ref: 56a659f634f2a591cf641eb875a4e7f457c40321
dir: /util/bitset.c/
#include <stdlib.h>
#include <stdio.h>
#include <stdarg.h>
#include <inttypes.h>
#include <assert.h>
#include <limits.h>
#include <string.h>
#include "util.h"
#define Sizetbits (CHAR_BIT * sizeof(size_t)) /* used in graph reprs */
/* Equalizes the size of a and b by
* growing the smaller to the size of the
* larger, zeroing out the new elements.
* This allows the code to simply iterate
* over both without keeping track of the
* minimum size.
*/
static void
eqsz(Bitset *a, Bitset *b)
{
size_t sz;
size_t i;
size_t *p;
if (a->nchunks > b->nchunks)
sz = a->nchunks;
else
sz = b->nchunks;
if (a->nchunks != sz) {
p = zalloc(sz * sizeof(size_t));
for (i = 0; i < a->nchunks; i++)
p[i] = a->chunks[i];
free(a->chunks);
a->chunks = p;
a->nchunks = sz;
}
if (b->nchunks != sz) {
p = zalloc(sz * sizeof(size_t));
for (i = 0; i < b->nchunks; i++)
p[i] = b->chunks[i];
free(b->chunks);
b->chunks = p;
b->nchunks = sz;
}
}
/* Creates a new all-zero bit set */
Bitset *
mkbs()
{
Bitset *bs;
bs = xalloc(sizeof(Bitset));
bs->nchunks = 1;
bs->chunks = zalloc(1 * sizeof(size_t));
return bs;
}
/* Frees a bitset. Safe to call on NULL. */
void
bsfree(Bitset *bs)
{
if (!bs)
return;
free(bs->chunks);
free(bs);
}
/* Duplicates a bitset. NULL is duplicated to NULL. */
Bitset *
bsdup(Bitset *a)
{
Bitset *bs;
if (!a)
return NULL;
bs = xalloc(sizeof(Bitset));
bs->nchunks = a->nchunks;
bs->chunks = xalloc(a->nchunks * sizeof(size_t));
memcpy(bs->chunks, a->chunks, a->nchunks * sizeof(size_t));
return bs;
}
/* Zeroes all values in a bit set */
Bitset *
bsclear(Bitset *bs)
{
size_t i;
if (!bs)
return mkbs();
for (i = 0; i < bs->nchunks; i++)
bs->chunks[i] = 0;
return bs;
}
/* Counts the number of values held in a bit set */
size_t
bscount(Bitset *bs)
{
size_t i, j, n;
n = 0;
for (i = 0; i < bs->nchunks; i++)
for (j = 0; j < sizeof(size_t) * CHAR_BIT; j++)
if (bs->chunks[i] & 1ULL << j)
n++;
return n;
}
inline
static int firstbit(size_t b)
{
int n;
static const char bits[] = {
4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0
};
n = 0;
if (!(b & 0xffffffff)) {
n += 32;
b >>= 32;
}
if (!(b & 0xffff)) {
n += 16;
b >>= 16;
}
if (!(b & 0xff)) {
n += 8;
b >>= 8;
}
if (!(b & 0xf)) {
n += 4;
b >>= 4;
}
n += bits[b & 0xf];
return n;
}
/* A slightly tricky function to iterate over the content
* of a bitset. It returns true immediately if 'elt' is in
* the bitset, otherwise it seeks forward to the next value
* held in the bitset and stores it in elt. If there are no
* more values, it returns false to stop iteration. Note,
* this means that you need to increment elt every time you
* pass through.
*
* Typical usage of this function:
*
* for (i = 0; bsiter(set, &i); i++)
* use(i);
*
* The increment of 'i' in the for loop is needed in order
* to prevent the function from returning the same value
* repeatedly.
*/
int
bsiter(Bitset *bs, size_t *elt)
{
size_t b, t, i;
i = *elt;
t = i/Sizetbits;
if (t >= bs->nchunks)
return 0;
b = bs->chunks[t];
b &= ~((1ull << (i%Sizetbits)) - 1);
while (!b) {
++t;
if (t >= bs->nchunks)
return 0;
b = bs->chunks[t];
}
*elt = Sizetbits*t + firstbit(b);
return 1;
}
/* Returns the largest value that the bitset can possibly
* hold. It's conservative, but scanning the entire bitset
* is a bit slow. This is mostly an aid to iterate over it. */
size_t
bsmax(Bitset *bs) { return bs->nchunks * Sizetbits; }
void
bsput(Bitset *bs, size_t elt)
{
size_t sz;
if (elt >= bs->nchunks * Sizetbits) {
sz = (elt / Sizetbits) + 1;
bs->chunks = zrealloc(bs->chunks, bs->nchunks * sizeof(size_t), sz * sizeof(size_t));
bs->nchunks = sz;
}
bs->chunks[elt / Sizetbits] |= 1ULL << (elt % Sizetbits);
}
void
bsdel(Bitset *bs, size_t elt)
{
if (elt < bs->nchunks * Sizetbits)
bs->chunks[elt / Sizetbits] &= ~(1ULL << (elt % Sizetbits));
}
void
bsunion(Bitset *a, Bitset *b)
{
size_t i;
eqsz(a, b);
for (i = 0; i < a->nchunks; i++)
a->chunks[i] |= b->chunks[i];
}
void
bsintersect(Bitset *a, Bitset *b)
{
size_t i;
eqsz(a, b);
for (i = 0; i < a->nchunks; i++)
a->chunks[i] &= b->chunks[i];
}
ulong
bshash(Bitset *bs)
{
if (!bs)
return 14247517;
else
return murmurhash2(bs->chunks, bs->nchunks * sizeof(size_t));
}
void
bsdiff(Bitset *a, Bitset *b)
{
size_t i;
eqsz(a, b);
for (i = 0; i < a->nchunks; i++)
a->chunks[i] &= ~b->chunks[i];
}
int
bseq(Bitset *a, Bitset *b)
{
size_t i;
if (!a || !b)
return bsisempty(a) && bsisempty(b);
eqsz(a, b);
for (i = 0; i < a->nchunks; i++) {
if (a->chunks[i] != b->chunks[i])
return 0;
}
return 1;
}
int
bsissubset(Bitset *set, Bitset *sub)
{
size_t i;
eqsz(set, sub);
for (i = 0; i < set->nchunks; i++)
if ((sub->chunks[i] & set->chunks[i]) != set->chunks[i])
return 0;
return 1;
}
int
bsisempty(Bitset *set)
{
size_t i;
if (!set)
return 1;
for (i = 0; i < set->nchunks; i++)
if (set->chunks[i])
return 0;
return 1;
}