75 lines
1.6 KiB
C
75 lines
1.6 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, u_int64_t n, int initzero)
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{
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u_int32_t *p;
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size_t sz = ((n+31)>>5) * 4;
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p = realloc(b, sz);
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if (p == NULL) return NULL;
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if (initzero) memset(p, 0, sz);
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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, 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) * 4;
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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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