mirror of
https://github.com/vbatts/tar-split.git
synced 2024-12-24 06:16:31 +00:00
6e38573de2
Write should return ErrWriteAfterClose instead of ErrWriteTooLong when called after Close. Change-Id: If5ec4ef924e4c56489e0d426976f7e5fad79be9b Reviewed-on: https://go-review.googlesource.com/9259 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> Signed-off-by: Vincent Batts <vbatts@hashbangbash.com>
396 lines
12 KiB
Go
396 lines
12 KiB
Go
// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package tar
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// TODO(dsymonds):
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// - catch more errors (no first header, etc.)
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import (
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"bytes"
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"errors"
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"fmt"
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"io"
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"os"
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"path"
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"strconv"
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"strings"
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"time"
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)
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var (
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ErrWriteTooLong = errors.New("archive/tar: write too long")
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ErrFieldTooLong = errors.New("archive/tar: header field too long")
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ErrWriteAfterClose = errors.New("archive/tar: write after close")
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errNameTooLong = errors.New("archive/tar: name too long")
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errInvalidHeader = errors.New("archive/tar: header field too long or contains invalid values")
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)
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// A Writer provides sequential writing of a tar archive in POSIX.1 format.
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// A tar archive consists of a sequence of files.
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// Call WriteHeader to begin a new file, and then call Write to supply that file's data,
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// writing at most hdr.Size bytes in total.
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type Writer struct {
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w io.Writer
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err error
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nb int64 // number of unwritten bytes for current file entry
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pad int64 // amount of padding to write after current file entry
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closed bool
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usedBinary bool // whether the binary numeric field extension was used
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preferPax bool // use pax header instead of binary numeric header
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hdrBuff [blockSize]byte // buffer to use in writeHeader when writing a regular header
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paxHdrBuff [blockSize]byte // buffer to use in writeHeader when writing a pax header
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}
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// NewWriter creates a new Writer writing to w.
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func NewWriter(w io.Writer) *Writer { return &Writer{w: w} }
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// Flush finishes writing the current file (optional).
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func (tw *Writer) Flush() error {
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if tw.nb > 0 {
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tw.err = fmt.Errorf("archive/tar: missed writing %d bytes", tw.nb)
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return tw.err
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}
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n := tw.nb + tw.pad
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for n > 0 && tw.err == nil {
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nr := n
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if nr > blockSize {
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nr = blockSize
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}
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var nw int
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nw, tw.err = tw.w.Write(zeroBlock[0:nr])
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n -= int64(nw)
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}
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tw.nb = 0
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tw.pad = 0
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return tw.err
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}
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// Write s into b, terminating it with a NUL if there is room.
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// If the value is too long for the field and allowPax is true add a paxheader record instead
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func (tw *Writer) cString(b []byte, s string, allowPax bool, paxKeyword string, paxHeaders map[string]string) {
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needsPaxHeader := allowPax && len(s) > len(b) || !isASCII(s)
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if needsPaxHeader {
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paxHeaders[paxKeyword] = s
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return
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}
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if len(s) > len(b) {
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if tw.err == nil {
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tw.err = ErrFieldTooLong
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}
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return
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}
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ascii := toASCII(s)
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copy(b, ascii)
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if len(ascii) < len(b) {
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b[len(ascii)] = 0
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}
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}
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// Encode x as an octal ASCII string and write it into b with leading zeros.
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func (tw *Writer) octal(b []byte, x int64) {
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s := strconv.FormatInt(x, 8)
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// leading zeros, but leave room for a NUL.
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for len(s)+1 < len(b) {
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s = "0" + s
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}
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tw.cString(b, s, false, paxNone, nil)
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}
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// Write x into b, either as octal or as binary (GNUtar/star extension).
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// If the value is too long for the field and writingPax is enabled both for the field and the add a paxheader record instead
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func (tw *Writer) numeric(b []byte, x int64, allowPax bool, paxKeyword string, paxHeaders map[string]string) {
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// Try octal first.
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s := strconv.FormatInt(x, 8)
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if len(s) < len(b) {
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tw.octal(b, x)
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return
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}
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// If it is too long for octal, and pax is preferred, use a pax header
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if allowPax && tw.preferPax {
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tw.octal(b, 0)
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s := strconv.FormatInt(x, 10)
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paxHeaders[paxKeyword] = s
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return
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}
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// Too big: use binary (big-endian).
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tw.usedBinary = true
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for i := len(b) - 1; x > 0 && i >= 0; i-- {
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b[i] = byte(x)
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x >>= 8
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}
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b[0] |= 0x80 // highest bit indicates binary format
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}
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var (
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minTime = time.Unix(0, 0)
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// There is room for 11 octal digits (33 bits) of mtime.
