > rarray->len)
{
guint i;
- g_ptr_array_maybe_expand (rarray, (length_unsigned - rarray->len));
+
+ if (G_UNLIKELY (rarray->null_terminated) &&
+ length_unsigned - rarray->len > G_MAXUINT - 1)
+ g_error ("array would overflow");
+
+ g_ptr_array_maybe_expand (rarray, (length_unsigned - rarray->len) + rarray->null_terminated);
+
/* This is not
* memset (array->pdata + array->len, 0,
* sizeof (gpointer) * (length_unsigned - array->len));
@@ -1543,11 +1643,13 @@ g_ptr_array_set_size (GPtrArray *array,
*/
for (i = rarray->len; i < length_unsigned; i++)
rarray->pdata[i] = NULL;
+
+ rarray->len = length_unsigned;
+
+ ptr_array_null_terminate (rarray);
}
else if (length_unsigned < rarray->len)
g_ptr_array_remove_range (array, length_unsigned, rarray->len - length_unsigned);
-
- rarray->len = length_unsigned;
}
static gpointer
@@ -1577,7 +1679,8 @@ ptr_array_remove_index (GPtrArray *array,
rarray->len -= 1;
- if (G_UNLIKELY (g_mem_gc_friendly))
+ if (G_UNLIKELY (g_mem_gc_friendly) ||
+ rarray->null_terminated)
rarray->pdata[rarray->len] = NULL;
return result;
@@ -1693,6 +1796,10 @@ g_ptr_array_remove_range (GPtrArray *array,
g_return_val_if_fail (rarray != NULL, NULL);
g_return_val_if_fail (rarray->len == 0 || (rarray->len != 0 && rarray->pdata != NULL), NULL);
g_return_val_if_fail (index_ <= rarray->len, NULL);
+
+ if (length == 0)
+ return array;
+
g_return_val_if_fail (index_ + length <= rarray->len, NULL);
if (rarray->element_free_func != NULL)
@@ -1714,6 +1821,8 @@ g_ptr_array_remove_range (GPtrArray *array,
for (i = 0; i < length; i++)
rarray->pdata[rarray->len + i] = NULL;
}
+ else
+ ptr_array_null_terminate (rarray);
return array;
}
@@ -1810,9 +1919,11 @@ g_ptr_array_add (GPtrArray *array,
g_return_if_fail (rarray);
g_return_if_fail (rarray->len == 0 || (rarray->len != 0 && rarray->pdata != NULL));
- g_ptr_array_maybe_expand (rarray, 1);
+ g_ptr_array_maybe_expand (rarray, 1u + rarray->null_terminated);
rarray->pdata[rarray->len++] = data;
+
+ ptr_array_null_terminate (rarray);
}
/**
@@ -1835,6 +1946,8 @@ g_ptr_array_add (GPtrArray *array,
* If @func is %NULL, then only the pointers (and not what they are
* pointing to) are copied to the new #GPtrArray.
*
+ * Whether @array_to_extend is %NULL terminated stays unchanged by this function.
+ *
* Since: 2.62
**/
void
@@ -1848,7 +1961,14 @@ g_ptr_array_extend (GPtrArray *array_to_extend,
g_return_if_fail (array_to_extend != NULL);
g_return_if_fail (array != NULL);
- g_ptr_array_maybe_expand (rarray_to_extend, array->len);
+ if (array->len == 0u)
+ return;
+
+ if (G_UNLIKELY (array->len == G_MAXUINT) &&
+ rarray_to_extend->null_terminated)
+ g_error ("adding %u to array would overflow", array->len);
+
+ g_ptr_array_maybe_expand (rarray_to_extend, array->len + rarray_to_extend->null_terminated);
if (func != NULL)
{
@@ -1858,13 +1978,15 @@ g_ptr_array_extend (GPtrArray *array_to_extend,
rarray_to_extend->pdata[i + rarray_to_extend->len] =
func (array->pdata[i], user_data);
}
- else if (array->len > 0)
+ else
{
memcpy (rarray_to_extend->pdata + rarray_to_extend->len, array->pdata,
array->len * sizeof (*array->pdata));
}
rarray_to_extend->len += array->len;
+
+ ptr_array_null_terminate (rarray_to_extend);
}
/**
@@ -1922,7 +2044,7 @@ g_ptr_array_insert (GPtrArray *array,
g_return_if_fail (index_ >= -1);
