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archive/tar: convert Reader.Next to be loop based

Motivation for change:
* Recursive logic is hard to follow, since it tends to apply
things in reverse. On the other hand, the tar formats tend to
describe meta headers as affecting the next entry.
* Recursion also applies changes in the wrong order. Two test
files are attached that use multiple headers. The previous Go
behavior differs from what GNU and BSD tar do.

Change-Id: Ic1557256fc1363c5cb26570e5d0b9f65a9e57341
Reviewed-on: https://go-review.googlesource.com/14624
Run-TryBot: Joe Tsai <joetsai@digital-static.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Joe Tsai 2015-09-16 00:58:56 -07:00 committed by Vincent Batts
parent 64935a5f0f
commit be9ac88117
4 changed files with 90 additions and 94 deletions

View file

@ -138,8 +138,6 @@ func NewReader(r io.Reader) *Reader { return &Reader{r: r} }
//
// io.EOF is returned at the end of the input.
func (tr *Reader) Next() (*Header, error) {
var p parser
var hdr *Header
if tr.RawAccounting {
if tr.rawBytes == nil {
tr.rawBytes = bytes.NewBuffer(nil)
@ -147,114 +145,88 @@ func (tr *Reader) Next() (*Header, error) {
tr.rawBytes.Reset()
}
}
if tr.err == nil {
tr.skipUnread()
}
if tr.err != nil {
return hdr, tr.err
return nil, tr.err
}
hdr = tr.readHeader()
if hdr == nil {
return hdr, tr.err
}
// Check for PAX/GNU header.
switch hdr.Typeflag {
case TypeXHeader:
// PAX extended header
headers, err := parsePAX(tr)
if err != nil {
return nil, err
}
// We actually read the whole file,
// but this skips alignment padding
tr.skipUnread()
var hdr *Header
var extHdrs map[string]string
// Externally, Next iterates through the tar archive as if it is a series of
// files. Internally, the tar format often uses fake "files" to add meta
// data that describes the next file. These meta data "files" should not
// normally be visible to the outside. As such, this loop iterates through
// one or more "header files" until it finds a "normal file".
loop:
for {
tr.err = tr.skipUnread()
if tr.err != nil {
return nil, tr.err
}
hdr = tr.readHeader()
if hdr == nil {
if tr.err != nil {
return nil, tr.err
}
mergePAX(hdr, headers)
// Check for a PAX format sparse file
sp, err := tr.checkForGNUSparsePAXHeaders(hdr, headers)
if err != nil {
tr.err = err
return nil, err
}
if sp != nil {
// Sparse files do not make sense when applied to the special header
// types that never have a data section.
if isHeaderOnlyType(hdr.Typeflag) {
tr.err = ErrHeader
return nil, tr.err
}
// Current file is a PAX format GNU sparse file.
// Set the current file reader to a sparse file reader.
tr.curr, tr.err = newSparseFileReader(tr.curr, sp, hdr.Size)
// Check for PAX/GNU special headers and files.
switch hdr.Typeflag {
case TypeXHeader:
extHdrs, tr.err = parsePAX(tr)
if tr.err != nil {
return nil, tr.err
}
}
return hdr, nil
case TypeGNULongName:
// We have a GNU long name header. Its contents are the real file name.
realname, err := ioutil.ReadAll(tr)
if err != nil {
return nil, err
}
var buf []byte
if tr.RawAccounting {
if _, err = tr.rawBytes.Write(realname); err != nil {
continue loop // This is a meta header affecting the next header
case TypeGNULongName, TypeGNULongLink:
var realname []byte
realname, tr.err = ioutil.ReadAll(tr)
if tr.err != nil {
return nil, tr.err
}
if tr.RawAccounting {
if _, tr.err = tr.rawBytes.Write(realname); tr.err != nil {
return nil, tr.err
}
}
// Convert GNU extensions to use PAX headers.
if extHdrs == nil {
extHdrs = make(map[string]string)
}
var p parser
switch hdr.Typeflag {
case TypeGNULongName:
extHdrs[paxPath] = p.parseString(realname)
case TypeGNULongLink:
extHdrs[paxLinkpath] = p.parseString(realname)
}
if p.err != nil {
tr.err = p.err
return nil, tr.err
}
continue loop // This is a meta header affecting the next header
default:
mergePAX(hdr, extHdrs)
// Check for a PAX format sparse file
sp, err := tr.checkForGNUSparsePAXHeaders(hdr, extHdrs)
if err != nil {
tr.err = err
return nil, err
}
buf = make([]byte, tr.rawBytes.Len())
copy(buf[:], tr.RawBytes())
}
hdr, err := tr.Next()
// since the above call to Next() resets the buffer, we need to throw the bytes over
if tr.RawAccounting {
buf = append(buf, tr.RawBytes()...)
if _, err = tr.rawBytes.Write(buf); err != nil {
return nil, err
if sp != nil {
// Current file is a PAX format GNU sparse file.
// Set the current file reader to a sparse file reader.
tr.curr, tr.err = newSparseFileReader(tr.curr, sp, hdr.Size)
if tr.err != nil {
return nil, tr.err
}
}
break loop // This is a file, so stop
}
hdr.Name = p.parseString(realname)
if p.err != nil {
return nil, p.err
}
return hdr, nil
case TypeGNULongLink:
// We have a GNU long link header.
realname, err := ioutil.ReadAll(tr)
if err != nil {
return nil, err
}
var buf []byte
if tr.RawAccounting {
if _, err = tr.rawBytes.Write(realname); err != nil {
return nil, err
}
buf = make([]byte, tr.rawBytes.Len())
copy(buf[:], tr.RawBytes())
}
hdr, err := tr.Next()
// since the above call to Next() resets the buffer, we need to throw the bytes over
if tr.RawAccounting {
buf = append(buf, tr.RawBytes()...)
if _, err = tr.rawBytes.Write(buf); err != nil {
return nil, err
}
}
hdr.Name = p.parseString(realname)
if p.err != nil {
return nil, p.err
}
return hdr, nil
}
return hdr, tr.err
return hdr, nil
}
// checkForGNUSparsePAXHeaders checks the PAX headers for GNU sparse headers. If they are found, then

View file

@ -288,6 +288,30 @@ var untarTests = []*untarTest{
},
},
},
{
// Matches the behavior of GNU, BSD, and STAR tar utilities.
file: "testdata/gnu-multi-hdrs.tar",
headers: []*Header{
{
Name: "GNU2/GNU2/long-path-name",
Linkname: "GNU4/GNU4/long-linkpath-name",
ModTime: time.Unix(0, 0),
Typeflag: '2',
},
},
},
{
// Matches the behavior of GNU and BSD tar utilities.
file: "testdata/pax-multi-hdrs.tar",
headers: []*Header{
{
Name: "bar",
Linkname: "PAX4/PAX4/long-linkpath-name",
ModTime: time.Unix(0, 0),
Typeflag: '2',
},
},
},
{
file: "testdata/neg-size.tar",
err: ErrHeader,

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