greenplumn bitmapset 源码
greenplumn bitmapset 代码
文件路径：/src/backend/nodes/bitmapset.c
/*-------------------------------------------------------------------------
*
* bitmapset.c
* PostgreSQL generic bitmap set package
*
* A bitmap set can represent any set of nonnegative integers, although
* it is mainly intended for sets where the maximum value is not large,
* say at most a few hundred. By convention, a NULL pointer is always
* accepted by all operations to represent the empty set. (But beware
* that this is not the only representation of the empty set. Use
* bms_is_empty() in preference to testing for NULL.)
*
*
* Copyright (c) 2003-2019, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/backend/nodes/bitmapset.c
*
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "common/hashfn.h"
#include "nodes/bitmapset.h"
#include "nodes/pg_list.h"
#include "port/pg_bitutils.h"
#define WORDNUM(x) ((x) / BITS_PER_BITMAPWORD)
#define BITNUM(x) ((x) % BITS_PER_BITMAPWORD)
#define BITMAPSET_SIZE(nwords) \
(offsetof(Bitmapset, words) + (nwords) * sizeof(bitmapword))
/*----------
* This is a well-known cute trick for isolating the rightmost one-bit
* in a word. It assumes two's complement arithmetic. Consider any
* nonzero value, and focus attention on the rightmost one. The value is
* then something like
* xxxxxx10000
* where x's are unspecified bits. The two's complement negative is formed
* by inverting all the bits and adding one. Inversion gives
* yyyyyy01111
* where each y is the inverse of the corresponding x. Incrementing gives
* yyyyyy10000
* and then ANDing with the original value gives
* 00000010000
* This works for all cases except original value = zero, where of course
* we get zero.
*----------
*/
#define RIGHTMOST_ONE(x) ((signedbitmapword) (x) & -((signedbitmapword) (x)))
#define HAS_MULTIPLE_ONES(x) ((bitmapword) RIGHTMOST_ONE(x) != (x))
/* Select appropriate bit-twiddling functions for bitmap word size */
#if BITS_PER_BITMAPWORD == 32
#define bmw_leftmost_one_pos(w) pg_leftmost_one_pos32(w)
#define bmw_rightmost_one_pos(w) pg_rightmost_one_pos32(w)
#define bmw_popcount(w) pg_popcount32(w)
#elif BITS_PER_BITMAPWORD == 64
#define bmw_leftmost_one_pos(w) pg_leftmost_one_pos64(w)
#define bmw_rightmost_one_pos(w) pg_rightmost_one_pos64(w)
#define bmw_popcount(w) pg_popcount64(w)
#else
#error "invalid BITS_PER_BITMAPWORD"
#endif
/*
* bms_copy - make a palloc'd copy of a bitmapset
*/
Bitmapset *
bms_copy(const Bitmapset *a)
{
Bitmapset *result;
size_t size;
if (a == NULL)
return NULL;
size = BITMAPSET_SIZE(a->nwords);
result = (Bitmapset *) palloc(size);
memcpy(result, a, size);
return result;
}
/*
* bms_equal - are two bitmapsets equal?
*
* This is logical not physical equality; in particular, a NULL pointer will
* be reported as equal to a palloc'd value containing no members.
*/
bool
bms_equal(const Bitmapset *a, const Bitmapset *b)
{
const Bitmapset *shorter;
const Bitmapset *longer;
int shortlen;
int longlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL)
{
if (b == NULL)
return true;
return bms_is_empty(b);
}
else if (b == NULL)
return bms_is_empty(a);
/* Identify shorter and longer input */
if (a->nwords <= b->nwords)
{
shorter = a;
longer = b;
}
else
{
shorter = b;
longer = a;
}
/* And process */
shortlen = shorter->nwords;
for (i = 0; i < shortlen; i++)
{
if (shorter->words[i] != longer->words[i])
return false;
}
longlen = longer->nwords;
for (; i < longlen; i++)
{
if (longer->words[i] != 0)
return false;
}
return true;
}
/*
* bms_compare - qsort-style comparator for bitmapsets
*
* This guarantees to report values as equal iff bms_equal would say they are
* equal. Otherwise, the highest-numbered bit that is set in one value but
* not the other determines the result. (This rule means that, for example,
* {6} is greater than {5}, which seems plausible.)
