mirror of
https://github.com/moby/moby.git
synced 2022-11-09 12:21:53 -05:00
197 lines
7.3 KiB
Go
197 lines
7.3 KiB
Go
// Copyright 2016 The Go Authors. All rights reserved.
|
|
// Use of this source code is governed by a BSD-style
|
|
// license that can be found in the LICENSE file.
|
|
|
|
package tar
|
|
|
|
// Constants to identify various tar formats.
|
|
const (
|
|
// The format is unknown.
|
|
formatUnknown = (1 << iota) / 2 // Sequence of 0, 1, 2, 4, 8, etc...
|
|
|
|
// The format of the original Unix V7 tar tool prior to standardization.
|
|
formatV7
|
|
|
|
// The old and new GNU formats, which are incompatible with USTAR.
|
|
// This does cover the old GNU sparse extension.
|
|
// This does not cover the GNU sparse extensions using PAX headers,
|
|
// versions 0.0, 0.1, and 1.0; these fall under the PAX format.
|
|
formatGNU
|
|
|
|
// Schily's tar format, which is incompatible with USTAR.
|
|
// This does not cover STAR extensions to the PAX format; these fall under
|
|
// the PAX format.
|
|
formatSTAR
|
|
|
|
// USTAR is the former standardization of tar defined in POSIX.1-1988.
|
|
// This is incompatible with the GNU and STAR formats.
|
|
formatUSTAR
|
|
|
|
// PAX is the latest standardization of tar defined in POSIX.1-2001.
|
|
// This is an extension of USTAR and is "backwards compatible" with it.
|
|
//
|
|
// Some newer formats add their own extensions to PAX, such as GNU sparse
|
|
// files and SCHILY extended attributes. Since they are backwards compatible
|
|
// with PAX, they will be labelled as "PAX".
|
|
formatPAX
|
|
)
|
|
|
|
// Magics used to identify various formats.
|
|
const (
|
|
magicGNU, versionGNU = "ustar ", " \x00"
|
|
magicUSTAR, versionUSTAR = "ustar\x00", "00"
|
|
trailerSTAR = "tar\x00"
|
|
)
|
|
|
|
// Size constants from various tar specifications.
|
|
const (
|
|
blockSize = 512 // Size of each block in a tar stream
|
|
nameSize = 100 // Max length of the name field in USTAR format
|
|
prefixSize = 155 // Max length of the prefix field in USTAR format
|
|
)
|
|
|
|
var zeroBlock block
|
|
|
|
type block [blockSize]byte
|
|
|
|
// Convert block to any number of formats.
|
|
func (b *block) V7() *headerV7 { return (*headerV7)(b) }
|
|
func (b *block) GNU() *headerGNU { return (*headerGNU)(b) }
|
|
func (b *block) STAR() *headerSTAR { return (*headerSTAR)(b) }
|
|
func (b *block) USTAR() *headerUSTAR { return (*headerUSTAR)(b) }
|
|
func (b *block) Sparse() sparseArray { return (sparseArray)(b[:]) }
|
|
|
|
// GetFormat checks that the block is a valid tar header based on the checksum.
|
|
// It then attempts to guess the specific format based on magic values.
|
|
// If the checksum fails, then formatUnknown is returned.
|
|
func (b *block) GetFormat() (format int) {
|
|
// Verify checksum.
|
|
var p parser
|
|
value := p.parseOctal(b.V7().Chksum())
|
|
chksum1, chksum2 := b.ComputeChecksum()
|
|
if p.err != nil || (value != chksum1 && value != chksum2) {
|
|
return formatUnknown
|
|
}
|
|
|
|
// Guess the magic values.
|
|
magic := string(b.USTAR().Magic())
|
|
version := string(b.USTAR().Version())
|
|
trailer := string(b.STAR().Trailer())
|
|
switch {
|
|
case magic == magicUSTAR && trailer == trailerSTAR:
|
|
return formatSTAR
|
|
case magic == magicUSTAR:
|
|
return formatUSTAR
|
|
case magic == magicGNU && version == versionGNU:
|
|
return formatGNU
|
|
default:
|
|
return formatV7
|
|
}
|
|
}
|
|
|
|
// SetFormat writes the magic values necessary for specified format
|
|
// and then updates the checksum accordingly.
|
|
func (b *block) SetFormat(format int) {
|
|
// Set the magic values.
|
|
switch format {
|
|
case formatV7:
|
|
// Do nothing.
|
|
case formatGNU:
|
|
copy(b.GNU().Magic(), magicGNU)
|
|
copy(b.GNU().Version(), versionGNU)
|
|
case formatSTAR:
|
|
copy(b.STAR().Magic(), magicUSTAR)
|
|
copy(b.STAR().Version(), versionUSTAR)
|
|
copy(b.STAR().Trailer(), trailerSTAR)
|
|
case formatUSTAR, formatPAX:
|
|
copy(b.USTAR().Magic(), magicUSTAR)
|
|
copy(b.USTAR().Version(), versionUSTAR)
|
|
default:
|
|
panic("invalid format")
|
|
}
|
|
|
|
// Update checksum.
|
|
// This field is special in that it is terminated by a NULL then space.
