mirror of
https://github.com/autc04/Retro68.git
synced 2024-09-08 20:55:01 +00:00
611 lines
17 KiB
Go
611 lines
17 KiB
Go
// Copyright 2010 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 zip
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import (
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"bufio"
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"encoding/binary"
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"errors"
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"fmt"
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"hash"
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"hash/crc32"
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"io"
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"os"
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"time"
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)
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var (
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ErrFormat = errors.New("zip: not a valid zip file")
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ErrAlgorithm = errors.New("zip: unsupported compression algorithm")
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ErrChecksum = errors.New("zip: checksum error")
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)
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type Reader struct {
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r io.ReaderAt
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File []*File
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Comment string
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decompressors map[uint16]Decompressor
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}
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type ReadCloser struct {
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f *os.File
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Reader
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}
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type File struct {
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FileHeader
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zip *Reader
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zipr io.ReaderAt
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zipsize int64
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headerOffset int64
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}
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func (f *File) hasDataDescriptor() bool {
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return f.Flags&0x8 != 0
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}
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// OpenReader will open the Zip file specified by name and return a ReadCloser.
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func OpenReader(name string) (*ReadCloser, error) {
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f, err := os.Open(name)
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if err != nil {
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return nil, err
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}
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fi, err := f.Stat()
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if err != nil {
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f.Close()
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return nil, err
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}
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r := new(ReadCloser)
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if err := r.init(f, fi.Size()); err != nil {
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f.Close()
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return nil, err
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}
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r.f = f
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return r, nil
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}
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// NewReader returns a new Reader reading from r, which is assumed to
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// have the given size in bytes.
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func NewReader(r io.ReaderAt, size int64) (*Reader, error) {
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zr := new(Reader)
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if err := zr.init(r, size); err != nil {
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return nil, err
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}
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return zr, nil
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}
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func (z *Reader) init(r io.ReaderAt, size int64) error {
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end, err := readDirectoryEnd(r, size)
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if err != nil {
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return err
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}
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if end.directoryRecords > uint64(size)/fileHeaderLen {
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return fmt.Errorf("archive/zip: TOC declares impossible %d files in %d byte zip", end.directoryRecords, size)
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}
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z.r = r
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z.File = make([]*File, 0, end.directoryRecords)
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z.Comment = end.comment
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rs := io.NewSectionReader(r, 0, size)
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if _, err = rs.Seek(int64(end.directoryOffset), io.SeekStart); err != nil {
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return err
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}
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buf := bufio.NewReader(rs)
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// The count of files inside a zip is truncated to fit in a uint16.
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// Gloss over this by reading headers until we encounter
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// a bad one, and then only report an ErrFormat or UnexpectedEOF if
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// the file count modulo 65536 is incorrect.
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for {
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f := &File{zip: z, zipr: r, zipsize: size}
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err = readDirectoryHeader(f, buf)
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if err == ErrFormat || err == io.ErrUnexpectedEOF {
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break
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}
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if err != nil {
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return err
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}
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z.File = append(z.File, f)
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}
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if uint16(len(z.File)) != uint16(end.directoryRecords) { // only compare 16 bits here
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// Return the readDirectoryHeader error if we read
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// the wrong number of directory entries.
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return err
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}
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return nil
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}
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// RegisterDecompressor registers or overrides a custom decompressor for a
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// specific method ID. If a decompressor for a given method is not found,
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// Reader will default to looking up the decompressor at the package level.
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func (z *Reader) RegisterDecompressor(method uint16, dcomp Decompressor) {
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if z.decompressors == nil {
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z.decompressors = make(map[uint16]Decompressor)
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}
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z.decompressors[method] = dcomp
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}
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func (z *Reader) decompressor(method uint16) Decompressor {
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dcomp := z.decompressors[method]
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if dcomp == nil {
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dcomp = decompressor(method)
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}
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return dcomp
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}
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// Close closes the Zip file, rendering it unusable for I/O.
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func (rc *ReadCloser) Close() error {
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return rc.f.Close()
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}
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// DataOffset returns the offset of the file's possibly-compressed
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// data, relative to the beginning of the zip file.
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//
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// Most callers should instead use Open, which transparently
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// decompresses data and verifies checksums.