*/
int
bms_compare(const Bitmapset *a, const Bitmapset *b)
{
int shortlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL)
return bms_is_empty(b) ? 0 : -1;
else if (b == NULL)
return bms_is_empty(a) ? 0 : +1;
/* Handle cases where one input is longer than the other */
shortlen = Min(a->nwords, b->nwords);
for (i = shortlen; i < a->nwords; i++)
{
if (a->words[i] != 0)
return +1;
}
for (i = shortlen; i < b->nwords; i++)
{
if (b->words[i] != 0)
return -1;
}
/* Process words in common */
i = shortlen;
while (--i >= 0)
{
bitmapword aw = a->words[i];
bitmapword bw = b->words[i];
if (aw != bw)
return (aw > bw) ? +1 : -1;
}
return 0;
}
/*
* bms_make_singleton - build a bitmapset containing a single member
*/
Bitmapset *
bms_make_singleton(int x)
{
Bitmapset *result;
int wordnum,
bitnum;
if (x < 0)
elog(ERROR, "negative bitmapset member not allowed");
wordnum = WORDNUM(x);
bitnum = BITNUM(x);
result = (Bitmapset *) palloc0(BITMAPSET_SIZE(wordnum + 1));
result->nwords = wordnum + 1;
result->words[wordnum] = ((bitmapword) 1 << bitnum);
return result;
}
/*
* bms_free - free a bitmapset
*
* Same as pfree except for allowing NULL input
*/
void
bms_free(Bitmapset *a)
{
if (a)
pfree(a);
}
/*
* These operations all make a freshly palloc'd result,
* leaving their inputs untouched
*/
/*
* bms_union - set union
*/
Bitmapset *
bms_union(const Bitmapset *a, const Bitmapset *b)
{
Bitmapset *result;
const Bitmapset *other;
int otherlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL)
return bms_copy(b);
if (b == NULL)
return bms_copy(a);
/* Identify shorter and longer input; copy the longer one */
if (a->nwords <= b->nwords)
{
result = bms_copy(b);
other = a;
}
else
{
result = bms_copy(a);
other = b;
}
/* And union the shorter input into the result */
otherlen = other->nwords;
for (i = 0; i < otherlen; i++)
result->words[i] |= other->words[i];
return result;
}
/*
* bms_intersect - set intersection
*/
Bitmapset *
bms_intersect(const Bitmapset *a, const Bitmapset *b)
{
Bitmapset *result;
const Bitmapset *other;
int resultlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL || b == NULL)
return NULL;
/* Identify shorter and longer input; copy the shorter one */
if (a->nwords <= b->nwords)
{
result = bms_copy(a);
other = b;
}
else
{
result = bms_copy(b);
other = a;
}
/* And intersect the longer input with the result */
resultlen = result->nwords;
for (i = 0; i < resultlen; i++)
result->words[i] &= other->words[i];
return result;
}
/*
* bms_difference - set difference (ie, A without members of B)
*/
Bitmapset *
bms_difference(const Bitmapset *a, const Bitmapset *b)
{
Bitmapset *result;
int shortlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL)
return NULL;
if (b == NULL)
return bms_copy(a);
/* Copy the left input */
result = bms_copy(a);
/* And remove b's bits from result */
shortlen = Min(a->nwords, b->nwords);
for (i = 0; i < shortlen; i++)
result->words[i] &= ~b->words[i];
return result;
}
/*
* bms_is_subset - is A a subset of B?
*/
bool
bms_is_subset(const Bitmapset *a, const Bitmapset *b)
{
int shortlen;
int longlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL)
return true; /* empty set is a subset of anything */
if (b == NULL)
return bms_is_empty(a);
/* Check common words */
shortlen = Min(a->nwords, b->nwords);
for (i = 0; i < shortlen; i++)
{
if ((a->words[i] & ~b->words[i]) != 0)
return false;
}
/* Check extra words */
if (a->nwords > b->nwords)
{
longlen = a->nwords;
for (; i < longlen; i++)
{
if (a->words[i] != 0)
return false;
}
}
return true;
}
/*
* bms_subset_compare - compare A and B for equality/subset relationships
*
* This is more efficient than testing bms_is_subset in both directions.
