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package docker
import (
"archive/tar"
"compress/gzip"
"fmt"
"io"
"os"
"path"
"strings"
"github.com/wagoodman/dive/dive/filetree"
"github.com/wagoodman/dive/dive/image"
)
type ImageArchive struct {
manifest manifest
config config
layerMap map[string]*filetree.FileTree
}
func NewImageArchive(tarFile io.ReadCloser) (*ImageArchive, error) {
img := &ImageArchive{
layerMap: make(map[string]*filetree.FileTree),
}
tarReader := tar.NewReader(tarFile)
// store discovered json files in a map so we can read the image in one pass
jsonFiles := make(map[string][]byte)
var currentLayer uint
for {
header, err := tarReader.Next()
if err == io.EOF {
break
}
if err != nil {
fmt.Println(err)
os.Exit(1)
}
name := header.Name
// some layer tars can be relative layer symlinks to other layer tars
if header.Typeflag == tar.TypeSymlink || header.Typeflag == tar.TypeReg {
if strings.HasSuffix(name, ".tar") {
currentLayer++
layerReader := tar.NewReader(tarReader)
tree, err := processLayerTar(name, layerReader)
if err != nil {
return img, err
}
// add the layer to the image
img.layerMap[tree.Name] = tree
} else if strings.HasSuffix(name, ".tar.gz") || strings.HasSuffix(name, "tgz") {
currentLayer++
// Add gzip reader
gz, err := gzip.NewReader(tarReader)
if err != nil {
return img, err
}
// Add tar reader
layerReader := tar.NewReader(gz)
// Process layer
tree, err := processLayerTar(name, layerReader)
if err != nil {
return img, err
}
// add the layer to the image
img.layerMap[tree.Name] = tree
} else if strings.HasSuffix(name, ".json") || strings.HasPrefix(name, "sha256:") {
fileBuffer, err := io.ReadAll(tarReader)
if err != nil {
return img, err
}
jsonFiles[name] = fileBuffer
}
}
}
manifestContent, exists := jsonFiles["manifest.json"]
if !exists {
return img, fmt.Errorf("could not find image manifest")
}
img.manifest = newManifest(manifestContent)
configContent, exists := jsonFiles[img.manifest.ConfigPath]
if !exists {
return img, fmt.Errorf("could not find image config")
}
img.config = newConfig(configContent)
return img, nil
}
func processLayerTar(name string, reader *tar.Reader) (*filetree.FileTree, error) {
tree := filetree.NewFileTree()
tree.Name = name
fileInfos, err := getFileList(reader)
if err != nil {
return nil, err
}
for _, element := range fileInfos {
tree.FileSize += uint64(element.Size)
_, _, err := tree.AddPath(element.Path, element)
if err != nil {
return nil, err
}
}
return tree, nil
}
func getFileList(tarReader *tar.Reader) ([]filetree.FileInfo, error) {
var files []filetree.FileInfo
for {
header, err := tarReader.Next()
if err == io.EOF {
break
} else if err != nil {
return nil, err
}
// always ensure relative path notations are not parsed as part of the filename
name := path.Clean(header.Name)
if name == "." {
continue
}
switch header.Typeflag {
case tar.TypeXGlobalHeader:
return nil, fmt.Errorf("unexptected tar file: (XGlobalHeader): type=%v name=%s", header.Typeflag, name)
case tar.TypeXHeader:
return nil, fmt.Errorf("unexptected tar file (XHeader): type=%v name=%s", header.Typeflag, name)
default:
files = append(files, filetree.NewFileInfoFromTarHeader(tarReader, header, name))
}
}
return files, nil
}
func (img *ImageArchive) ToImage() (*image.Image, error) {
trees := make([]*filetree.FileTree, 0)
// build the content tree
for _, treeName := range img.manifest.LayerTarPaths {
tr, exists := img.layerMap[treeName]
if exists {
trees = append(trees, tr)
continue
}
return nil, fmt.Errorf("could not find '%s' in parsed layers", treeName)
}
// build the layers array
layers := make([]*image.Layer, 0)
// note that the engineResolver config stores images in reverse chronological order, so iterate backwards through layers
// as you iterate chronologically through history (ignoring history items that have no layer contents)
// Note: history is not required metadata in a docker image!
histIdx := 0
for idx, tree := range trees {
// ignore empty layers, we are only observing layers with content
historyObj := historyEntry{
CreatedBy: "(missing)",
}
for nextHistIdx := histIdx; nextHistIdx < len(img.config.History); nextHistIdx++ {
if !img.config.History[nextHistIdx].EmptyLayer {
histIdx = nextHistIdx
break
}
}
if histIdx < len(img.config.History) && !img.config.History[histIdx].EmptyLayer {
historyObj = img.config.History[histIdx]
histIdx++
}
historyObj.Size = tree.FileSize
dockerLayer := layer{
history: historyObj,
index: idx,
tree: tree,
}
layers = append(layers, dockerLayer.ToLayer())
}
return &image.Image{
Trees: trees,
Layers: layers,
}, nil
}
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