Commit 130af61d authored by Tim Peters's avatar Tim Peters

BTree_lastBucket(): documented what this returns (between who owns

references, what must not be and what may be a ghost, and exactly what
"last" means, it was surprisingly unclear).  Also simplified the
implementation (to my eyes -- it's arguable, but I'm the one working
on it, so my eyes count <wink>).  I believe this routine is key to
fixing the range-search bug efficiently.
parent 6c211f2c
...@@ -12,7 +12,7 @@ ...@@ -12,7 +12,7 @@
****************************************************************************/ ****************************************************************************/
#define BTREETEMPLATE_C "$Id: BTreeTemplate.c,v 1.46 2002/06/12 20:51:46 tim_one Exp $\n" #define BTREETEMPLATE_C "$Id: BTreeTemplate.c,v 1.47 2002/06/13 02:12:27 tim_one Exp $\n"
/* /*
** _BTree_get ** _BTree_get
...@@ -280,30 +280,41 @@ BTree_grow(BTree *self, int index, int noval) ...@@ -280,30 +280,41 @@ BTree_grow(BTree *self, int index, int noval)
return 0; return 0;
} }
/* Return the rightmost bucket reachable from following child pointers
* from self. The caller gets a new reference to this bucket. Note that
* bucket 'next' pointers are not followed: if self is an interior node
* of a BTree, this returns the rightmost bucket in that node's subtree.
* In case of error, returns NULL.
*
* self must not be a ghost; this isn't checked. The result may be a ghost.
*
* Pragmatics: Note that the rightmost bucket's last key is the largest
* key in self's subtree.
*/
static Bucket * static Bucket *
BTree_lastBucket(BTree *self) BTree_lastBucket(BTree *self)
{ {
PyObject *o; Sized *pchild;
Bucket *result;
UNLESS (self->data && self->len) UNLESS (self->data && self->len) {
{ IndexError(-1); /*XXX*/
IndexError(-1); /*XXX*/ return NULL;
return NULL;
} }
o = OBJECT(self->data[self->len - 1].child); pchild = self->data[self->len - 1].child;
Py_INCREF(o); if (SameType_Check(self, pchild)) {
self = BTREE(pchild);
UNLESS (SameType_Check(self, o)) return BUCKET(o); PER_USE_OR_RETURN(self, NULL);
result = BTree_lastBucket(self);
self=BTREE(o); PER_ALLOW_DEACTIVATION(self);
PER_ACCESSED(self);
PER_USE_OR_RETURN(self, NULL); }
ASSIGN(o, OBJECT(BTree_lastBucket(self))); else {
PER_ALLOW_DEACTIVATION(self); Py_INCREF(pchild);
PER_ACCESSED(self); result = BUCKET(pchild);
}
return BUCKET(o); return result;
} }
static int static int
......
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