*/
BMS_Comparison
bms_subset_compare(const Bitmapset *a, const Bitmapset *b)
{
BMS_Comparison result;
int shortlen;
int longlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL)
{
if (b == NULL)
return BMS_EQUAL;
return bms_is_empty(b) ? BMS_EQUAL : BMS_SUBSET1;
}
if (b == NULL)
return bms_is_empty(a) ? BMS_EQUAL : BMS_SUBSET2;
/* Check common words */
result = BMS_EQUAL; /* status so far */
shortlen = Min(a->nwords, b->nwords);
for (i = 0; i < shortlen; i++)
{
bitmapword aword = a->words[i];
bitmapword bword = b->words[i];
if ((aword & ~bword) != 0)
{
/* a is not a subset of b */
if (result == BMS_SUBSET1)
return BMS_DIFFERENT;
result = BMS_SUBSET2;
}
if ((bword & ~aword) != 0)
{
/* b is not a subset of a */
if (result == BMS_SUBSET2)
return BMS_DIFFERENT;
result = BMS_SUBSET1;
}
}
/* Check extra words */
if (a->nwords > b->nwords)
{
longlen = a->nwords;
for (; i < longlen; i++)
{
if (a->words[i] != 0)
{
/* a is not a subset of b */
if (result == BMS_SUBSET1)
return BMS_DIFFERENT;
result = BMS_SUBSET2;
}
}
}
else if (a->nwords < b->nwords)
{
longlen = b->nwords;
for (; i < longlen; i++)
{
if (b->words[i] != 0)
{
/* b is not a subset of a */
if (result == BMS_SUBSET2)
return BMS_DIFFERENT;
result = BMS_SUBSET1;
}
}
}
return result;
}
/*
* bms_is_member - is X a member of A?
*/
bool
bms_is_member(int x, const Bitmapset *a)
{
int wordnum,
bitnum;
/* XXX better to just return false for x<0 ? */
if (x < 0)
elog(ERROR, "negative bitmapset member not allowed");
if (a == NULL)
return false;
wordnum = WORDNUM(x);
bitnum = BITNUM(x);
if (wordnum >= a->nwords)
return false;
if ((a->words[wordnum] & ((bitmapword) 1 << bitnum)) != 0)
return true;
return false;
}
/*
* bms_member_index
* determine 0-based index of member x in the bitmap
*
* Returns (-1) when x is not a member.
*/
int
bms_member_index(Bitmapset *a, int x)
{
int i;
int bitnum;
int wordnum;
int result = 0;
bitmapword mask;
/* return -1 if not a member of the bitmap */
if (!bms_is_member(x, a))
return -1;
wordnum = WORDNUM(x);
bitnum = BITNUM(x);
/* count bits in preceding words */
for (i = 0; i < wordnum; i++)
{
bitmapword w = a->words[i];
/* No need to count the bits in a zero word */
if (w != 0)
result += bmw_popcount(w);
}
/*
* Now add bits of the last word, but only those before the item. We can
* do that by applying a mask and then using popcount again. To get
* 0-based index, we want to count only preceding bits, not the item
* itself, so we subtract 1.
*/
mask = ((bitmapword) 1 << bitnum) - 1;
result += bmw_popcount(a->words[wordnum] & mask);
return result;
}
/*
* bms_overlap - do sets overlap (ie, have a nonempty intersection)?
*/
bool
bms_overlap(const Bitmapset *a, const Bitmapset *b)
{
int shortlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL || b == NULL)
return false;
/* Check words in common */
shortlen = Min(a->nwords, b->nwords);
for (i = 0; i < shortlen; i++)
{
if ((a->words[i] & b->words[i]) != 0)
return true;
}
return false;
}
/*
* bms_overlap_list - does a set overlap an integer list?
*/
bool
bms_overlap_list(const Bitmapset *a, const List *b)
{
ListCell *lc;
int wordnum,
bitnum;
if (a == NULL || b == NIL)
return false;
foreach(lc, b)
{
int x = lfirst_int(lc);
if (x < 0)
elog(ERROR, "negative bitmapset member not allowed");
wordnum = WORDNUM(x);
bitnum = BITNUM(x);
if (wordnum < a->nwords)
if ((a->words[wordnum] & ((bitmapword) 1 << bitnum)) != 0)
return true;
}
return false;
}
/*
* bms_nonempty_difference - do sets have a nonempty difference?
