From 73df946d56c74384511a194dd01dbe099584fd1a Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 28 Apr 2024 15:14:23 +0200 Subject: Adding upstream version 1.16.10. Signed-off-by: Daniel Baumann --- src/archive/tar/reader.go | 857 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 857 insertions(+) create mode 100644 src/archive/tar/reader.go (limited to 'src/archive/tar/reader.go') diff --git a/src/archive/tar/reader.go b/src/archive/tar/reader.go new file mode 100644 index 0000000..1b1d5b4 --- /dev/null +++ b/src/archive/tar/reader.go @@ -0,0 +1,857 @@ +// Copyright 2009 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 + +import ( + "bytes" + "io" + "strconv" + "strings" + "time" +) + +// Reader provides sequential access to the contents of a tar archive. +// Reader.Next advances to the next file in the archive (including the first), +// and then Reader can be treated as an io.Reader to access the file's data. +type Reader struct { + r io.Reader + pad int64 // Amount of padding (ignored) after current file entry + curr fileReader // Reader for current file entry + blk block // Buffer to use as temporary local storage + + // err is a persistent error. + // It is only the responsibility of every exported method of Reader to + // ensure that this error is sticky. + err error +} + +type fileReader interface { + io.Reader + fileState + + WriteTo(io.Writer) (int64, error) +} + +// NewReader creates a new Reader reading from r. +func NewReader(r io.Reader) *Reader { + return &Reader{r: r, curr: ®FileReader{r, 0}} +} + +// Next advances to the next entry in the tar archive. +// The Header.Size determines how many bytes can be read for the next file. +// Any remaining data in the current file is automatically discarded. +// +// io.EOF is returned at the end of the input. +func (tr *Reader) Next() (*Header, error) { + if tr.err != nil { + return nil, tr.err + } + hdr, err := tr.next() + tr.err = err + return hdr, err +} + +func (tr *Reader) next() (*Header, error) { + var paxHdrs map[string]string + var gnuLongName, gnuLongLink 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". + format := FormatUSTAR | FormatPAX | FormatGNU + for { + // Discard the remainder of the file and any padding. + if err := discard(tr.r, tr.curr.PhysicalRemaining()); err != nil { + return nil, err + } + if _, err := tryReadFull(tr.r, tr.blk[:tr.pad]); err != nil { + return nil, err + } + tr.pad = 0 + + hdr, rawHdr, err := tr.readHeader() + if err != nil { + return nil, err + } + if err := tr.handleRegularFile(hdr); err != nil { + return nil, err + } + format.mayOnlyBe(hdr.Format) + + // Check for PAX/GNU special headers and files. + switch hdr.Typeflag { + case TypeXHeader, TypeXGlobalHeader: + format.mayOnlyBe(FormatPAX) + paxHdrs, err = parsePAX(tr) + if err != nil { + return nil, err + } + if hdr.Typeflag == TypeXGlobalHeader { + mergePAX(hdr, paxHdrs) + return &Header{ + Name: hdr.Name, + Typeflag: hdr.Typeflag, + Xattrs: hdr.Xattrs, + PAXRecords: hdr.PAXRecords, + Format: format, + }, nil + } + continue // This is a meta header affecting the next header + case TypeGNULongName, TypeGNULongLink: + format.mayOnlyBe(FormatGNU) + realname, err := io.ReadAll(tr) + if err != nil { + return nil, err + } + + var p parser + switch hdr.Typeflag { + case TypeGNULongName: + gnuLongName = p.parseString(realname) + case TypeGNULongLink: + gnuLongLink = p.parseString(realname) + } + continue // This is a meta header affecting the next header + default: + // The old GNU sparse format is handled here since it is technically + // just a regular file with additional attributes. + + if err := mergePAX(hdr, paxHdrs); err != nil { + return nil, err + } + if gnuLongName != "" { + hdr.Name = gnuLongName + } + if gnuLongLink != "" { + hdr.Linkname = gnuLongLink + } + if hdr.Typeflag == TypeRegA { + if strings.HasSuffix(hdr.Name, "/") { + hdr.Typeflag = TypeDir // Legacy archives use trailing slash for directories + } else { + hdr.Typeflag = TypeReg + } + } + + // The extended headers may have updated the size. + // Thus, setup the regFileReader again after merging PAX headers. + if err := tr.handleRegularFile(hdr); err != nil { + return nil, err + } + + // Sparse formats rely on being able to read from the logical data + // section; there must be a preceding call to handleRegularFile. + if err := tr.handleSparseFile(hdr, rawHdr); err != nil { + return nil, err + } + + // Set the final guess at the format. + if format.has(FormatUSTAR) && format.has(FormatPAX) { + format.mayOnlyBe(FormatUSTAR) + } + hdr.Format = format + return hdr, nil // This is a file, so stop + } + } +} + +// handleRegularFile sets up the current file reader and padding such that it +// can only read the following logical data section. It will properly handle +// special headers that contain no data section. +func (tr *Reader) handleRegularFile(hdr *Header) error { + nb := hdr.Size + if isHeaderOnlyType(hdr.Typeflag) { + nb = 0 + } + if nb < 0 { + return ErrHeader + } + + tr.pad = blockPadding(nb) + tr.curr = ®FileReader{r: tr.r, nb: nb} + return nil +} + +// handleSparseFile checks if the current file is a sparse format of any type +// and sets the curr reader appropriately. +func (tr *Reader) handleSparseFile(hdr *Header, rawHdr *block) error { + var spd sparseDatas + var err error + if hdr.Typeflag == TypeGNUSparse { + spd, err = tr.readOldGNUSparseMap(hdr, rawHdr) + } else { + spd, err = tr.readGNUSparsePAXHeaders(hdr) + } + + // If sp is non-nil, then this is a sparse file. + // Note that it is possible for len(sp) == 0. + if err == nil && spd != nil { + if isHeaderOnlyType(hdr.Typeflag) || !validateSparseEntries(spd, hdr.Size) { + return ErrHeader + } + sph := invertSparseEntries(spd, hdr.Size) + tr.curr = &sparseFileReader{tr.curr, sph, 0} + } + return err +} + +// readGNUSparsePAXHeaders checks the PAX headers for GNU sparse headers. +// If they are found, then this function reads the sparse map and returns it. +// This assumes that 0.0 headers have already been converted to 0.1 headers +// by the PAX header parsing logic. +func (tr *Reader) readGNUSparsePAXHeaders(hdr *Header) (sparseDatas, error) { + // Identify the version of GNU headers. + var is1x0 bool + major, minor := hdr.PAXRecords[paxGNUSparseMajor], hdr.PAXRecords[paxGNUSparseMinor] + switch { + case major == "0" && (minor == "0" || minor == "1"): + is1x0 = false + case major == "1" && minor == "0": + is1x0 = true + case major != "" || minor != "": + return nil, nil // Unknown GNU sparse PAX version + case hdr.PAXRecords[paxGNUSparseMap] != "": + is1x0 = false // 0.0 and 0.1 did not have explicit version records, so guess + default: + return nil, nil // Not a PAX format GNU sparse file. + } + hdr.Format.mayOnlyBe(FormatPAX) + + // Update hdr from GNU sparse PAX headers. + if name := hdr.PAXRecords[paxGNUSparseName]; name != "" { + hdr.Name = name + } + size := hdr.PAXRecords[paxGNUSparseSize] + if size == "" { + size = hdr.PAXRecords[paxGNUSparseRealSize] + } + if size != "" { + n, err := strconv.ParseInt(size, 10, 64) + if err != nil { + return nil, ErrHeader + } + hdr.Size = n + } + + // Read the sparse map according to the appropriate format. + if is1x0 { + return readGNUSparseMap1x0(tr.curr) + } + return readGNUSparseMap0x1(hdr.PAXRecords) +} + +// mergePAX merges paxHdrs into hdr for all relevant fields of Header. +func mergePAX(hdr *Header, paxHdrs map[string]string) (err error) { + for k, v := range paxHdrs { + if v == "" { + continue // Keep the original USTAR value + } + var id64 int64 + switch k { + case paxPath: + hdr.Name = v + case paxLinkpath: + hdr.Linkname = v + case paxUname: + hdr.Uname = v + case paxGname: + hdr.Gname = v + case paxUid: + id64, err = strconv.ParseInt(v, 10, 64) + hdr.Uid = int(id64) // Integer overflow possible + case paxGid: + id64, err = strconv.ParseInt(v, 10, 64) + hdr.Gid = int(id64) // Integer overflow possible + case paxAtime: + hdr.AccessTime, err = parsePAXTime(v) + case paxMtime: + hdr.ModTime, err = parsePAXTime(v) + case paxCtime: + hdr.ChangeTime, err = parsePAXTime(v) + case paxSize: + hdr.Size, err = strconv.ParseInt(v, 10, 64) + default: + if strings.HasPrefix(k, paxSchilyXattr) { + if hdr.Xattrs == nil { + hdr.Xattrs = make(map[string]string) + } + hdr.Xattrs[k[len(paxSchilyXattr):]] = v + } + } + if err != nil { + return ErrHeader + } + } + hdr.PAXRecords = paxHdrs + return nil +} + +// parsePAX parses PAX headers. +// If an extended header (type 'x') is invalid, ErrHeader is returned +func parsePAX(r io.Reader) (map[string]string, error) { + buf, err := io.ReadAll(r) + if err != nil { + return nil, err + } + sbuf := string(buf) + + // For GNU PAX sparse format 0.0 support. + // This function transforms the sparse format 0.0 headers into format 0.1 + // headers since 0.0 headers were not PAX compliant. + var sparseMap []string + + paxHdrs := make(map[string]string) + for len(sbuf) > 0 { + key, value, residual, err := parsePAXRecord(sbuf) + if err != nil { + return nil, ErrHeader + } + sbuf = residual + + switch key { + case paxGNUSparseOffset, paxGNUSparseNumBytes: + // Validate sparse header order and value. + if (len(sparseMap)%2 == 0 && key != paxGNUSparseOffset) || + (len(sparseMap)%2 == 1 && key != paxGNUSparseNumBytes) || + strings.Contains(value, ",") { + return nil, ErrHeader + } + sparseMap = append(sparseMap, value) + default: + paxHdrs[key] = value + } + } + if len(sparseMap) > 0 { + paxHdrs[paxGNUSparseMap] = strings.Join(sparseMap, ",") + } + return paxHdrs, nil +} + +// readHeader reads the next block header and assumes that the underlying reader +// is already aligned to a block boundary. It returns the raw block of the +// header in case further processing is required. +// +// The err will be set to io.EOF only when one of the following occurs: +// * Exactly 0 bytes are read and EOF is hit. +// * Exactly 1 block of zeros is read and EOF is hit. +// * At least 2 blocks of zeros are read. +func (tr *Reader) readHeader() (*Header, *block, error) { + // Two blocks of zero bytes marks the end of the archive. + if _, err := io.ReadFull(tr.r, tr.blk[:]); err != nil { + return nil, nil, err // EOF is okay here; exactly 0 bytes read + } + if bytes.Equal(tr.blk[:], zeroBlock[:]) { + if _, err := io.ReadFull(tr.r, tr.blk[:]); err != nil { + return nil, nil, err // EOF is okay here; exactly 1 block of zeros read + } + if bytes.Equal(tr.blk[:], zeroBlock[:]) { + return nil, nil, io.EOF // normal EOF; exactly 2 block of zeros read + } + return nil, nil, ErrHeader // Zero block and then non-zero block + } + + // Verify the header matches a known format. + format := tr.blk.GetFormat() + if format == FormatUnknown { + return nil, nil, ErrHeader + } + + var p parser + hdr := new(Header) + + // Unpack the V7 header. + v7 := tr.blk.V7() + hdr.Typeflag = v7.TypeFlag()[0] + hdr.Name = p.parseString(v7.Name()) + hdr.Linkname = p.parseString(v7.LinkName()) + hdr.Size = p.parseNumeric(v7.Size()) + hdr.Mode = p.parseNumeric(v7.Mode()) + hdr.Uid = int(p.parseNumeric(v7.UID())) + hdr.Gid = int(p.parseNumeric(v7.GID())) + hdr.ModTime = time.Unix(p.parseNumeric(v7.ModTime()), 0) + + // Unpack format specific fields. + if format > formatV7 { + ustar := tr.blk.USTAR() + hdr.Uname = p.parseString(ustar.UserName()) + hdr.Gname = p.parseString(ustar.GroupName()) + hdr.Devmajor = p.parseNumeric(ustar.DevMajor()) + hdr.Devminor = p.parseNumeric(ustar.DevMinor()) + + var prefix string + switch { + case format.has(FormatUSTAR | FormatPAX): + hdr.Format = format + ustar := tr.blk.USTAR() + prefix = p.parseString(ustar.Prefix()) + + // For Format detection, check if block is properly formatted since + // the parser is more liberal than what USTAR actually permits. + notASCII := func(r rune) bool { return r >= 0x80 } + if bytes.IndexFunc(tr.blk[:], notASCII) >= 0 { + hdr.Format = FormatUnknown // Non-ASCII characters in block. + } + nul := func(b []byte) bool { return int(b[len(b)-1]) == 0 } + if !