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Commit 49592586 authored by Tim Peters's avatar Tim Peters
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firstBucketOffset(), lastBucketOffset(): removed these functions. Their 

purpose wasn't clear, and the few places that bothered to call them seemed
to be trying to cater to empty buckets.  But empty buckets aren't legitimate
in a BTree (or, if they are, lots of BTree code is broken).

BTreeItems struct:  finished figuring out what's in this, and documented it.

BTreeItems_seek():  rewrote and simplified, to avoid use of the now-
removed XYZBucketOffset() functions.  Repaired places where bucket access
time wasn't getting updated.  There are still insecurities in its use of
PreviousBucket() (for another day).

BTreeItems_slice():  now that I know what it is <wink>, create an empty
slice in the intended way.

NewBTreeItems():  documented its calling sequence, and added code to
protect against a NULL highbucket argument.

BTree_maxminKey():  no longer calls the XYZBucketOffset() functions.
parent 81a354c7
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Showing with 130 additions and 249 deletions
src/BTrees/BTreeItemsTemplate.c
View file @ 49592586
......@@ -12,7 +12,7 @@
****************************************************************************/
#define BTREEITEMSTEMPLATE_C "$Id: BTreeItemsTemplate.c,v 1.13 2002/06/10 14:44:55 tim_one Exp $\n"
#define BTREEITEMSTEMPLATE_C "$Id: BTreeItemsTemplate.c,v 1.14 2002/06/17 23:39:56 tim_one Exp $\n"
/* A BTreeItems struct is returned from calling .items(), .keys() or
* .values() on a BTree-based data structure, and is also the result of
......@@ -20,30 +20,34 @@
*
* The start of the slice is in firstbucket, at offset first. The end of
* the slice is in lastbucket, at offset last. Both endpoints are inclusive.
* It should be possible to get from firstbucket to lastbucket via following
* It must possible to get from firstbucket to lastbucket via following
* bucket 'next' pointers zero or more times. firstbucket, first, lastbucket,
* and last are readonly after initialization. An empty slice is represented
* by [XXX (firstbucket == NULL) or (firstbucket == lastbucket and
* first > last) XXX].
* by firstbucket == lastbucket == currentbucket == NULL.
*
* 'kind' determines whether this slice represents 'k'eys alone, 'v'alues
* alone, or 'i'items (key+value pairs). 'kind' is also readonly after
* initialization.
*
* [XXX currentoffset and currentbucket appear to be used to return function
* results XXX]
*
* [XXX pseudoindex may be the index corresponding to the position identified
* by the currentbucket+currenoffset pair. Seems to be a kind of search
* finger. XXX]
* The combination of currentbucket, currentoffset and pseudoindex acts as
* a search finger. Offset currentoffset in bucket currentbucket is at index
* pseudoindex, where pseudoindex==0 corresponds to offset first in bucket
* firstbucket, and pseudoindex==-1 corresponds to offset last in bucket
* lastbucket. The function BTreeItems_seek() can be used to set this combo
* correctly for any in-bounds index, and uses this combo on input to avoid
* needing to search from the start (or end) on each call. Calling
* BTreeItems_seek() with consecutive larger positions is very efficent.
* Calling it with consecutive smaller positions is more efficient than if
* a search finger weren't being used at all, but is still quadratic time
* in the number of buckets in the slice.
*/
typedef struct {
PyObject_HEAD
Bucket *firstbucket; /* First bucket */
Bucket *currentbucket; /* Current bucket */
Bucket *currentbucket; /* Current bucket (search finger) */
Bucket *lastbucket; /* Last bucket */
int currentoffset; /* Offset in currentbucket */
int pseudoindex; /* It's an indicator (what?) */
int pseudoindex; /* search finger index */
int first; /* Start offset in firstbucket */
int last; /* End offset in lastbucket */
char kind; /* 'k', 'v', 'i' */
......@@ -117,15 +121,16 @@ BTreeItems_length( BTreeItems *self)
