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- #ifndef FS_CEPH_FRAG_H
- #define FS_CEPH_FRAG_H
- /*
- * "Frags" are a way to describe a subset of a 32-bit number space,
- * using a mask and a value to match against that mask. Any given frag
- * (subset of the number space) can be partitioned into 2^n sub-frags.
- *
- * Frags are encoded into a 32-bit word:
- * 8 upper bits = "bits"
- * 24 lower bits = "value"
- * (We could go to 5+27 bits, but who cares.)
- *
- * We use the _most_ significant bits of the 24 bit value. This makes
- * values logically sort.
- *
- * Unfortunately, because the "bits" field is still in the high bits, we
- * can't sort encoded frags numerically. However, it does allow you
- * to feed encoded frags as values into frag_contains_value.
- */
- static inline __u32 ceph_frag_make(__u32 b, __u32 v)
- {
- return (b << 24) |
- (v & (0xffffffu << (24-b)) & 0xffffffu);
- }
- static inline __u32 ceph_frag_bits(__u32 f)
- {
- return f >> 24;
- }
- static inline __u32 ceph_frag_value(__u32 f)
- {
- return f & 0xffffffu;
- }
- static inline __u32 ceph_frag_mask(__u32 f)
- {
- return (0xffffffu << (24-ceph_frag_bits(f))) & 0xffffffu;
- }
- static inline __u32 ceph_frag_mask_shift(__u32 f)
- {
- return 24 - ceph_frag_bits(f);
- }
- static inline int ceph_frag_contains_value(__u32 f, __u32 v)
- {
- return (v & ceph_frag_mask(f)) == ceph_frag_value(f);
- }
- static inline int ceph_frag_contains_frag(__u32 f, __u32 sub)
- {
- /* is sub as specific as us, and contained by us? */
- return ceph_frag_bits(sub) >= ceph_frag_bits(f) &&
- (ceph_frag_value(sub) & ceph_frag_mask(f)) == ceph_frag_value(f);
- }
- static inline __u32 ceph_frag_parent(__u32 f)
- {
- return ceph_frag_make(ceph_frag_bits(f) - 1,
- ceph_frag_value(f) & (ceph_frag_mask(f) << 1));
- }
- static inline int ceph_frag_is_left_child(__u32 f)
- {
- return ceph_frag_bits(f) > 0 &&
- (ceph_frag_value(f) & (0x1000000 >> ceph_frag_bits(f))) == 0;
- }
- static inline int ceph_frag_is_right_child(__u32 f)
- {
- return ceph_frag_bits(f) > 0 &&
- (ceph_frag_value(f) & (0x1000000 >> ceph_frag_bits(f))) == 1;
- }
- static inline __u32 ceph_frag_sibling(__u32 f)
- {
- return ceph_frag_make(ceph_frag_bits(f),
- ceph_frag_value(f) ^ (0x1000000 >> ceph_frag_bits(f)));
- }
- static inline __u32 ceph_frag_left_child(__u32 f)
- {
- return ceph_frag_make(ceph_frag_bits(f)+1, ceph_frag_value(f));
- }
- static inline __u32 ceph_frag_right_child(__u32 f)
- {
- return ceph_frag_make(ceph_frag_bits(f)+1,
- ceph_frag_value(f) | (0x1000000 >> (1+ceph_frag_bits(f))));
- }
- static inline __u32 ceph_frag_make_child(__u32 f, int by, int i)
- {
- int newbits = ceph_frag_bits(f) + by;
- return ceph_frag_make(newbits,
- ceph_frag_value(f) | (i << (24 - newbits)));
- }
- static inline int ceph_frag_is_leftmost(__u32 f)
- {
- return ceph_frag_value(f) == 0;
- }
- static inline int ceph_frag_is_rightmost(__u32 f)
- {
- return ceph_frag_value(f) == ceph_frag_mask(f);
- }
- static inline __u32 ceph_frag_next(__u32 f)
- {
- return ceph_frag_make(ceph_frag_bits(f),
- ceph_frag_value(f) + (0x1000000 >> ceph_frag_bits(f)));
- }
- /*
- * comparator to sort frags logically, as when traversing the
- * number space in ascending order...
- */
- int ceph_frag_compare(__u32 a, __u32 b);
- #endif
|
