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131 lines
2.9 KiB
131 lines
2.9 KiB
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#include <linux/ceph/types.h> |
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#include <linux/module.h> |
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/* |
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* Robert Jenkin's hash function. |
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* https://burtleburtle.net/bob/hash/evahash.html |
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* This is in the public domain. |
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*/ |
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#define mix(a, b, c) \ |
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do { \ |
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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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} while (0) |
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unsigned int ceph_str_hash_rjenkins(const char *str, unsigned int length) |
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{ |
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const unsigned char *k = (const unsigned char *)str; |
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__u32 a, b, c; /* the internal state */ |
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__u32 len; /* how many key bytes still need mixing */ |
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/* Set up the internal state */ |
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len = length; |
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a = 0x9e3779b9; /* the golden ratio; an arbitrary value */ |
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b = a; |
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c = 0; /* variable initialization of internal state */ |
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/* handle most of the key */ |
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while (len >= 12) { |
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a = a + (k[0] + ((__u32)k[1] << 8) + ((__u32)k[2] << 16) + |
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((__u32)k[3] << 24)); |
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b = b + (k[4] + ((__u32)k[5] << 8) + ((__u32)k[6] << 16) + |
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((__u32)k[7] << 24)); |
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c = c + (k[8] + ((__u32)k[9] << 8) + ((__u32)k[10] << 16) + |
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((__u32)k[11] << 24)); |
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mix(a, b, c); |
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k = k + 12; |
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len = len - 12; |
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} |
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/* handle the last 11 bytes */ |
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c = c + length; |
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switch (len) { |
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case 11: |
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c = c + ((__u32)k[10] << 24); |
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fallthrough; |
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case 10: |
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c = c + ((__u32)k[9] << 16); |
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fallthrough; |
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case 9: |
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c = c + ((__u32)k[8] << 8); |
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/* the first byte of c is reserved for the length */ |
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fallthrough; |
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case 8: |
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b = b + ((__u32)k[7] << 24); |
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fallthrough; |
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case 7: |
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b = b + ((__u32)k[6] << 16); |
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fallthrough; |
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case 6: |
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b = b + ((__u32)k[5] << 8); |
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fallthrough; |
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case 5: |
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b = b + k[4]; |
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fallthrough; |
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case 4: |
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a = a + ((__u32)k[3] << 24); |
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fallthrough; |
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case 3: |
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a = a + ((__u32)k[2] << 16); |
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fallthrough; |
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case 2: |
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a = a + ((__u32)k[1] << 8); |
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fallthrough; |
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case 1: |
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a = a + k[0]; |
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/* case 0: nothing left to add */ |
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} |
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mix(a, b, c); |
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return c; |
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} |
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/* |
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* linux dcache hash |
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*/ |
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unsigned int ceph_str_hash_linux(const char *str, unsigned int length) |
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{ |
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unsigned long hash = 0; |
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unsigned char c; |
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while (length--) { |
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c = *str++; |
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hash = (hash + (c << 4) + (c >> 4)) * 11; |
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} |
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return hash; |
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} |
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unsigned int ceph_str_hash(int type, const char *s, unsigned int len) |
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{ |
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switch (type) { |
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case CEPH_STR_HASH_LINUX: |
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return ceph_str_hash_linux(s, len); |
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case CEPH_STR_HASH_RJENKINS: |
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return ceph_str_hash_rjenkins(s, len); |
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default: |
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return -1; |
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} |
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} |
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EXPORT_SYMBOL(ceph_str_hash); |
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const char *ceph_str_hash_name(int type) |
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{ |
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switch (type) { |
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case CEPH_STR_HASH_LINUX: |
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return "linux"; |
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case CEPH_STR_HASH_RJENKINS: |
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return "rjenkins"; |
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default: |
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return "unknown"; |
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} |
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} |
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EXPORT_SYMBOL(ceph_str_hash_name);
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