diff_utils.go

/*
Copyright 2017 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 util

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"

	pkgutil "github.com/GoogleCloudPlatform/container-diff/pkg/util"
	"github.com/golang/glog"
	"github.com/pmezard/go-difflib/difflib"
)

type DirDiff struct {
	Adds []pkgutil.DirectoryEntry
	Dels []pkgutil.DirectoryEntry
	Mods []EntryDiff
}

type EntryDiff struct {
	Name  string
	Size1 int64
	Size2 int64
}

// Modification of difflib's unified differ
func GetAdditions(a, b []string) []string {
	matcher := difflib.NewMatcher(a, b)
	differences := matcher.GetGroupedOpCodes(0)

	adds := []string{}
	for _, group := range differences {
		for _, opCode := range group {
			j1, j2 := opCode.J1, opCode.J2
			if opCode.Tag == 'r' || opCode.Tag == 'i' {
				for _, line := range b[j1:j2] {
					adds = append(adds, line)
				}
			}
		}
	}
	return adds
}

func GetDeletions(a, b []string) []string {
	matcher := difflib.NewMatcher(a, b)
	differences := matcher.GetGroupedOpCodes(0)

	dels := []string{}
	for _, group := range differences {
		for _, opCode := range group {
			i1, i2 := opCode.I1, opCode.I2
			if opCode.Tag == 'r' || opCode.Tag == 'd' {
				for _, line := range a[i1:i2] {
					dels = append(dels, line)
				}
			}
		}
	}
	return dels
}

func GetMatches(a, b []string) []string {
	matcher := difflib.NewMatcher(a, b)
	matchindexes := matcher.GetMatchingBlocks()

	matches := []string{}
	for i, match := range matchindexes {
		if i != len(matchindexes)-1 {
			start := match.A
			end := match.A + match.Size
			for _, line := range a[start:end] {
				matches = append(matches, line)
			}
		}
	}
	return matches
}

// DiffDirectory takes the diff of two directories, assuming both are completely unpacked
func DiffDirectory(d1, d2 pkgutil.Directory) (DirDiff, bool) {
	adds := GetAddedEntries(d1, d2)
	sort.Strings(adds)
	addedEntries := pkgutil.CreateDirectoryEntries(d2.Root, adds)

	dels := GetDeletedEntries(d1, d2)
	sort.Strings(dels)
	deletedEntries := pkgutil.CreateDirectoryEntries(d1.Root, dels)

	mods := GetModifiedEntries(d1, d2)
	sort.Strings(mods)
	modifiedEntries := createEntryDiffs(d1.Root, d2.Root, mods)

	var same bool
	if len(adds) == 0 && len(dels) == 0 && len(mods) == 0 {
		same = true
	} else {
		same = false
	}

	return DirDiff{addedEntries, deletedEntries, modifiedEntries}, same
}

// Checks for content differences between files of the same name from different directories
func GetModifiedEntries(d1, d2 pkgutil.Directory) []string {
	d1files := d1.Content
	d2files := d2.Content

	filematches := GetMatches(d1files, d2files)

	modified := []string{}
	for _, f := range filematches {
		f1path := fmt.Sprintf("%s%s", d1.Root, f)
		f2path := fmt.Sprintf("%s%s", d2.Root, f)

		f1stat, err := os.Stat(f1path)
		if err != nil {
			glog.Errorf("Error checking directory entry %s: %s\n", f, err)
			continue
		}
		f2stat, err := os.Stat(f2path)
		if err != nil {
			glog.Errorf("Error checking directory entry %s: %s\n", f, err)
			continue
		}

		// If the directory entry in question is a tar, verify that the two have the same size
		if pkgutil.IsTar(f1path) {
			if f1stat.Size() != f2stat.Size() {
				modified = append(modified, f)
			}
			continue
		}

		// If the directory entry is not a tar and not a directory, then it's a file so make sure the file contents are the same
		// Note: We skip over directory entries because to compare directories, we compare their contents
		if !f1stat.IsDir() {
			same, err := pkgutil.CheckSameFile(f1path, f2path)
			if err != nil {
				glog.Errorf("Error diffing contents of %s and %s: %s\n", f1path, f2path, err)
				continue
			}
			if !same {
				modified = append(modified, f)
			}
		}
	}
	return modified
}

func GetAddedEntries(d1, d2 pkgutil.Directory) []string {
	return GetAdditions(d1.Content, d2.Content)
}

func GetDeletedEntries(d1, d2 pkgutil.Directory) []string {
	return GetDeletions(d1.Content, d2.Content)
}

func createEntryDiffs(root1, root2 string, entryNames []string) (entries []EntryDiff) {
	for _, name := range entryNames {
		entryPath1 := filepath.Join(root1, name)
		size1 := pkgutil.GetSize(entryPath1)

		entryPath2 := filepath.Join(root2, name)
		size2 := pkgutil.GetSize(entryPath2)

		entry := EntryDiff{
			Name:  name,
			Size1: size1,
			Size2: size2,
		}
		entries = append(entries, entry)
	}
	return entries
}