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go-mtree/tar.go
Vincent Batts 08b1000418
vis: adding a pure golang Vis()
The current Vis() and Unvis() are using the C implementation from
MTREE(8).

But that means that cgo is used, which is not always desired.

Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>
2016-12-07 16:12:28 -05:00

457 lines
12 KiB
Go

package mtree
import (
"archive/tar"
"fmt"
"io"
"io/ioutil"
"log"
"os"
"path/filepath"
"strings"
)
// Streamer creates a file hierarchy out of a tar stream
type Streamer interface {
io.ReadCloser
Hierarchy() (*DirectoryHierarchy, error)
}
var tarDefaultSetKeywords = []KeyVal{
"type=file",
"flags=none",
"mode=0664",
}
// NewTarStreamer streams a tar archive and creates a file hierarchy based off
// of the tar metadata headers
func NewTarStreamer(r io.Reader, excludes []ExcludeFunc, keywords []Keyword) Streamer {
pR, pW := io.Pipe()
ts := &tarStream{
pipeReader: pR,
pipeWriter: pW,
creator: dhCreator{DH: &DirectoryHierarchy{}},
teeReader: io.TeeReader(r, pW),
tarReader: tar.NewReader(pR),
keywords: keywords,
hardlinks: map[string][]string{},
excludes: excludes,
}
go ts.readHeaders()
return ts
}
type tarStream struct {
root *Entry
hardlinks map[string][]string
creator dhCreator
pipeReader *io.PipeReader
pipeWriter *io.PipeWriter
teeReader io.Reader
tarReader *tar.Reader
keywords []Keyword
excludes []ExcludeFunc
err error
}
func (ts *tarStream) readHeaders() {
// remove "time" keyword
notimekws := []Keyword{}
for _, kw := range ts.keywords {
if !InKeywordSlice(kw, notimekws) {
if kw == "time" {
if !InKeywordSlice("tar_time", ts.keywords) {
notimekws = append(notimekws, "tar_time")
}
} else {
notimekws = append(notimekws, kw)
}
}
}
ts.keywords = notimekws
// We have to start with the directory we're in, and anything beyond these
// items is determined at the time a tar is extracted.
ts.root = &Entry{
Name: ".",
Type: RelativeType,
Prev: &Entry{
Raw: "# .",
Type: CommentType,
},
Set: nil,
Keywords: []KeyVal{"type=dir"},
}
// insert signature and metadata comments first (user, machine, tree, date)
for _, e := range signatureEntries("<user specified tar archive>") {
e.Pos = len(ts.creator.DH.Entries)
ts.creator.DH.Entries = append(ts.creator.DH.Entries, e)
}
// insert keyword metadata next
for _, e := range keywordEntries(ts.keywords) {
e.Pos = len(ts.creator.DH.Entries)
ts.creator.DH.Entries = append(ts.creator.DH.Entries, e)
}
hdrloop:
for {
hdr, err := ts.tarReader.Next()
if err != nil {
ts.pipeReader.CloseWithError(err)
return
}
for _, ex := range ts.excludes {
if ex(hdr.Name, hdr.FileInfo()) {
continue hdrloop
}
}
// Because the content of the file may need to be read by several
// KeywordFuncs, it needs to be an io.Seeker as well. So, just reading from
// ts.tarReader is not enough.
tmpFile, err := ioutil.TempFile("", "ts.payload.")
