#include <libpspp/abt.h>
+#include <stdbool.h>
+
+#include <libpspp/assertion.h>
+
static struct abt_node **down_link (struct abt *, struct abt_node *);
static struct abt_node *skew (struct abt *, struct abt_node *);
static struct abt_node *split (struct abt *, struct abt_node *);
/* Initializes ABT as an empty ABT that uses COMPARE and
- REAUGMENT functions, passing in AUX as auxiliary data. */
+ REAUGMENT functions, passing in AUX as auxiliary data.
+
+ The comparison function is optional. If it is null, this
+ indicates that the tree is being used for its augmentations
+ only. ABT functions that compare nodes may not be used with
+ trees that lack comparison functions; contrariwise, other
+ functions that could disrupt the ordering of a tree may not be
+ used if a comparison function is specified. Refer to
+ individual function descriptions for details. */
void
abt_init (struct abt *abt,
abt_compare_func *compare,
abt_reaugment_func *reaugment,
- const void *aux)
+ const void *aux)
{
+ assert (reaugment != NULL);
abt->root = NULL;
abt->compare = compare;
abt->reaugment = reaugment;
/* Inserts the given NODE into ABT.
Returns a null pointer if successful.
Returns the existing node already in ABT equal to NODE, on
- failure. */
+ failure.
+ This function may be used only if ABT has a comparison
+ function. */
struct abt_node *
-abt_insert (struct abt *abt, struct abt_node *node)
+abt_insert (struct abt *abt, struct abt_node *node)
{
node->down[0] = NULL;
node->down[1] = NULL;
node->level = 1;
- if (abt->root == NULL)
+ if (abt->root == NULL)
{
abt->root = node;
node->up = NULL;
abt_reaugmented (abt, node);
}
- else
+ else
{
struct abt_node *p = abt->root;
- for (;;)
+ for (;;)
{
int cmp, dir;
break;
}
p = p->down[dir];
- }
+ }
}
- while ((node = node->up) != NULL)
+ while ((node = node->up) != NULL)
{
node = skew (abt, node);
node = split (abt, node);
return NULL;
}
+/* Inserts NODE before or after node P in ABT, depending on the
+ value of AFTER.
+ If P is null, then the node is inserted as the first node in
+ the tree, if AFTER is true, or the last node, if AFTER is
+ false. */
+static inline void
+insert_relative (struct abt *abt, struct abt_node *p, bool after,
+ struct abt_node *node)
+{
+ node->down[0] = NULL;
+ node->down[1] = NULL;
+ node->level = 1;
+
+ if (abt->root == NULL)
+ {
+ assert (p == NULL);
+ abt->root = node;
+ node->up = NULL;
+ abt_reaugmented (abt, node);
+ }
+ else
+ {
+ int dir = after;
+ if (p == NULL)
+ {
+ p = abt->root;
+ dir = !after;
+ }
+ while (p->down[dir] != NULL)
+ {
+ p = p->down[dir];
+ dir = !after;
+ }
+ p->down[dir] = node;
+ node->up = p;
+ abt_reaugmented (abt, node);
+ }
+
+ while ((node = node->up) != NULL)
+ {
+ node = skew (abt, node);
+ node = split (abt, node);
+ }
+}
+
+/* Inserts NODE after node P in ABT.
+ If P is null, then the node is inserted as the first node in
+ the tree.
+ This function may be used only if ABT lacks a comparison
+ function. */
+void
+abt_insert_after (struct abt *abt,
+ const struct abt_node *p, struct abt_node *node)
+{
+ assert (abt->compare == NULL);
+ insert_relative (abt, (struct abt_node *) p, true, node);
+}
+
+/* Inserts NODE before node P in ABT.
+ If P is null, then the node is inserted as the last node in
+ the tree.
+ This function may be used only if ABT lacks a comparison
+ function. */
+void
+abt_insert_before (struct abt *abt,
+ const struct abt_node *p, struct abt_node *node)
+{
+ assert (abt->compare == NULL);
+ insert_relative (abt, (struct abt_node *) p, false, node);
+}
+
/* Deletes P from ABT. */
void
abt_delete (struct abt *abt, struct abt_node *p)
}
/* Returns the node with minimum value in ABT, or a null pointer
- if ABT is empty. */
+ if ABT is empty. */
struct abt_node *
-abt_first (const struct abt *abt)
+abt_first (const struct abt *abt)
{
struct abt_node *p = abt->root;
- if (p != NULL)
+ if (p != NULL)
while (p->down[0] != NULL)
p = p->down[0];
return p;
}
/* Returns the node with maximum value in ABT, or a null pointer
- if ABT is empty. */
+ if ABT is empty. */
struct abt_node *
-abt_last (const struct abt *abt)
+abt_last (const struct abt *abt)
{
struct abt_node *p = abt->root;
- if (p != NULL)
+ if (p != NULL)
while (p->down[1] != NULL)
p = p->down[1];
return p;
}
/* Searches ABT for a node equal to TARGET.
