Format
#include <builtin.h>unsigned int __btr(unsigned int *pBits, unsigned int bit)
Language Level: None
__ btr tests and resets a bit within a 4 byte memory operand. The
address of the memory operand is pBits
and the bit number is bit.
Bits are numbered 0 through 31 with 0 being the least significant
bit. The test and reset operation is only atomic on uni-processor
machines.
Return Value
The original value of the selected bit is returned as an
unsigned integer.
Example
This example tests and resets bit 8 of a 32-bit unsigned
integer.
#include <stdio.h> #include <builtin.h>
unsigned int mem = 0x01010101;
int main(void)
{
if (__btr(&mem, 8))
{
printf("Bit 8 should now be zero.\n");
}
printf("mem = %.8x\n", mem);
/******************************************
The output should be:
Bit 8 should now be zero.
mem = 01010001
*****************************************/
return 0; }
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__bts -- Test and Set a Bit
__smp_btr -- Bit Test and Reset Atomically
__smp_bts -- Bit Test and Set Atomically