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git-svn-id: https://ceph.svn.sf.net/svnroot/ceph@2100 29311d96-e01e-0410-9327-a35deaab8ce9
81 lines
2.1 KiB
C
81 lines
2.1 KiB
C
#ifndef _CRUSH_HASH_H
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#define _CRUSH_HASH_H
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// Robert Jenkins' function for mixing 32-bit values
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// http://burtleburtle.net/bob/hash/evahash.html
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// a, b = random bits, c = input and output
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#define hashmix(a,b,c) \
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a=a-b; a=a-c; a=a^(c>>13); \
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b=b-c; b=b-a; b=b^(a<<8); \
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c=c-a; c=c-b; c=c^(b>>13); \
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a=a-b; a=a-c; a=a^(c>>12); \
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b=b-c; b=b-a; b=b^(a<<16); \
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c=c-a; c=c-b; c=c^(b>>5); \
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a=a-b; a=a-c; a=a^(c>>3); \
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b=b-c; b=b-a; b=b^(a<<10); \
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c=c-a; c=c-b; c=c^(b>>15);
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#define crush_hash_seed 1315423911
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static __inline__ unsigned crush_hash32(unsigned a) {
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unsigned hash = crush_hash_seed ^ a;
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unsigned b = a;
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unsigned x = 231232;
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unsigned y = 1232;
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hashmix(b, x, hash);
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hashmix(y, a, hash);
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return (hash & 0xFFFFFFFF);
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}
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static __inline__ unsigned crush_hash32_2(unsigned a, unsigned b) {
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unsigned hash = crush_hash_seed ^ a ^ b;
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unsigned x = 231232;
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unsigned y = 1232;
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hashmix(a, b, hash);
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hashmix(x, a, hash);
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hashmix(b, y, hash);
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return (hash & 0xFFFFFFFF);
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}
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static __inline__ unsigned crush_hash32_3(unsigned a, unsigned b, unsigned c) {
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unsigned int hash = crush_hash_seed ^ a ^ b ^ c;
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unsigned x = 231232;
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unsigned y = 1232;
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hashmix(a, b, hash);
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hashmix(c, x, hash);
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hashmix(y, a, hash);
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hashmix(b, x, hash);
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hashmix(y, c, hash);
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return (hash & 0xFFFFFFFF);
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}
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static __inline__ unsigned crush_hash32_4(unsigned a, unsigned b, unsigned c, unsigned d) {
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unsigned int hash = crush_hash_seed ^a ^ b ^ c ^ d;
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unsigned x = 231232;
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unsigned y = 1232;
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hashmix(a, b, hash);
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hashmix(c, d, hash);
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hashmix(a, x, hash);
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hashmix(y, b, hash);
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hashmix(c, x, hash);
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hashmix(y, d, hash);
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return (hash & 0xFFFFFFFF);
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}
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static __inline__ unsigned crush_hash32_5(unsigned a, unsigned b, unsigned c, unsigned d, unsigned e) {
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unsigned int hash = crush_hash_seed ^ a ^ b ^ c ^ d ^ e;
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unsigned x = 231232;
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unsigned y = 1232;
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hashmix(a, b, hash);
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hashmix(c, d, hash);
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hashmix(e, x, hash);
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hashmix(y, a, hash);
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hashmix(b, x, hash);
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hashmix(y, c, hash);
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hashmix(d, x, hash);
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hashmix(y, e, hash);
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return (hash & 0xFFFFFFFF);
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}
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#endif
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