(nul(v7.Size()) && nul(v7.Mode()) && nul(v7.UID()) && nul(v7.GID()) && + nul(v7.ModTime()) && nul(ustar.DevMajor()) && nul(ustar.DevMinor())) { + hdr.Format = FormatUnknown // Numeric fields must end in NUL + } + case format.has(formatSTAR): + star := tr.blk.STAR() + prefix = p.parseString(star.Prefix()) + hdr.AccessTime = time.Unix(p.parseNumeric(star.AccessTime()), 0) + hdr.ChangeTime = time.Unix(p.parseNumeric(star.ChangeTime()), 0) + case format.has(FormatGNU): + hdr.Format = format + var p2 parser + gnu := tr.blk.GNU() + if b := gnu.AccessTime(); b[0] != 0 { + hdr.AccessTime = time.Unix(p2.parseNumeric(b), 0) + } + if b := gnu.ChangeTime(); b[0] != 0 { + hdr.ChangeTime = time.Unix(p2.parseNumeric(b), 0) + } + + // Prior to Go1.8, the Writer had a bug where it would output + // an invalid tar file in certain rare situations because the logic + // incorrectly believed that the old GNU format had a prefix field. + // This is wrong and leads to an output file that mangles the + // atime and ctime fields, which are often left unused. + // + // In order to continue reading tar files created by former, buggy + // versions of Go, we skeptically parse the atime and ctime fields. + // If we are unable to parse them and the prefix field looks like + // an ASCII string, then we fallback on the pre-Go1.8 behavior + // of treating these fields as the USTAR prefix field. + // + // Note that this will not use the fallback logic for all possible + // files generated by a pre-Go1.8 toolchain. If the generated file + // happened to have a prefix field that parses as valid + // atime and ctime fields (e.g., when they are valid octal strings), + // then it is impossible to distinguish between a valid GNU file + // and an invalid pre-Go1.8 file. + // + // See https://golang.org/issues/12594 + // See https://golang.org/issues/21005 + if p2.err != nil { + hdr.AccessTime, hdr.ChangeTime = time.Time{}, time.Time{} + ustar := tr.blk.USTAR() + if s := p.parseString(ustar.Prefix()); isASCII(s) { + prefix = s + } + hdr.Format = FormatUnknown // Buggy file is not GNU + } + } + if len(prefix) > 0 { + hdr.Name = prefix + "/" + hdr.Name + } + } + return hdr, &tr.blk, p.err +} + +// readOldGNUSparseMap reads the sparse map from the old GNU sparse format. +// The sparse map is stored in the tar header if it's small enough. +// If it's larger than four entries, then one or more extension headers are used +// to store the rest of the sparse map. +// +// The Header.Size does not reflect the size of any extended headers used. +// Thus, this function will read from the raw io.Reader to fetch extra headers. +// This method mutates blk in the process. +func (tr *Reader) readOldGNUSparseMap(hdr *Header, blk *block) (sparseDatas, error) { + // Make sure that the input format is GNU. + // Unfortunately, the STAR format also has a sparse header format that uses + // the same type flag but has a completely different layout. + if blk.GetFormat() != FormatGNU { + return nil, ErrHeader + } + hdr.Format.mayOnlyBe(FormatGNU) + + var p parser + hdr.Size = p.parseNumeric(blk.GNU().RealSize()) + if p.err != nil { + return nil, p.err + } + s := blk.GNU().Sparse() + spd := make(sparseDatas, 0, s.MaxEntries()) + for { + for i := 0; i < s.MaxEntries(); i++ { + // This termination