blob: 37868fac2ab524e6640ac509bc09d67dbe9e0cfe [file] [log] [blame]
// Copyright 2018 The Wuffs Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// +build ignore
package main
// print-crc32-magic-numbers.go prints the std/crc32 magic number tables.
//
// Usage: go run print-crc32-magic-numbers.go
import (
"fmt"
"hash/crc32"
"os"
)
func main() {
if err := main1(); err != nil {
os.Stderr.WriteString(err.Error() + "\n")
os.Exit(1)
}
}
func main1() error {
tables := [16]crc32.Table{}
tables[0] = *crc32.MakeTable(crc32.IEEE)
// See "Multi-Byte Lookup Tables" in std/crc32/README.md for more detail on
// the slicing-by-M algorithm. We use an M of 16.
for i := 0; i < 256; i++ {
crc := tables[0][i]
for j := 1; j < 16; j++ {
crc = tables[0][crc&0xFF] ^ (crc >> 8)
tables[j][i] = crc
}
}
for i, t := range tables {
if i != 0 {
fmt.Println("],[")
}
for j, x := range t {
fmt.Printf("0x%08X,", x)
if j&7 == 7 {
fmt.Println()
}
}
}
return nil
}