/*
** BTreeItems_seek
**
** Find the ith position in the BTreeItems. Pseudoindex is used to
** determine motion relative to the current bucket.
** Find the ith position in the BTreeItems.
**
** Arguments: self The BTree
** i the index to seek to, positive for a forward
** index (0..n) or negative (-m..-1) (m=n+1)
** i the index to seek to, in 0 .. len(self)-1, or in
** -len(self) .. -1, as for indexing a Python sequence.
**
**
** Returns 0 if successful, -1 on failure to seek
** Returns 0 if successful, -1 on failure to seek (like out-of-bounds).
** Upon successful return, index i is at offset self->currentoffset in bucket
** self->currentbucket.
*/
static int
BTreeItems_seek(BTreeItems *self, int i)
......@@ -133,174 +138,99 @@ BTreeItems_seek(BTreeItems *self, int i)
int delta, pseudoindex, currentoffset;
Bucket *b, *currentbucket;
currentbucket=self->currentbucket;
UNLESS(currentbucket)
{
IndexError(i);
return -1;
}
pseudoindex = self->pseudoindex;
currentoffset = self->currentoffset;
currentbucket = self->currentbucket;
if (currentbucket == NULL) goto no_match;
pseudoindex=self->pseudoindex;
Py_INCREF(currentbucket);
currentoffset=self->currentoffset;
/* Make sure that the index and psuedoindex have the same sign */
if (pseudoindex < 0 && i >=0)
{
/* Make sure that the index and pseudoindex have the same sign. */
if (pseudoindex < 0 && i >= 0) {
/* Position to the start of the sequence. */
ASSIGNB(currentbucket, self->firstbucket);
Py_INCREF(currentbucket);
currentbucket = self->firstbucket;
currentoffset = self->first;
UNLESS (PER_USE(currentbucket)) goto err;
/* We need to be careful that we have a valid offset! */
if (currentoffset >= currentbucket->len)
{
switch (firstBucketOffset(&currentbucket, &currentoffset))
{
case 0: goto no_match;
case -1: goto err;
}
}
pseudoindex = 0;
}
else if (self->pseudoindex >= 0 && i < 0)
{
else if (pseudoindex >= 0 && i < 0) {
/* Position to the end of the sequence. */
ASSIGNBC(currentbucket, self->lastbucket);
currentbucket = self->lastbucket;
currentoffset = self->last;
UNLESS (PER_USE(currentbucket)) goto err;
/* We need to be careful that we have a valid offset! */
if (currentoffset >= currentbucket->len)
{
switch (lastBucketOffset(&currentbucket, &currentoffset,
self->firstbucket, i))
{
case 0: goto no_match;
case -1: goto err;
}
}
pseudoindex = -1;
}
else
{
UNLESS (PER_USE(currentbucket)) goto err;
/* We need to be careful that we have a valid offset! */
if (currentoffset >= currentbucket->len) goto no_match;
}
/* Whew, we got here so we have a valid offset! */
PER_USE_OR_RETURN(currentbucket, -1);
delta = i - pseudoindex;
if (delta)
while (delta)
{
if (delta < 0)
{
/* First, would we drop below zero? */
if (pseudoindex >= 0 && pseudoindex + delta < 0) goto no_match;
/* Next, do we have to backup a bucket? */
if (currentoffset + delta < 0)
{
if (currentbucket == self->firstbucket) goto no_match;
b=PreviousBucket(currentbucket, self->firstbucket, i);
if (b==NULL) goto no_match;
while (delta > 0) { /* move right */
int max;
/* Want to move right delta positions; the most we can move right in
* this bucket is currentbucket->len - currentoffset - 1 positions.
