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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 19:23:18 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 19:23:18 +0000
commit43a123c1ae6613b3efeed291fa552ecd909d3acf (patch)
treefd92518b7024bc74031f78a1cf9e454b65e73665 /src/hash/crc64/crc64.go
parentInitial commit. (diff)
downloadgolang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.tar.xz
golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.zip
Adding upstream version 1.20.14.upstream/1.20.14upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/hash/crc64/crc64.go')
-rw-r--r--src/hash/crc64/crc64.go226
1 files changed, 226 insertions, 0 deletions
diff --git a/src/hash/crc64/crc64.go b/src/hash/crc64/crc64.go
new file mode 100644
index 0000000..26b2573
--- /dev/null
+++ b/src/hash/crc64/crc64.go
@@ -0,0 +1,226 @@
+// 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 crc64 implements the 64-bit cyclic redundancy check, or CRC-64,
+// checksum. See https://en.wikipedia.org/wiki/Cyclic_redundancy_check for
+// information.
+package crc64
+
+import (
+ "errors"
+ "hash"
+ "sync"
+)
+
+// The size of a CRC-64 checksum in bytes.
+const Size = 8
+
+// Predefined polynomials.
+const (
+ // The ISO polynomial, defined in ISO 3309 and used in HDLC.
+ ISO = 0xD800000000000000
+
+ // The ECMA polynomial, defined in ECMA 182.
+ ECMA = 0xC96C5795D7870F42
+)
+
+// Table is a 256-word table representing the polynomial for efficient processing.
+type Table [256]uint64
+
+var (
+ slicing8TablesBuildOnce sync.Once
+ slicing8TableISO *[8]Table
+ slicing8TableECMA *[8]Table
+)
+
+func buildSlicing8TablesOnce() {
+ slicing8TablesBuildOnce.Do(buildSlicing8Tables)
+}
+
+func buildSlicing8Tables() {
+ slicing8TableISO = makeSlicingBy8Table(makeTable(ISO))
+ slicing8TableECMA = makeSlicingBy8Table(makeTable(ECMA))
+}
+
+// MakeTable returns a Table constructed from the specified polynomial.
+// The contents of this Table must not be modified.
+func MakeTable(poly uint64) *Table {
+ buildSlicing8TablesOnce()
+ switch poly {
+ case ISO:
+ return &slicing8TableISO[0]
+ case ECMA:
+ return &slicing8TableECMA[0]
+ default:
+ return makeTable(poly)
+ }
+}
+
+func makeTable(poly uint64) *Table {
+ t := new(Table)
+ for i := 0; i < 256; i++ {
+ crc := uint64(i)
+ for j := 0; j < 8; j++ {
+ if crc&1 == 1 {
+ crc = (crc >> 1) ^ poly
+ } else {
+ crc >>= 1
+ }
+ }
+ t[i] = crc
+ }
+ return t
+}
+
+func makeSlicingBy8Table(t *Table) *[8]Table {
+ var helperTable [8]Table
+ helperTable[0] = *t
+ for i := 0; i < 256; i++ {
+ crc := t[i]
+ for j := 1; j < 8; j++ {
+ crc = t[crc&0xff] ^ (crc >> 8)
+ helperTable[j][i] = crc
+ }
+ }
+ return &helperTable
+}
+
+// digest represents the partial evaluation of a checksum.
+type digest struct {
+ crc uint64
+ tab *Table
+}
+
+// New creates a new hash.Hash64 computing the CRC-64 checksum using the
+// polynomial represented by the Table. Its Sum method will lay the
+// value out in big-endian byte order. The returned Hash64 also
+// implements encoding.BinaryMarshaler and encoding.BinaryUnmarshaler to
+// marshal and unmarshal the internal state of the hash.
+func New(tab *Table) hash.Hash64 { return &digest{0, tab} }
+
+func (d *digest) Size() int { return Size }
+
+func (d *digest) BlockSize() int { return 1 }
+
+func (d *digest) Reset() { d.crc = 0 }
+
+const (
+ magic = "crc\x02"
+ marshaledSize = len(magic) + 8 + 8
+)
+
+func (d *digest) MarshalBinary() ([]byte, error) {
+ b := make([]byte, 0, marshaledSize)
+ b = append(b, magic...)
