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1/* SPDX-License-Identifier: GPL-2.0 */2#ifndef FS_CEPH_FRAG_H3#define FS_CEPH_FRAG_H4 5/*6 * "Frags" are a way to describe a subset of a 32-bit number space,7 * using a mask and a value to match against that mask. Any given frag8 * (subset of the number space) can be partitioned into 2^n sub-frags.9 *10 * Frags are encoded into a 32-bit word:11 * 8 upper bits = "bits"12 * 24 lower bits = "value"13 * (We could go to 5+27 bits, but who cares.)14 *15 * We use the _most_ significant bits of the 24 bit value. This makes16 * values logically sort.17 *18 * Unfortunately, because the "bits" field is still in the high bits, we19 * can't sort encoded frags numerically. However, it does allow you20 * to feed encoded frags as values into frag_contains_value.21 */22static inline __u32 ceph_frag_make(__u32 b, __u32 v)23{24 return (b << 24) |25 (v & (0xffffffu << (24-b)) & 0xffffffu);26}27static inline __u32 ceph_frag_bits(__u32 f)28{29 return f >> 24;30}31static inline __u32 ceph_frag_value(__u32 f)32{33 return f & 0xffffffu;34}35static inline __u32 ceph_frag_mask(__u32 f)36{37 return (0xffffffu << (24-ceph_frag_bits(f))) & 0xffffffu;38}39static inline __u32 ceph_frag_mask_shift(__u32 f)40{41 return 24 - ceph_frag_bits(f);42}43 44static inline bool ceph_frag_contains_value(__u32 f, __u32 v)45{46 return (v & ceph_frag_mask(f)) == ceph_frag_value(f);47}48 49static inline __u32 ceph_frag_make_child(__u32 f, int by, int i)50{51 int newbits = ceph_frag_bits(f) + by;52 return ceph_frag_make(newbits,53 ceph_frag_value(f) | (i << (24 - newbits)));54}55static inline bool ceph_frag_is_leftmost(__u32 f)56{57 return ceph_frag_value(f) == 0;58}59static inline bool ceph_frag_is_rightmost(__u32 f)60{61 return ceph_frag_value(f) == ceph_frag_mask(f);62}63static inline __u32 ceph_frag_next(__u32 f)64{65 return ceph_frag_make(ceph_frag_bits(f),66 ceph_frag_value(f) + (0x1000000 >> ceph_frag_bits(f)));67}68 69/*70 * comparator to sort frags logically, as when traversing the71 * number space in ascending order...72 */73int ceph_frag_compare(__u32 a, __u32 b);74 75#endif76