Browse Source

sys: bitfield: add bf_get_unset

dev/timer
Kaspar Schleiser 7 years ago
parent
commit
fb9a862177
  1. 1
      sys/bitfield/Makefile
  2. 48
      sys/bitfield/bitfield.c
  3. 13
      sys/include/bitfield.h

1
sys/bitfield/Makefile

@ -0,0 +1 @@
include $(RIOTBASE)/Makefile.base

48
sys/bitfield/bitfield.c

@ -0,0 +1,48 @@
/*
* Copyright (C) 2015 Kaspar Schleiser <kaspar@schleiser.de>
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup sys_util
* @{
*
* @file
* @brief Bitfield auxillary functions
*
* @author Kaspar Schleiser <kaspar@schleiser.de>
*
* @}
*/
#include <stdint.h>
#include "bitfield.h"
#include "irq.h"
int bf_get_unset(uint8_t field[], int size)
{
int result = -1;
int nbytes = (size + 7) / 8;
int i = 0;
unsigned state = disableIRQ();
/* skip full bytes */
for (int j = 0; (j < nbytes) && (field[j] == 255); j++) {
i += 8;
}
for (; i < size; i++) {
if (!bf_isset(field, i)) {
bf_set(field, i);
result = i;
break;
}
}
restoreIRQ(state);
return(result);
}

13
sys/include/bitfield.h

@ -85,6 +85,19 @@ static inline bool bf_isset(uint8_t field[], size_t idx)
return (field[idx / 8] & (1u << (idx % 8)));
}
/**
* @brief Atomically get the number of an unset bit and set it
*
* This function can be used to record e.g., empty entries in an array.
*
* @param[in,out] field The bitfield
* @param[in] size The size of the bitfield
*
* @return number of bit that was set
* @return -1 if no bit was unset
*/
int bf_get_unset(uint8_t field[], int size);
#ifdef __cplusplus
}
#endif

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