cbits_api.md

STC cbits: Bitset

A cbits represents either a dynamically sized sequence of bits, or a compile-time fixed sized bitset. It provides accesses to the value of individual bits via cbits_test() (or cbits_at()) and provides the bitwise operators that one can apply to builtin integers.

For the dynamic The number of bits in the set is specified at runtime via a parameter to the constructor cbits_with_size() or by cbits_resize(). A cbits bitset can be manipulated by standard logic operators and converted to and from strings.

See the c++ class std::bitset or boost::dynamic_bitset for a functional description.

Header file

All cbits definitions and prototypes are available by including a single header file.

// if i_type is defined, the bitset will be fixed-size of N bits on the stack, and with the given type name.
#define i_type MyBits, MY_MAX_BITS
#include "stc/cbits.h"

// otherwise, just include the header. The type name is cbits, data will be dynamically allocated.
#include "stc/cbits.h"

Methods

cbits           cbits_from(const char* str);
cbits           cbits_with_size(isize size, bool value);                // size must be <= N if N is defined
cbits           cbits_with_pattern(isize size, size_t pattern);
cbits           cbits_clone(cbits other);

void            cbits_clear(cbits* self);
void            cbits_copy(cbits* self, cbits other);
bool            cbits_resize(cbits* self, isize size, bool value);      // NB! only for dynamic bitsets!
void            cbits_drop(cbits* self);

cbits*          cbits_take(cbits* self, const cbits* other);            // give other to self
cbits           cbits_move(cbits* self);                                // transfer self to caller

isize           cbits_size(const cbits* self);
isize           cbits_count(const cbits* self);                         // count number of bits set

bool            cbits_test(const cbits* self, isize i);
bool            cbits_at(const cbits* self, isize i);                   // cbits_test() with bounds check.
bool            cbits_subset_of(const cbits* self, const cbits* other); // is set a subset of other?
bool            cbits_disjoint(const cbits* self, const cbits* other);  // no common bits
char*           cbits_to_str(const cbits* self, char* str, isize start, isize stop);

void            cbits_print(const cbits* self);
void            cbits_print(const cbits* self, FILE* fp);
void            cbits_print(const cbits* self, FILE* fp, isize start, isize stop);
void            cbits_print(TYPE Bits, const Bits* self, FILE* fp);     // for fixed size bitsets
void            cbits_print(TYPE Bits, const Bits* self, FILE* fp, isize start, isize stop);

void            cbits_set(cbits* self, isize i);
void            cbits_reset(cbits* self, isize i);
void            cbits_set_value(cbits* self, isize i, bool value);
void            cbits_set_all(cbits* self, bool value);
void            cbits_set_pattern(cbits* self, size_t pattern);
void            cbits_flip_all(cbits* self);
void            cbits_flip(cbits* self, isize i);

void            cbits_intersect(cbits* self, const cbits* other);
void            cbits_union(cbits* self, const cbits* other);
void            cbits_xor(cbits* self, const cbits* other);             // set of disjoint bits

Types

cbits	Type definition	Used to represent...
cbits	struct { ... }	The cbits type
cbits_iter	struct { ... }	The cbits iterator type

Example

#include "stc/cbits.h"
#include <stdio.h>
#include <math.h>
#include <time.h>

cbits sieveOfEratosthenes(isize n)
{
    cbits bits = cbits_with_size(n/2, true);
    isize q = (isize)sqrt(n);

    for (isize i = 3; i <= q; i += 2) {
        for (isize j = i; j < n; j += 2) {
            if (cbits_test(&bits, j/2)) {
                i = j;
                break;
            }
        }
        for (isize j = i*i; j < n; j += i*2)
            cbits_reset(&bits, j/2);
    }
    return bits;
}

int main(void)
{
    isize n = 100000000;
    printf("computing prime numbers up to %" c_ZI "\n", n);

    clock_t t1 = clock();
    cbits primes = sieveOfEratosthenes(n + 1);
    isize nprimes = cbits_count(&primes);
    t1 = clock() - t1;

    printf("number of primes: %" c_ZI ", time: %f\n", nprimes, (float)t1/CLOCKS_PER_SEC);

    printf(" 2");
    for (isize i = 3; i < 1000; i += 2)
       if (cbits_test(&primes, i/2)) printf(" %" c_ZI, i);
    puts("");

    cbits_drop(&primes);
}

Output:

computing prime numbers up to 100000000
done
number of primes: 5761455
2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 101 103 107 109 113 127 131 137 139 149 151 157 163 167 173 179 181 191 193 197 199 211 223 227 229 233 239 241 251 257 263 269 271 277 281 283 293 307 311 313 317 331 337 347 349 353 359 367 373 379 383 389 397 401 409 419 421 431 433 439 443 449 457 461 463 467 479 487 491 499 503 509 521 523 541 547 557 563 569 571 577 587 593 599 601 607 613 617 619 631 641 643 647 653 659 661 673 677 683 691 701 709 719 727 733 739 743 751 757 761 769 773 787 797 809 811 821 823 827 829 839 853 857 859 863 877 881 883 887 907 911 919 929 937 941 947 953 967 971 977 983 991 997