1 // Copyright 2009 The Go Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style 3 // license that can be found in the LICENSE file. 4 5 // Package hash provides interfaces for hash functions. 6 package hash 7 8 import "io" 9 10 // Hash is the common interface implemented by all hash functions. 11 // 12 // Hash implementations in the standard library (e.g. hash/crc32 and 13 // crypto/sha256) implement the encoding.BinaryMarshaler and 14 // encoding.BinaryUnmarshaler interfaces. Marshaling a hash implementation 15 // allows its internal state to be saved and used for additional processing 16 // later, without having to re-write the data previously written to the hash. 17 // The hash state may contain portions of the input in its original form, 18 // which users are expected to handle for any possible security implications. 19 // 20 // Compatibility: Any future changes to hash or crypto packages will endeavor 21 // to maintain compatibility with state encoded using previous versions. 22 // That is, any released versions of the packages should be able to 23 // decode data written with any previously released version, 24 // subject to issues such as security fixes. 25 // See the Go compatibility document for background: https://golang.org/doc/go1compat 26 type Hash interface { 27 // Write (via the embedded io.Writer interface) adds more data to the running hash. 28 // It never returns an error. 29 io.Writer 30 31 // Sum appends the current hash to b and returns the resulting slice. 32 // It does not change the underlying hash state. 33 Sum(b []byte) []byte 34 35 // Reset resets the Hash to its initial state. 36 Reset() 37 38 // Size returns the number of bytes Sum will return. 39 Size() int 40 41 // BlockSize returns the hash's underlying block size. 42 // The Write method must be able to accept any amount 43 // of data, but it may operate more efficiently if all writes 44 // are a multiple of the block size. 45 BlockSize() int 46 } 47 48 // Hash32 is the common interface implemented by all 32-bit hash functions. 49 type Hash32 interface { 50 Hash 51 Sum32() uint32 52 } 53 54 // Hash64 is the common interface implemented by all 64-bit hash functions. 55 type Hash64 interface { 56 Hash 57 Sum64() uint64 58 } 59