LXR linux/include/linux/ceph/ceph

   1#ifndef FS_CEPH_FRAG_H
   2#define FS_CEPH_FRAG_H
   3
   4/*
   5 * "Frags" are a way to describe a subset of a 32-bit number space,
   6 * using a mask and a value to match against that mask.  Any given frag
   7 * (subset of the number space) can be partitioned into 2^n sub-frags.
   8 *
   9 * Frags are encoded into a 32-bit word:
  10 *   8 upper bits = "bits"
  11 *  24 lower bits = "value"
  12 * (We could go to 5+27 bits, but who cares.)
  13 *
  14 * We use the _most_ significant bits of the 24 bit value.  This makes
  15 * values logically sort.
  16 *
  17 * Unfortunately, because the "bits" field is still in the high bits, we
  18 * can't sort encoded frags numerically.  However, it does allow you
  19 * to feed encoded frags as values into frag_contains_value.
  20 */
  21static inline __u32 ceph_frag_make(__u32 b, __u32 v)
  22{
  23        return (b << 24) |
  24                (v & (0xffffffu << (24-b)) & 0xffffffu);
  25}
  26static inline __u32 ceph_frag_bits(__u32 f)
  27{
  28        return f >> 24;
  29}
  30static inline __u32 ceph_frag_value(__u32 f)
  31{
  32        return f & 0xffffffu;
  33}
  34static inline __u32 ceph_frag_mask(__u32 f)
  35{
  36        return (0xffffffu << (24-ceph_frag_bits(f))) & 0xffffffu;
  37}
  38static inline __u32 ceph_frag_mask_shift(__u32 f)
  39{
  40        return 24 - ceph_frag_bits(f);
  41}
  42
  43static inline int ceph_frag_contains_value(__u32 f, __u32 v)
  44{
  45        return (v & ceph_frag_mask(f)) == ceph_frag_value(f);
  46}
  47static inline int ceph_frag_contains_frag(__u32 f, __u32 sub)
  48{
  49        /* is sub as specific as us, and contained by us? */
  50        return ceph_frag_bits(sub) >= ceph_frag_bits(f) &&
  51               (ceph_frag_value(sub) & ceph_frag_mask(f)) == ceph_frag_value(f);
  52}
  53
  54static inline __u32 ceph_frag_parent(__u32 f)
  55{
  56        return ceph_frag_make(ceph_frag_bits(f) - 1,
  57                         ceph_frag_value(f) & (ceph_frag_mask(f) << 1));
  58}
  59static inline int ceph_frag_is_left_child(__u32 f)
  60{
  61        return ceph_frag_bits(f) > 0 &&
  62                (ceph_frag_value(f) & (0x1000000 >> ceph_frag_bits(f))) == 0;
  63}
  64static inline int ceph_frag_is_right_child(__u32 f)
  65{
  66        return ceph_frag_bits(f) > 0 &&
  67                (ceph_frag_value(f) & (0x1000000 >> ceph_frag_bits(f))) == 1;
  68}
  69static inline __u32 ceph_frag_sibling(__u32 f)
  70{
  71        return ceph_frag_make(ceph_frag_bits(f),
  72                      ceph_frag_value(f) ^ (0x1000000 >> ceph_frag_bits(f)));
  73}
  74static inline __u32 ceph_frag_left_child(__u32 f)
  75{
  76        return ceph_frag_make(ceph_frag_bits(f)+1, ceph_frag_value(f));
  77}
  78static inline __u32 ceph_frag_right_child(__u32 f)
  79{
  80        return ceph_frag_make(ceph_frag_bits(f)+1,
  81              ceph_frag_value(f) | (0x1000000 >> (1+ceph_frag_bits(f))));
  82}
  83static inline __u32 ceph_frag_make_child(__u32 f, int by, int i)
  84{
  85        int newbits = ceph_frag_bits(f) + by;
  86        return ceph_frag_make(newbits,
  87                         ceph_frag_value(f) | (i << (24 - newbits)));
  88}
  89static inline int ceph_frag_is_leftmost(__u32 f)
  90{
  91        return ceph_frag_value(f) == 0;
  92}
  93static inline int ceph_frag_is_rightmost(__u32 f)
  94{
  95        return ceph_frag_value(f) == ceph_frag_mask(f);
  96}
  97static inline __u32 ceph_frag_next(__u32 f)
  98{
  99        return ceph_frag_make(ceph_frag_bits(f),
 100                         ceph_frag_value(f) + (0x1000000 >> ceph_frag_bits(f)));
 101}
 102
 103/*
 104 * comparator to sort frags logically, as when traversing the
 105 * number space in ascending order...
 106 */
 107int ceph_frag_compare(__u32 a, __u32 b);
 108
 109#endif
 110