*/
bool
bms_nonempty_difference(const Bitmapset *a, const Bitmapset *b)
{
int shortlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL)
return false;
if (b == NULL)
return !bms_is_empty(a);
/* Check words in common */
shortlen = Min(a->nwords, b->nwords);
for (i = 0; i < shortlen; i++)
{
if ((a->words[i] & ~b->words[i]) != 0)
return true;
}
/* Check extra words in a */
for (; i < a->nwords; i++)
{
if (a->words[i] != 0)
return true;
}
return false;
}
/*
* bms_singleton_member - return the sole integer member of set
*
* Raises error if |a| is not 1.
*/
int
bms_singleton_member(const Bitmapset *a)
{
int result = -1;
int nwords;
int wordnum;
if (a == NULL)
elog(ERROR, "bitmapset is empty");
nwords = a->nwords;
for (wordnum = 0; wordnum < nwords; wordnum++)
{
bitmapword w = a->words[wordnum];
if (w != 0)
{
if (result >= 0 || HAS_MULTIPLE_ONES(w))
elog(ERROR, "bitmapset has multiple members");
result = wordnum * BITS_PER_BITMAPWORD;
result += bmw_rightmost_one_pos(w);
}
}
if (result < 0)
elog(ERROR, "bitmapset is empty");
return result;
}
/*
* bms_get_singleton_member
*
* Test whether the given set is a singleton.
* If so, set *member to the value of its sole member, and return true.
* If not, return false, without changing *member.
*
* This is more convenient and faster than calling bms_membership() and then
* bms_singleton_member(), if we don't care about distinguishing empty sets
* from multiple-member sets.
*/
bool
bms_get_singleton_member(const Bitmapset *a, int *member)
{
int result = -1;
int nwords;
int wordnum;
if (a == NULL)
return false;
nwords = a->nwords;
for (wordnum = 0; wordnum < nwords; wordnum++)
{
bitmapword w = a->words[wordnum];
if (w != 0)
{
if (result >= 0 || HAS_MULTIPLE_ONES(w))
return false;
result = wordnum * BITS_PER_BITMAPWORD;
result += bmw_rightmost_one_pos(w);
}
}
if (result < 0)
return false;
*member = result;
return true;
}
/*
* bms_num_members - count members of set
*/
int
bms_num_members(const Bitmapset *a)
{
int result = 0;
int nwords;
int wordnum;
if (a == NULL)
return 0;
nwords = a->nwords;
for (wordnum = 0; wordnum < nwords; wordnum++)
{
bitmapword w = a->words[wordnum];
/* No need to count the bits in a zero word */
if (w != 0)
result += bmw_popcount(w);
}
return result;
}
/*
* bms_membership - does a set have zero, one, or multiple members?
*
* This is faster than making an exact count with bms_num_members().
*/
BMS_Membership
bms_membership(const Bitmapset *a)
{
BMS_Membership result = BMS_EMPTY_SET;
int nwords;
int wordnum;
if (a == NULL)
return BMS_EMPTY_SET;
nwords = a->nwords;
for (wordnum = 0; wordnum < nwords; wordnum++)
{
bitmapword w = a->words[wordnum];
if (w != 0)
{
if (result != BMS_EMPTY_SET || HAS_MULTIPLE_ONES(w))
return BMS_MULTIPLE;
result = BMS_SINGLETON;
}
}
return result;
}
/*
* bms_is_empty - is a set empty?
*
* This is even faster than bms_membership().
*/
bool
bms_is_empty(const Bitmapset *a)
{
int nwords;
int wordnum;
if (a == NULL)
return true;
nwords = a->nwords;
for (wordnum = 0; wordnum < nwords; wordnum++)
{
bitmapword w = a->words[wordnum];
if (w != 0)
return false;
}
return true;
}
/*
* These operations all "recycle" their non-const inputs, ie, either
* return the modified input or pfree it if it can't hold the result.
