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// Copyright 2011 The Go Authors. All rights reserved.

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

// Package crypto collects common cryptographic constants.

package crypto

import (

        "hash"

)

// Hash identifies a cryptographic hash function that is implemented in another

// package.

type Hash uint

const (

        MD4       Hash = 1 + iota // import code.google.com/p/go.crypto/md4

        MD5                       // import crypto/md5

        SHA1                      // import crypto/sha1

        SHA224                    // import crypto/sha256

        SHA256                    // import crypto/sha256

        SHA384                    // import crypto/sha512

        SHA512                    // import crypto/sha512

        MD5SHA1                   // no implementation; MD5+SHA1 used for TLS RSA

        RIPEMD160                 // import code.google.com/p/go.crypto/ripemd160

        maxHash

)

var digestSizes = []uint8{

        MD4:       16,

        MD5:       16,

        SHA1:      20,

        SHA224:    28,

        SHA256:    32,

        SHA384:    48,

        SHA512:    64,

        MD5SHA1:   36,

        RIPEMD160: 20,

}

// Size returns the length, in bytes, of a digest resulting from the given hash

// function. It doesn't require that the hash function in question be linked

// into the program.

func (h Hash) Size() int {

        if h > 0 && h < maxHash {

                return int(digestSizes[h])

        }

        panic("crypto: Size of unknown hash function")

}

var hashes = make([]func() hash.Hash, maxHash)

// New returns a new hash.Hash calculating the given hash function. New panics

// if the hash function is not linked into the binary.

func (h Hash) New() hash.Hash {

        if h > 0 && h < maxHash {

                f := hashes[h]

                if f != nil {

                        return f()

                }

        }

        panic("crypto: requested hash function is unavailable")

}

// Available reports whether the given hash function is linked into the binary.

func (h Hash) Available() bool {

        return h < maxHash && hashes[h] != nil

}

// RegisterHash registers a function that returns a new instance of the given

// hash function. This is intended to be called from the init function in

// packages that implement hash functions.

func RegisterHash(h Hash, f func() hash.Hash) {

        if h >= maxHash {

                panic("crypto: RegisterHash of unknown hash function")

        }

        hashes[h] = f

}

// PrivateKey represents a private key using an unspecified algorithm.

type PrivateKey interface{}