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-rw-r--r--src/archive/tar/reader.go857
1 files changed, 857 insertions, 0 deletions
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: &regFileReader{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 = &regFileReader{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
+}
generated by cgit v1.2.3 (git 2.39.1) at 2025-01-10 21:40:46 +0000