bitops.h
int _inline_bt(unsigned *p, unsigned index); int _inline_btc(unsigned *p, unsigned index); int _inline_btr(unsigned *p, unsigned index); int _inline_bts(unsigned *p, unsigned index);
p[index / (sizeof(unsigned)*8)] & (1 << (index & ((sizeof(unsigned)*8) - 1)))_inline_bt tests the bit.
_inline_btc tests and complements the bit.
_inline_btr tests and resets (sets to 0) the bit.
_inline_bts tests and sets the bit.
These functions are inlined by the compiler, bringing to bear the full power of the code generator on them. This can result in some surprising speedups when they are used as part of a bit array solution.
Return Value
All return a non-zero value if the bit was set, and a zero
if it was clear.
Compatibility
DOS, Windows 3.x, Phar Lap, DOSX, Win32
See Also
_inline_bsf,
_inline_bsr
Example
#include <stdio.h>
#include <bitops.h>
int main()
{
unsigned array[2];
array[0] = 2;
array[1] = 0x100;
printf("btc(array, 35) = %d\n", _inline_btc(array, 35));
printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]);
printf("btc(array, 35) = %d\n", _inline_btc(array, 35));
printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]);
printf("bts(array, 35) = %d\n", _inline_bts(array, 35));
printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]);
printf("btr(array, 35) = %d\n", _inline_btr(array, 35));
printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]);
printf("bt(array, 1) = %d\n", _inline_bt(array, 1));
printf("array = [0]:x%x, [1]:x%x\n", array[0], array[1]);
return 0;
}
Output
btc(array, 35) = 0 array = [0]:x2, [1]:x108 btc(array, 35) = -1 array = [0]:x2, [1]:x100 bts(array, 35) = 0 array = [0]:x2, [1]:x108 btr(array, 35) = -1 array = [0]:x2, [1]:x100 bt(array, 1) = -1 array = [0]:x2, [1]:x100Bugs