81 lines
2.1 KiB
Go
81 lines
2.1 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package jenkins implements Jenkins's one_at_a_time, non-cryptographic hash
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// functions created by by Bob Jenkins.
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//
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// See https://en.wikipedia.org/wiki/Jenkins_hash_function#cite_note-dobbsx-1
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//
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package jenkins
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import (
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"hash"
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)
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// Sum32 represents Jenkins's one_at_a_time hash.
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//
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// Use the Sum32 type directly (as opposed to New32 below)
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// to avoid allocations.
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type Sum32 uint32
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// New32 returns a new 32-bit Jenkins's one_at_a_time hash.Hash.
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//
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// Its Sum method will lay the value out in big-endian byte order.
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func New32() hash.Hash32 {
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var s Sum32
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return &s
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}
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// Reset resets the hash to its initial state.
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func (s *Sum32) Reset() { *s = 0 }
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// Sum32 returns the hash value
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func (s *Sum32) Sum32() uint32 {
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hash := *s
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hash += (hash << 3)
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hash ^= hash >> 11
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hash += hash << 15
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return uint32(hash)
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}
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// Write adds more data to the running hash.
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//
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// It never returns an error.
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func (s *Sum32) Write(data []byte) (int, error) {
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hash := *s
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for _, b := range data {
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hash += Sum32(b)
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hash += hash << 10
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hash ^= hash >> 6
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}
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*s = hash
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return len(data), nil
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}
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// Size returns the number of bytes Sum will return.
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func (s *Sum32) Size() int { return 4 }
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// BlockSize returns the hash's underlying block size.
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func (s *Sum32) BlockSize() int { return 1 }
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// Sum appends the current hash to in and returns the resulting slice.
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//
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// It does not change the underlying hash state.
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func (s *Sum32) Sum(in []byte) []byte {
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v := s.Sum32()
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return append(in, byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
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}
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