Gzip file implementing the same methods as *os.File

gzipfile.go

package main

import (
	"compress/gzip"
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"os"
)

var errNotImplemented = errors.New("not implemented")

type File interface {
	Chdir() error
	Chmod(mode os.FileMode) error
	Chown(uid, gid int) error
	Close() error
	Fd() uintptr
	Name() string
	Read(b []byte) (n int, err error)
	ReadAt(b []byte, off int64) (n int, err error)
	Readdir(n int) (fi []os.FileInfo, err error)
	Readdirnames(n int) (names []string, err error)
	Seek(offset int64, whence int) (ret int64, err error)
	Stat() (fi os.FileInfo, err error)
	Sync() (err error)
	Truncate(size int64) error
	Write(b []byte) (n int, err error)
	WriteAt(b []byte, off int64) (n int, err error)
	WriteString(s string) (ret int, err error)
}

type GzipFile struct {
	file   *os.File
	reader *gzip.Reader
	writer *gzip.Writer
}

func Open(path string) (*GzipFile, error) {
	file, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	reader, err := gzip.NewReader(file)
	if err != nil {
		return nil, err
	}
	return &GzipFile{file, reader, nil}, nil
}

func Create(path string) (*GzipFile, error) {
	file, err := os.Create(path)
	if err != nil {
		return nil, err
	}
	writer := gzip.NewWriter(file)
	return &GzipFile{file, nil, writer}, nil
}

func (f *GzipFile) Chdir() error {
	return f.file.Chdir()
}

func (f *GzipFile) Chmod(mode os.FileMode) error {
	return f.file.Chmod(mode)
}

func (f *GzipFile) Chown(uid, gid int) error {
	return f.file.Chown(uid, gid)
}

func (f *GzipFile) Close() error {
	if f.writer != nil {
		err := f.writer.Close()
		if err != nil {
			return err
		}
	}
	if f.reader != nil {
		err := f.reader.Close()
		if err != nil {
			return err
		}
	}
	return f.file.Close()
}

func (f *GzipFile) Fd() uintptr {
	return f.file.Fd()
}

func (f *GzipFile) Name() string {
	return f.file.Name()
}

func (f *GzipFile) Read(b []byte) (n int, err error) {
	return f.reader.Read(b)
}

func (f *GzipFile) ReadAt(b []byte, off int64) (n int, err error) {
	return 0, errNotImplemented
}

func (f *GzipFile) Readdir(n int) (fi []os.FileInfo, err error) {
	return nil, errNotImplemented
}

func (f *GzipFile) Readdirnames(n int) (names []string, err error) {
	return nil, errNotImplemented
}

func (f *GzipFile) Seek(offset int64, whence int) (ret int64, err error) {
	return 0, errNotImplemented
}

func (f *GzipFile) Stat() (fi os.FileInfo, err error) {
	return nil, errNotImplemented
}

func (f *GzipFile) Sync() (err error) {
	return f.file.Sync()
}

func (f *GzipFile) Truncate(size int64) error {
	return f.file.Truncate(size)
}

func (f *GzipFile) Write(b []byte) (n int, err error) {
	return f.writer.Write(b)
}

func (f *GzipFile) WriteAt(b []byte, off int64) (n int, err error) {
	return 0, errNotImplemented
}

func (f *GzipFile) WriteString(s string) (ret int, err error) {
	return f.writer.Write([]byte(s))
}

func main() {
	file, err := Create("/tmp/12345")
	if err != nil {
		log.Fatal(err)
	}
	file.WriteString("Hello World\n")
	file.Close()

	file, err = Open("/tmp/12345")
	if err != nil {
		log.Fatal(err)
	}

	content, err := ioutil.ReadAll(file)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Print(string(content))
}