gtsocial-umbx

gunzip.go (10176B)

---

 // 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 gzip implements reading and writing of gzip format compressed files,
 // as specified in RFC 1952.
 package gzip
 
 import (
 	"bufio"
 	"compress/gzip"
 	"encoding/binary"
 	"hash/crc32"
 	"io"
 	"time"
 
 	"github.com/klauspost/compress/flate"
 )
 
 const (
 	gzipID1     = 0x1f
 	gzipID2     = 0x8b
 	gzipDeflate = 8
 	flagText    = 1 << 0
 	flagHdrCrc  = 1 << 1
 	flagExtra   = 1 << 2
 	flagName    = 1 << 3
 	flagComment = 1 << 4
 )
 
 var (
 	// ErrChecksum is returned when reading GZIP data that has an invalid checksum.
 	ErrChecksum = gzip.ErrChecksum
 	// ErrHeader is returned when reading GZIP data that has an invalid header.
 	ErrHeader = gzip.ErrHeader
 )
 
 var le = binary.LittleEndian
 
 // noEOF converts io.EOF to io.ErrUnexpectedEOF.
 func noEOF(err error) error {
 	if err == io.EOF {
 		return io.ErrUnexpectedEOF
 	}
 	return err
 }
 
 // The gzip file stores a header giving metadata about the compressed file.
 // That header is exposed as the fields of the Writer and Reader structs.
 //
 // Strings must be UTF-8 encoded and may only contain Unicode code points
 // U+0001 through U+00FF, due to limitations of the GZIP file format.
 type Header struct {
 	Comment string    // comment
 	Extra   []byte    // "extra data"
 	ModTime time.Time // modification time
 	Name    string    // file name
 	OS      byte      // operating system type
 }
 
 // A Reader is an io.Reader that can be read to retrieve
 // uncompressed data from a gzip-format compressed file.
 //
 // In general, a gzip file can be a concatenation of gzip files,
 // each with its own header. Reads from the Reader
 // return the concatenation of the uncompressed data of each.
 // Only the first header is recorded in the Reader fields.
 //
 // Gzip files store a length and checksum of the uncompressed data.
 // The Reader will return a ErrChecksum when Read
 // reaches the end of the uncompressed data if it does not
 // have the expected length or checksum. Clients should treat data
 // returned by Read as tentative until they receive the io.EOF
 // marking the end of the data.
 type Reader struct {
 	Header       // valid after NewReader or Reader.Reset
 	r            flate.Reader
 	br           *bufio.Reader
 	decompressor io.ReadCloser
 	digest       uint32 // CRC-32, IEEE polynomial (section 8)
 	size         uint32 // Uncompressed size (section 2.3.1)
 	buf          [512]byte
 	err          error
 	multistream  bool
 }
 
 // NewReader creates a new Reader reading the given reader.
 // If r does not also implement io.ByteReader,
 // the decompressor may read more data than necessary from r.
 //
 // It is the caller's responsibility to call Close on the Reader when done.
 //
 // The Reader.Header fields will be valid in the Reader returned.
 func NewReader(r io.Reader) (*Reader, error) {
 	z := new(Reader)
 	if err := z.Reset(r); err != nil {
 		return nil, err
 	}
 	return z, nil
 }
 
 // Reset discards the Reader z's state and makes it equivalent to the
 // result of its original state from NewReader, but reading from r instead.
 // This permits reusing a Reader rather than allocating a new one.
 func (z *Reader) Reset(r io.Reader) error {
 	*z = Reader{
 		decompressor: z.decompressor,
 		multistream:  true,
 	}
 	if rr, ok := r.(flate.Reader); ok {
 		z.r = rr
 	} else {
 		// Reuse if we can.
 		if z.br != nil {
 			z.br.Reset(r)
 		} else {
 			z.br = bufio.NewReader(r)
 		}
 		z.r = z.br
 	}
 	z.Header, z.err = z.readHeader()
 	return z.err
 }
 
