59 lines
1.4 KiB
Go
59 lines
1.4 KiB
Go
// Copyright 2023 Dolthub, Inc.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//go:build !amd64 || nosimd
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package swiss
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import (
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"math/bits"
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"unsafe"
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)
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const (
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groupSize = 8
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maxAvgGroupLoad = 7
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loBits uint64 = 0x0101010101010101
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hiBits uint64 = 0x8080808080808080
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)
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type bitset uint64
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func metaMatchH2(m *metadata, h h2) bitset {
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// https://graphics.stanford.edu/~seander/bithacks.html##ValueInWord
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return hasZeroByte(castUint64(m) ^ (loBits * uint64(h)))
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}
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func metaMatchEmpty(m *metadata) bitset {
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return hasZeroByte(castUint64(m) ^ hiBits)
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}
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func nextMatch(b *bitset) uint32 {
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s := uint32(bits.TrailingZeros64(uint64(*b)))
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*b &= ^(1 << s) // clear bit |s|
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return s >> 3 // div by 8
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}
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func hasZeroByte(x uint64) bitset {
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return bitset(((x - loBits) & ^(x)) & hiBits)
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}
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func castUint64(m *metadata) uint64 {
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return *(*uint64)((unsafe.Pointer)(m))
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}
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//go:linkname fastrand runtime.fastrand
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func fastrand() uint32
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