*
* These should generally be used in the style
*
* foo = bms_add_member(foo, x);
*/
/*
* bms_add_member - add a specified member to set
*
* Input set is modified or recycled!
*/
Bitmapset *
bms_add_member(Bitmapset *a, int x)
{
int wordnum,
bitnum;
if (x < 0)
elog(ERROR, "negative bitmapset member not allowed");
if (a == NULL)
return bms_make_singleton(x);
wordnum = WORDNUM(x);
bitnum = BITNUM(x);
/* enlarge the set if necessary */
if (wordnum >= a->nwords)
{
int oldnwords = a->nwords;
int i;
a = (Bitmapset *) repalloc(a, BITMAPSET_SIZE(wordnum + 1));
a->nwords = wordnum + 1;
/* zero out the enlarged portion */
for (i = oldnwords; i < a->nwords; i++)
a->words[i] = 0;
}
a->words[wordnum] |= ((bitmapword) 1 << bitnum);
return a;
}
bool
bms_covers_member(const Bitmapset *a, int x)
{
int wordnum;
if (x < 0)
elog(ERROR, "negative bitmapset member not allowed");
if (a == NULL)
return false;
wordnum = WORDNUM(x);
return (wordnum < a->nwords);
}
Bitmapset *
bms_resize(Bitmapset *a, int wc)
{
Bitmapset *result;
if (a && a->nwords >= wc)
return a;
if (a)
{
result = (Bitmapset *) repalloc(a, BITMAPSET_SIZE(wc));
/* do not access a again */
MemSet(result->words + result->nwords, 0,
(wc - result->nwords) * sizeof(bitmapword));
result->nwords = wc;
}
else
{
result = palloc0(BITMAPSET_SIZE(wc));
result->nwords = wc;
}
return result;
}
/*
* bms_del_member - remove a specified member from set
*
* No error if x is not currently a member of set
*
* Input set is modified in-place!
*/
Bitmapset *
bms_del_member(Bitmapset *a, int x)
{
int wordnum,
bitnum;
if (x < 0)
elog(ERROR, "negative bitmapset member not allowed");
if (a == NULL)
return NULL;
wordnum = WORDNUM(x);
bitnum = BITNUM(x);
if (wordnum < a->nwords)
a->words[wordnum] &= ~((bitmapword) 1 << bitnum);
return a;
}
/*
* bms_add_members - like bms_union, but left input is recycled
*/
Bitmapset *
bms_add_members(Bitmapset *a, const Bitmapset *b)
{
Bitmapset *result;
const Bitmapset *other;
int otherlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL)
return bms_copy(b);
if (b == NULL)
return a;
/* Identify shorter and longer input; copy the longer one if needed */
if (a->nwords < b->nwords)
{
result = bms_copy(b);
other = a;
}
else
{
result = a;
other = b;
}
/* And union the shorter input into the result */
otherlen = other->nwords;
for (i = 0; i < otherlen; i++)
result->words[i] |= other->words[i];
if (result != a)
pfree(a);
return result;
}
/*
* bms_add_range
* Add members in the range of 'lower' to 'upper' to the set.
*
* Note this could also be done by calling bms_add_member in a loop, however,
* using this function will be faster when the range is large as we work at
* the bitmapword level rather than at bit level.
*/
Bitmapset *
bms_add_range(Bitmapset *a, int lower, int upper)
{
int lwordnum,
lbitnum,
uwordnum,
ushiftbits,
wordnum;
/* do nothing if nothing is called for, without further checking */
if (upper < lower)
return a;
if (lower < 0)
elog(ERROR, "negative bitmapset member not allowed");
uwordnum = WORDNUM(upper);
if (a == NULL)
{
a = (Bitmapset *) palloc0(BITMAPSET_SIZE(uwordnum + 1));
a->nwords = uwordnum + 1;
}
else if (uwordnum >= a->nwords)
{
int oldnwords = a->nwords;
int i;
/* ensure we have enough words to store the upper bit */
a = (Bitmapset *) repalloc(a, BITMAPSET_SIZE(uwordnum + 1));
a->nwords = uwordnum + 1;
/* zero out the enlarged portion */
for (i = oldnwords; i < a->nwords; i++)
a->words[i] = 0;
}
wordnum = lwordnum = WORDNUM(lower);
lbitnum = BITNUM(lower);
ushiftbits = BITS_PER_BITMAPWORD - (BITNUM(upper) + 1);
/*
* Special case when lwordnum is the same as uwordnum we must perform the
* upper and lower masking on the word.
