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