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// Package appsluggr packages a given binary into a Heroku-compatible slug.
package appsluggr
import (
"archive/tar"
"compress/gzip"
"io"
"log"
"log/slog"
"os"
"path/filepath"
"strings"
"github.com/otiai10/copy"
"github.com/rogpeppe/go-internal/dirhash"
)
// Must calls Pack and panics on an error.
//
// This is useful for using appsluggr from yeet scripts.
func Must(fname, outFname string, extraFiles ...map[string]string) {
if err := Pack(fname, outFname, extraFiles...); err != nil {
log.Panicf("error packing %s into %s: %v", fname, outFname, err)
}
}
// Pack takes a statically linked binary and packs it into a Heroku-compatible slug image
// at outFname.
func Pack(fname string, outFname string, extraFiles ...map[string]string) error {
dir, err := os.MkdirTemp("", "appsluggr")
if err != nil {
return err
}
defer os.RemoveAll(dir)
fout, err := os.Create(outFname)
if err != nil {
return err
}
defer fout.Close()
gzw := gzip.NewWriter(fout)
defer gzw.Close()
tw := tar.NewWriter(gzw)
defer tw.Close()
os.MkdirAll(filepath.Join(dir, "bin"), 0777)
if err := copy.Copy(fname, filepath.Join(dir, "bin", "main")); err != nil {
return err
}
for _, finfo := range extraFiles {
for src, dst := range finfo {
slog.Debug("copying file", "src", src, "dst", dst)
if err := copy.Copy(src, filepath.Join(dir, dst)); err != nil {
return err
}
}
}
if err := os.WriteFile(filepath.Join(dir, "Procfile"), []byte("web: /app/bin/main\n"), 0777); err != nil {
return err
}
hash, err := dirhash.HashDir(dir, os.Args[0], dirhash.Hash1)
if err != nil {
return err
}
gzw.Comment = hash
log.Printf("hash: %s", hash)
return filepath.Walk(dir, func(file string, fi os.FileInfo, err error) error {
// return on any error
if err != nil {
log.Printf("got error on %s: %v", file, err)
return err
}
if fi.IsDir() {
return nil // not a file. ignore.
}
// create a new dir/file header
header, err := tar.FileInfoHeader(fi, fi.Name())
if err != nil {
return err
}
// update the name to correctly reflect the desired destination when untaring
header.Name = strings.TrimPrefix(strings.Replace(file, dir, "", -1), string(filepath.Separator))
// write the header
if err := tw.WriteHeader(header); err != nil {
return err
}
// return on non-regular files (thanks to [kumo](https://medium.com/@komuw/just-like-you-did-fbdd7df829d3) for this suggested update)
if !fi.Mode().IsRegular() {
return nil
}
// open files for taring
f, err := os.Open(file)
if err != nil {
return err
}
// copy file data into tar writer
if _, err := io.Copy(tw, f); err != nil {
return err
}
// manually close here after each file operation; defering would cause each file close
// to wait until all operations have completed.
f.Close()
return nil
})
}
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