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maxTime = minTime.Add((1<<33 - 1) * time.Second)
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)
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// WriteHeader writes hdr and prepares to accept the file's contents.
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// WriteHeader calls Flush if it is not the first header.
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// Calling after a Close will return ErrWriteAfterClose.
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func (tw *Writer) WriteHeader(hdr *Header) error {
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return tw.writeHeader(hdr, true)
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}
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// WriteHeader writes hdr and prepares to accept the file's contents.
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// WriteHeader calls Flush if it is not the first header.
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// Calling after a Close will return ErrWriteAfterClose.
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// As this method is called internally by writePax header to allow it to
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// suppress writing the pax header.
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func (tw *Writer) writeHeader(hdr *Header, allowPax bool) error {
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if tw.closed {
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return ErrWriteAfterClose
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}
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if tw.err == nil {
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tw.Flush()
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}
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if tw.err != nil {
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return tw.err
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}
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// a map to hold pax header records, if any are needed
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paxHeaders := make(map[string]string)
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// TODO(shanemhansen): we might want to use PAX headers for
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// subsecond time resolution, but for now let's just capture
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// too long fields or non ascii characters
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var header []byte
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// We need to select which scratch buffer to use carefully,
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// since this method is called recursively to write PAX headers.
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// If allowPax is true, this is the non-recursive call, and we will use hdrBuff.
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// If allowPax is false, we are being called by writePAXHeader, and hdrBuff is
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// already being used by the non-recursive call, so we must use paxHdrBuff.
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header = tw.hdrBuff[:]
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if !allowPax {
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header = tw.paxHdrBuff[:]
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}
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copy(header, zeroBlock)
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s := slicer(header)
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// keep a reference to the filename to allow to overwrite it later if we detect that we can use ustar longnames instead of pax
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pathHeaderBytes := s.next(fileNameSize)
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tw.cString(pathHeaderBytes, hdr.Name, true, paxPath, paxHeaders)
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// Handle out of range ModTime carefully.
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var modTime int64
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if !hdr.ModTime.Before(minTime) && !hdr.ModTime.After(maxTime) {
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modTime = hdr.ModTime.Unix()
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}
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tw.octal(s.next(8), hdr.Mode) // 100:108
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tw.numeric(s.next(8), int64(hdr.Uid), true, paxUid, paxHeaders) // 108:116
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tw.numeric(s.next(8), int64(hdr.Gid), true, paxGid, paxHeaders) // 116:124
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tw.numeric(s.next(12), hdr.Size, true, paxSize, paxHeaders) // 124:136
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tw.numeric(s.next(12), modTime, false, paxNone, nil) // 136:148 --- consider using pax for finer granularity
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s.next(8) // chksum (148:156)
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s.next(1)[0] = hdr.Typeflag // 156:157
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tw.cString(s.next(100), hdr.Linkname, true, paxLinkpath, paxHeaders)
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copy(s.next(8), []byte("ustar\x0000")) // 257:265
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tw.cString(s.next(32), hdr.Uname, true, paxUname, paxHeaders) // 265:297
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tw.cString(s.next(32), hdr.Gname, true, paxGname, paxHeaders) // 297:329
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tw.numeric(s.next(8), hdr.Devmajor, false, paxNone, nil) // 329:337
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tw.numeric(s.next(8), hdr.Devminor, false, paxNone, nil) // 337:345
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// keep a reference to the prefix to allow to overwrite it later if we detect that we can use ustar longnames instead of pax
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prefixHeaderBytes := s.next(155)
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tw.cString(prefixHeaderBytes, "", false, paxNone, nil) // 345:500 prefix
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// Use the GNU magic instead of POSIX magic if we used any GNU extensions.
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if tw.usedBinary {
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copy(header[257:265], []byte("ustar \x00"))
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}
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_, paxPathUsed := paxHeaders[paxPath]
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// try to use a ustar header when only the name is too long
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if !tw.preferPax && len(paxHeaders) == 1 && paxPathUsed {
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suffix := hdr.Name
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prefix := ""
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if len(hdr.Name) > fileNameSize && isASCII(hdr.Name) {
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var err error
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prefix, suffix, err = tw.splitUSTARLongName(hdr.Name)
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if err == nil {
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// ok we can use a ustar long name instead of pax, now correct the fields
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// remove the path field from the pax header. this will suppress the pax header
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delete(paxHeaders, paxPath)
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// update the path fields
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tw.cString(pathHeaderBytes, suffix, false, paxNone, nil)
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tw.cString(prefixHeaderBytes, prefix, false, paxNone, nil)
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// Use the ustar magic if we used ustar long names.
