github.com/mdempsky/go@v0.0.0-20151201204031-5dd372bd1e70/src/crypto/md5/md5.go (about)

     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  //go:generate go run gen.go -full -output md5block.go
     6  
     7  // Package md5 implements the MD5 hash algorithm as defined in RFC 1321.
     8  package md5
     9  
    10  import (
    11  	"crypto"
    12  	"hash"
    13  )
    14  
    15  func init() {
    16  	crypto.RegisterHash(crypto.MD5, New)
    17  }
    18  
    19  // The size of an MD5 checksum in bytes.
    20  const Size = 16
    21  
    22  // The blocksize of MD5 in bytes.
    23  const BlockSize = 64
    24  
    25  const (
    26  	chunk = 64
    27  	init0 = 0x67452301
    28  	init1 = 0xEFCDAB89
    29  	init2 = 0x98BADCFE
    30  	init3 = 0x10325476
    31  )
    32  
    33  // digest represents the partial evaluation of a checksum.
    34  type digest struct {
    35  	s   [4]uint32
    36  	x   [chunk]byte
    37  	nx  int
    38  	len uint64
    39  }
    40  
    41  func (d *digest) Reset() {
    42  	d.s[0] = init0
    43  	d.s[1] = init1
    44  	d.s[2] = init2
    45  	d.s[3] = init3
    46  	d.nx = 0
    47  	d.len = 0
    48  }
    49  
    50  // New returns a new hash.Hash computing the MD5 checksum.
    51  func New() hash.Hash {
    52  	d := new(digest)
    53  	d.Reset()
    54  	return d
    55  }
    56  
    57  func (d *digest) Size() int { return Size }
    58  
    59  func (d *digest) BlockSize() int { return BlockSize }
    60  
    61  func (d *digest) Write(p []byte) (nn int, err error) {
    62  	nn = len(p)
    63  	d.len += uint64(nn)
    64  	if d.nx > 0 {
    65  		n := copy(d.x[d.nx:], p)
    66  		d.nx += n
    67  		if d.nx == chunk {
    68  			block(d, d.x[:])
    69  			d.nx = 0
    70  		}
    71  		p = p[n:]
    72  	}
    73  	if len(p) >= chunk {
    74  		n := len(p) &^ (chunk - 1)
    75  		block(d, p[:n])
    76  		p = p[n:]
    77  	}
    78  	if len(p) > 0 {
    79  		d.nx = copy(d.x[:], p)
    80  	}
    81  	return
    82  }
    83  
    84  func (d0 *digest) Sum(in []byte) []byte {
    85  	// Make a copy of d0 so that caller can keep writing and summing.
    86  	d := *d0
    87  	hash := d.checkSum()
    88  	return append(in, hash[:]...)
    89  }
    90  
    91  func (d *digest) checkSum() [Size]byte {
    92  	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
    93  	len := d.len
    94  	var tmp [64]byte
    95  	tmp[0] = 0x80
    96  	if len%64 < 56 {
    97  		d.Write(tmp[0 : 56-len%64])
    98  	} else {
    99  		d.Write(tmp[0 : 64+56-len%64])
   100  	}
   101  
   102  	// Length in bits.
   103  	len <<= 3
   104  	for i := uint(0); i < 8; i++ {
   105  		tmp[i] = byte(len >> (8 * i))
   106  	}
   107  	d.Write(tmp[0:8])
   108  
   109  	if d.nx != 0 {
   110  		panic("d.nx != 0")
   111  	}
   112  
   113  	var digest [Size]byte
   114  	for i, s := range d.s {
   115  		digest[i*4] = byte(s)
   116  		digest[i*4+1] = byte(s >> 8)
   117  		digest[i*4+2] = byte(s >> 16)
   118  		digest[i*4+3] = byte(s >> 24)
   119  	}
   120  
   121  	return digest
   122  }
   123  
   124  // Sum returns the MD5 checksum of the data.
   125  func Sum(data []byte) [Size]byte {
   126  	var d digest
   127  	d.Reset()
   128  	d.Write(data)
   129  	return d.checkSum()
   130  }