githaven/vendor/github.com/ulikunitz/xz/internal/hash/roller.go

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2021-02-28 23:08:33 +00:00
// Copyright 2014-2021 Ulrich Kunitz. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package hash
// Roller provides an interface for rolling hashes. The hash value will become
// valid after hash has been called Len times.
type Roller interface {
Len() int
RollByte(x byte) uint64
}
// Hashes computes all hash values for the array p. Note that the state of the
// roller is changed.
func Hashes(r Roller, p []byte) []uint64 {
n := r.Len()
if len(p) < n {
return nil
}
h := make([]uint64, len(p)-n+1)
for i := 0; i < n-1; i++ {
r.RollByte(p[i])
}
for i := range h {
h[i] = r.RollByte(p[i+n-1])
}
return h
}