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3631ab7df2
Use fasthash64 to hash filenames to uint64_t and store in khash set. Significantly reduces malloc/free'ing and memory usage.
85 lines
2.5 KiB
C++
85 lines
2.5 KiB
C++
/* The MIT License
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Copyright (C) 2012 Zilong Tan (eric.zltan@gmail.com)
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Permission is hereby granted, free of charge, to any person
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obtaining a copy of this software and associated documentation
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files (the "Software"), to deal in the Software without
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restriction, including without limitation the rights to use, copy,
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modify, merge, publish, distribute, sublicense, and/or sell copies
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of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
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BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
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ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
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CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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SOFTWARE.
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*/
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#include "fasthash.h"
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// Compression function for Merkle-Damgard construction.
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// This function is generated using the framework provided.
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#define mix(h) ({ \
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(h) ^= (h) >> 23; \
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(h) *= 0x2127599bf4325c37ULL; \
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(h) ^= (h) >> 47; })
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uint64_t
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fasthash64(const void *buf,
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size_t len,
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uint64_t seed)
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{
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const uint64_t m = 0x880355f21e6d1965ULL;
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const uint64_t *pos = (const uint64_t *)buf;
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const uint64_t *end = pos + (len / 8);
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const unsigned char *pos2;
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uint64_t h = seed ^ (len * m);
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uint64_t v;
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while (pos != end) {
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v = *pos++;
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h ^= mix(v);
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h *= m;
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}
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pos2 = (const unsigned char*)pos;
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v = 0;
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switch (len & 7) {
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case 7: v ^= (uint64_t)pos2[6] << 48;
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case 6: v ^= (uint64_t)pos2[5] << 40;
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case 5: v ^= (uint64_t)pos2[4] << 32;
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case 4: v ^= (uint64_t)pos2[3] << 24;
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case 3: v ^= (uint64_t)pos2[2] << 16;
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case 2: v ^= (uint64_t)pos2[1] << 8;
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case 1: v ^= (uint64_t)pos2[0];
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h ^= mix(v);
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h *= m;
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}
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return mix(h);
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}
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uint32_t
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fasthash32(const void *buf,
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size_t len,
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uint32_t seed)
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{
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// the following trick converts the 64-bit hashcode to Fermat
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// residue, which shall retain information from both the higher
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// and lower parts of hashcode.
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uint64_t h;
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h = fasthash64(buf, len, seed);
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return (h - (h >> 32));
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}
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