Import files from compare_target_files for use in diff_target_files

Copied from cl/240594925.

Bug: 121158314
Test: copied unit tests
Change-Id: I2e91126285dcd33171ff8b8dbfcfa5d48501f535

cmd/diff_target_files/zip_artifact.go

@@ -0,0 +1,174 @@
+// Copyright 2019 Google Inc. All rights reserved.
+//
+// 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 main
+
+import (
+	"archive/zip"
+	"context"
+	"fmt"
+	"hash/crc32"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+// ZipArtifact represents a zip file that may be local or remote.
+type ZipArtifact interface {
+	// Files returns the list of files contained in the zip file.
+	Files() ([]*ZipArtifactFile, error)
+
+	// Close closes the zip file artifact.
+	Close()
+}
+
+// localZipArtifact is a handle to a local zip file artifact.
+type localZipArtifact struct {
+	zr    *zip.ReadCloser
+	files []*ZipArtifactFile
+}
+
+// NewLocalZipArtifact returns a ZipArtifact for a local zip file..
+func NewLocalZipArtifact(name string) (ZipArtifact, error) {
+	zr, err := zip.OpenReader(name)
+	if err != nil {
+		return nil, err
+	}
+
+	var files []*ZipArtifactFile
+	for _, zf := range zr.File {
+		files = append(files, &ZipArtifactFile{zf})
+	}
+
+	return &localZipArtifact{
+		zr:    zr,
+		files: files,
+	}, nil
+}
+
+// Files returns the list of files contained in the local zip file artifact.
+func (z *localZipArtifact) Files() ([]*ZipArtifactFile, error) {
+	return z.files, nil
+}
+
+// Close closes the buffered reader of the local zip file artifact.
+func (z *localZipArtifact) Close() {
+	z.zr.Close()
+}
+
+// ZipArtifactFile contains a zip.File handle to the data inside the remote *-target_files-*.zip
+// build artifact.
+type ZipArtifactFile struct {
+	*zip.File
+}
+
+// Extract begins extract a file from inside a ZipArtifact.  It returns an
+// ExtractedZipArtifactFile handle.
+func (zf *ZipArtifactFile) Extract(ctx context.Context, dir string,
+	limiter chan bool) *ExtractedZipArtifactFile {
+
+	d := &ExtractedZipArtifactFile{
+		initCh: make(chan struct{}),
+	}
+
+	go func() {
+		defer close(d.initCh)
+		limiter <- true
+		defer func() { <-limiter }()
+
+		zr, err := zf.Open()
+		if err != nil {
+			d.err = err
+			return
+		}
+		defer zr.Close()
+
+		crc := crc32.NewIEEE()
+		r := io.TeeReader(zr, crc)
+
+		if filepath.Clean(zf.Name) != zf.Name {
+			d.err = fmt.Errorf("invalid filename %q", zf.Name)
+			return
+		}
+		path := filepath.Join(dir, zf.Name)
+
+		err = os.MkdirAll(filepath.Dir(path), 0777)
+		if err != nil {
+			d.err = err
+			return
+		}
+
+		err = os.Remove(path)
+		if err != nil && !os.IsNotExist(err) {
+			d.err = err
+			return
+		}
+
+		if zf.Mode().IsRegular() {
+			w, err := os.OpenFile(path, os.O_CREATE|os.O_WRONLY, zf.Mode())
+			if err != nil {
+				d.err = err
+				return
+			}
+			defer w.Close()
+
+			_, err = io.Copy(w, r)
+			if err != nil {
+				d.err = err
+				return
+			}
+		} else if zf.Mode()&os.ModeSymlink != 0 {
+			target, err := ioutil.ReadAll(r)
+			if err != nil {
+				d.err = err
+				return
+			}
+
+			err = os.Symlink(string(target), path)
+			if err != nil {
+				d.err = err
+				return
+			}
+		} else {
+			d.err = fmt.Errorf("unknown mode %q", zf.Mode())
+			return
+		}
+
+		if crc.Sum32() != zf.CRC32 {
+			d.err = fmt.Errorf("crc mismatch for %v", zf.Name)
+			return
+		}
+
+		d.path = path
+	}()
+
+	return d
+}
+
+// ExtractedZipArtifactFile is a handle to a downloaded file from a remoteZipArtifact.  The download
+// may still be in progress, and will be complete with Path() returns.
+type ExtractedZipArtifactFile struct {
+	initCh chan struct{}
+	err    error
+
+	path string
+}
+
+// Path returns the path to the downloaded file and any errors that occurred during the download.
+// It will block until the download is complete.
+func (d *ExtractedZipArtifactFile) Path() (string, error) {
+	<-d.initCh
+	return d.path, d.err
+}