pkg: move /crc to /pkg/crc

pkg/crc/crc.go

@@ -0,0 +1,41 @@
+// 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 crc
+
+import (
+	"hash"
+	"hash/crc32"
+)
+
+// The size of a CRC-32 checksum in bytes.
+const Size = 4
+
+type digest struct {
+	crc uint32
+	tab *crc32.Table
+}
+
+// New creates a new hash.Hash32 computing the CRC-32 checksum
+// using the polynomial represented by the Table.
+// Modified by xiangli to take a prevcrc.
+func New(prev uint32, tab *crc32.Table) hash.Hash32 { return &digest{prev, tab} }
+
+func (d *digest) Size() int { return Size }
+
+func (d *digest) BlockSize() int { return 1 }
+
+func (d *digest) Reset() { d.crc = 0 }
+
+func (d *digest) Write(p []byte) (n int, err error) {
+	d.crc = crc32.Update(d.crc, d.tab, p)
+	return len(p), nil
+}
+
+func (d *digest) Sum32() uint32 { return d.crc }
+
+func (d *digest) Sum(in []byte) []byte {
+	s := d.Sum32()
+	return append(in, byte(s>>24), byte(s>>16), byte(s>>8), byte(s))
+}