341 lines
11 KiB
D
341 lines
11 KiB
D
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/**
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* Non-cryptographic, lookup hash functions.
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*
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* Copyright: Eugene Wissner 2018-2020.
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* License: $(LINK2 https://www.mozilla.org/en-US/MPL/2.0/,
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* Mozilla Public License, v. 2.0).
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* Authors: $(LINK2 mailto:info@caraus.de, Eugene Wissner)
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* Source: $(LINK2 https://github.com/caraus-ecms/tanya/blob/master/source/tanya/hash/lookup.d,
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* tanya/hash/lookup.d)
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*/
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module tanya.hash.lookup;
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import tanya.meta.trait;
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import tanya.range.primitive;
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private struct Hasher
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{
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static if (size_t.sizeof == 4)
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{
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enum uint offsetBasis = 2166136261;
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enum uint prime = 16777619;
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}
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else static if (size_t.sizeof == 8)
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{
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enum ulong offsetBasis = 14695981039346656037UL;
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enum ulong prime = 1099511628211UL;
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}
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else static if (size_t.sizeof == 16)
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{
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enum size_t offsetBasis = (size_t(0x6c62272e07bb0142UL) << 64) + 0x62b821756295c58dUL;
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enum size_t prime = (size_t(1) << 88) + (1 << 8) + 0x3b;
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}
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else
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{
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static assert(false, "FNV requires at least 32-bit hash length");
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}
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size_t hash = offsetBasis;
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void opCall(T)(auto ref T key)
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{
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static if (is(typeof(key.toHash()) == size_t))
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{
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opCall(key.toHash()); // Combine user-defined hashes
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}
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else static if (isScalarType!T || isPointer!T)
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{
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// Treat as an array of words
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static if (T.sizeof % size_t.sizeof == 0
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&& T.alignof >= size_t.alignof)
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alias CastT = size_t;
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// (64-bit or 128-bit) Treat as an array of ints
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else static if (T.sizeof % uint.sizeof == 0
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&& T.alignof >= uint.alignof)
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alias CastT = uint;
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// Treat as an array of bytes
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else
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alias CastT = ubyte;
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add((() @trusted => (cast(const CastT*) &key)[0 .. T.sizeof / CastT.sizeof])());
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}
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else static if (isArray!T && isScalarType!(ElementType!T))
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{
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// Treat as an array of words
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static if (ElementType!T.sizeof % size_t.sizeof == 0
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&& ElementType!T.alignof >= size_t.alignof)
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alias CastT = size_t;
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// (64-bit or 128-bit) Treat as an array of ints
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else static if (ElementType!T.sizeof % uint.sizeof == 0
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&& ElementType!T.alignof >= uint.alignof)
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alias CastT = uint;
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// Treat as an array of bytes
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else
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alias CastT = ubyte;
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add(cast(const CastT[]) key);
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}
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else static if (is(T == typeof(null)))
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{
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add(key);
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}
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else static if (isInputRange!T && !isInfinite!T)
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{
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foreach (e; key)
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{
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opCall(e);
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}
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}
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else
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{
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static assert(false, "Hash function is not available");
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}
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}
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void add(scope const ubyte[] key) @nogc nothrow pure @safe
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{
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// FNV-1a
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foreach (c; key)
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{
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this.hash = (this.hash ^ c) * prime;
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}
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}
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void add(scope const size_t[] key) @nogc nothrow pure @safe
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{
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static if (size_t.sizeof == 4)
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{
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// Partial MurmurHash3_x86_32 (no finalization)
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enum uint c1 = 0xcc9e2d51;
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enum uint c2 = 0x1b873593;
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alias h1 = hash;
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foreach (x; key)
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{
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auto k1 = x * c1;
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k1 = (k1 << 15) | (k1 >> (32 - 15));
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k1 *= c2;
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h1 ^= k1;
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h1 = (h1 << 13) | (h1 >> (32 - 13));
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h1 = h1 * 5 + 0xe6546b64;
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}
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}
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else static if (size_t.sizeof == 8)
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{
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// Partial 64-bit MurmurHash64A (no finalization)
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alias h = hash;
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enum ulong m = 0xc6a4a7935bd1e995UL;
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foreach (x; key)
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{
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auto k = x * m;
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k ^= k >>> 47;
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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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}
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else static if (size_t.sizeof == 16)
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{
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// Partial MurmurHash3_x64_128 (no finalization)
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// treating each size_t as a pair of ulong.