g_return_if_fail (index_ <= (gint)rarray->len);
- g_ptr_array_maybe_expand (rarray, 1);
+ g_ptr_array_maybe_expand (rarray, 1u + rarray->null_terminated);
if (index_ < 0)
index_ = rarray->len;
@@ -1934,6 +2056,8 @@ g_ptr_array_insert (GPtrArray *array,
rarray->len++;
rarray->pdata[index_] = data;
+
+ ptr_array_null_terminate (rarray);
}
/* Please keep this doc-comment in sync with pointer_array_sort_example()
diff --git a/glib/garray.h b/glib/garray.h
index 67131b5b3..b8a63a79d 100644
--- a/glib/garray.h
+++ b/glib/garray.h
@@ -152,6 +152,10 @@ GPtrArray* g_ptr_array_sized_new (guint reserved_size);
GLIB_AVAILABLE_IN_ALL
GPtrArray* g_ptr_array_new_full (guint reserved_size,
GDestroyNotify element_free_func);
+GLIB_AVAILABLE_IN_2_68
+GPtrArray* g_ptr_array_new_null_terminated (guint reserved_size,
+ GDestroyNotify element_free_func,
+ gboolean null_terminated);
GLIB_AVAILABLE_IN_ALL
gpointer* g_ptr_array_free (GPtrArray *array,
gboolean free_seg);
@@ -223,6 +227,9 @@ gboolean g_ptr_array_find_with_equal_func (GPtrArray *haystack,
GEqualFunc equal_func,
guint *index_);
+GLIB_AVAILABLE_IN_2_68
+gboolean g_ptr_array_is_null_terminated (GPtrArray *array);
+
/* Byte arrays, an array of guint8. Implemented as a GArray,
* but type-safe.
diff --git a/glib/tests/array-test.c b/glib/tests/array-test.c
index adedfc19f..5214cf0b9 100644
--- a/glib/tests/array-test.c
+++ b/glib/tests/array-test.c
@@ -845,6 +845,23 @@ test_array_copy_sized (void)
g_array_unref (array1);
}
+#define _assert_ptr_array_null_terminated(array, null_terminated) \
+ G_STMT_START \
+ { \
+ GPtrArray *const _array = (array); \
+ const gboolean _null_terminated = (null_terminated); \
+ \
+ g_assert_cmpint(_null_terminated, ==, g_ptr_array_is_null_terminated(_array)); \
+ if (_array->pdata) \
+ { \
+ if (_null_terminated) \
+ g_assert (!_array->pdata[_array->len]); \
+ } \
+ else \
+ g_assert_cmpint (_array->len, ==, 0); \
+ } \
+ G_STMT_END
+
/* Check g_ptr_array_steal() function */
static void
pointer_array_steal (void)
@@ -936,16 +953,26 @@ pointer_array_insert (void)
}
static void
-pointer_array_ref_count (void)
+pointer_array_ref_count (gconstpointer test_data)
{
+ const gboolean NULL_TERMINATED = GPOINTER_TO_INT(test_data);
GPtrArray *gparray;
GPtrArray *gparray2;
gint i;
gint sum = 0;
- gparray = g_ptr_array_new ();
+ if (NULL_TERMINATED || (g_test_rand_int () % 2))
+ gparray = g_ptr_array_new_null_terminated (0, NULL, NULL_TERMINATED);
+ else
+ gparray = g_ptr_array_new ();
+
+ _assert_ptr_array_null_terminated(gparray, NULL_TERMINATED);
+
for (i = 0; i < 10000; i++)
- g_ptr_array_add (gparray, GINT_TO_POINTER (i));
+ {
+ g_ptr_array_add (gparray, GINT_TO_POINTER (i));
+ _assert_ptr_array_null_terminated(gparray, NULL_TERMINATED);
+ }
/* check we can ref, unref and still access the array */
gparray2 = g_ptr_array_ref (gparray);
@@ -954,6 +981,8 @@ pointer_array_ref_count (void)
for (i = 0; i < 10000; i++)
g_assert (g_ptr_array_index (gparray, i) == GINT_TO_POINTER (i));
+ _assert_ptr_array_null_terminated(gparray, NULL_TERMINATED);
+
g_ptr_array_foreach (gparray, sum_up, &sum);
g_assert (sum == 49995000);
@@ -962,6 +991,8 @@ pointer_array_ref_count (void)
g_ptr_array_free (gparray, TRUE);
g_assert_cmpint (gparray2->len, ==, 0);
+ _assert_ptr_array_null_terminated(gparray, NULL_TERMINATED);