condition is identical to GNU and BSD tar. + if s.Entry(i).Offset()[0] == 0x00 { + break // Don't return, need to process extended headers (even if empty) + } + offset := p.parseNumeric(s.Entry(i).Offset()) + length := p.parseNumeric(s.Entry(i).Length()) + if p.err != nil { + return nil, p.err + } + spd = append(spd, sparseEntry{Offset: offset, Length: length}) + } + + if s.IsExtended()[0] > 0 { + // There are more entries. Read an extension header and parse its entries. + if _, err := mustReadFull(tr.r, blk[:]); err != nil { + return nil, err + } + s = blk.Sparse() + continue + } + return spd, nil // Done + } +} + +// readGNUSparseMap1x0 reads the sparse map as stored in GNU's PAX sparse format +// version 1.0. The format of the sparse map consists of a series of +// newline-terminated numeric fields. The first field is the number of entries +// and is always present. Following this are the entries, consisting of two +// fields (offset, length). This function must stop reading at the end +// boundary of the block containing the last newline. +// +// Note that the GNU manual says that numeric values should be encoded in octal +// format. However, the GNU tar utility itself outputs these values in decimal. +// As such, this library treats values as being encoded in decimal. +func readGNUSparseMap1x0(r io.Reader) (sparseDatas, error) { + var ( + cntNewline int64 + buf bytes.Buffer + blk block + ) + + // feedTokens copies data in blocks from r into buf until there are + // at least cnt newlines in buf. It will not read more blocks than needed. + feedTokens := func(n int64) error { + for cntNewline < n { + if _, err := mustReadFull(r, blk[:]); err != nil { + return err + } + buf.Write(blk[:]) + for _, c := range blk { + if c == '\n' { + cntNewline++ + } + } + } + return nil + } + + // nextToken gets the next token delimited by a newline. This assumes that + // at least one newline exists in the buffer. + nextToken := func() string { + cntNewline-- + tok, _ := buf.ReadString('\n') + return strings.TrimRight(tok, "\n") + } + + // Parse for the number of entries. + // Use integer overflow resistant math to check this. + if err := feedTokens(1); err != nil { + return nil, err + } + numEntries, err := strconv.ParseInt(nextToken(), 10, 0) // Intentionally parse as native int + if err != nil || numEntries < 0 || int(2*numEntries) < int(numEntries) { + return nil, ErrHeader + } + + // Parse for all member entries. + // numEntries is trusted after this since a potential attacker must have + // committed resources proportional to what this library used. + if err := feedTokens(2 * numEntries); err != nil { + return nil, err + } + spd := make(sparseDatas, 0, numEntries) + for i := int64(0); i < numEntries; i++ { + offset, err1 := strconv.ParseInt(nextToken(), 10, 64) + length, err2 := strconv.ParseInt(nextToken(), 10, 64) + if err1 != nil || err2 != nil { + return nil, ErrHeader + } + spd = append(spd, sparseEntry{Offset: offset, Length: length}) + } + return spd, nil +} + +// readGNUSparseMap0x1 reads the sparse map as stored in GNU's PAX sparse format +// version 0.1. The sparse map is stored in the PAX headers. +func readGNUSparseMap0x1(paxHdrs map[string]string) (sparseDatas, error) { + // Get number of entries. + // Use integer overflow resistant math to check this. + numEntriesStr := paxHdrs[paxGNUSparseNumBlocks] + numEntries, err := strconv.ParseInt(numEntriesStr, 10, 0) // Intentionally parse as native int + if err != nil || numEntries < 0 || int(2*numEntries) < int(numEntries) { + return nil, ErrHeader + } + + // There should be two numbers in sparseMap for each entry. + sparseMap := strings.Split(paxHdrs[paxGNUSparseMap], ",") + if len(sparseMap) == 1 && sparseMap[0] == "" { + sparseMap = sparseMap[:0] + } + if int64(len(sparseMap)) != 2*numEntries { + return nil, ErrHeader + } + + // Loop through the entries in the sparse map. + // numEntries is trusted now. + spd := make(sparseDatas, 0, numEntries) + for len(sparseMap) >= 2 { + offset, err1 := strconv.ParseInt(sparseMap[0], 10, 64) + length, err2 := strconv.ParseInt(sparseMap[1], 10, 64) + if err1 != nil || err2 != nil { + return nil, ErrHeader + } + spd = append(spd, sparseEntry{Offset: offset, Length: length}) + sparseMap = sparseMap[2:] + } + return spd, nil +} + +// Read reads from the current file in the tar archive. +// It returns (0, io.EOF) when it reaches the end of that file, +// until Next is called to advance to the next file. +// +// If the current file is sparse, then the regions marked as a hole +// are read back as NUL-bytes. +// +// Calling Read on special types like TypeLink, TypeSymlink, TypeChar, +// TypeBlock, TypeDir, and TypeFifo returns (0, io.EOF) regardless of what +// the Header.Size claims. +func (tr *Reader) Read(b []byte) (int, error) { + if tr.err != nil { + return 0, tr.err + } + n, err := tr.curr.Read(b) + if err != nil && err != io.EOF { + tr.err = err + } + return n, err +} + +// writeTo writes the content of the current file to w. +// The bytes written matches the number of remaining bytes in the current file. +// +// If the current file is sparse and w is an io.WriteSeeker, +// then writeTo uses Seek to skip past holes defined in Header.SparseHoles, +// assuming that skipped regions are filled with NULs. +// This always writes the last byte to ensure w is the right size. +// +// TODO(dsnet): Re-export this when adding sparse file support. +// See https://golang.org/issue/22735 +func (tr *Reader) writeTo(w io.Writer) (int64, error) { + if tr.err != nil { + return 0, tr.err + } + n, err := tr.curr.WriteTo(w) + if err != nil { + tr.err = err + } + return n, err +} + +// regFileReader is a fileReader for reading data from a regular file entry. +type regFileReader struct { + r io.Reader // Underlying Reader + nb int64 // Number of remaining bytes to read +} + +func (fr *regFileReader) Read(b []byte) (n int, err error) { + if int64(len(b)) > fr.nb { + b = b[:fr.nb] + } + if len(b) > 0 { + n, err = fr.r.Read(b) + fr.nb -= int64(n) + } + switch { + case err == io.EOF && fr.nb > 0: + return n, io.ErrUnexpectedEOF + case err == nil && fr.nb == 0: + return n, io.EOF + default: + return n, err + } +} + +func (fr *regFileReader) WriteTo(w io.Writer) (int64, error) { + return io.Copy(w, struct{ io.Reader }{fr}) +} + +func (fr regFileReader) LogicalRemaining() int64 { + return fr.nb +} + +func (fr regFileReader) PhysicalRemaining() int64 { + return fr.nb +} + +// sparseFileReader is a fileReader for reading data from a sparse file entry. +type sparseFileReader struct { + fr fileReader // Underlying fileReader + sp sparseHoles // Normalized list of sparse holes + pos int64 // Current position in sparse file +} + +func (sr *sparseFileReader) Read(b []byte) (n int, err error) { + finished := int64(len(b)) >= sr.LogicalRemaining() + if finished { + b = b[:sr.LogicalRemaining()] + } + + b0 := b + endPos := sr.pos + int64(len(b)) + for endPos > sr.pos && err == nil { + var nf int // Bytes read in fragment + holeStart, holeEnd := sr.sp[0].Offset, sr.sp[0].endOffset() + if sr.pos < holeStart { // In a data fragment + bf := b[:min(int64(len(b)), holeStart-sr.pos)] + nf, err = tryReadFull(sr.fr, bf) + } else { // In a hole fragment + bf := b[:min(int64(len(b)), holeEnd-sr.pos)] + nf, err = tryReadFull(zeroReader{}, bf) + } + b = b[nf:] + sr.pos += int64(nf) + if sr.pos >= holeEnd && len(sr.sp) > 1 { + sr.sp = sr.sp[1:] // Ensure last fragment always remains + } + } + + n = len(b0) - len(b) + switch { + case err == io.EOF: + return n, errMissData // Less data in dense file than sparse file + case err != nil: + return n, err + case sr.LogicalRemaining() == 0 && sr.PhysicalRemaining() > 0: + return n, errUnrefData // More data in dense file than sparse file + case finished: + return n, io.EOF + default: + return n, nil + } +} + +func (sr *sparseFileReader) WriteTo(w io.Writer) (n int64, err error) { + ws, ok := w.