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#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
typedef uint32_t bitfield_t;
enum { BITFIELD_BITS = sizeof(bitfield_t) * 8 };
static inline int bindex(int b) { return b / BITFIELD_BITS; }
static inline int boffset(int b) { return b % BITFIELD_BITS; }
#define bptr(st) (&((st)->bits))
struct _Bits
{
uint32_t nw;
bitfield_t bits;
};
typedef struct _Bits * Bits;
static inline Bits bits_alloc(int n)
{
uint32_t nw = (n / BITFIELD_BITS);
if (nw * BITFIELD_BITS < n) nw += 1;
int sz = sizeof(int) + (nw * sizeof(bitfield_t));
/* printf("wants %d bits : alloc %d bytes (1 uint32_t[%lu] + %d bitfields[%lu])\n", n, sz, sizeof(uint32_t), nw, (nw * sizeof(bitfield_t))); */
Bits b = calloc(1, sz);
/* memset(b, 0, sz); */
b->nw = nw;
return b;
}
static inline void bits_free(Bits bits)
{
free(bits);
}
static inline void set_bit(Bits bits, int b)
{
bptr(bits)[bindex(b)] |= (bitfield_t)(1 << boffset(b));
}
static inline void reset_bit(Bits bits, int b)
{
bptr(bits)[bindex(b)] &= ~(1 << boffset(b));
}
static inline int get_bit(Bits bits, int b)
{
int of = boffset(b);
return (bptr(bits)[bindex(b)] & (1 << of)) >> of;
}
static inline Bits bits_copy(Bits dst, Bits src)
{
if (dst->nw != src->nw) return 0;
return memcpy(&dst->bits, &src->bits, (sizeof(bitfield_t) * src->nw));
}
static void assert(int value, int expected, char*msg)
{
if (value != expected) {
fprintf(stderr, "Error %s\n", msg);
exit(1);
}
}
int main(int argc, char **argv, char **env)
{
printf("bits in an bitfield_t : %d\n", BITFIELD_BITS);
Bits a = bits_alloc(33);
Bits b = bits_alloc(33);
set_bit(a, 31);
set_bit(a, 32);
set_bit(a, 33);
assert(get_bit(a, 30), 0, "bit 30 is not 0");
assert(get_bit(a, 31), 1, "bit 31 is not 1");
assert(get_bit(a, 32), 1, "bit 32 is not 1");
assert(get_bit(a, 33), 1, "bit 33 is not 1");
assert(get_bit(a, 34), 0, "bit 34 is not 0");
reset_bit(a, 32);
assert(get_bit(a, 30), 0, "bit 30 is not 0");
assert(get_bit(a, 31), 1, "bit 31 is not 1");
assert(get_bit(a, 32), 0, "bit 32 is not 0");
assert(get_bit(a, 33), 1, "bit 33 is not 1");
assert(get_bit(a, 34), 0, "bit 34 is not 0");
set_bit(a, 32);
reset_bit(a, 33);
reset_bit(a, 31);
assert(get_bit(a, 30), 0, "bit 30 is not 0");
assert(get_bit(a, 31), 0, "bit 31 is not 0");
assert(get_bit(a, 32), 1, "bit 32 is not 1");
assert(get_bit(a, 33), 0, "bit 33 is not 0");
assert(get_bit(a, 34), 0, "bit 34 is not 0");
bits_copy(b, a);
assert(get_bit(b, 30), 0, "bit 30 is not 0");
assert(get_bit(b, 31), 0, "bit 31 is not 0");
assert(get_bit(b, 32), 1, "bit 32 is not 1");
assert(get_bit(b, 33), 0, "bit 33 is not 0");
assert(get_bit(b, 34), 0, "bit 34 is not 0");
bits_free(a);
bits_free(b);
printf("Success\n");
return 0;
}
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