src/pkg/fs/build_context.go

// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package fs

import (
	"archive/tar"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
)

func tarFile(src, dst string) error {
	dirPath := filepath.Dir(src)
	baseName := filepath.Base(src)
	cmd := exec.Command("tar", "cf", dst, "-C", dirPath, baseName)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	return cmd.Run()
}

func tarDir(root, dst string) error {
	args := []string{"cf", dst, "-C", root}
	inputFiles, err := filepath.Glob(filepath.Join(root, "*"))
	if err != nil {
		return err
	}
	var relInputFiles []string
	for _, path := range inputFiles {
		relPath, err := filepath.Rel(root, path)
		if err != nil {
			return err
		}
		relInputFiles = append(relInputFiles, relPath)
	}
	if relInputFiles == nil {
		relInputFiles = []string{"."}
	}
	args = append(args, relInputFiles...)
	cmd := exec.Command("tar", args...)
	cmd.Stdout = os.Stdout
	cmd.Stderr = os.Stderr
	return cmd.Run()
}

// CreateBuildContextArchive creates a tar archive of the given build context.
func CreateBuildContextArchive(src, dst string) error {
	if _, err := os.Stat(dst); !os.IsNotExist(err) {
		return fmt.Errorf("dst path already exists: %s", dst)
	}
	if err := os.MkdirAll(filepath.Dir(dst), 0774); err != nil {
		return err
	}
	info, err := os.Stat(src)
	if err != nil {
		return err
	}
	switch {
	case info.IsDir():
		return tarDir(src, dst)
	case info.Mode().IsRegular():
		return tarFile(src, dst)
	default:
		return fmt.Errorf("input path %s is neither a directory nor a regular file", src)
	}
}

// ArchiveHasObject determines if the given tar archive contains the given object.
func ArchiveHasObject(archive string, path string) (bool, error) {
	reader, err := os.Open(archive)
	if err != nil {
		return false, err
	}
	defer reader.Close()
	tarReader := tar.NewReader(reader)
	for {
		hdr, err := tarReader.Next()
		if err == io.EOF {
			break
		}
		if err != nil {
			return false, err
		}
		if hdr.Name == path {
			return true, nil
		}
	}
	return false, nil
}