(io.WriteSeeker) + if ok { + if _, err := ws.Seek(0, io.SeekCurrent); err != nil { + ok = false // Not all io.Seeker can really seek + } + } + if !ok { + return io.Copy(w, struct{ io.Reader }{sr}) + } + + var writeLastByte bool + pos0 := sr.pos + for sr.LogicalRemaining() > 0 && !writeLastByte && err == nil { + var nf int64 // Size of fragment + holeStart, holeEnd := sr.sp[0].Offset, sr.sp[0].endOffset() + if sr.pos < holeStart { // In a data fragment + nf = holeStart - sr.pos + nf, err = io.CopyN(ws, sr.fr, nf) + } else { // In a hole fragment + nf = holeEnd - sr.pos + if sr.PhysicalRemaining() == 0 { + writeLastByte = true + nf-- + } + _, err = ws.Seek(nf, io.SeekCurrent) + } + sr.pos += nf + if sr.pos >= holeEnd && len(sr.sp) > 1 { + sr.sp = sr.sp[1:] // Ensure last fragment always remains + } + } + + // If the last fragment is a hole, then seek to 1-byte before EOF, and + // write a single byte to ensure the file is the right size. + if writeLastByte && err == nil { + _, err = ws.Write([]byte{0}) + sr.pos++ + } + + n = sr.pos - pos0 + switch { + case err == io.EOF: + return n, errMissData // Less data in dense file than sparse file + case err != nil: + return n, err + case sr.LogicalRemaining() == 0 && sr.PhysicalRemaining() > 0: + return n, errUnrefData // More data in dense file than sparse file + default: + return n, nil + } +} + +func (sr sparseFileReader) LogicalRemaining() int64 { + return sr.sp[len(sr.sp)-1].endOffset() - sr.pos +} +func (sr sparseFileReader) PhysicalRemaining() int64 { + return sr.fr.PhysicalRemaining() +} + +type zeroReader struct{} + +func (zeroReader) Read(b []byte) (int, error) { + for i := range b { + b[i] = 0 + } + return len(b), nil +} + +// mustReadFull is like io.ReadFull except it returns +// io.ErrUnexpectedEOF when io.EOF is hit before len(b) bytes are read. +func mustReadFull(r io.Reader, b []byte) (int, error) { + n, err := tryReadFull(r, b) + if err == io.EOF { + err = io.ErrUnexpectedEOF + } + return n, err +} + +// tryReadFull is like io.ReadFull except it returns +// io.EOF when it is hit before len(b) bytes are read. +func tryReadFull(r io.Reader, b []byte) (n int, err error) { + for len(b) > n && err == nil { + var nn int + nn, err = r.Read(b[n:]) + n += nn + } + if len(b) == n && err == io.EOF { + err = nil + } + return n, err +} + +// discard skips n bytes in r, reporting an error if unable to do so. +func discard(r io.Reader, n int64) error { + // If possible, Seek to the last byte before the end of the data section. + // Do this because Seek is often lazy about reporting errors; this will mask + // the fact that the stream may be truncated. We can rely on the + // io.CopyN done shortly afterwards to trigger any IO errors. + var seekSkipped int64 // Number of bytes skipped via Seek + if sr, ok := r.(io.Seeker); ok && n > 1 { + // Not all io.Seeker can actually Seek. For example, os.Stdin implements + // io.Seeker, but calling Seek always returns an error and performs + // no action. Thus, we try an innocent seek to the current position + // to see if Seek is really supported. + pos1, err := sr.Seek(0, io.SeekCurrent) + if pos1 >= 0 && err == nil { + // Seek seems supported, so perform the real Seek. + pos2, err := sr.Seek(n-1, io.SeekCurrent) + if pos2 < 0 || err != nil { + return err + } + seekSkipped = pos2 - pos1 + } + } + + copySkipped, err := io.CopyN(io.Discard, r, n-seekSkipped) + if err == io.EOF && seekSkipped+copySkipped < n { + err = io.ErrUnexpectedEOF + } + return err +} -- cgit v1.2.3