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if len(prefix) > 0 && !tw.usedBinary {
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copy(header[257:265], []byte("ustar\x00"))
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}
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}
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}
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}
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// The chksum field is terminated by a NUL and a space.
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// This is different from the other octal fields.
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chksum, _ := checksum(header)
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tw.octal(header[148:155], chksum)
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header[155] = ' '
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if tw.err != nil {
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// problem with header; probably integer too big for a field.
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return tw.err
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}
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if allowPax {
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for k, v := range hdr.Xattrs {
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paxHeaders[paxXattr+k] = v
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}
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}
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if len(paxHeaders) > 0 {
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if !allowPax {
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return errInvalidHeader
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}
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if err := tw.writePAXHeader(hdr, paxHeaders); err != nil {
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return err
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}
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}
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tw.nb = int64(hdr.Size)
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tw.pad = (blockSize - (tw.nb % blockSize)) % blockSize
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_, tw.err = tw.w.Write(header)
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return tw.err
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}
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// writeUSTARLongName splits a USTAR long name hdr.Name.
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// name must be < 256 characters. errNameTooLong is returned
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// if hdr.Name can't be split. The splitting heuristic
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// is compatible with gnu tar.
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func (tw *Writer) splitUSTARLongName(name string) (prefix, suffix string, err error) {
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length := len(name)
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if length > fileNamePrefixSize+1 {
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length = fileNamePrefixSize + 1
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} else if name[length-1] == '/' {
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length--
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}
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i := strings.LastIndex(name[:length], "/")
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// nlen contains the resulting length in the name field.
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// plen contains the resulting length in the prefix field.
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nlen := len(name) - i - 1
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plen := i
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if i <= 0 || nlen > fileNameSize || nlen == 0 || plen > fileNamePrefixSize {
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err = errNameTooLong
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return
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}
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prefix, suffix = name[:i], name[i+1:]
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return
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}
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// writePaxHeader writes an extended pax header to the
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// archive.
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func (tw *Writer) writePAXHeader(hdr *Header, paxHeaders map[string]string) error {
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// Prepare extended header
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ext := new(Header)
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ext.Typeflag = TypeXHeader
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// Setting ModTime is required for reader parsing to
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// succeed, and seems harmless enough.
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ext.ModTime = hdr.ModTime
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// The spec asks that we namespace our pseudo files
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// with the current pid.
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pid := os.Getpid()
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dir, file := path.Split(hdr.Name)
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fullName := path.Join(dir,
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fmt.Sprintf("PaxHeaders.%d", pid), file)
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ascii := toASCII(fullName)
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if len(ascii) > 100 {
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ascii = ascii[:100]
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}
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ext.Name = ascii
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// Construct the body
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var buf bytes.Buffer
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for k, v := range paxHeaders {
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fmt.Fprint(&buf, paxHeader(k+"="+v))
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}
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ext.Size = int64(len(buf.Bytes()))
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if err := tw.writeHeader(ext, false); err != nil {
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return err
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}
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if _, err := tw.Write(buf.Bytes()); err != nil {
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return err
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}
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if err := tw.Flush(); err != nil {
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return err
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}
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return nil
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}
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// paxHeader formats a single pax record, prefixing it with the appropriate length
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func paxHeader(msg string) string {
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const padding = 2 // Extra padding for space and newline
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size := len(msg) + padding
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size += len(strconv.Itoa(size))
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record := fmt.Sprintf("%d %s\n", size, msg)
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if len(record) != size {
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// Final adjustment if adding size increased
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// the number of digits in size
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size = len(record)
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record = fmt.Sprintf("%d %s\n", size, msg)
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}
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return record
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}
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// Write writes to the current entry in the tar archive.
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// Write returns the error ErrWriteTooLong if more than
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// hdr.Size bytes are written after WriteHeader.
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func (tw *Writer) Write(b []byte) (n int, err error) {
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if tw.closed {
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err = ErrWriteAfterClose
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return
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}
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overwrite := false
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if int64(len(b)) > tw.nb {
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b = b[0:tw.nb]
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overwrite = true
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}
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n, err = tw.w.Write(b)
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tw.nb -= int64(n)
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if err == nil && overwrite {
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err = ErrWriteTooLong
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return
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}
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tw.err = err
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return
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}
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// Close closes the tar archive, flushing any unwritten
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// data to the underlying writer.
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func (tw *Writer) Close() error {
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if tw.err != nil || tw.closed {
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return tw.err
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}
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tw.Flush()
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tw.closed = true
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if tw.err != nil {
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return tw.err
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}
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// trailer: two zero blocks
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for i := 0; i < 2; i++ {
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_, tw.err = tw.w.Write(zeroBlock)
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if tw.err != nil {
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break
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}
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}
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return tw.err
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}
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