*/
max = currentbucket->len - currentoffset - 1;
if (delta <= max) {
currentoffset += delta;
pseudoindex += delta;
if (currentbucket == self->lastbucket
&& currentoffset > self->last) {
PER_ALLOW_DEACTIVATION(currentbucket);
PER_ACCESSED(currentbucket);
ASSIGNB(currentbucket, b);
UNLESS (PER_USE(currentbucket)) goto err;
delta += currentoffset;
pseudoindex -= currentoffset + 1;
if ((currentoffset = currentbucket->len - 1) < 0)
/* We backed into an empty bucket. Fix the psuedo index */
if (++pseudoindex == 0) goto no_match;
}
else
{ /* Local adjustment */
pseudoindex += delta;
currentoffset += delta;
goto no_match;
}
if (currentbucket == self->firstbucket &&
currentoffset < self->first) goto no_match;
break;
}
else if (delta > 0)
{
/* Simple backwards range check */
if (pseudoindex < 0 && pseudoindex + delta >= 0)
goto no_match;
/* Next, do we go forward a bucket? */
if (currentoffset + delta >= currentbucket->len)
{
while (1)
{
if (currentbucket == self->lastbucket) goto no_match;
if ((b=currentbucket->next) == NULL) goto no_match;
delta -= currentbucket->len - currentoffset;
pseudoindex += (currentbucket->len - currentoffset);
Py_INCREF(b);
/* Move to start of next bucket. */
b = currentbucket->next;
PER_ALLOW_DEACTIVATION(currentbucket);
PER_ACCESSED(currentbucket);
ASSIGNB(currentbucket, b);
UNLESS (PER_USE(currentbucket)) goto err;
if (currentbucket == self->lastbucket || b == NULL) goto no_match;
currentbucket = b;
PER_USE_OR_RETURN(currentbucket, -1);
pseudoindex += max + 1;
delta -= max + 1;
currentoffset = 0;
if (currentbucket->len) break;
}
}
else
{ /* Local adjustment */
pseudoindex += delta;
while (delta < 0) { /* move left */
/* Want to move left -delta positions; the most we can move left in
* this bucket is currentoffset positions.
*/
if ((-delta) <= currentoffset) {
currentoffset += delta;
pseudoindex += delta;
if (currentbucket == self->firstbucket
&& currentoffset < self->first) {
PER_ALLOW_DEACTIVATION(currentbucket);
PER_ACCESSED(currentbucket);
goto no_match;
}
if (currentbucket == self->lastbucket &&
currentoffset > self->last) goto no_match;
}
delta = i - pseudoindex;
break;
}
else
{ /* Sanity check current bucket/offset */
if (currentbucket == self->firstbucket &&currentoffset < self->first)
goto no_match;
if (currentbucket == self->lastbucket && currentoffset > self->last)
goto no_match;
/* Move to end of previous bucket. */
PER_ALLOW_DEACTIVATION(currentbucket);
PER_ACCESSED(currentbucket);
if (currentbucket == self->firstbucket) goto no_match;
b = PreviousBucket(currentbucket, self->firstbucket, i);
if (b == NULL) goto no_match; /* XXX this could be another error */
Py_DECREF(b); /* we didn't really want it incref'ed to begin with */
currentbucket = b;
PER_USE_OR_RETURN(currentbucket, -1);
pseudoindex -= currentoffset + 1;
delta += currentoffset + 1;
currentoffset = currentbucket->len - 1;
}
PER_ALLOW_DEACTIVATION(currentbucket);
PER_ACCESSED(currentbucket);
if (currentbucket==self->currentbucket) Py_DECREF(currentbucket);
else ASSIGNB(self->currentbucket, currentbucket);
self->pseudoindex=pseudoindex;
self->currentoffset=currentoffset;
assert(pseudoindex == i);
Py_INCREF(currentbucket);
Py_DECREF(self->currentbucket);
self->currentbucket = currentbucket;
self->currentoffset = currentoffset;
self->pseudoindex = pseudoindex;
return 0;
no_match:
no_match:
IndexError(i);
PER_ALLOW_DEACTIVATION(currentbucket);
err:
Py_XDECREF(currentbucket);
return -1;
}
/*
** BTreeItems_item
**
......@@ -419,7 +349,7 @@ BTreeItems_slice(BTreeItems *self, int ilow, int ihigh)
*/
if (ilow == ihigh) {
/* empty slice */
lowbucket = highbucket = self->currentbucket;
lowbucket = highbucket = NULL;
lowoffset = 1;
highoffset = 0;
}
......@@ -487,6 +417,12 @@ static PyTypeObject BTreeItemsType = {
"Sequence type used to iterate over BTree items." /* Documentation string */
};
/* Returns a new BTreeItems object representing the contiguous slice from
* offset lowoffset in bucket lowbucket through offset highoffset in bucket
* highbucket, inclusive. Pass lowbucket == NULL for an empty slice.