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func (f *File) DataOffset() (offset int64, err error) {
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bodyOffset, err := f.findBodyOffset()
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if err != nil {
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return
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}
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return f.headerOffset + bodyOffset, nil
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}
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// Open returns a ReadCloser that provides access to the File's contents.
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// Multiple files may be read concurrently.
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func (f *File) Open() (io.ReadCloser, error) {
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bodyOffset, err := f.findBodyOffset()
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if err != nil {
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return nil, err
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}
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size := int64(f.CompressedSize64)
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r := io.NewSectionReader(f.zipr, f.headerOffset+bodyOffset, size)
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dcomp := f.zip.decompressor(f.Method)
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if dcomp == nil {
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return nil, ErrAlgorithm
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}
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var rc io.ReadCloser = dcomp(r)
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var desr io.Reader
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if f.hasDataDescriptor() {
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desr = io.NewSectionReader(f.zipr, f.headerOffset+bodyOffset+size, dataDescriptorLen)
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}
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rc = &checksumReader{
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rc: rc,
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hash: crc32.NewIEEE(),
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f: f,
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desr: desr,
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}
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return rc, nil
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}
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type checksumReader struct {
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rc io.ReadCloser
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hash hash.Hash32
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nread uint64 // number of bytes read so far
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f *File
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desr io.Reader // if non-nil, where to read the data descriptor
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err error // sticky error
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}
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func (r *checksumReader) Read(b []byte) (n int, err error) {
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if r.err != nil {
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return 0, r.err
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}
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n, err = r.rc.Read(b)
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r.hash.Write(b[:n])
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r.nread += uint64(n)
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if err == nil {
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return
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}
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if err == io.EOF {
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if r.nread != r.f.UncompressedSize64 {
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return 0, io.ErrUnexpectedEOF
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}
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if r.desr != nil {
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if err1 := readDataDescriptor(r.desr, r.f); err1 != nil {
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if err1 == io.EOF {
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err = io.ErrUnexpectedEOF
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} else {
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err = err1
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}
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} else if r.hash.Sum32() != r.f.CRC32 {
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err = ErrChecksum
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}
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} else {
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// If there's not a data descriptor, we still compare
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// the CRC32 of what we've read against the file header
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// or TOC's CRC32, if it seems like it was set.
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if r.f.CRC32 != 0 && r.hash.Sum32() != r.f.CRC32 {
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err = ErrChecksum
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}
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}
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}
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r.err = err
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return
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}
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func (r *checksumReader) Close() error { return r.rc.Close() }
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// findBodyOffset does the minimum work to verify the file has a header
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// and returns the file body offset.
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func (f *File) findBodyOffset() (int64, error) {
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var buf [fileHeaderLen]byte
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if _, err := f.zipr.ReadAt(buf[:], f.headerOffset); err != nil {
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return 0, err
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}
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b := readBuf(buf[:])
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if sig := b.uint32(); sig != fileHeaderSignature {
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return 0, ErrFormat
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}
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b = b[22:] // skip over most of the header
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filenameLen := int(b.uint16())
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extraLen := int(b.uint16())
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return int64(fileHeaderLen + filenameLen + extraLen), nil
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}
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// readDirectoryHeader attempts to read a directory header from r.
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// It returns io.ErrUnexpectedEOF if it cannot read a complete header,
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// and ErrFormat if it doesn't find a valid header signature.
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func readDirectoryHeader(f *File, r io.Reader) error {
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var buf [directoryHeaderLen]byte
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if _, err := io.ReadFull(r, buf[:]); err != nil {
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return err
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}
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b := readBuf(buf[:])
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if sig := b.uint32(); sig != directoryHeaderSignature {
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return ErrFormat
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}
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f.CreatorVersion = b.uint16()
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f.ReaderVersion = b.uint16()
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f.Flags = b.uint16()
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f.Method = b.uint16()
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f.ModifiedTime = b.uint16()
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f.ModifiedDate = b.uint16()
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f.CRC32 = b.uint32()
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f.CompressedSize = b.uint32()
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f.UncompressedSize = b.uint32()
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f.CompressedSize64 = uint64(f.CompressedSize)
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f.UncompressedSize64 = uint64(f.UncompressedSize)
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filenameLen := int(b.uint16())
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extraLen := int(b.uint16())
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commentLen := int(b.uint16())
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b = b[4:] // skipped start disk number and internal attributes (2x uint16)
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f.ExternalAttrs = b.uint32()
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f.headerOffset = int64(b.uint32())
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d := make([]byte, filenameLen+extraLen+commentLen)
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if _, err := io.ReadFull(r, d); err != nil {
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return err
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}
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f.Name = string(d[:filenameLen])
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f.Extra = d[filenameLen : filenameLen+extraLen]
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f.Comment = string(d[filenameLen+extraLen:])
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// Determine the character encoding.
