lib/bitopts.c

   1 #include <stdio.h>
   2 #include <stdint.h>
   3 #include <bitopts.h>
   4
   5 /*
   6  *  The bit opts function from Extprogs lib
   7  */
   8
   9
  10 /*
  11  * Set the bit and return it's original value
  12  */
  13 int set_bit(void * addr, unsigned int nr)
  14 {
  15         int             mask, retval;
  16         unsigned char   *ADDR = (unsigned char *) addr;
  17
  18         ADDR += nr >> 3;
  19         mask = 1 << (nr & 0x07);
  20         retval = mask & *ADDR;
  21         *ADDR |= mask;
  22         return retval;
  23 }
  24
  25 /*
  26  * Clear the bit and return it's original value
  27  */
  28 int clear_bit(void * addr, unsigned int nr)
  29 {
  30         int             mask, retval;
  31         unsigned char   *ADDR = (unsigned char *) addr;
  32
  33         ADDR += nr >> 3;
  34         mask = 1 << (nr & 0x07);
  35         retval = mask & *ADDR;
  36         *ADDR &= ~mask;
  37         return retval;
  38 }
  39
  40 int test_bit(const void * addr, unsigned int nr)
  41 {
  42         int                     mask;
  43         const unsigned char     *ADDR = (const unsigned char *) addr;
  44
  45         ADDR += nr >> 3;
  46         mask = 1 << (nr & 0x07);
  47         return (mask & *ADDR);
  48 }
  49
  50 unsigned long find_first_zero(void *buf, void *end)
  51 {
  52         unsigned long *p = (unsigned long *)buf;
  53         unsigned long block = 0;
  54         int i;
  55
  56         while (*p == 0xffffffff && (void *)p < end) {
  57                 p++;
  58                 block += 32;
  59         }
  60         if ((void *)p >= end)
  61                 return -1;
  62
  63         for (i = 0; i < 32; i++)
  64                 if (test_bit(p, i) == 0)
  65                         return block + i;
  66
  67         /* Just to avoid the compile warning message */
  68         return -1;
  69 }