* The currentbucket is set to lowbucket, currentoffset ot lowoffset, and
* pseudoindex to 0. kind is 'k', 'v' or 'i' (see BTreeItems struct docs).
*/
static PyObject *
newBTreeItems(char kind,
Bucket *lowbucket, int lowoffset,
......@@ -495,12 +431,13 @@ newBTreeItems(char kind,
BTreeItems *self;
UNLESS (self = PyObject_NEW(BTreeItems, &BTreeItemsType)) return NULL;
self->kind=kind;
self->kind = kind;
self->first=lowoffset;
self->last=highoffset;
self->first = lowoffset;
self->last = highoffset;
if (! lowbucket || (lowbucket==highbucket && lowoffset > highoffset))
if (! lowbucket || ! highbucket
|| (lowbucket == highbucket && lowoffset > highoffset))
{
self->firstbucket = 0;
self->lastbucket = 0;
......
src/BTrees/BTreeModuleTemplate.c
View file @ 49592586
......@@ -298,43 +298,6 @@ PreviousBucket(Bucket *current, Bucket *first, int i)
}
}
static int
firstBucketOffset(Bucket **bucket, int *offset)
{
Bucket *b;
*offset = (*bucket)->len - 1;
while ((*bucket)->len < 1)
{
b=(*bucket)->next;
if (b==NULL) return 0;
Py_INCREF(b);
PER_ALLOW_DEACTIVATION((*bucket));
ASSIGNB((*bucket), b);
UNLESS (PER_USE(*bucket)) return -1;
*offset = 0;
}
return 1;
}
static int
lastBucketOffset(Bucket **bucket, int *offset, Bucket *firstbucket, int i)
{
Bucket *b;
*offset = (*bucket)->len - 1;
while ((*bucket)->len < 1)
{
b=PreviousBucket((*bucket), firstbucket, i);
if (b==NULL) return 0;
PER_ALLOW_DEACTIVATION((*bucket));
ASSIGNB((*bucket), b);
UNLESS (PER_USE(*bucket)) return -1;
*offset = (*bucket)->len - 1;
}
return 1;
}
static void *
PyMalloc(size_t sz)
{
......@@ -409,7 +372,7 @@ static char BTree_module_documentation[] =
"\n"
MASTER_ID
BTREEITEMSTEMPLATE_C
"$Id: BTreeModuleTemplate.c,v 1.32 2002/06/17 19:21:39 tim_one Exp $\n"
"$Id: BTreeModuleTemplate.c,v 1.33 2002/06/17 23:39:56 tim_one Exp $\n"
BTREETEMPLATE_C
BUCKETTEMPLATE_C
KEYMACROS_H
......
src/BTrees/BTreeTemplate.c
View file @ 49592586
......@@ -12,7 +12,7 @@
****************************************************************************/
#define BTREETEMPLATE_C "$Id: BTreeTemplate.c,v 1.59 2002/06/17 20:31:40 tim_one Exp $\n"
#define BTREETEMPLATE_C "$Id: BTreeTemplate.c,v 1.60 2002/06/17 23:39:56 tim_one Exp $\n"
/*
** _BTree_get
......@@ -1100,19 +1100,8 @@ BTree_maxminKey(BTree *self, PyObject *args, int min)
else if (min)
{
bucket = self->firstbucket;
PER_ALLOW_DEACTIVATION(self);
PER_ACCESSED(self);
UNLESS (PER_USE(bucket)) return NULL;
Py_INCREF(bucket);
offset = 0;
if (offset >= bucket->len)
{
switch (firstBucketOffset(&bucket, &offset))
{
case 0: goto empty;
case -1: goto err;
}
}
}
else
{
......@@ -1124,16 +1113,8 @@ BTree_maxminKey(BTree *self, PyObject *args, int min)
Py_DECREF(bucket);
return NULL;
}
if (bucket->len)
assert(bucket->len);
offset = bucket->len - 1;
else
{
switch (lastBucketOffset(&bucket, &offset, self->firstbucket, -1))
{
case 0: goto empty;
case -1: goto err;
}
}
}
COPY_KEY_TO_OBJECT(key, bucket->keys[offset]);
......
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