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nmea-checksum.go
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/
nmea-checksum.go
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// https://en.wikipedia.org/wiki/NMEA_0183
package main
import (
"bufio"
"flag"
"fmt"
"io"
"os"
"strings"
)
func main() {
flag.Usage = usage
flag.Parse()
if flag.NArg() < 1 {
nmea(os.Stdin)
} else {
for _, name := range flag.Args() {
f, err := os.Open(name)
if err != nil {
fmt.Fprintln(os.Stderr, err)
continue
}
nmea(f)
f.Close()
}
}
}
func usage() {
fmt.Fprintln(os.Stderr, "usage: [options] <file> ...")
flag.PrintDefaults()
os.Exit(2)
}
func nmea(r io.Reader) {
s := bufio.NewScanner(r)
for s.Scan() {
ln := trim(s.Text())
fmt.Printf("$%s*%02x\n", ln, xor(ln))
}
}
func trim(s string) string {
i := strings.IndexRune(s, '$')
j := strings.IndexRune(s, '*')
if i < 0 {
i = 0
}
if j < 0 {
j = len(s)
}
return s[i:j]
}
func xor(s string) int {
var v int
for _, r := range s {
v ^= int(r)
}
return v
}