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55a7738837
The previous implementation had some pretty short cycles and two fixed points (1711463637 and 2389024350). If two keys hashed to one of these values insertions and lookups would loop forever. This version is based on a standard xorshift PRNG with period 2**32-1. The all-zero state is usually forbidden, so we insert it into the cycle at an arbitrary location.
63 lines
1.7 KiB
C++
63 lines
1.7 KiB
C++
/*
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* Copyright (c) 2020, the SerenityOS developers.
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibTest/TestCase.h>
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#include <AK/HashFunctions.h>
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#include <AK/Types.h>
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TEST_CASE(int_hash)
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{
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static_assert(int_hash(42) == 3564735745u);
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static_assert(int_hash(0) == 1177991625u);
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}
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TEST_CASE(double_hash)
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{
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static_assert(double_hash(666) == 171644115u);
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static_assert(double_hash(0) == 1189591134u);
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static_assert(double_hash(0xBA5EDB01) == 0u);
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}
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TEST_CASE(pair_int_hash)
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{
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static_assert(pair_int_hash(42, 17) == 339337046u);
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static_assert(pair_int_hash(0, 0) == 954888656u);
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}
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TEST_CASE(u64_hash)
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{
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static_assert(u64_hash(42) == 2824066580u);
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static_assert(u64_hash(0) == 954888656u);
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}
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TEST_CASE(ptr_hash)
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{
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// These tests are not static_asserts because the values are
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// different and the goal is to bind the behavior.
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if constexpr (sizeof(FlatPtr) == 8) {
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EXPECT_EQ(ptr_hash(FlatPtr(42)), 2824066580u);
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EXPECT_EQ(ptr_hash(FlatPtr(0)), 954888656u);
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EXPECT_EQ(ptr_hash(reinterpret_cast<const void*>(42)), 2824066580u);
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EXPECT_EQ(ptr_hash(reinterpret_cast<const void*>(0)), 954888656u);
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} else {
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EXPECT_EQ(ptr_hash(FlatPtr(42)), 3564735745u);
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EXPECT_EQ(ptr_hash(FlatPtr(0)), 1177991625u);
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EXPECT_EQ(ptr_hash(reinterpret_cast<const void*>(42)), 3564735745u);
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EXPECT_EQ(ptr_hash(reinterpret_cast<const void*>(0)), 1177991625u);
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}
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}
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TEST_CASE(constexpr_ptr_hash)
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{
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// This test does not check the result because the goal is just to
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// ensure the function can be executed in a constexpr context. The
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// "ptr_hash" test binds the result.
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static_assert(ptr_hash(FlatPtr(42)));
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}
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