matchlen_generic.go•684 B
//go:build !amd64 || appengine || !gc || noasm
// +build !amd64 appengine !gc noasm
// Copyright 2019+ Klaus Post. All rights reserved.
// License information can be found in the LICENSE file.
package zstd
import (
"math/bits"
"github.com/klauspost/compress/internal/le"
)
// matchLen returns the maximum common prefix length of a and b.
// a must be the shortest of the two.
func matchLen(a, b []byte) (n int) {
left := len(a)
for left >= 8 {
diff := le.Load64(a, n) ^ le.Load64(b, n)
if diff != 0 {
return n + bits.TrailingZeros64(diff)>>3
}
n += 8
left -= 8
}
a = a[n:]
b = b[n:]
for i := range a {
if a[i] != b[i] {
break
}
n++
}
return n
}