github.com/tcnksm/go@v0.0.0-20141208075154-439b32936367/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 := len(p)
    66  		if n > chunk-d.nx {
    67  			n = chunk - d.nx
    68  		}
    69  		for i := 0; i < n; i++ {
    70  			d.x[d.nx+i] = p[i]
    71  		}
    72  		d.nx += n
    73  		if d.nx == chunk {
    74  			block(d, d.x[0:chunk])
    75  			d.nx = 0
    76  		}
    77  		p = p[n:]
    78  	}
    79  	if len(p) >= chunk {
    80  		n := len(p) &^ (chunk - 1)
    81  		block(d, p[:n])
    82  		p = p[n:]
    83  	}
    84  	if len(p) > 0 {
    85  		d.nx = copy(d.x[:], p)
    86  	}
    87  	return
    88  }
    89  
    90  func (d0 *digest) Sum(in []byte) []byte {
    91  	// Make a copy of d0 so that caller can keep writing and summing.
    92  	d := *d0
    93  	hash := d.checkSum()
    94  	return append(in, hash[:]...)
    95  }
    96  
    97  func (d *digest) checkSum() [Size]byte {
    98  	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
    99  	len := d.len
   100  	var tmp [64]byte
   101  	tmp[0] = 0x80
   102  	if len%64 < 56 {
   103  		d.Write(tmp[0 : 56-len%64])
   104  	} else {
   105  		d.Write(tmp[0 : 64+56-len%64])
   106  	}
   107  
   108  	// Length in bits.
   109  	len <<= 3
   110  	for i := uint(0); i < 8; i++ {
   111  		tmp[i] = byte(len >> (8 * i))
   112  	}
   113  	d.Write(tmp[0:8])
   114  
   115  	if d.nx != 0 {
   116  		panic("d.nx != 0")
   117  	}
   118  
   119  	var digest [Size]byte
   120  	for i, s := range d.s {
   121  		digest[i*4] = byte(s)
   122  		digest[i*4+1] = byte(s >> 8)
   123  		digest[i*4+2] = byte(s >> 16)
   124  		digest[i*4+3] = byte(s >> 24)
   125  	}
   126  
   127  	return digest
   128  }
   129  
   130  // Sum returns the MD5 checksum of the data.
   131  func Sum(data []byte) [Size]byte {
   132  	var d digest
   133  	d.Reset()
   134  	d.Write(data)
   135  	return d.checkSum()
   136  }