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utf8Valid1, utf8Require1 := detectUTF8(f.Name)
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utf8Valid2, utf8Require2 := detectUTF8(f.Comment)
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switch {
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case !utf8Valid1 || !utf8Valid2:
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// Name and Comment definitely not UTF-8.
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f.NonUTF8 = true
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case !utf8Require1 && !utf8Require2:
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// Name and Comment use only single-byte runes that overlap with UTF-8.
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f.NonUTF8 = false
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default:
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// Might be UTF-8, might be some other encoding; preserve existing flag.
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// Some ZIP writers use UTF-8 encoding without setting the UTF-8 flag.
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// Since it is impossible to always distinguish valid UTF-8 from some
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// other encoding (e.g., GBK or Shift-JIS), we trust the flag.
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f.NonUTF8 = f.Flags&0x800 == 0
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}
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needUSize := f.UncompressedSize == ^uint32(0)
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needCSize := f.CompressedSize == ^uint32(0)
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needHeaderOffset := f.headerOffset == int64(^uint32(0))
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// Best effort to find what we need.
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// Other zip authors might not even follow the basic format,
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// and we'll just ignore the Extra content in that case.
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var modified time.Time
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parseExtras:
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for extra := readBuf(f.Extra); len(extra) >= 4; { // need at least tag and size
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fieldTag := extra.uint16()
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fieldSize := int(extra.uint16())
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if len(extra) < fieldSize {
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break
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}
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fieldBuf := extra.sub(fieldSize)
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switch fieldTag {
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case zip64ExtraID:
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// update directory values from the zip64 extra block.
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// They should only be consulted if the sizes read earlier
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// are maxed out.
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// See golang.org/issue/13367.
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if needUSize {
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needUSize = false
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if len(fieldBuf) < 8 {
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return ErrFormat
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}
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f.UncompressedSize64 = fieldBuf.uint64()
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}
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if needCSize {
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needCSize = false
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if len(fieldBuf) < 8 {
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return ErrFormat
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}
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f.CompressedSize64 = fieldBuf.uint64()
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}
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if needHeaderOffset {
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needHeaderOffset = false
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if len(fieldBuf) < 8 {
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return ErrFormat
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}
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f.headerOffset = int64(fieldBuf.uint64())
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}
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case ntfsExtraID:
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if len(fieldBuf) < 4 {
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continue parseExtras
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}
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fieldBuf.uint32() // reserved (ignored)
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for len(fieldBuf) >= 4 { // need at least tag and size
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attrTag := fieldBuf.uint16()
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attrSize := int(fieldBuf.uint16())
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if len(fieldBuf) < attrSize {
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continue parseExtras
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}
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attrBuf := fieldBuf.sub(attrSize)
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if attrTag != 1 || attrSize != 24 {
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continue // Ignore irrelevant attributes
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}
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const ticksPerSecond = 1e7 // Windows timestamp resolution
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ts := int64(attrBuf.uint64()) // ModTime since Windows epoch
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secs := int64(ts / ticksPerSecond)
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nsecs := (1e9 / ticksPerSecond) * int64(ts%ticksPerSecond)
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epoch := time.Date(1601, time.January, 1, 0, 0, 0, 0, time.UTC)
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modified = time.Unix(epoch.Unix()+secs, nsecs)
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}
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case unixExtraID, infoZipUnixExtraID:
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if len(fieldBuf) < 8 {
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continue parseExtras
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}
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fieldBuf.uint32() // AcTime (ignored)
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ts := int64(fieldBuf.uint32()) // ModTime since Unix epoch
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modified = time.Unix(ts, 0)
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case extTimeExtraID:
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if len(fieldBuf) < 5 || fieldBuf.uint8()&1 == 0 {
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continue parseExtras
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}
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ts := int64(fieldBuf.uint32()) // ModTime since Unix epoch
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modified = time.Unix(ts, 0)
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}
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}
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msdosModified := msDosTimeToTime(f.ModifiedDate, f.ModifiedTime)
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f.Modified = msdosModified
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if !modified.IsZero() {
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f.Modified = modified.UTC()
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// If legacy MS-DOS timestamps are set, we can use the delta between
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// the legacy and extended versions to estimate timezone offset.
