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