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