 // Multistream controls whether the reader supports multistream files.
 //
 // If enabled (the default), the Reader expects the input to be a sequence
 // of individually gzipped data streams, each with its own header and
 // trailer, ending at EOF. The effect is that the concatenation of a sequence
 // of gzipped files is treated as equivalent to the gzip of the concatenation
 // of the sequence. This is standard behavior for gzip readers.
 //
 // Calling Multistream(false) disables this behavior; disabling the behavior
 // can be useful when reading file formats that distinguish individual gzip
 // data streams or mix gzip data streams with other data streams.
 // In this mode, when the Reader reaches the end of the data stream,
 // Read returns io.EOF. If the underlying reader implements io.ByteReader,
 // it will be left positioned just after the gzip stream.
 // To start the next stream, call z.Reset(r) followed by z.Multistream(false).
 // If there is no next stream, z.Reset(r) will return io.EOF.
 func (z *Reader) Multistream(ok bool) {
 	z.multistream = ok
 }
 
 // readString reads a NUL-terminated string from z.r.
 // It treats the bytes read as being encoded as ISO 8859-1 (Latin-1) and
 // will output a string encoded using UTF-8.
 // This method always updates z.digest with the data read.
 func (z *Reader) readString() (string, error) {
 	var err error
 	needConv := false
 	for i := 0; ; i++ {
 		if i >= len(z.buf) {
 			return "", ErrHeader
 		}
 		z.buf[i], err = z.r.ReadByte()
 		if err != nil {
 			return "", err
 		}
 		if z.buf[i] > 0x7f {
 			needConv = true
 		}
 		if z.buf[i] == 0 {
 			// Digest covers the NUL terminator.
 			z.digest = crc32.Update(z.digest, crc32.IEEETable, z.buf[:i+1])
 
 			// Strings are ISO 8859-1, Latin-1 (RFC 1952, section 2.3.1).
 			if needConv {
 				s := make([]rune, 0, i)
 				for _, v := range z.buf[:i] {
 					s = append(s, rune(v))
 				}
 				return string(s), nil
 			}
 			return string(z.buf[:i]), nil
 		}
 	}
 }
 
 // readHeader reads the GZIP header according to section 2.3.1.
 // This method does not set z.err.
 func (z *Reader) readHeader() (hdr Header, err error) {
 	if _, err = io.ReadFull(z.r, z.buf[:10]); err != nil {
 		// RFC 1952, section 2.2, says the following:
 		//	A gzip file consists of a series of "members" (compressed data sets).
 		//
 		// Other than this, the specification does not clarify whether a
 		// "series" is defined as "one or more" or "zero or more". To err on the
 		// side of caution, Go interprets this to mean "zero or more".
 		// Thus, it is okay to return io.EOF here.
 		return hdr, err
 	}
 	if z.buf[0] != gzipID1 || z.buf[1] != gzipID2 || z.buf[2] != gzipDeflate {
 		return hdr, ErrHeader
 	}
 	flg := z.buf[3]
 	hdr.ModTime = time.Unix(int64(le.Uint32(z.buf[4:8])), 0)
 	// z.buf[8] is XFL and is currently ignored.
 	hdr.OS = z.buf[9]
 	z.digest = crc32.ChecksumIEEE(z.buf[:10])
 
 	if flg&flagExtra != 0 {
 		if _, err = io.ReadFull(z.r, z.buf[:2]); err != nil {
 			return hdr, noEOF(err)
 		}
 		z.digest = crc32.Update(z.digest, crc32.IEEETable, z.buf[:2])
 		data := make([]byte, le.Uint16(z.buf[:2]))
 		if _, err = io.ReadFull(z.r, data); err != nil {
 			return hdr, noEOF(err)
 		}
 		z.digest = crc32.Update(z.digest, crc32.IEEETable, data)
 		hdr.Extra = data
 	}
 
 	var s string
 	if flg&flagName != 0 {
 		if s, err = z.readString(); err != nil {
 			return hdr, err
 		}
 		hdr.Name = s
 	}
 
 	if flg&flagComment != 0 {
 		if s, err = z.readString(); err != nil {
 			return hdr, err
 		}
 		hdr.Comment = s
 	}
 
 	if flg&flagHdrCrc != 0 {
 		if _, err = io.ReadFull(z.r, z.buf[:2]); err != nil {
 			return hdr, noEOF(err)
 		}
 		digest := le.Uint16(z.buf[:2])
 		if digest != uint16(z.digest) {
 			return hdr, ErrHeader
 		}
 	}
 
 	z.digest = 0
 	if z.decompressor == nil {
 		z.decompressor = flate.NewReader(z.r)
 	} else {
 		z.decompressor.(flate.Resetter).Reset(z.r, nil)
 	}
 	return hdr, nil
 }
 