+
g_ptr_array_unref (gparray2);
}
@@ -1600,19 +1631,32 @@ steal_destroy_notify (gpointer data)
/* Test that g_ptr_array_steal_index() and g_ptr_array_steal_index_fast() can
* remove elements from a pointer array without the #GDestroyNotify being called. */
static void
-pointer_array_steal_index (void)
+pointer_array_steal_index (gconstpointer test_data)
{
+ const gboolean NULL_TERMINATED = GPOINTER_TO_INT(test_data);
guint i1 = 0, i2 = 0, i3 = 0, i4 = 0;
gpointer out1, out2;
- GPtrArray *array = g_ptr_array_new_with_free_func (steal_destroy_notify);
+ GPtrArray *array;
+
+ if (NULL_TERMINATED || (g_test_rand_int () % 2))
+ array = g_ptr_array_new_null_terminated (0, steal_destroy_notify, NULL_TERMINATED);
+ else
+ array = g_ptr_array_new_with_free_func (steal_destroy_notify);
+
+ _assert_ptr_array_null_terminated(array, NULL_TERMINATED);
g_ptr_array_add (array, &i1);
g_ptr_array_add (array, &i2);
+
+ _assert_ptr_array_null_terminated(array, NULL_TERMINATED);
+
g_ptr_array_add (array, &i3);
g_ptr_array_add (array, &i4);
g_assert_cmpuint (array->len, ==, 4);
+ _assert_ptr_array_null_terminated(array, NULL_TERMINATED);
+
/* Remove a single element. */
out1 = g_ptr_array_steal_index (array, 0);
g_assert_true (out1 == &i1);
@@ -1624,6 +1668,8 @@ pointer_array_steal_index (void)
g_assert_true (g_ptr_array_index (array, 1) == &i3);
g_assert_true (g_ptr_array_index (array, 2) == &i4);
+ _assert_ptr_array_null_terminated(array, NULL_TERMINATED);
+
/* Remove another element, quickly. */
out2 = g_ptr_array_steal_index_fast (array, 0);
g_assert_true (out2 == &i2);
@@ -1634,6 +1680,8 @@ pointer_array_steal_index (void)
g_assert_true (g_ptr_array_index (array, 0) == &i4);
g_assert_true (g_ptr_array_index (array, 1) == &i3);
+ _assert_ptr_array_null_terminated(array, NULL_TERMINATED);
+
/* Check that destroying the pointer array doesn’t affect the stolen elements. */
g_ptr_array_unref (array);
@@ -2020,7 +2068,8 @@ main (int argc, char *argv[])
/* pointer arrays */
g_test_add_func ("/pointerarray/add", pointer_array_add);
g_test_add_func ("/pointerarray/insert", pointer_array_insert);
- g_test_add_func ("/pointerarray/ref-count", pointer_array_ref_count);
+ g_test_add_data_func ("/pointerarray/ref-count/0", GINT_TO_POINTER (0), pointer_array_ref_count);
+ g_test_add_data_func ("/pointerarray/ref-count/1", GINT_TO_POINTER (1), pointer_array_ref_count);
g_test_add_func ("/pointerarray/free-func", pointer_array_free_func);
g_test_add_func ("/pointerarray/array_copy", pointer_array_copy);
g_test_add_func ("/pointerarray/array_extend", pointer_array_extend);
@@ -2032,7 +2081,8 @@ main (int argc, char *argv[])
g_test_add_func ("/pointerarray/find/empty", pointer_array_find_empty);
g_test_add_func ("/pointerarray/find/non-empty", pointer_array_find_non_empty);
g_test_add_func ("/pointerarray/steal", pointer_array_steal);
- g_test_add_func ("/pointerarray/steal_index", pointer_array_steal_index);
+ g_test_add_data_func ("/pointerarray/steal_index/0", GINT_TO_POINTER (0), pointer_array_steal_index);
+ g_test_add_data_func ("/pointerarray/steal_index/1", GINT_TO_POINTER (1), pointer_array_steal_index);
/* byte arrays */
g_test_add_func ("/bytearray/steal", byte_array_steal);
[
Date Prev][
Date Next] [
Thread Prev][
Thread Next]
[
Thread Index]
[
Date Index]
[
Author Index]
