/
main.go
69 lines (60 loc) · 1.24 KB
/
main.go
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package main
import (
"flag"
"fmt"
"hash/crc32"
"os"
"strings"
)
var (
polynomial = flag.String("polynomial", "ieee", "polynomial: ieee, castagnoli, koopman")
output = flag.String("output", "dec", "output format: hex, dec, oct")
)
func main() {
flag.Parse()
if flag.NArg() < 1 || flag.Arg(0) == "" {
fmt.Printf("usage: crc32 <file>\n")
os.Exit(1)
}
filename := flag.Arg(0)
var poly uint32
switch strings.ToLower(*polynomial) {
case "ieee":
poly = crc32.IEEE
case "castagnoli":
poly = crc32.Castagnoli
case "koopman":
poly = crc32.Koopman
default:
fmt.Printf("unknown -polynomial %s\n", *polynomial)
os.Exit(1)
}
var format string
switch strings.ToLower(*output) {
case "hex":
format = "%x\n"
case "dec":
format = "%d\n"
case "oct":
format = "%o\n"
default:
fmt.Printf("unknown -output %s\n", *output)
os.Exit(1)
}
f, err := os.Open(filename)
if err != nil {
fmt.Printf("%s: %s\n", filename, err)
os.Exit(1)
}
defer f.Close()
// http://blog.vzv.ca/2012/06/crc64-file-hash-in-gogolang.html
h := crc32.New(crc32.MakeTable(poly))
buf := make([]byte, 8192)
read, err := f.Read(buf)
for read > -1 && err == nil {
h.Write(buf)
read, err = f.Read(buf)
}
s := h.Sum32()
fmt.Printf(format, s)
}