if err != nil {
ts.pipeReader.CloseWithError(err)
return
}
// for good measure
if err := tmpFile.Chmod(0600); err != nil {
tmpFile.Close()
os.Remove(tmpFile.Name())
ts.pipeReader.CloseWithError(err)
return
}
if _, err := io.Copy(tmpFile, ts.tarReader); err != nil {
tmpFile.Close()
os.Remove(tmpFile.Name())
ts.pipeReader.CloseWithError(err)
return
}
// Alright, it's either file or directory
encodedName, err := Vis(filepath.Base(hdr.Name), DefaultVisFlags)
if err != nil {
tmpFile.Close()
os.Remove(tmpFile.Name())
ts.pipeReader.CloseWithError(err)
return
}
e := Entry{
Name: encodedName,
Type: RelativeType,
}
// Keep track of which files are hardlinks so we can resolve them later
if hdr.Typeflag == tar.TypeLink {
linkFunc := KeywordFuncs["link"]
kv, err := linkFunc(hdr.Name, hdr.FileInfo(), nil)
if err != nil {
log.Println(err)
break
}
linkname, err := Unvis(KeyVal(kv).Value())
if err != nil {
log.Println(err)
break
}
if _, ok := ts.hardlinks[linkname]; !ok {
ts.hardlinks[linkname] = []string{hdr.Name}
} else {
ts.hardlinks[linkname] = append(ts.hardlinks[linkname], hdr.Name)
}
}
// now collect keywords on the file
for _, keyword := range ts.keywords {
if keyFunc, ok := KeywordFuncs[keyword]; ok {
// We can't extract directories on to disk, so "size" keyword
// is irrelevant for now
if hdr.FileInfo().IsDir() && keyword == "size" {
continue
}
val, err := keyFunc(hdr.Name, hdr.FileInfo(), tmpFile)
if err != nil {
ts.setErr(err)
}
// for good measure, check that we actually get a value for a keyword
if val != "" {
e.Keywords = append(e.Keywords, val)
}
// don't forget to reset the reader
if _, err := tmpFile.Seek(0, 0); err != nil {
tmpFile.Close()
os.Remove(tmpFile.Name())
ts.pipeReader.CloseWithError(err)
return
}
}
}
// collect meta-set keywords for a directory so that we can build the
// actual sets in `flatten`
if hdr.FileInfo().IsDir() {
s := Entry{
Name: "meta-set",
Type: SpecialType,
}
for _, setKW := range SetKeywords {
if keyFunc, ok := KeywordFuncs[setKW]; ok {
val, err := keyFunc(hdr.Name, hdr.FileInfo(), tmpFile)
if err != nil {
ts.setErr(err)
}
if val != "" {
s.Keywords = append(s.Keywords, val)
}
if _, err := tmpFile.Seek(0, 0); err != nil {
tmpFile.Close()
os.Remove(tmpFile.Name())
ts.pipeReader.CloseWithError(err)
}
}
}
e.Set = &s
}
err = populateTree(ts.root, &e, hdr)
if err != nil {
ts.setErr(err)
}
tmpFile.Close()
os.Remove(tmpFile.Name())
}
}
// populateTree creates a pseudo file tree hierarchy using an Entry's Parent and
// Children fields. When examining the Entry e to insert in the tree, we
// determine if the path to that Entry exists yet. If it does, insert it in the
// appropriate position in the tree. If not, create a path up until the Entry's
// directory that it is contained in. Then, insert the Entry.
// root: the "." Entry
// e: the Entry we are looking to insert
// hdr: the tar header struct associated with e
func populateTree(root, e *Entry, hdr *tar.Header) error {
if root == nil || e == nil {
return fmt.Errorf("cannot populate or insert nil Entry's")
} else if root.Prev == nil {
return fmt.Errorf("root needs to be an Entry associated with a directory")
}
isDir := hdr.FileInfo().IsDir()
wd := filepath.Clean(hdr.Name)
if !isDir {
// directory up until the actual file
wd = filepath.Dir(wd)
if wd == "." {
root.Children = append([]*Entry{e}, root.Children...)
e.Parent = root
return nil
}
}
dirNames := strings.Split(wd, "/")
parent := root
for _, name := range dirNames[:] {
encoded, err := Vis(name, DefaultVisFlags)
if err != nil {
return err
}
if node := parent.Descend(encoded); node == nil {
// Entry for directory doesn't exist in tree relative to root.
// We don't know if this directory is an actual tar header (because a
// user could have just specified a path to a deep file), so we must
// specify this placeholder directory as a "type=dir", and Set=nil.
newEntry := Entry{
Name: encoded,
Type: RelativeType,
Parent: parent,
Keywords: []KeyVal{"type=dir"}, // temp data
Set: nil, // temp data
}
pathname, err := newEntry.Path()
if err != nil {
return err
}
newEntry.Prev = &Entry{
Type: CommentType,
Raw: "# " + pathname,
}
parent.Children = append(parent.Children, &newEntry)
parent = &newEntry
} else {
// Entry for directory exists in tree, just keep going
parent = node
}
}
if !isDir {
parent.Children = append([]*Entry{e}, parent.Children...)
e.Parent = parent
} else {
// fill in the actual data from e
parent.Keywords = e.Keywords
parent.Set = e.Set
}
return nil
}
// After constructing a pseudo file hierarchy tree, we want to "flatten" this
// tree by putting the Entries into a slice with appropriate positioning.
