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// Copyright 2009 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.
// SHA1 block step.
// In its own file so that a faster assembly or C version
// can be substituted easily.
package sha1
const (
_K0 = 0x5A827999
_K1 = 0x6ED9EBA1
_K2 = 0x8F1BBCDC
_K3 = 0xCA62C1D6
)
func _Block(dig *digest, p []byte) int {
var w [80]uint32
n := 0
h0, h1, h2, h3, h4 := dig.h[0], dig.h[1], dig.h[2], dig.h[3], dig.h[4]
for len(p) >= _Chunk {
// Can interlace the computation of w with the
// rounds below if needed for speed.
for i := 0; i < 16; i++ {
j := i * 4
w[i] = uint32(p[j])<<24 | uint32(p[j+1])<<16 | uint32(p[j+2])<<8 | uint32(p[j+3])
}
for i := 16; i < 80; i++ {
tmp := w[i-3] ^ w[i-8] ^ w[i-14] ^ w[i-16]
w[i] = tmp<<1 | tmp>>(32-1)
}
a, b, c, d, e := h0, h1, h2, h3, h4
// Each of the four 20-iteration rounds
// differs only in the computation of f and
// the choice of K (_K0, _K1, etc).
for i := 0; i < 20; i++ {
f := b&c | (^b)&d
a5 := a<<5 | a>>(32-5)
b30 := b<<30 | b>>(32-30)
t := a5 + f + e + w[i] + _K0
a, b, c, d, e = t, a, b30, c, d
}
for i := 20; i < 40; i++ {
f := b ^ c ^ d
a5 := a<<5 | a>>(32-5)
b30 := b<<30 | b>>(32-30)
t := a5 + f + e + w[i] + _K1
a, b, c, d, e = t, a, b30, c, d
}
for i := 40; i < 60; i++ {
f := b&c | b&d | c&d
a5 := a<<5 | a>>(32-5)
b30 := b<<30 | b>>(32-30)
t := a5 + f + e + w[i] + _K2
a, b, c, d, e = t, a, b30, c, d
}
for i := 60; i < 80; i++ {
f := b ^ c ^ d
a5 := a<<5 | a>>(32-5)
b30 := b<<30 | b>>(32-30)
t := a5 + f + e + w[i] + _K3
a, b, c, d, e = t, a, b30, c, d
}
h0 += a
h1 += b
h2 += c
h3 += d
h4 += e
p = p[_Chunk:]
n += _Chunk
}
dig.h[0], dig.h[1], dig.h[2], dig.h[3], dig.h[4] = h0, h1, h2, h3, h4
return n
}
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