- Returns the node if found, or a null pointer otherwise. */
+ Returns the node if found, or a null pointer otherwise.
+ This function may be used only if ABT has a comparison
+ function. */
struct abt_node *
abt_find (const struct abt *abt, const struct abt_node *target)
{
const struct abt_node *p;
int cmp;
-
+
for (p = abt->root; p != NULL; p = p->down[cmp > 0])
{
cmp = abt->compare (target, p, abt->aux);
if (cmp == 0)
return (struct abt_node *) p;
}
-
+
return NULL;
}
Returns a null pointer if P is the maximum node in ABT or if P
is null and ABT is empty. */
struct abt_node *
-abt_next (const struct abt *abt, const struct abt_node *p)
+abt_next (const struct abt *abt, const struct abt_node *p)
{
- if (p == NULL)
+ if (p == NULL)
return abt_first (abt);
else if (p->down[1] == NULL)
{
Returns a null pointer if P is the minimum node in ABT or if P
is null and ABT is empty. */
struct abt_node *
-abt_prev (const struct abt *abt, const struct abt_node *p)
+abt_prev (const struct abt *abt, const struct abt_node *p)
{
- if (p == NULL)
+ if (p == NULL)
return abt_last (abt);
else if (p->down[0] == NULL)
{
affected nodes from the tree, update their values, then
re-insert all of them. */
void
-abt_reaugmented (const struct abt *abt, struct abt_node *p)
+abt_reaugmented (const struct abt *abt, struct abt_node *p)
{
for (; p != NULL; p = p->up)
abt->reaugment (p, p->down[0], p->down[1], abt->aux);
can actually retain its relative position in ABT, e.g. its key
has only been adjusted slightly. Otherwise, it is more
efficient to simply remove P from ABT, change its key, and
- re-insert P.
+ re-insert P.
It is not safe to update more than one node's key, then to
call this function for each node. Instead, update a single
node's key, call this function, update another node's key, and
so on. Alternatively, remove all affected nodes from the
- tree, update their keys, then re-insert all of them. */
+ tree, update their keys, then re-insert all of them.
+
+ This function may be used only if ABT has a comparison
+ function. If it doesn't, then you probably just want
+ abt_reaugmented. */
struct abt_node *
-abt_changed (struct abt *abt, struct abt_node *p)
+abt_changed (struct abt *abt, struct abt_node *p)
{
struct abt_node *prev = abt_prev (abt, p);
struct abt_node *next = abt_next (abt, p);
if ((prev != NULL && abt->compare (prev, p, abt->aux) >= 0)
- || (next != NULL && abt->compare (p, next, abt->aux) >= 0))
+ || (next != NULL && abt->compare (p, next, abt->aux) >= 0))
{
abt_delete (abt, p);
return abt_insert (abt, p);
}
- else
+ else
{
abt_reaugmented (abt, p);
- return NULL;
+ return NULL;
}
}
function for each node. Instead, move a single node, call
this function, move another node, and so on. Alternatively,
remove all affected nodes from the tree, move them, then
- re-insert all of them. */
+ re-insert all of them.
+
+ This function may be used only if ABT has a comparison
+ function. */
void
-abt_moved (struct abt *abt, struct abt_node *p)
+abt_moved (struct abt *abt, struct abt_node *p)
{
- if (p->up != NULL)
+ if (p->up != NULL)
{
int d = p->up->down[0] == NULL || abt->compare (p, p->up, abt->aux) > 0;
- p->up->down[d] = p;
+ p->up->down[d] = p;
}
else
abt->root = p;
/* Returns the address of the pointer that points down to P
within ABT. */
static struct abt_node **
-down_link (struct abt *abt, struct abt_node *p)
+down_link (struct abt *abt, struct abt_node *p)
{
return (p->up != NULL
? &p->up->down[p->up->down[0] != p]
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