c5d2796069
This PR avoids undefined behavior in `String.Slice.hash` on unaligned substrings. This could produce a SIGILL on some Arm platforms. Closes #12317
61 lines
1.4 KiB
C++
61 lines
1.4 KiB
C++
/*
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Copyright (c) 2013 Microsoft Corporation. All rights reserved.
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Released under Apache 2.0 license as described in the file LICENSE.
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Author: Leonardo de Moura
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*/
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#include <cstring>
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#include "runtime/hash.h"
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namespace lean {
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//-----------------------------------------------------------------------------
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// MurmurHash2, 64-bit versions, by Austin Appleby
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// https://sites.google.com/site/murmurhash/
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static uint64 MurmurHash64A(void const * key, size_t len, uint64 seed) {
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const uint64 m = 0xc6a4a7935bd1e995;
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const int r = 47;
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uint64 h = seed ^ (len * m);
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const unsigned char * data = reinterpret_cast<const unsigned char *>(key);
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const unsigned char * end = data + (len/8)*8;
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while (data != end) {
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uint64 k;
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memcpy(&k, data, 8);
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data += 8;
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k *= m;
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k ^= k >> r;
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k *= m;
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h ^= k;
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h *= m;
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}
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const unsigned char * data2 = (const unsigned char *) data;
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switch (len & 7) {
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case 7: h ^= uint64(data2[6]) << 48;
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case 6: h ^= uint64(data2[5]) << 40;
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case 5: h ^= uint64(data2[4]) << 32;
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case 4: h ^= uint64(data2[3]) << 24;
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case 3: h ^= uint64(data2[2]) << 16;
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case 2: h ^= uint64(data2[1]) << 8;
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case 1: h ^= uint64(data2[0]);
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h *= m;
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};
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h ^= h >> r;
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h *= m;
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h ^= h >> r;
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return h;
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}
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uint64 hash_str(size_t len, unsigned char const * str, uint64 init_value) {
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return MurmurHash64A(str, len, init_value);
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}
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}
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