130 lines
2.8 KiB
C
130 lines
2.8 KiB
C
/*
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bit vector primitives
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todo:
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* reverse
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* nreverse
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(- rotate left/right)
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* shl_to
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* not
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- shr_row, shl_row
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These routines are the back end supporting bit matrices. Many operations
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on bit matrices are slow (such as accessing or setting a single element!)
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but certain operations are privileged and lend themselves to extremely
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efficient implementation due to the bit-vector nature of machine integers.
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These are:
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done:
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& | $ ~ copy reverse fill sum prod
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todo:
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shift trans rowswap
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would be nice:
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channel interleave
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Important note:
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Out-of-place functions always assume dest and source have the same amount
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of space available.
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shr_to, shl_to, not_to, and reverse_to assume source and dest don't overlap
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and_to, or_to, and xor_to allow overlap.
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*/
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#include <stdlib.h>
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#include <assert.h>
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#include <string.h>
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#include "dtypes.h"
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#include "bitvector.h"
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#ifdef WIN32
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#include <malloc.h>
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#endif
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u_int32_t *bitvector_resize(u_int32_t *b, uint64_t oldsz, uint64_t newsz,
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int initzero)
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{
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u_int32_t *p;
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size_t sz = ((newsz+31)>>5) * sizeof(uint32_t);
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p = LLT_REALLOC(b, sz);
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if (p == NULL) return NULL;
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if (initzero && newsz>oldsz) {
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size_t osz = ((oldsz+31)>>5) * sizeof(uint32_t);
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memset(&p[osz/sizeof(uint32_t)], 0, sz-osz);
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}
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return p;
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}
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u_int32_t *bitvector_new(u_int64_t n, int initzero)
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{
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return bitvector_resize(NULL, 0, n, initzero);
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}
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size_t bitvector_nwords(u_int64_t nbits)
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{
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return ((nbits+31)>>5);
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}
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void bitvector_set(u_int32_t *b, u_int64_t n, u_int32_t c)
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{
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if (c)
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b[n>>5] |= (1<<(n&31));
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else
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b[n>>5] &= ~(1<<(n&31));
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}
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u_int32_t bitvector_get(u_int32_t *b, u_int64_t n)
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{
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return b[n>>5] & (1<<(n&31));
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}
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static int ntz(uint32_t x)
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{
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int n;
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if (x == 0) return 32;
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n = 1;
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if ((x & 0x0000FFFF) == 0) {n = n +16; x = x >>16;}
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if ((x & 0x000000FF) == 0) {n = n + 8; x = x >> 8;}
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if ((x & 0x0000000F) == 0) {n = n + 4; x = x >> 4;}
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if ((x & 0x00000003) == 0) {n = n + 2; x = x >> 2;}
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return n - (x & 1);
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}
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// given a bitvector of n bits, starting at bit n0 find the next
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// set bit, including n0.
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// returns n if no set bits.
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uint32_t bitvector_next(uint32_t *b, uint64_t n0, uint64_t n)
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{
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if (n0 >= n) return n;
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uint32_t i = n0>>5;
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uint32_t nb = n0&31;
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uint32_t nw = (n+31)>>5;
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uint32_t w;
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if (i < nw-1 || (n&31)==0)
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w = b[i]>>nb;
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else
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w = (b[i]&lomask(n&31))>>nb;
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if (w != 0)
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return ntz(w)+n0;
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if (i == nw-1)
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return n;
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i++;
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while (i < nw-1) {
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w = b[i];
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if (w != 0) {
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return ntz(w) + (i<<5);
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}
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i++;
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}
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w = b[i];
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nb = n&31;
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i = ntz(w);
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if (nb == 0)
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return i + (n-32);
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if (i >= nb)
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return n;
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return i + (n-nb);
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}
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