*/
if (lwordnum == uwordnum)
{
a->words[lwordnum] |= ~(bitmapword) (((bitmapword) 1 << lbitnum) - 1)
& (~(bitmapword) 0) >> ushiftbits;
}
else
{
/* turn on lbitnum and all bits left of it */
a->words[wordnum++] |= ~(bitmapword) (((bitmapword) 1 << lbitnum) - 1);
/* turn on all bits for any intermediate words */
while (wordnum < uwordnum)
a->words[wordnum++] = ~(bitmapword) 0;
/* turn on upper's bit and all bits right of it. */
a->words[uwordnum] |= (~(bitmapword) 0) >> ushiftbits;
}
return a;
}
/*
* bms_int_members - like bms_intersect, but left input is recycled
*/
Bitmapset *
bms_int_members(Bitmapset *a, const Bitmapset *b)
{
int shortlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL)
return NULL;
if (b == NULL)
{
pfree(a);
return NULL;
}
/* Intersect b into a; we need never copy */
shortlen = Min(a->nwords, b->nwords);
for (i = 0; i < shortlen; i++)
a->words[i] &= b->words[i];
for (; i < a->nwords; i++)
a->words[i] = 0;
return a;
}
/*
* bms_del_members - like bms_difference, but left input is recycled
*/
Bitmapset *
bms_del_members(Bitmapset *a, const Bitmapset *b)
{
int shortlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL)
return NULL;
if (b == NULL)
return a;
/* Remove b's bits from a; we need never copy */
shortlen = Min(a->nwords, b->nwords);
for (i = 0; i < shortlen; i++)
a->words[i] &= ~b->words[i];
return a;
}
/*
* bms_join - like bms_union, but *both* inputs are recycled
*/
Bitmapset *
bms_join(Bitmapset *a, Bitmapset *b)
{
Bitmapset *result;
Bitmapset *other;
int otherlen;
int i;
/* Handle cases where either input is NULL */
if (a == NULL)
return b;
if (b == NULL)
return a;
/* Identify shorter and longer input; use longer one as result */
if (a->nwords < b->nwords)
{
result = b;
other = a;
}
else
{
result = a;
other = b;
}
/* And union the shorter input into the result */
otherlen = other->nwords;
for (i = 0; i < otherlen; i++)
result->words[i] |= other->words[i];
if (other != result) /* pure paranoia */
pfree(other);
return result;
}
/*
* bms_first_member - find and remove first member of a set
*
* Returns -1 if set is empty. NB: set is destructively modified!
*
* This is intended as support for iterating through the members of a set.
* The typical pattern is
*
* while ((x = bms_first_member(inputset)) >= 0)
* process member x;
*
* CAUTION: this destroys the content of "inputset". If the set must
* not be modified, use bms_next_member instead.
*/
int
bms_first_member(Bitmapset *a)
{
int nwords;
int wordnum;
if (a == NULL)
return -1;
nwords = a->nwords;
for (wordnum = 0; wordnum < nwords; wordnum++)
{
bitmapword w = a->words[wordnum];
if (w != 0)
{
int result;
w = RIGHTMOST_ONE(w);
a->words[wordnum] &= ~w;
result = wordnum * BITS_PER_BITMAPWORD;
result += bmw_rightmost_one_pos(w);
return result;
}
}
return -1;
}
/*
* bms_next_member - find next member of a set
*
* Returns smallest member greater than "prevbit", or -2 if there is none.
* "prevbit" must NOT be less than -1, or the behavior is unpredictable.
*
* This is intended as support for iterating through the members of a set.
* The typical pattern is
*
* x = -1;
* while ((x = bms_next_member(inputset, x)) >= 0)
* process member x;
*
* Notice that when there are no more members, we return -2, not -1 as you
* might expect. The rationale for that is to allow distinguishing the
* loop-not-started state (x == -1) from the loop-completed state (x == -2).
