mirrors/emacs
1
Fork 0
mirror of git://git.sv.gnu.org/emacs.git synced 2026-01-18 08:51:45 -08:00
Code Issues Projects Releases Wiki Activity

itree.c: Clarify how the sentinel is used

Browse source 
* src/itree.c (null_is_sane): New function.
(interval_tree_iter_start): Use it to make sure we haven't garbled null.
(itree_init): Fully initialize `itree_null` here...
(interval_tree_clear): ...instead of here.
(interval_tree_propagate_limit): Remove special code that read NULL->parent.
(interval_tree_remove): Do it explicitly before the call in those two
places where it can happen.
This commit is contained in:
Stefan Monnier 2022-10-05 12:12:01 -04:00
parent 4f4327c0b0
commit aa5a32ca2c
1 changed files with 37 additions and 16 deletions
Download patch file Download diff file Expand all files Collapse all files

53
src/itree.c
View file

@ -114,6 +114,19 @@ static struct interval_generator* interval_generator_create (struct interval_tre
/* The sentinel node, the null node. */
struct interval_node itree_null;
static inline bool
null_is_sane (void)
{
/* The sentinel node has most of its fields read-only, except for `parent`,
`left`, `right` which are write only. */
return itree_null.red == false
&& itree_null.otick == 0
&& itree_null.offset == 0
&& itree_null.begin == PTRDIFF_MIN
&& itree_null.end == PTRDIFF_MIN
&& itree_null.limit == PTRDIFF_MIN;
}
/* +------------------------------------------------------------------------------------+ */
typedef uintptr_t nodeptr_and_flag;
@ -149,7 +162,13 @@ static struct interval_generator *iter;
static void
itree_init (void)
{
itree_null.parent = itree_null.left = itree_null.right = ITREE_NULL;
struct interval_node *null = ITREE_NULL;
null->left = null->right = null->parent = null;
null->offset = null->otick = 0;
null->begin = PTRDIFF_MIN;
null->end = PTRDIFF_MIN;
null->limit = PTRDIFF_MIN; /* => max(x, null.limit) = x */
null->red = false;
iter = interval_generator_create (NULL);
}
@ -310,6 +329,7 @@ interval_node_set_region (struct interval_tree *tree,
else if (end != node->end)
{
node->end = max (node->begin, end);
eassert (node != ITREE_NULL);
interval_tree_propagate_limit (node);
}
}
@ -334,16 +354,7 @@ interval_tree_create (void)
void
interval_tree_clear (struct interval_tree *tree)
{
/* FIXME: Why is this done? */
struct interval_node *null = ITREE_NULL;
null->left = null->right = null->parent = null;
null->offset = null->otick = 0;
null->begin = PTRDIFF_MIN;
null->end = PTRDIFF_MIN;
null->limit = PTRDIFF_MIN; /* => max(x, null.limit) = x */
null->red = false;
tree->root = null;
tree->root = ITREE_NULL;
tree->otick = 1;
tree->size = 0;
}
@ -461,7 +472,9 @@ interval_tree_remove (struct interval_tree *tree, struct interval_node *node)
if (!node->red)
broken = subst;
interval_tree_transplant (tree, subst, node);
interval_tree_propagate_limit (subst);
interval_tree_propagate_limit
/* FIXME: null->parent is supposed to be write only! */
(subst == ITREE_NULL ? ITREE_NULL->parent : subst);
}
else
{
@ -472,7 +485,12 @@ interval_tree_remove (struct interval_tree *tree, struct interval_node *node)
broken = min->right;
eassert (min != ITREE_NULL);
if (min->parent == node)
min_right->parent = min; /* set parent, if min_right = null */
{
if (min_right == ITREE_NULL)
ITREE_NULL->parent = min; /* set parent, if min_right = null */
else
eassert (min_right->parent == min);
}
else
{
interval_tree_transplant (tree, min->right, min);
@ -484,7 +502,9 @@ interval_tree_remove (struct interval_tree *tree, struct interval_node *node)
min->left = node->left;
min->left->parent = min;
min->red = node->red;
interval_tree_propagate_limit (min_right);
interval_tree_propagate_limit
/* FIXME: null->parent is supposed to be write only! */
(min_right == ITREE_NULL ? ITREE_NULL->parent : min_right);
interval_tree_propagate_limit (min);
}
@ -523,6 +543,7 @@ interval_tree_iter_start (struct interval_tree *tree,
enum interval_tree_order order,
const char* file, int line)
{
eassert (null_is_sane ());
/* struct interval_generator *iter = tree->iter; */
if (iter->running)
{
@ -625,6 +646,7 @@ interval_tree_insert_gap (struct interval_tree *tree, ptrdiff_t pos, ptrdiff_t l
if (node->end > pos || (node->end == pos && node->rear_advance))
{
node->end += length;
eassert (node != ITREE_NULL);
interval_tree_propagate_limit (node);
}
}
@ -689,6 +711,7 @@ interval_tree_delete_gap (struct interval_tree *tree, ptrdiff_t pos, ptrdiff_t l
if (node->end > pos)
{
node->end = max (pos , node->end - length);
eassert (node != ITREE_NULL);
interval_tree_propagate_limit (node);
}
}
@ -875,8 +898,6 @@ interval_tree_inherit_offset (uintmax_t otick, struct interval_node *node)
static void
interval_tree_propagate_limit (struct interval_node *node)
{
if (node == ITREE_NULL)
node = node->parent;
if (node == ITREE_NULL)
return;