hash.go

     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
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