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Signed-off-by: Olivier Gambier <olivier@docker.com>

vendor/github.com/stevvooe/resumable/sha256/sha256.go

@@ -0,0 +1,193 @@
+// 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.
+
+// Package sha256 implements the SHA224 and SHA256 hash algorithms as defined
+// in FIPS 180-4.
+package sha256
+
+import (
+	"crypto"
+	"hash"
+)
+
+func init() {
+	crypto.RegisterHash(crypto.SHA224, New224)
+	crypto.RegisterHash(crypto.SHA256, New)
+}
+
+// The size of a SHA256 checksum in bytes.
+const Size = 32
+
+// The size of a SHA224 checksum in bytes.
+const Size224 = 28
+
+// The blocksize of SHA256 and SHA224 in bytes.
+const BlockSize = 64
+
+const (
+	chunk     = 64
+	init0     = 0x6A09E667
+	init1     = 0xBB67AE85
+	init2     = 0x3C6EF372
+	init3     = 0xA54FF53A
+	init4     = 0x510E527F
+	init5     = 0x9B05688C
+	init6     = 0x1F83D9AB
+	init7     = 0x5BE0CD19
+	init0_224 = 0xC1059ED8
+	init1_224 = 0x367CD507
+	init2_224 = 0x3070DD17
+	init3_224 = 0xF70E5939
+	init4_224 = 0xFFC00B31
+	init5_224 = 0x68581511
+	init6_224 = 0x64F98FA7
+	init7_224 = 0xBEFA4FA4
+)
+
+// digest represents the partial evaluation of a checksum.
+type digest struct {
+	h     [8]uint32
+	x     [chunk]byte
+	nx    int
+	len   uint64
+	is224 bool // mark if this digest is SHA-224
+}
+
+func (d *digest) Reset() {
+	if !d.is224 {
+		d.h[0] = init0
+		d.h[1] = init1
+		d.h[2] = init2
+		d.h[3] = init3
+		d.h[4] = init4
+		d.h[5] = init5
+		d.h[6] = init6
+		d.h[7] = init7
+	} else {
+		d.h[0] = init0_224
+		d.h[1] = init1_224
+		d.h[2] = init2_224
+		d.h[3] = init3_224
+		d.h[4] = init4_224
+		d.h[5] = init5_224
+		d.h[6] = init6_224
+		d.h[7] = init7_224
+	}
+	d.nx = 0
+	d.len = 0
+}
+
+// New returns a new hash.Hash computing the SHA256 checksum.
+func New() hash.Hash {
+	d := new(digest)
+	d.Reset()
+	return d
+}
+
+// New224 returns a new hash.Hash computing the SHA224 checksum.
+func New224() hash.Hash {
+	d := new(digest)
+	d.is224 = true
+	d.Reset()
+	return d
+}
+
+func (d *digest) Size() int {
+	if !d.is224 {
+		return Size
+	}
+	return Size224
+}
+
+func (d *digest) BlockSize() int { return BlockSize }
+
+func (d *digest) Write(p []byte) (nn int, err error) {
+	nn = len(p)
+	d.len += uint64(nn)
+	if d.nx > 0 {
+		n := copy(d.x[d.nx:], p)
+		d.nx += n
+		if d.nx == chunk {
+			block(d, d.x[:])
+			d.nx = 0
+		}
+		p = p[n:]
+	}
+	if len(p) >= chunk {
+		n := len(p) &^ (chunk - 1)
+		block(d, p[:n])
+		p = p[n:]
+	}
+	if len(p) > 0 {
+		d.nx = copy(d.x[:], p)
+	}
+	return
+}
+
+func (d0 *digest) Sum(in []byte) []byte {
+	// Make a copy of d0 so that caller can keep writing and summing.
+	d := *d0
+	hash := d.checkSum()
+	if d.is224 {
+		return append(in, hash[:Size224]...)
+	}
+	return append(in, hash[:]...)
+}
+
+func (d *digest) checkSum() [Size]byte {
+	len := d.len
+	// Padding.  Add a 1 bit and 0 bits until 56 bytes mod 64.
+	var tmp [64]byte
+	tmp[0] = 0x80
+	if len%64 < 56 {
+		d.Write(tmp[0 : 56-len%64])
+	} else {
+		d.Write(tmp[0 : 64+56-len%64])
+	}
+
+	// Length in bits.
+	len <<= 3
+	for i := uint(0); i < 8; i++ {
+		tmp[i] = byte(len >> (56 - 8*i))
+	}
+	d.Write(tmp[0:8])
+
+	if d.nx != 0 {
+		panic("d.nx != 0")
+	}
+
+	h := d.h[:]
+	if d.is224 {
+		h = d.h[:7]
+	}
+
+	var digest [Size]byte
+	for i, s := range h {
+		digest[i*4] = byte(s >> 24)
+		digest[i*4+1] = byte(s >> 16)
+		digest[i*4+2] = byte(s >> 8)
+		digest[i*4+3] = byte(s)
+	}
+
+	return digest
+}
+
+// Sum256 returns the SHA256 checksum of the data.
+func Sum256(data []byte) [Size]byte {
+	var d digest
+	d.Reset()
+	d.Write(data)
+	return d.checkSum()
+}
+
+// Sum224 returns the SHA224 checksum of the data.
+func Sum224(data []byte) (sum224 [Size224]byte) {
+	var d digest
+	d.is224 = true
+	d.Reset()
+	d.Write(data)
+	sum := d.checkSum()
+	copy(sum224[:], sum[:Size224])
+	return
+}