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linkonce.go
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linkonce.go
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package main
import (
"bufio"
"bytes"
"flag"
"io/fs"
"log"
"os"
"path/filepath"
)
var (
verbose *bool
dest *string
stateFile *string
already map[string]bool
)
func walk(path string, d fs.DirEntry, err error) error {
if !d.IsDir() && !already[path] {
if *verbose {
log.Println(path)
}
newpath := filepath.Join(*dest, path)
err := os.Link(path, newpath)
if err != nil {
destdir := filepath.Dir(newpath)
err = os.MkdirAll(destdir, 0755)
if err != nil {
log.Fatal("could not create hard link dest dir", destdir,
":", err)
}
err = os.Link(path, newpath)
if err != nil {
log.Fatal("could not create hard link", newpath,
":", err)
}
}
already[path] = true
}
return nil
}
func makeDest() {
if *dest == "" {
log.Fatal("must specify a destination directory")
}
err := os.MkdirAll(*dest, 0755)
if err != nil {
log.Fatal("error creating destination directory:", err)
}
}
func readState() {
f, err := os.Open(*stateFile)
if err != nil {
return
}
scanner := bufio.NewScanner(f)
scanner.Split(
// based on bufio.ScanLines, just looking for NUL separators
func(data []byte, atEOF bool) (advance int, token []byte, err error) {
if atEOF && len(data) == 0 {
return 0, nil, nil
}
if i := bytes.IndexByte(data, 0); i >= 0 {
// We have a full NULL-separated path.
return i + 1, data[0:i], nil
}
// If we're at EOF, we have a final, non-terminated path.
// Return it.
if atEOF {
return len(data), data, nil
}
// Request more data.
return 0, nil, nil
},
)
for scanner.Scan() {
already[scanner.Text()] = true
}
}
func saveState() {
f, err := os.OpenFile(*stateFile+".tmp",
os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
if err != nil {
log.Fatal("could not create temp state file:", err)
}
buf := bufio.NewWriter(f)
for dir, _ := range already {
_, err = buf.WriteString(dir)
if err != nil {
log.Fatal("error writing state file:", err)
}
err = buf.WriteByte(0)
if err != nil {
log.Fatal("error writing state file:", err)
}
}
err = buf.Flush()
if err != nil {
log.Fatal("error flushing state file:", err)
}
err = f.Close()
if err != nil {
log.Fatal("error closing state file:", err)
}
err = os.Rename(*stateFile+".tmp", *stateFile)
if err != nil {
log.Fatal("error renaming temp state file:", err)
}
}
func main() {
verbose = flag.Bool("v", false, "verbose output")
dest = flag.String("d", "", "destination directory")
stateFile = flag.String("s", ".linkonce",
"state file to remember already linked files")
flag.Parse()
makeDest()
already = make(map[string]bool, 20000)
readState()
err := filepath.WalkDir(".", walk)
if err != nil {
log.Fatal("error walking tree:", err)
}
saveState()
}