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83 lines
1.9 KiB
83 lines
1.9 KiB
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package crc32 implements the 32-bit cyclic redundancy check, or CRC-32,
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// checksum. See http://en.wikipedia.org/wiki/Cyclic_redundancy_check for
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// information.
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package crc32c
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import (
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"hash"
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"io"
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)
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// The size of a CRC-32 checksum in bytes.
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const Size = 4
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// digest represents the partial evaluation of a checksum.
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type digest struct {
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crc uint32
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}
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// New creates a new hash.Hash32 computing the CRC-32 checksum
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// using the polynomial represented by the Table.
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func New() hash.Hash32 {
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return &digest{crc: 0}
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}
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// Return size of crc
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func (d *digest) Size() int { return Size }
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// Stub
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func (d *digest) BlockSize() int { return 1 }
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// Get crc in bytes
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func (d *digest) Sum(in []byte) []byte {
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s := d.crc
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return append(in, byte(s>>24), byte(s>>16), byte(s>>8), byte(s))
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}
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// Return current crc in digest object
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func (d *digest) Sum32() uint32 { return d.crc }
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// Reset default crc
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func (d *digest) Reset() { d.crc = 0 }
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// Update returns the result of adding the bytes in p to the crc.
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func (d *digest) update(crc uint32, p []byte) uint32 {
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return updateCastanagoliPCL(crc, p)
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}
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// Write data
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func (d *digest) Write(p []byte) (n int, err error) {
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d.crc = d.update(d.crc, p)
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return len(p), nil
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}
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/// Convenience functions
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// Single caller crc helper
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func Sum32(data []byte) uint32 {
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crc32 := New()
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crc32.Reset()
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crc32.Write(data)
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return crc32.Sum32()
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}
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// Low memory footprint io.Reader based crc helper
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func Sum(reader io.Reader) (uint32, error) {
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h := New()
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var err error
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for err == nil {
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length := 0
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byteBuffer := make([]byte, 1024*1024)
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length, err = reader.Read(byteBuffer)
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byteBuffer = byteBuffer[0:length]
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h.Write(byteBuffer)
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}
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if err != io.EOF {
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return 0, err
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}
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return h.Sum32(), nil
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}
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