add simple zip example

This commit is contained in:
AJ ONeal 2019-08-05 02:00:28 -06:00
parent 0a5f44eca7
commit da2fc01c62
3 changed files with 192 additions and 0 deletions

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zip/README.md Normal file
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# Go Zip Example
An example of how to zip a directory in Go.
- Utilizes `filepath.Walk` to traverse a directory (or single file)
- Handles each of
- Files (deflated, compressed)
- Directories (empty, not compressed)
- Symlinks (not compressed)
- Skips irregular files (pipes, sockets, devices, chars)
- Names zip file after the name of the directory
- Trims path prefix
```bash
git clone https://git.coolaj86.com/coolaj86/go-examples.git
pushd go-examples/zip
```
```bash
go run . path/to/whatever
```
```txt
wrote whatever.zip
```
Separates concerns into functions for readability:
- func main()
- func Zip(w io.Writer, src string, trim string) error
- zipOne
- zipDirectory
- zipFile
- zipSymlink

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zip/main.go Normal file
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package main
import (
"fmt"
"os"
"path/filepath"
"strings"
)
func usage() {
fmt.Println("Usage: go run go-zip.go <path/to/things>")
}
func main() {
if len(os.Args) < 2 || len(os.Args) > 3 {
usage()
os.Exit(1)
}
dir := strings.TrimSuffix(os.Args[1], string(filepath.Separator))
base := filepath.Base(dir)
// ../foo/whatever => ../foo/
trim := strings.TrimSuffix(dir, base)
// ./ => error
// ../../ => error
if "" == base || "." == base || ".." == base {
// TODO also don't allow ../self
fmt.Println("Error: Cannot zip the directory containing the output file")
os.Exit(1)
}
f, err := os.OpenFile(base+".zip", os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0644)
if nil != err {
panic(err)
}
defer f.Close()
// ./whatever => whatever.zip
// ./path/to/whatever => whatever.zip
if err := Zip(f, dir, trim); nil != err {
panic(err)
}
fmt.Println("wrote", base+".zip")
}

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zip/zip.go Normal file
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package main
import (
"archive/zip"
"fmt"
"io"
"os"
"path/filepath"
"strings"
)
// Zip walks `src`, omitting `trim`, writing to `w`
func Zip(w io.Writer, src string, trim string) error {
zw := zip.NewWriter(w)
defer zw.Close()
return filepath.Walk(src, func(path string, fi os.FileInfo, err error) error {
// path includes fi.Name() already
if nil != err {
fmt.Println("warning: skipped", path+": ", err)
return nil
}
zipOne(zw, path, fi, trim)
return nil
})
}
func zipOne(zw *zip.Writer, path string, fi os.FileInfo, trim string) error {
h, err := zip.FileInfoHeader(fi)
if nil != err {
return err
}
h.Name = strings.TrimPrefix(strings.TrimPrefix(path, trim), string(filepath.Separator))
if fi.IsDir() {
fmt.Printf("directory: %s\n\t%q\n", path, h.Name)
return zipDirectory(zw, h)
}
// Allow zipping a single file
if "" == h.Name {
h.Name = path
}
if fi.Mode().IsRegular() {
fmt.Printf("file: %s\n\t%q\n", path, h.Name)
return zipFile(zw, h, path)
}
if os.ModeSymlink == (fi.Mode() & os.ModeType) {
fmt.Printf("symlink: %s\n\t%q\n", path, h.Name)
return zipSymlink(zw, h, path)
}
fmt.Printf("skipping: %s\n\t(irregular file type)\n", path)
return nil
}
func zipDirectory(zw *zip.Writer, h *zip.FileHeader) error {
// directories must end in / for go
h.Name = strings.TrimPrefix(h.Name+"/", "/")
// skip top-level, trimmed directory
if "" == h.Name {
return nil
}
if _, err := zw.CreateHeader(h); nil != err {
return err
}
return nil
}
func zipFile(zw *zip.Writer, h *zip.FileHeader, path string) error {
r, err := os.Open(path)
if nil != err {
return err
}
defer r.Close()
// Files should be zipped (not dirs, and symlinks... meh)
// TODO investigate if files below a certain size shouldn't be deflated
h.Method = zip.Deflate
w, err := zw.CreateHeader(h)
if nil != err {
return err
}
if _, err := io.Copy(w, r); nil != err {
return err
}
return nil
}
func zipSymlink(zw *zip.Writer, h *zip.FileHeader, path string) error {
w, err := zw.CreateHeader(h)
if nil != err {
return err
}
// TODO make sure that this is within the root directory
targetpath, err := os.Readlink(path)
if nil != err {
return err
}
if _, err := w.Write([]byte(targetpath)); nil != err {
return err
}
return nil
}