 // Read implements io.Reader, reading uncompressed bytes from its underlying Reader.
 func (z *Reader) Read(p []byte) (n int, err error) {
 	if z.err != nil {
 		return 0, z.err
 	}
 
 	for n == 0 {
 		n, z.err = z.decompressor.Read(p)
 		z.digest = crc32.Update(z.digest, crc32.IEEETable, p[:n])
 		z.size += uint32(n)
 		if z.err != io.EOF {
 			// In the normal case we return here.
 			return n, z.err
 		}
 
 		// Finished file; check checksum and size.
 		if _, err := io.ReadFull(z.r, z.buf[:8]); err != nil {
 			z.err = noEOF(err)
 			return n, z.err
 		}
 		digest := le.Uint32(z.buf[:4])
 		size := le.Uint32(z.buf[4:8])
 		if digest != z.digest || size != z.size {
 			z.err = ErrChecksum
 			return n, z.err
 		}
 		z.digest, z.size = 0, 0
 
 		// File is ok; check if there is another.
 		if !z.multistream {
 			return n, io.EOF
 		}
 		z.err = nil // Remove io.EOF
 
 		if _, z.err = z.readHeader(); z.err != nil {
 			return n, z.err
 		}
 	}
 
 	return n, nil
 }
 
 type crcer interface {
 	io.Writer
 	Sum32() uint32
 	Reset()
 }
 type crcUpdater struct {
 	z *Reader
 }
 
 func (c *crcUpdater) Write(p []byte) (int, error) {
 	c.z.digest = crc32.Update(c.z.digest, crc32.IEEETable, p)
 	return len(p), nil
 }
 
 func (c *crcUpdater) Sum32() uint32 {
 	return c.z.digest
 }
 
 func (c *crcUpdater) Reset() {
 	c.z.digest = 0
 }
 
 // WriteTo support the io.WriteTo interface for io.Copy and friends.
 func (z *Reader) WriteTo(w io.Writer) (int64, error) {
 	total := int64(0)
 	crcWriter := crcer(crc32.NewIEEE())
 	if z.digest != 0 {
 		crcWriter = &crcUpdater{z: z}
 	}
 	for {
 		if z.err != nil {
 			if z.err == io.EOF {
 				return total, nil
 			}
 			return total, z.err
 		}
 
 		// We write both to output and digest.
 		mw := io.MultiWriter(w, crcWriter)
 		n, err := z.decompressor.(io.WriterTo).WriteTo(mw)
 		total += n
 		z.size += uint32(n)
 		if err != nil {
 			z.err = err
 			return total, z.err
 		}
 
 		// Finished file; check checksum + size.
 		if _, err := io.ReadFull(z.r, z.buf[0:8]); err != nil {
 			if err == io.EOF {
 				err = io.ErrUnexpectedEOF
 			}
 			z.err = err
 			return total, err
 		}
 		z.digest = crcWriter.Sum32()
 		digest := le.Uint32(z.buf[:4])
 		size := le.Uint32(z.buf[4:8])
 		if digest != z.digest || size != z.size {
 			z.err = ErrChecksum
 			return total, z.err
 		}
 		z.digest, z.size = 0, 0
 
 		// File is ok; check if there is another.
 		if !z.multistream {
 			return total, nil
 		}
 		crcWriter.Reset()
 		z.err = nil // Remove io.EOF
 
 		if _, z.err = z.readHeader(); z.err != nil {
 			if z.err == io.EOF {
 				return total, nil
 			}
 			return total, z.err
 		}
 	}
 }
 
 // Close closes the Reader. It does not close the underlying io.Reader.
 // In order for the GZIP checksum to be verified, the reader must be
 // fully consumed until the io.EOF.
 func (z *Reader) Close() error { return z.decompressor.Close() }