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.
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.)
14 * We use the _most_ significant bits of the 24 bit value. This makes
15 * values logically sort.
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.
21 static inline __u32 ceph_frag_make(__u32 b, __u32 v)
24 (v & (0xffffffu << (24-b)) & 0xffffffu);
26 static inline __u32 ceph_frag_bits(__u32 f)
30 static inline __u32 ceph_frag_value(__u32 f)
34 static inline __u32 ceph_frag_mask(__u32 f)
36 return (0xffffffu << (24-ceph_frag_bits(f))) & 0xffffffu;
38 static inline __u32 ceph_frag_mask_shift(__u32 f)
40 return 24 - ceph_frag_bits(f);
43 static inline bool ceph_frag_contains_value(__u32 f, __u32 v)
45 return (v & ceph_frag_mask(f)) == ceph_frag_value(f);
48 static inline __u32 ceph_frag_make_child(__u32 f, int by, int i)
50 int newbits = ceph_frag_bits(f) + by;
51 return ceph_frag_make(newbits,
52 ceph_frag_value(f) | (i << (24 - newbits)));
54 static inline bool ceph_frag_is_leftmost(__u32 f)
56 return ceph_frag_value(f) == 0;
58 static inline bool ceph_frag_is_rightmost(__u32 f)
60 return ceph_frag_value(f) == ceph_frag_mask(f);
62 static inline __u32 ceph_frag_next(__u32 f)
64 return ceph_frag_make(ceph_frag_bits(f),
65 ceph_frag_value(f) + (0x1000000 >> ceph_frag_bits(f)));
69 * comparator to sort frags logically, as when traversing the
70 * number space in ascending order...
72 int ceph_frag_compare(__u32 a, __u32 b);