example use of decompress package

readmember.go

package main

import (
	"fmt"
	"io"
	"os"
	"os/user"
	"path/filepath"

	"github.com/richardlehane/siegfried"
	"github.com/richardlehane/siegfried/pkg/decompress"
)

func ReadMember(path, member string, fn func(io.Reader) error) error {
	// load a siegfried signature file
	usr, err := user.Current()
	if err != nil {
		return err
	}
	sf, err := siegfried.Load(filepath.Join(usr.HomeDir, "siegfried", "default.sig"))
	if err != nil {
		return err
	}
	// define idRdr func to recurse on nested contents within compressed files
	var idRdr func(rdr io.Reader, name, mime string, sz int64) error
	idRdr = func(rdr io.Reader, name, mime string, sz int64) error {
		buf, err := sf.Buffer(rdr) // get a siegfried buffer. Buffers allows us to create multiple indpendent readers from a single source
		defer sf.Put(buf)          // return the buffer to siegfried's pool of buffers when done
		if err != nil {
			return err
		}
		if name == member { // call the passed function here if the name matches
			err = fn(buf.Reader()) // new Reader() method gets a reader off a buffer
			if err != nil {
				return err
			}
		}
		ids, err := sf.IdentifyBuffer(buf, nil, name, mime) // can of course use these sf IDs for other stuff here
		if err != nil {
			return err
		}
		arc := decompress.IsArc(ids)
		if arc > 0 {
			dec, err := decompress.New(arc, buf, name, sz)
			if err != nil {
				return err
			}
			for err = dec.Next(); err == nil; err = dec.Next() {
				err = idRdr(dec.Reader(), dec.Path(), dec.MIME(), dec.Size()) // recurse on the contents of the archive
				if err != nil {
					return err
				}
			}
			return err
		}
		return nil
	}
	info, err := os.Stat(path)
	if err != nil {
		return err
	}
	f, err := os.Open(path)
	defer f.Close()
	if err != nil {
		return err
	}
	return idRdr(f, path, "", info.Size())
}

func main() {
	fn := func(rdr io.Reader) error {
		buf := make([]byte, 5)
		rdr.Read(buf)
		fmt.Println(buf)
		return nil
	}
	fmt.Println(ReadMember("compare.zip", "compare.zip#fmt-134_fmt-15.zip", fn))
}