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//
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// A non-UTC timezone is always used (even if offset is zero).
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// Thus, FileHeader.Modified.Location() == time.UTC is useful for
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// determining whether extended timestamps are present.
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// This is necessary for users that need to do additional time
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// calculations when dealing with legacy ZIP formats.
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if f.ModifiedTime != 0 || f.ModifiedDate != 0 {
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f.Modified = modified.In(timeZone(msdosModified.Sub(modified)))
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}
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}
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// Assume that uncompressed size 2³²-1 could plausibly happen in
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// an old zip32 file that was sharding inputs into the largest chunks
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// possible (or is just malicious; search the web for 42.zip).
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// If needUSize is true still, it means we didn't see a zip64 extension.
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// As long as the compressed size is not also 2³²-1 (implausible)
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// and the header is not also 2³²-1 (equally implausible),
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// accept the uncompressed size 2³²-1 as valid.
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// If nothing else, this keeps archive/zip working with 42.zip.
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_ = needUSize
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if needCSize || needHeaderOffset {
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return ErrFormat
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}
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return nil
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}
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func readDataDescriptor(r io.Reader, f *File) error {
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var buf [dataDescriptorLen]byte
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// The spec says: "Although not originally assigned a
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// signature, the value 0x08074b50 has commonly been adopted
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// as a signature value for the data descriptor record.
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// Implementers should be aware that ZIP files may be
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// encountered with or without this signature marking data
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// descriptors and should account for either case when reading
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// ZIP files to ensure compatibility."
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//
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// dataDescriptorLen includes the size of the signature but
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// first read just those 4 bytes to see if it exists.
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if _, err := io.ReadFull(r, buf[:4]); err != nil {
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return err
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}
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off := 0
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maybeSig := readBuf(buf[:4])
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if maybeSig.uint32() != dataDescriptorSignature {
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// No data descriptor signature. Keep these four
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// bytes.
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off += 4
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}
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if _, err := io.ReadFull(r, buf[off:12]); err != nil {
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return err
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}
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b := readBuf(buf[:12])
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if b.uint32() != f.CRC32 {
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return ErrChecksum
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}
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// The two sizes that follow here can be either 32 bits or 64 bits
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// but the spec is not very clear on this and different
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// interpretations has been made causing incompatibilities. We
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// already have the sizes from the central directory so we can
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// just ignore these.
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return nil
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}
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func readDirectoryEnd(r io.ReaderAt, size int64) (dir *directoryEnd, err error) {
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// look for directoryEndSignature in the last 1k, then in the last 65k
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var buf []byte
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var directoryEndOffset int64
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for i, bLen := range []int64{1024, 65 * 1024} {
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if bLen > size {
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bLen = size
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}
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buf = make([]byte, int(bLen))
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if _, err := r.ReadAt(buf, size-bLen); err != nil && err != io.EOF {
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return nil, err
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}
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if p := findSignatureInBlock(buf); p >= 0 {
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buf = buf[p:]
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directoryEndOffset = size - bLen + int64(p)
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break
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}
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if i == 1 || bLen == size {
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return nil, ErrFormat
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}
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}
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// read header into struct
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b := readBuf(buf[4:]) // skip signature
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d := &directoryEnd{
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diskNbr: uint32(b.uint16()),
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dirDiskNbr: uint32(b.uint16()),
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dirRecordsThisDisk: uint64(b.uint16()),
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directoryRecords: uint64(b.uint16()),
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directorySize: uint64(b.uint32()),
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directoryOffset: uint64(b.uint32()),
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commentLen: b.uint16(),
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}
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l := int(d.commentLen)
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if l > len(b) {
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return nil, errors.New("zip: invalid comment length")
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}
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d.comment = string(b[:l])
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// These values mean that the file can be a zip64 file
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if d.directoryRecords == 0xffff || d.directorySize == 0xffff || d.directoryOffset == 0xffffffff {
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p, err := findDirectory64End(r, directoryEndOffset)
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if err == nil && p >= 0 {
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err = readDirectory64End(r, p, d)
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}
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if err != nil {
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return nil, err
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}
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}
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// Make sure directoryOffset points to somewhere in our file.
