buildr/modules/packaging/ociimg/tar.go

package ociimg

import (
	"archive/tar"
	"errors"
	"io/fs"
	"os"
	"path"
	"path/filepath"
	"strings"

	"code.icb4dc0.de/buildr/buildr/internal/ioutils"
)

func buildDirFromContent(cwd string, content map[string]string) (*dirNode, error) {
	rootNode := newDirNode()
	for origSource, target := range content {
		source := origSource
		if !filepath.IsAbs(source) {
			source = filepath.Join(cwd, source)
		}

		info, err := os.Stat(source)
		if err != nil {
			return nil, err
		}

		if !info.IsDir() {
			if strings.HasSuffix(target, "/") {
				_, fileName := filepath.Split(source)
				target = filepath.Join(target, fileName)
			}

			rootNode.addFile(source, target)

			continue
		}

		walkErr := filepath.WalkDir(source, func(path string, d fs.DirEntry, err error) error {
			if err != nil {
				return err
			}

			relativeToSource, err := filepath.Rel(source, path)
			if err != nil {
				return err
			} else if relativeToSource == "." {
				return nil
			}

			if d.IsDir() {
				rootNode.addDir(relativeToSource)
			} else {
				rootNode.addFile(path, filepath.Join(target, relativeToSource))
			}

			return nil
		})

		if walkErr != nil {
			return nil, walkErr
		}
	}

	return rootNode, nil
}

type fileToTar struct {
	sourcePath     string
	targetFileName string
}

func newDirNode() *dirNode {
	return &dirNode{
		children: make(map[string]*dirNode),
	}
}

type dirNode struct {
	children map[string]*dirNode
	files    []fileToTar
}

func (n *dirNode) addDir(dirPath string) {
	current := n
	for _, segment := range strings.Split(dirPath, "/") {
		if child, ok := n.children[segment]; ok {
			current = child
		} else {
			newNode := newDirNode()
			current.children[segment] = newNode
			current = newNode
		}
	}
}

func (n *dirNode) addFile(sourcePath, targetPath string) {
	if !filepath.IsAbs(targetPath) {
		targetPath = filepath.Join("", targetPath)
	}
	dirPath, fileName := filepath.Split(targetPath)
	current := n
	for _, segment := range strings.Split(dirPath, "/") {
		if segment == "" {
			continue
		}
		if child, ok := current.children[segment]; ok {
			current = child
		} else {
			newNode := &dirNode{
				children: make(map[string]*dirNode),
			}
			current.children[segment] = newNode
			current = newNode
		}
	}

	current.files = append(current.files, fileToTar{
		sourcePath:     sourcePath,
		targetFileName: fileName,
	})
}

func (n *dirNode) writeToTar(writer *tar.Writer, parent string) error {
	for segment, child := range n.children {
		segmentPath := filepath.Join(parent, segment)
		header := &tar.Header{
			Name:     segmentPath,
			Typeflag: tar.TypeDir,
			// Use a fixed Mode, so that this isn't sensitive to the directory and umask
			// under which it was created. Additionally, windows can only set 0222,
			// 0444, or 0666, none of which are executable.
			Mode:    0o555,
			ModTime: defaultCreationTime,
		}

		if err := writer.WriteHeader(header); err != nil {
			return err
		}

		if err := child.writeToTar(writer, segmentPath); err != nil {
			return err
		}
	}

	for i := range n.files {
		fileSpec := n.files[i]
		info, err := os.Stat(fileSpec.sourcePath)
		if err != nil {
			return err
		}

		f, err := os.Open(fileSpec.sourcePath)
		if err != nil {
			return err
		}

		header := &tar.Header{
			Name:     path.Join(parent, fileSpec.targetFileName),
			Size:     info.Size(),
			Typeflag: tar.TypeReg,
			// Use a fixed Mode, so that this isn't sensitive to the directory and umask
			// under which it was created. Additionally, windows can only set 0222,
			// 0444, or 0666, none of which are executable.
			Mode:    0o555,
			ModTime: defaultCreationTime,
		}

		if err = writer.WriteHeader(header); err != nil {
			return errors.Join(err, f.Close())
		}

		if _, err = ioutils.CopyWithPooledBuffer(writer, f); err != nil {
			return errors.Join(err, f.Close())
		}

		if err := f.Close(); err != nil {
			return err
		}
	}

	return nil
}