115 lines
3.3 KiB
Go
115 lines
3.3 KiB
Go
/*
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* Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package crc32
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import (
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"hash"
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c "github.com/goplus/llgo/runtime/internal/clite"
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"github.com/goplus/llgo/runtime/internal/clite/zlib"
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)
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// llgo:skipall
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type _crc32 struct{}
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// The size of a CRC-32 checksum in bytes.
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const Size = 4
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// Predefined polynomials.
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const (
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// IEEE is by far and away the most common CRC-32 polynomial.
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// Used by ethernet (IEEE 802.3), v.42, fddi, gzip, zip, png, ...
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IEEE = 0xedb88320
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// Castagnoli's polynomial, used in iSCSI.
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// Has better error detection characteristics than IEEE.
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// https://dx.doi.org/10.1109/26.231911
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Castagnoli = 0x82f63b78
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// Koopman's polynomial.
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// Also has better error detection characteristics than IEEE.
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// https://dx.doi.org/10.1109/DSN.2002.1028931
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Koopman = 0xeb31d82e
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)
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// Table is a 256-word table representing the polynomial for efficient processing.
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type Table [256]uint32
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// IEEETable is the table for the IEEE polynomial.
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var IEEETable *Table = new(Table)
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// MakeTable returns a Table constructed from the specified polynomial.
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// The contents of this Table must not be modified.
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func MakeTable(poly uint32) *Table {
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if poly == IEEE {
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return IEEETable
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}
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panic("todo: hash/crc32.MakeTable")
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}
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type digest uint32
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func (d *digest) Size() int { return Size }
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func (d *digest) BlockSize() int { return 1 }
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func (d *digest) Reset() { *d = 0 }
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func (d *digest) Write(p []byte) (n int, err error) {
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*d = digest(zlib.Crc32ZBytes(c.Ulong(*d), p))
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return len(p), nil
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}
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func (d *digest) Sum32() uint32 { return uint32(*d) }
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func (d *digest) Sum(in []byte) []byte {
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s := d.Sum32()
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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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func New(tab *Table) hash.Hash32 {
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if tab == IEEETable {
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return new(digest)
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}
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panic("todo: hash/crc32.New")
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}
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// NewIEEE creates a new hash.Hash32 computing the CRC-32 checksum using
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// the IEEE polynomial. Its Sum method will lay the value out in
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// big-endian byte order. The returned Hash32 also implements
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// encoding.BinaryMarshaler and encoding.BinaryUnmarshaler to marshal
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// and unmarshal the internal state of the hash.
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func NewIEEE() hash.Hash32 { return New(IEEETable) }
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// Update returns the result of adding the bytes in p to the crc.
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func Update(crc uint32, tab *Table, p []byte) uint32 {
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if tab == IEEETable {
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return uint32(zlib.Crc32ZBytes(c.Ulong(crc), p))
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}
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panic("todo: hash/crc32.Update")
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}
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// Checksum returns the CRC-32 checksum of data
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// using the polynomial represented by the Table.
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func Checksum(data []byte, tab *Table) uint32 { return Update(0, tab, data) }
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// ChecksumIEEE returns the CRC-32 checksum of data
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// using the IEEE polynomial.
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func ChecksumIEEE(data []byte) uint32 {
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return uint32(zlib.Crc32ZBytes(0, data))
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}
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