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if o := int64(d.directoryOffset); o < 0 || o >= size {
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return nil, ErrFormat
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}
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return d, nil
|
|
}
|
|
|
|
// findDirectory64End tries to read the zip64 locator just before the
|
|
// directory end and returns the offset of the zip64 directory end if
|
|
// found.
|
|
func findDirectory64End(r io.ReaderAt, directoryEndOffset int64) (int64, error) {
|
|
locOffset := directoryEndOffset - directory64LocLen
|
|
if locOffset < 0 {
|
|
return -1, nil // no need to look for a header outside the file
|
|
}
|
|
buf := make([]byte, directory64LocLen)
|
|
if _, err := r.ReadAt(buf, locOffset); err != nil {
|
|
return -1, err
|
|
}
|
|
b := readBuf(buf)
|
|
if sig := b.uint32(); sig != directory64LocSignature {
|
|
return -1, nil
|
|
}
|
|
if b.uint32() != 0 { // number of the disk with the start of the zip64 end of central directory
|
|
return -1, nil // the file is not a valid zip64-file
|
|
}
|
|
p := b.uint64() // relative offset of the zip64 end of central directory record
|
|
if b.uint32() != 1 { // total number of disks
|
|
return -1, nil // the file is not a valid zip64-file
|
|
}
|
|
return int64(p), nil
|
|
}
|
|
|
|
// readDirectory64End reads the zip64 directory end and updates the
|
|
// directory end with the zip64 directory end values.
|
|
func readDirectory64End(r io.ReaderAt, offset int64, d *directoryEnd) (err error) {
|
|
buf := make([]byte, directory64EndLen)
|
|
if _, err := r.ReadAt(buf, offset); err != nil {
|
|
return err
|
|
}
|
|
|
|
b := readBuf(buf)
|
|
if sig := b.uint32(); sig != directory64EndSignature {
|
|
return ErrFormat
|
|
}
|
|
|
|
b = b[12:] // skip dir size, version and version needed (uint64 + 2x uint16)
|
|
d.diskNbr = b.uint32() // number of this disk
|
|
d.dirDiskNbr = b.uint32() // number of the disk with the start of the central directory
|
|
d.dirRecordsThisDisk = b.uint64() // total number of entries in the central directory on this disk
|
|
d.directoryRecords = b.uint64() // total number of entries in the central directory
|
|
d.directorySize = b.uint64() // size of the central directory
|
|
d.directoryOffset = b.uint64() // offset of start of central directory with respect to the starting disk number
|
|
|
|
return nil
|
|
}
|
|
|
|
func findSignatureInBlock(b []byte) int {
|
|
for i := len(b) - directoryEndLen; i >= 0; i-- {
|
|
// defined from directoryEndSignature in struct.go
|
|
if b[i] == 'P' && b[i+1] == 'K' && b[i+2] == 0x05 && b[i+3] == 0x06 {
|
|
// n is length of comment
|
|
n := int(b[i+directoryEndLen-2]) | int(b[i+directoryEndLen-1])<<8
|
|
if n+directoryEndLen+i <= len(b) {
|
|
return i
|
|
}
|
|
}
|
|
}
|
|
return -1
|
|
}
|
|
|
|
type readBuf []byte
|
|
|
|
func (b *readBuf) uint8() uint8 {
|
|
v := (*b)[0]
|
|
*b = (*b)[1:]
|
|
return v
|
|
}
|
|
|
|
func (b *readBuf) uint16() uint16 {
|
|
v := binary.LittleEndian.Uint16(*b)
|
|
*b = (*b)[2:]
|
|
return v
|
|
}
|
|
|
|
func (b *readBuf) uint32() uint32 {
|
|
v := binary.LittleEndian.Uint32(*b)
|
|
*b = (*b)[4:]
|
|
return v
|
|
}
|
|
|
|
func (b *readBuf) uint64() uint64 {
|
|
v := binary.LittleEndian.Uint64(*b)
|
|
*b = (*b)[8:]
|
|
return v
|
|
}
|
|
|
|
func (b *readBuf) sub(n int) readBuf {
|
|
b2 := (*b)[:n]
|
|
*b = (*b)[n:]
|
|
return b2
|
|
}
|