// root: the "head" of the sub-tree to flatten
// creator: a dhCreator that helps with the '/set' keyword
// keywords: keywords specified by the user that should be evaluated
func flatten(root *Entry, creator *dhCreator, keywords []Keyword) {
if root == nil || creator == nil {
return
}
if root.Prev != nil {
// root.Prev != nil implies root is a directory
creator.DH.Entries = append(creator.DH.Entries,
Entry{
Type: BlankType,
Pos: len(creator.DH.Entries),
})
root.Prev.Pos = len(creator.DH.Entries)
creator.DH.Entries = append(creator.DH.Entries, *root.Prev)
if root.Set != nil {
// Check if we need a new set
consolidatedKeys := keyvalSelector(append(tarDefaultSetKeywords, root.Set.Keywords...), keywords)
if creator.curSet == nil {
creator.curSet = &Entry{
Type: SpecialType,
Name: "/set",
Keywords: consolidatedKeys,
Pos: len(creator.DH.Entries),
}
creator.DH.Entries = append(creator.DH.Entries, *creator.curSet)
} else {
needNewSet := false
for _, k := range root.Set.Keywords {
if !inKeyValSlice(k, creator.curSet.Keywords) {
needNewSet = true
break
}
}
if needNewSet {
creator.curSet = &Entry{
Name: "/set",
Type: SpecialType,
Pos: len(creator.DH.Entries),
Keywords: consolidatedKeys,
}
creator.DH.Entries = append(creator.DH.Entries, *creator.curSet)
}
}
} else if creator.curSet != nil {
// Getting into here implies that the Entry's set has not and
// was not supposed to be evaluated, thus, we need to reset curSet
creator.DH.Entries = append(creator.DH.Entries, Entry{
Name: "/unset",
Type: SpecialType,
Pos: len(creator.DH.Entries),
})
creator.curSet = nil
}
}
root.Set = creator.curSet
if creator.curSet != nil {
root.Keywords = keyValDifference(root.Keywords, creator.curSet.Keywords)
}
root.Pos = len(creator.DH.Entries)
creator.DH.Entries = append(creator.DH.Entries, *root)
for _, c := range root.Children {
flatten(c, creator, keywords)
}
if root.Prev != nil {
// Show a comment when stepping out
root.Prev.Pos = len(creator.DH.Entries)
creator.DH.Entries = append(creator.DH.Entries, *root.Prev)
dotEntry := Entry{
Type: DotDotType,
Name: "..",
Pos: len(creator.DH.Entries),
}
creator.DH.Entries = append(creator.DH.Entries, dotEntry)
}
return
}
// resolveHardlinks goes through an Entry tree, and finds the Entry's associated
// with hardlinks and fills them in with the actual data from the base file.
func resolveHardlinks(root *Entry, hardlinks map[string][]string, countlinks bool) {
originals := make(map[string]*Entry)
for base, links := range hardlinks {
var basefile *Entry
if seen, ok := originals[base]; !ok {
basefile = root.Find(base)
if basefile == nil {
log.Printf("%s does not exist in this tree\n", base)
continue
}
originals[base] = basefile
} else {
basefile = seen
}
for _, link := range links {
linkfile := root.Find(link)
if linkfile == nil {
log.Printf("%s does not exist in this tree\n", link)
continue
}
linkfile.Keywords = basefile.Keywords
if countlinks {
linkfile.Keywords = append(linkfile.Keywords, KeyVal(fmt.Sprintf("nlink=%d", len(links)+1)))
}
}
if countlinks {
basefile.Keywords = append(basefile.Keywords, KeyVal(fmt.Sprintf("nlink=%d", len(links)+1)))
}
}
}
// filter takes in a pointer to an Entry, and returns a slice of Entry's that
// satisfy the predicate p
func filter(root *Entry, p func(*Entry) bool) []Entry {
if root != nil {
var validEntrys []Entry
if len(root.Children) > 0 || root.Prev != nil {
for _, c := range root.Children {
// filter the sub-directory
if c.Prev != nil {
validEntrys = append(validEntrys, filter(c, p)...)
}
if p(c) {
if c.Prev == nil {
validEntrys = append([]Entry{*c}, validEntrys...)
} else {
validEntrys = append(validEntrys, *c)
}
}
}
return validEntrys
}
}
return nil
}
func (ts *tarStream) setErr(err error) {
ts.err = err
}
func (ts *tarStream) Read(p []byte) (n int, err error) {
return ts.teeReader.Read(p)
}
func (ts *tarStream) Close() error {
return ts.pipeReader.Close()
}
// Hierarchy returns the DirectoryHierarchy of the archive. It flattens the
// Entry tree before returning the DirectoryHierarchy
func (ts *tarStream) Hierarchy() (*DirectoryHierarchy, error) {
if ts.err != nil && ts.err != io.EOF {
return nil, ts.err
}
if ts.root == nil {
return nil, fmt.Errorf("root Entry not found, nothing to flatten")
}
resolveHardlinks(ts.root, ts.hardlinks, InKeywordSlice(Keyword("nlink"), ts.keywords))
flatten(ts.root, &ts.creator, ts.keywords)
return ts.creator.DH, nil
}