73 lines
1.4 KiB
C++
73 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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#pragma once
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#include "debug.h"
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namespace lean {
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void mix(unsigned & a, unsigned & b, unsigned & c);
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unsigned hash_str(unsigned len, char const * str, unsigned init_value);
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inline unsigned hash(unsigned h1, unsigned h2) {
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h2 -= h1; h2 ^= (h1 << 8);
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h1 -= h2; h2 ^= (h1 << 16);
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h2 -= h1; h2 ^= (h1 << 10);
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return h2;
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}
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template<typename H>
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unsigned hash(unsigned n, H h, unsigned init_value = 31) {
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unsigned a, b, c;
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lean_assert(n > 0);
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a = b = 0x9e3779b9;
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c = 11;
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switch (n) {
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case 1:
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a += init_value;
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b = h(0);
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mix(a, b, c);
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return c;
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case 2:
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a += init_value;
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b += h(0);
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c += h(1);
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mix(a, b, c);
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return c;
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case 3:
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a += h(0);
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b += h(1);
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c += h(2);
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mix(a, b, c);
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a += init_value;
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mix(a, b, c);
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return c;
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default:
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while (n >= 3) {
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n--;
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a += h(n);
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n--;
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b += h(n);
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n--;
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c += h(n);
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mix(a, b, c);
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}
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a += init_value;
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switch (n) {
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case 2: b += h(1);
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case 1: c += h(0);
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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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}
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