move rootfs to its own package

This commit is contained in:
Motiejus Jakštys 2021-05-24 00:11:57 +03:00
parent ce445b19b7
commit 3279b52973
4 changed files with 44 additions and 39 deletions

10
BUILD
View File

@ -2,13 +2,13 @@ load("@io_bazel_rules_go//go:def.bzl", "go_binary", "go_library")
go_library(
name = "undocker_lib",
srcs = [
"main.go",
"rootfs.go",
],
srcs = ["main.go"],
importpath = "github.com/motiejus/code/undocker",
visibility = ["//visibility:private"],
deps = ["@com_github_jessevdk_go_flags//:go-flags"],
deps = [
"//src/undocker/rootfs:rootfs_lib",
"@com_github_jessevdk_go_flags//:go-flags",
],
)
go_binary(

28
main.go
View File

@ -1,9 +1,11 @@
package main
import (
"errors"
"os"
goflags "github.com/jessevdk/go-flags"
"github.com/motiejus/code/undocker/rootfs"
)
type (
@ -31,3 +33,29 @@ func run(args []string) error {
return nil
}
type cmdRootFS struct {
PositionalArgs struct {
Infile goflags.Filename `long:"infile" description:"Input tarball"`
Outfile string `long:"outfile" description:"Output tarball (flattened file system)"`
} `positional-args:"yes" required:"yes"`
}
func (r *cmdRootFS) Execute(args []string) error {
if len(args) != 0 {
return errors.New("too many args")
}
in, err := os.Open(string(r.PositionalArgs.Infile))
if err != nil {
return err
}
defer in.Close()
out, err := os.Create(string(r.PositionalArgs.Outfile))
if err != nil {
return err
}
defer out.Close()
return rootfs.Rootfs(in, out)
}

8
rootfs/BUILD Normal file
View File

@ -0,0 +1,8 @@
load("@io_bazel_rules_go//go:def.bzl", "go_library")
go_library(
name = "rootfs_lib",
srcs = ["rootfs.go"],
importpath = "github.com/motiejus/code/undocker/rootfs",
visibility = ["//visibility:public"],
)

View File

@ -1,53 +1,23 @@
package main
package rootfs
import (
"archive/tar"
"encoding/json"
"errors"
"fmt"
"io"
"os"
"strings"
goflags "github.com/jessevdk/go-flags"
)
type cmdRootFS struct {
PositionalArgs struct {
Infile goflags.Filename `long:"infile" description:"Input tarball"`
Outfile string `long:"outfile" description:"Output tarball (flattened file system)"`
} `positional-args:"yes" required:"yes"`
}
const (
_manifestJSON = "manifest.json"
)
func (r *cmdRootFS) Execute(args []string) error {
if len(args) != 0 {
return errors.New("too many args")
}
in, err := os.Open(string(r.PositionalArgs.Infile))
if err != nil {
return err
}
defer in.Close()
out, err := os.Create(string(r.PositionalArgs.Outfile))
if err != nil {
return err
}
defer out.Close()
return r.rootfs(in, out)
}
type dockerManifestJSON []struct {
Config string `json:"Config"`
Layers []string `json:"Layers"`
}
// rootfs accepts a docker layer tarball and writes it to outfile.
// Rootfs accepts a docker layer tarball and writes it to outfile.
// 1. create map[string]io.ReadSeeker for each layer.
// 2. parse manifest.json and get the layer order.
// 3. go through each layer in order and write:
@ -56,7 +26,7 @@ type dockerManifestJSON []struct {
// I) layer name
// II) offset (0 being the first file in the layer)
// 4. go through
func (r *cmdRootFS) rootfs(in io.ReadSeeker, out io.Writer) error {
func Rootfs(in io.ReadSeeker, out io.Writer) error {
tr := tar.NewReader(in)
tw := tar.NewWriter(out)
// layerOffsets maps a layer name (a9b123c0daa/layer.tar) to it's offset
@ -88,7 +58,6 @@ func (r *cmdRootFS) rootfs(in io.ReadSeeker, out io.Writer) error {
return fmt.Errorf("seek: %w", err)
}
layerOffsets[hdr.Name] = here
//fmt.Printf("%s\t%x\n", hdr.Name, here)
}
}