ref: 8eb100a3cf52ee288ba5643020152c1ff838ab4a
dir: /llt/bitvector.c/
/*
bit vector primitives
todo:
* reverse
* nreverse
(- rotate left/right)
* shl_to
* not
- shr_row, shl_row
These routines are the back end supporting bit matrices. Many operations
on bit matrices are slow (such as accessing or setting a single element!)
but certain operations are privileged and lend themselves to extremely
efficient implementation due to the bit-vector nature of machine integers.
These are:
done:
& | $ ~ copy reverse fill sum prod
todo:
shift trans rowswap
would be nice:
channel interleave
Important note:
Out-of-place functions always assume dest and source have the same amount
of space available.
shr_to, shl_to, not_to, and reverse_to assume source and dest don't overlap
and_to, or_to, and xor_to allow overlap.
*/
#include <stdlib.h>
#include <assert.h>
#include <string.h>
#include "dtypes.h"
#include "bitvector.h"
#ifdef WIN32
#include <malloc.h>
#endif
u_int32_t *bitvector_resize(u_int32_t *b, u_int64_t n, int initzero)
{
u_int32_t *p;
size_t sz = ((n+31)>>5) * 4;
p = realloc(b, sz);
if (p == NULL) return NULL;
if (initzero) memset(p, 0, sz);
return p;
}
u_int32_t *bitvector_new(u_int64_t n, int initzero)
{
return bitvector_resize(NULL, n, initzero);
}
size_t bitvector_nwords(u_int64_t nbits)
{
return ((nbits+31)>>5);
}
void bitvector_set(u_int32_t *b, u_int64_t n, u_int32_t c)
{
if (c)
b[n>>5] |= (1<<(n&31));
else
b[n>>5] &= ~(1<<(n&31));
}
u_int32_t bitvector_get(u_int32_t *b, u_int64_t n)
{
return b[n>>5] & (1<<(n&31));
}