github.com/xushiwei/go@v0.0.0-20130601165731-2b9d83f45bc9/src/pkg/crypto/sha1/sha1.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  // Package sha1 implements the SHA1 hash algorithm as defined in RFC 3174.
     6  package sha1
     7  
     8  import (
     9  	"crypto"
    10  	"hash"
    11  )
    12  
    13  func init() {
    14  	crypto.RegisterHash(crypto.SHA1, New)
    15  }
    16  
    17  // The size of a SHA1 checksum in bytes.
    18  const Size = 20
    19  
    20  // The blocksize of SHA1 in bytes.
    21  const BlockSize = 64
    22  
    23  const (
    24  	chunk = 64
    25  	init0 = 0x67452301
    26  	init1 = 0xEFCDAB89
    27  	init2 = 0x98BADCFE
    28  	init3 = 0x10325476
    29  	init4 = 0xC3D2E1F0
    30  )
    31  
    32  // digest represents the partial evaluation of a checksum.
    33  type digest struct {
    34  	h   [5]uint32
    35  	x   [chunk]byte
    36  	nx  int
    37  	len uint64
    38  }
    39  
    40  func (d *digest) Reset() {
    41  	d.h[0] = init0
    42  	d.h[1] = init1
    43  	d.h[2] = init2
    44  	d.h[3] = init3
    45  	d.h[4] = init4
    46  	d.nx = 0
    47  	d.len = 0
    48  }
    49  
    50  // New returns a new hash.Hash computing the SHA1 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:])
    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  
    94  	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
    95  	len := d.len
    96  	var tmp [64]byte
    97  	tmp[0] = 0x80
    98  	if len%64 < 56 {
    99  		d.Write(tmp[0 : 56-len%64])
   100  	} else {
   101  		d.Write(tmp[0 : 64+56-len%64])
   102  	}
   103  
   104  	// Length in bits.
   105  	len <<= 3
   106  	for i := uint(0); i < 8; i++ {
   107  		tmp[i] = byte(len >> (56 - 8*i))
   108  	}
   109  	d.Write(tmp[0:8])
   110  
   111  	if d.nx != 0 {
   112  		panic("d.nx != 0")
   113  	}
   114  
   115  	var digest [Size]byte
   116  	for i, s := range d.h {
   117  		digest[i*4] = byte(s >> 24)
   118  		digest[i*4+1] = byte(s >> 16)
   119  		digest[i*4+2] = byte(s >> 8)
   120  		digest[i*4+3] = byte(s)
   121  	}
   122  
   123  	return append(in, digest[:]...)
   124  }