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ulong h1 = cast(ulong) hash;
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ulong h2 = cast(ulong) (hash >> 64);
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enum ulong c1 = 0x87c37b91114253d5UL;
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enum ulong c2 = 0x4cf5ad432745937fUL;
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foreach (x; key)
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{
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auto k1 = cast(ulong) x;
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auto k2 = cast(ulong) (x >> 64);
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k1 *= c1; k1 = (k1 << 32) | (k1 >> (64 - 31)); k1 *= c2; h1 ^= k1;
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h1 = (h1 << 27) | (h1 >> (64 - 27)); h1 += h2; h1 = h1*5+0x52dce729;
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k2 *= c2; k2 = (k2 << 33) | (k2 >> (64 - 33)); k2 *= c1; h2 ^= k2;
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h2 = (h2 << 31) | (h2 >> (64 - 31)); h2 += h1; h2 = h2*5+0x38495ab5;
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}
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hash = cast(size_t) h1 + ((cast(size_t) h2) << 64);
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}
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else
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{
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static assert(0, "Hash length must be either 32, 64, or 128 bits.");
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}
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}
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static if (size_t.sizeof != uint.sizeof)
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void add(scope const uint[] key) @nogc nothrow pure @trusted
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{
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static if (size_t.sizeof == 8)
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{
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// Partial 32-bit MurmurHash64B (no finalization)
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enum uint m = 0x5bd1e995;
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enum r = 24;
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uint h1 = cast(uint) hash;
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uint h2 = cast(uint) (hash >> 32);
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const(uint)* data = key.ptr;
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auto len = key.length;
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for (; len >= 2; data += 2, len -= 2)
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{
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uint k1 = data[0];
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k1 *= m; k1 ^= k1 >> r; k1 *= m;
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h1 *= m; h1 ^= k1;
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uint k2 = data[1];
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k2 *= m; k2 ^= k2 >> r; k2 *= m;
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h2 *= m; h2 ^= k2;
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}
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if (len)
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{
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uint k1 = data[0];
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k1 *= m; k1 ^= k1 >> r; k1 *= m;
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h1 *= m; h1 ^= k1;
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}
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hash = cast(ulong) h1 + ((cast(ulong) h2) << 32);
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}
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else static if (size_t.sizeof == 16)
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{
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// Partial MurmurHash3_x86_128 (no finalization)
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enum uint c1 = 0x239b961b;
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enum uint c2 = 0xab0e9789;
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enum uint c3 = 0x38b34ae5;
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enum uint c4 = 0xa1e38b93;
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uint h1 = cast(uint) hash;
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uint h2 = cast(uint) (hash >> 32);
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uint h3 = cast(uint) (hash >> 64);
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uint h4 = cast(uint) (hash >> 96);
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const(uint)* data = key.ptr;
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auto len = key.length;
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for (; len >= 4; data += 4, len -= 4)
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{
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uint k1 = data[0];
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uint k2 = data[1];
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uint k3 = data[2];
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uint k4 = data[3];
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h1 = (h1 << 19) | (h1 >> (32 - 19)); h1 += h2; h1 = h1*5+0x561ccd1b;
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k2 *= c2; k2 = (k2 << 16) | (k2 >> (32 - 16)); k2 *= c3; h2 ^= k2;
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h2 = (h2 << 17) | (h2 >> (32 - 17)); h2 += h3; h2 = h2*5+0x0bcaa747;
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k3 *= c3; k3 = (k3 << 17) | (k3 >> (32 - 17)); k3 *= c4; h3 ^= k3;
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h3 = (h3 << 15) | (h3 >> (32 - 15)); h3 += h4; h3 = h3*5+0x96cd1c35;
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k4 *= c4; k4 = (k4 << 18) | (k4 >> (32 - 18)); k4 *= c1; h4 ^= k4;
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h4 = (h4 << 13) | (h4 >> (32 - 13)); h4 += h1; h4 = h4*5+0x32ac3b17;
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}
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uint k1, k2, k3;
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switch (len) // 0, 1, 2, 3
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{
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case 3:
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k3 = data[2];
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k3 *= c3; k3 = (k3 << 17) | (k3 >> (32 - 17)); k3 *= c4; h3 ^= k3;
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goto case;
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case 2:
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k2 = data[1];
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k2 *= c2; k2 = (k2 << 16) | (k2 >> (32 - 16)); k2 *= c3; h2 ^= k2;
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goto case;
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case 1:
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k1 = data[0];
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k1 *= c1; k1 = (k1 << 15) | (k1 >> (32 - 15)); k1 *= c2; h1 ^= k1;
