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package xsync
import (
"math/bits"
"runtime"
_ "unsafe"
)
// test-only assert()-like flag
var assertionsEnabled = false
const (
// cacheLineSize is used in paddings to prevent false sharing;
// 64B are used instead of 128B as a compromise between
// memory footprint and performance; 128B usage may give ~30%
// improvement on NUMA machines.
cacheLineSize = 64
)
// nextPowOf2 computes the next highest power of 2 of 32-bit v.
// Source: https://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
func nextPowOf2(v uint32) uint32 {
if v == 0 {
return 1
}
v--
v |= v >> 1
v |= v >> 2
v |= v >> 4
v |= v >> 8
v |= v >> 16
v++
return v
}
func parallelism() uint32 {
maxProcs := uint32(runtime.GOMAXPROCS(0))
numCores := uint32(runtime.NumCPU())
if maxProcs < numCores {
return maxProcs
}
return numCores
}
//go:noescape
//go:linkname runtime_fastrand runtime.fastrand
func runtime_fastrand() uint32
func broadcast(b uint8) uint64 {
return 0x101010101010101 * uint64(b)
}
func firstMarkedByteIndex(w uint64) int {
return bits.TrailingZeros64(w) >> 3
}
// SWAR byte search: may produce false positives, e.g. for 0x0100,
// so make sure to double-check bytes found by this function.
func markZeroBytes(w uint64) uint64 {
return ((w - 0x0101010101010101) & (^w) & 0x8080808080808080)
}
func setByte(w uint64, b uint8, idx int) uint64 {
shift := idx << 3
return (w &^ (0xff << shift)) | (uint64(b) << shift)
}
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