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package keyset
import (
"bytes"
"github.com/segmentio/asm/cpu"
"github.com/segmentio/asm/cpu/arm64"
"github.com/segmentio/asm/cpu/x86"
)
// New prepares a set of keys for use with Lookup.
//
// An optimized routine is used if the processor supports AVX instructions and
// the maximum length of any of the keys is less than or equal to 16. If New
// returns nil, this indicates that an optimized routine is not available, and
// the caller should use a fallback.
func New(keys [][]byte) []byte {
maxWidth, hasNullByte := checkKeys(keys)
if hasNullByte || maxWidth > 16 || !(cpu.X86.Has(x86.AVX) || cpu.ARM64.Has(arm64.ASIMD)) {
return nil
}
set := make([]byte, len(keys)*16)
for i, k := range keys {
copy(set[i*16:], k)
}
return set
}
func checkKeys(keys [][]byte) (maxWidth int, hasNullByte bool) {
for _, k := range keys {
if len(k) > maxWidth {
maxWidth = len(k)
}
if bytes.IndexByte(k, 0) >= 0 {
hasNullByte = true
}
}
return
}
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