* It makes no difference in simple loop usage, but complex iteration logic
* might need such an ability.
*/
int
bms_next_member(const Bitmapset *a, int prevbit)
{
int nwords;
int wordnum;
bitmapword mask;
if (a == NULL)
return -2;
nwords = a->nwords;
prevbit++;
mask = (~(bitmapword) 0) << BITNUM(prevbit);
for (wordnum = WORDNUM(prevbit); wordnum < nwords; wordnum++)
{
bitmapword w = a->words[wordnum];
/* ignore bits before prevbit */
w &= mask;
if (w != 0)
{
int result;
result = wordnum * BITS_PER_BITMAPWORD;
result += bmw_rightmost_one_pos(w);
return result;
}
/* in subsequent words, consider all bits */
mask = (~(bitmapword) 0);
}
return -2;
}
/*
* bms_prev_member - find prev member of a set
*
* Returns largest member less than "prevbit", or -2 if there is none.
* "prevbit" must NOT be more than one above the highest possible bit that can
* be set at the Bitmapset at its current size.
*
* To ease finding the highest set bit for the initial loop, the special
* prevbit value of -1 can be passed to have the function find the highest
* valued member in the set.
*
* This is intended as support for iterating through the members of a set in
* reverse. The typical pattern is
*
* x = -1;
* while ((x = bms_prev_member(inputset, x)) >= 0)
* process member x;
*
* Notice that when there are no more members, we return -2, not -1 as you
* might expect. The rationale for that is to allow distinguishing the
* loop-not-started state (x == -1) from the loop-completed state (x == -2).
* It makes no difference in simple loop usage, but complex iteration logic
* might need such an ability.
*/
int
bms_prev_member(const Bitmapset *a, int prevbit)
{
int wordnum;
int ushiftbits;
bitmapword mask;
/*
* If set is NULL or if there are no more bits to the right then we've
* nothing to do.
*/
if (a == NULL || prevbit == 0)
return -2;
/* transform -1 to the highest possible bit we could have set */
if (prevbit == -1)
prevbit = a->nwords * BITS_PER_BITMAPWORD - 1;
else
prevbit--;
ushiftbits = BITS_PER_BITMAPWORD - (BITNUM(prevbit) + 1);
mask = (~(bitmapword) 0) >> ushiftbits;
for (wordnum = WORDNUM(prevbit); wordnum >= 0; wordnum--)
{
bitmapword w = a->words[wordnum];
/* mask out bits left of prevbit */
w &= mask;
if (w != 0)
{
int result;
result = wordnum * BITS_PER_BITMAPWORD;
result += bmw_leftmost_one_pos(w);
return result;
}
/* in subsequent words, consider all bits */
mask = (~(bitmapword) 0);
}
return -2;
}
/*
* bms_hash_value - compute a hash key for a Bitmapset
*
* Note: we must ensure that any two bitmapsets that are bms_equal() will
* hash to the same value; in practice this means that trailing all-zero
* words must not affect the result. Hence we strip those before applying
* hash_any().
*/
uint32
bms_hash_value(const Bitmapset *a)
{
int lastword;
if (a == NULL)
return 0; /* All empty sets hash to 0 */
for (lastword = a->nwords; --lastword >= 0;)
{
if (a->words[lastword] != 0)
break;
}
if (lastword < 0)
return 0; /* All empty sets hash to 0 */
return DatumGetUInt32(hash_any((const unsigned char *) a->words,
(lastword + 1) * sizeof(bitmapword)));
}
/*
* bitmap_hash - hash function for keys that are (pointers to) Bitmapsets
*
* Note: don't forget to specify bitmap_match as the match function!
*/
uint32
bitmap_hash(const void *key, Size keysize)
{
Assert(keysize == sizeof(Bitmapset *));
return bms_hash_value(*((const Bitmapset *const *) key));
}
/*
* bitmap_match - match function to use with bitmap_hash
*/
int
bitmap_match(const void *key1, const void *key2, Size keysize)
{
Assert(keysize == sizeof(Bitmapset *));
return !bms_equal(*((const Bitmapset *const *) key1),
*((const Bitmapset *const *) key2));
}
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