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break;
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}
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hash = cast(size_t) h1 +
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((cast(size_t) h2) << 32) +
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((cast(size_t) h3) << 64) +
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((cast(size_t) h4) << 96);
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}
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else
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{
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static assert(0, "Hash length must be either 32, 64, or 128 bits.");
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}
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}
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}
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/**
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* Takes an argument of an arbitrary type $(D_PARAM T) and calculates the hash
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* value.
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*
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* Hash calculation is supported for all scalar types. Aggregate types, like
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* $(D_KEYWORD struct)s, should implement `toHash`-function:
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* ---
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* size_t toHash() const
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* {
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* return hash;
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* }
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* ---
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*
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* For pointers and for scalar types implicitly convertible to `size_t` this
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* is an identity operation (i.e. the value is cast to `size_t` and returned
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* unaltered). Integer types wider than `size_t` are XOR folded down to
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* `size_t`. Other scalar types use an architecture-dependent hash function
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* based on their width and alignment.
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* If the type provides a `toHash`-function, only `toHash()` is called and its
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* result is returned.
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*
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* This function also accepts input ranges that contain hashable elements.
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* Individual values are combined then and the resulting hash is returned.
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*
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* Params:
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* T = Hashable type.
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* key = Hashable value.
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*
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* Returns: Calculated hash value.
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*
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* See_Also: $(LINK http://www.isthe.com/chongo/tech/comp/fnv/).
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*/
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size_t hash(T)(auto ref T key)
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{
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static if (is(typeof(key.toHash()) == size_t))
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{
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return key.toHash();
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}
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else static if ((isIntegral!T || isSomeChar!T || isBoolean!T)
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&& T.sizeof <= size_t.sizeof)
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{
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return cast(size_t) key;
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}
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else static if (isIntegral!T && T.sizeof > size_t.sizeof)
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{
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return cast(size_t) (key ^ (key >>> (size_t.sizeof * 8)));
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}
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else static if (isPointer!T || is(T : typeof(null)))
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{
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return (() @trusted => cast(size_t) key)();
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}
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else
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{
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Hasher hasher;
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hasher(key);
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return hasher.hash;
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}
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}
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/**
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* Determines whether $(D_PARAM hasher) is hash function for $(D_PARAM T), i.e.
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* it is callable with a value of type $(D_PARAM T) and returns a
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* $(D_PSYMBOL size_t) value.
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*
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* Params:
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* hasher = Hash function candidate.
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* T = Type to test the hash function with.
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*
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* Returns: $(D_KEYWORD true) if $(D_PARAM hasher) is a hash function for
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* $(D_PARAM T), $(D_KEYWORD false) otherwise.
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*/
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template isHashFunction(alias hasher, T)
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{
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private alias wrapper = (T x) => hasher(x);
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enum bool isHashFunction = is(typeof(wrapper(T.init)) == size_t);
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}
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///
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@nogc nothrow pure @safe unittest
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{
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static assert(isHashFunction!(hash, int));
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}
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