|
|
var f formatter
|
|
field := b.V7().Chksum()
|
|
chksum, _ := b.ComputeChecksum() // Possible values are 256..128776
|
|
f.formatOctal(field[:7], chksum) // Never fails since 128776 < 262143
|
|
field[7] = ' '
|
|
}
|
|
|
|
// ComputeChecksum computes the checksum for the header block.
|
|
// POSIX specifies a sum of the unsigned byte values, but the Sun tar used
|
|
// signed byte values.
|
|
// We compute and return both.
|
|
func (b *block) ComputeChecksum() (unsigned, signed int64) {
|
|
for i, c := range b {
|
|
if 148 <= i && i < 156 {
|
|
c = ' ' // Treat the checksum field itself as all spaces.
|
|
}
|
|
unsigned += int64(uint8(c))
|
|
signed += int64(int8(c))
|
|
}
|
|
return unsigned, signed
|
|
}
|
|
|
|
type headerV7 [blockSize]byte
|
|
|
|
func (h *headerV7) Name() []byte { return h[000:][:100] }
|
|
func (h *headerV7) Mode() []byte { return h[100:][:8] }
|
|
func (h *headerV7) UID() []byte { return h[108:][:8] }
|
|
func (h *headerV7) GID() []byte { return h[116:][:8] }
|
|
func (h *headerV7) Size() []byte { return h[124:][:12] }
|
|
func (h *headerV7) ModTime() []byte { return h[136:][:12] }
|
|
func (h *headerV7) Chksum() []byte { return h[148:][:8] }
|
|
func (h *headerV7) TypeFlag() []byte { return h[156:][:1] }
|
|
func (h *headerV7) LinkName() []byte { return h[157:][:100] }
|
|
|
|
type headerGNU [blockSize]byte
|
|
|
|
func (h *headerGNU) V7() *headerV7 { return (*headerV7)(h) }
|
|
func (h *headerGNU) Magic() []byte { return h[257:][:6] }
|
|
func (h *headerGNU) Version() []byte { return h[263:][:2] }
|
|
func (h *headerGNU) UserName() []byte { return h[265:][:32] }
|
|
func (h *headerGNU) GroupName() []byte { return h[297:][:32] }
|
|
func (h *headerGNU) DevMajor() []byte { return h[329:][:8] }
|
|
func (h *headerGNU) DevMinor() []byte { return h[337:][:8] }
|
|
func (h *headerGNU) AccessTime() []byte { return h[345:][:12] }
|
|
func (h *headerGNU) ChangeTime() []byte { return h[357:][:12] }
|
|
func (h *headerGNU) Sparse() sparseArray { return (sparseArray)(h[386:][:24*4+1]) }
|
|
func (h *headerGNU) RealSize() []byte { return h[483:][:12] }
|
|
|
|
type headerSTAR [blockSize]byte
|
|
|
|
func (h *headerSTAR) V7() *headerV7 { return (*headerV7)(h) }
|
|
func (h *headerSTAR) Magic() []byte { return h[257:][:6] }
|
|
func (h *headerSTAR) Version() []byte { return h[263:][:2] }
|
|
func (h *headerSTAR) UserName() []byte { return h[265:][:32] }
|
|
func (h *headerSTAR) GroupName() []byte { return h[297:][:32] }
|
|
func (h *headerSTAR) DevMajor() []byte { return h[329:][:8] }
|
|
func (h *headerSTAR) DevMinor() []byte { return h[337:][:8] }
|
|
func (h *headerSTAR) Prefix() []byte { return h[345:][:131] }
|
|
func (h *headerSTAR) AccessTime() []byte { return h[476:][:12] }
|
|
func (h *headerSTAR) ChangeTime() []byte { return h[488:][:12] }
|
|
func (h *headerSTAR) Trailer() []byte { return h[508:][:4] }
|
|
|
|
type headerUSTAR [blockSize]byte
|
|
|
|
func (h *headerUSTAR) V7() *headerV7 { return (*headerV7)(h) }
|
|
func (h *headerUSTAR) Magic() []byte { return h[257:][:6] }
|
|
func (h *headerUSTAR) Version() []byte { return h[263:][:2] }
|
|
func (h *headerUSTAR) UserName() []byte { return h[265:][:32] }
|
|
func (h *headerUSTAR) GroupName() []byte { return h[297:][:32] }
|
|
func (h *headerUSTAR) DevMajor() []byte { return h[329:][:8] }
|
|
func (h *headerUSTAR) DevMinor() []byte { return h[337:][:8] }
|
|
func (h *headerUSTAR) Prefix() []byte { return h[345:][:155] }
|
|
|
|
type sparseArray []byte
|
|
|
|
func (s sparseArray) Entry(i int) sparseNode { return (sparseNode)(s[i*24:]) }
|
|
func (s sparseArray) IsExtended() []byte { return s[24*s.MaxEntries():][:1] }
|
|
func (s sparseArray) MaxEntries() int { return len(s) / 24 }
|
|
|
|
type sparseNode []byte
|
|
|
|
func (s sparseNode) Offset() []byte { return s[00:][:12] }
|
|
func (s sparseNode) NumBytes() []byte { return s[12:][:12] }
|