+ b = appendUint64(b, tableSum(d.tab))
+ b = appendUint64(b, d.crc)
+ return b, nil
+}
+
+func (d *digest) UnmarshalBinary(b []byte) error {
+ if len(b) < len(magic) || string(b[:len(magic)]) != magic {
+ return errors.New("hash/crc64: invalid hash state identifier")
+ }
+ if len(b) != marshaledSize {
+ return errors.New("hash/crc64: invalid hash state size")
+ }
+ if tableSum(d.tab) != readUint64(b[4:]) {
+ return errors.New("hash/crc64: tables do not match")
+ }
+ d.crc = readUint64(b[12:])
+ return nil
+}
+
+func appendUint64(b []byte, x uint64) []byte {
+ a := [8]byte{
+ byte(x >> 56),
+ byte(x >> 48),
+ byte(x >> 40),
+ byte(x >> 32),
+ byte(x >> 24),
+ byte(x >> 16),
+ byte(x >> 8),
+ byte(x),
+ }
+ return append(b, a[:]...)
+}
+
+func readUint64(b []byte) uint64 {
+ _ = b[7]
+ return uint64(b[7]) | uint64(b[6])<<8 | uint64(b[5])<<16 | uint64(b[4])<<24 |
+ uint64(b[3])<<32 | uint64(b[2])<<40 | uint64(b[1])<<48 | uint64(b[0])<<56
+}
+
+func update(crc uint64, tab *Table, p []byte) uint64 {
+ buildSlicing8TablesOnce()
+ crc = ^crc
+ // Table comparison is somewhat expensive, so avoid it for small sizes
+ for len(p) >= 64 {
+ var helperTable *[8]Table
+ if *tab == slicing8TableECMA[0] {
+ helperTable = slicing8TableECMA
+ } else if *tab == slicing8TableISO[0] {
+ helperTable = slicing8TableISO
+ // For smaller sizes creating extended table takes too much time
+ } else if len(p) >= 2048 {
+ // According to the tests between various x86 and arm CPUs, 2k is a reasonable
+ // threshold for now. This may change in the future.
+ helperTable = makeSlicingBy8Table(tab)
+ } else {
+ break
+ }
+ // Update using slicing-by-8
+ for len(p) > 8 {
+ crc ^= uint64(p[0]) | uint64(p[1])<<8 | uint64(p[2])<<16 | uint64(p[3])<<24 |
+ uint64(p[4])<<32 | uint64(p[5])<<40 | uint64(p[6])<<48 | uint64(p[7])<<56
+ crc = helperTable[7][crc&0xff] ^
+ helperTable[6][(crc>>8)&0xff] ^
+ helperTable[5][(crc>>16)&0xff] ^
+ helperTable[4][(crc>>24)&0xff] ^
+ helperTable[3][(crc>>32)&0xff] ^
+ helperTable[2][(crc>>40)&0xff] ^
+ helperTable[1][(crc>>48)&0xff] ^
+ helperTable[0][crc>>56]
+ p = p[8:]
+ }
+ }
+ // For reminders or small sizes
+ for _, v := range p {
+ crc = tab[byte(crc)^v] ^ (crc >> 8)
+ }
+ return ^crc
+}
+
+// Update returns the result of adding the bytes in p to the crc.
+func Update(crc uint64, tab *Table, p []byte) uint64 {
+ return update(crc, tab, p)
+}
+
+func (d *digest) Write(p []byte) (n int, err error) {
+ d.crc = update(d.crc, d.tab, p)
+ return len(p), nil
+}
+
+func (d *digest) Sum64() uint64 { return d.crc }
+
+func (d *digest) Sum(in []byte) []byte {
+ s := d.Sum64()
+ return append(in, byte(s>>56), byte(s>>48), byte(s>>40), byte(s>>32), byte(s>>24), byte(s>>16), byte(s>>8), byte(s))
+}
+
+// Checksum returns the CRC-64 checksum of data
+// using the polynomial represented by the Table.
+func Checksum(data []byte, tab *Table) uint64 { return update(0, tab, data) }
+
+// tableSum returns the ISO checksum of table t.
+func tableSum(t *Table) uint64 {
+ var a [2048]byte
+ b := a[:0]
+ if t != nil {
+ for _, x := range t {
+ b = appendUint64(b, x)
+ }
+ }
+ return Checksum(b, MakeTable(ISO))
+}