// Copyright 2014-2017 Ulrich Kunitz. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package xz supports the compression and decompression of xz files. It
// supports version 1.0.4 of the specification without the non-LZMA2
// filters. See http://tukaani.org/xz/xz-file-format-1.0.4.txt
package xz
import (
"bytes"
"errors"
"fmt"
"hash"
"io"
"github.com/ulikunitz/xz/internal/xlog"
"github.com/ulikunitz/xz/lzma"
)
// ReaderConfig defines the parameters for the xz reader. The
// SingleStream parameter requests the reader to assume that the
// underlying stream contains only a single stream.
type ReaderConfig struct {
DictCap int
SingleStream bool
}
// fill replaces all zero values with their default values.
func (c *ReaderConfig) fill() {
if c.DictCap == 0 {
c.DictCap = 8 * 1024 * 1024
}
}
// Verify checks the reader parameters for Validity. Zero values will be
// replaced by default values.
func (c *ReaderConfig) Verify() error {
if c == nil {
return errors.New("xz: reader parameters are nil")
}
lc := lzma.Reader2Config{DictCap: c.DictCap}
if err := lc.Verify(); err != nil {
return err
}
return nil
}
// Reader supports the reading of one or multiple xz streams.
type Reader struct {
ReaderConfig
xz io.Reader
sr *streamReader
}
// streamReader decodes a single xz stream
type streamReader struct {
ReaderConfig
xz io.Reader
br *blockReader
newHash func() hash.Hash
h header
index []record
}
// NewReader creates a new xz reader using the default parameters.
// The function reads and checks the header of the first XZ stream. The
// reader will process multiple streams including padding.
func NewReader(xz io.Reader) (r *Reader, err error) {
return ReaderConfig{}.NewReader(xz)
}
// NewReader creates an xz stream reader. The created reader will be
// able to process multiple streams and padding unless a SingleStream
// has been set in the reader configuration c.
func (c ReaderConfig) NewReader(xz io.Reader) (r *Reader, err error) {
if err = c.Verify(); err != nil {
return nil, err
}
r = &Reader{
ReaderConfig: c,
xz: xz,
}
if r.sr, err = c.newStreamReader(xz); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return nil, err
}
return r, nil
}
var errUnexpectedData = errors.New("xz: unexpected data after stream")
// Read reads uncompressed data from the stream.
func (r *Reader) Read(p []byte) (n int, err error) {
for n < len(p) {
if r.sr == nil {
if r.SingleStream {
data := make([]byte, 1)
_, err = io.ReadFull(r.xz, data)
if err != io.EOF {
return n, errUnexpectedData
}
return n, io.EOF
}
for {
r.sr, err = r.ReaderConfig.newStreamReader(r.xz)
if err != errPadding {
break
}
}
if err != nil {
return n, err
}
}
k, err := r.sr.Read(p[n:])
n += k
if err != nil {
if err == io.EOF {
r.sr = nil
continue
}
return n, err
}
}
return n, nil
}
var errPadding = errors.New("xz: padding (4 zero bytes) encountered")
// newStreamReader creates a new xz stream reader using the given configuration
// parameters. NewReader reads and checks the header of the xz stream.
func (c ReaderConfig) newStreamReader(xz io.Reader) (r *streamReader, err error) {
if err = c.Verify(); err != nil {
return nil, err
}
data := make([]byte, HeaderLen)
if _, err := io.ReadFull(xz, data[:4]); err != nil {
return nil, err
}
if bytes.Equal(data[:4], []byte{0, 0, 0, 0}) {
return nil, errPadding
}
if _, err = io.ReadFull(xz, data[4:]); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return nil, err
}
r = &streamReader{
ReaderConfig: c,
xz: xz,
index: make([]record, 0, 4),
}
if err = r.h.UnmarshalBinary(data); err != nil {
return nil, err
}
xlog.Debugf("xz header %s", r.h)
if r.newHash, err = newHashFunc(r.h.flags); err != nil {
return nil, err
}
return r, nil
}
// errIndex indicates an error with the xz file index.
var errIndex = errors.New("xz: error in xz file index")
// readTail reads the index body and the xz footer.
func (r *streamReader) readTail() error {
index, n, err := readIndexBody(r.xz)
if err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return err
}
if len(index) != len(r.index) {
return fmt.Errorf("xz: index length is %d; want %d",
len(index), len(r.index))
}
for i, rec := range r.index {
if rec != index[i] {
return fmt.Errorf("xz: record %d is %v; want %v",
i, rec, index[i])
}
}
p := make([]byte, footerLen)
if _, err = io.ReadFull(r.xz, p); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return err
}
var f footer
if err = f.UnmarshalBinary(p); err != nil {
return err
}
xlog.Debugf("xz footer %s", f)
if f.flags != r.h.flags {
return errors.New("xz: footer flags incorrect")
}
if f.indexSize != int64(n)+1 {
return errors.New("xz: index size in footer wrong")
}
return nil
}
// Read reads actual data from the xz stream.
func (r *streamReader) Read(p []byte) (n int, err error) {
for n < len(p) {
if r.br == nil {
bh, hlen, err := readBlockHeader(r.xz)
if err != nil {
if err == errIndexIndicator {
if err = r.readTail(); err != nil {
return n, err
}
return n, io.EOF
}
return n, err
}
xlog.Debugf("block %v", *bh)
r.br, err = r.ReaderConfig.newBlockReader(r.xz, bh,
hlen, r.newHash())
if err != nil {
return n, err
}
}
k, err := r.br.Read(p[n:])
n += k
if err != nil {
if err == io.EOF {
r.index = append(r.index, r.br.record())
r.br = nil
} else {
return n, err
}
}
}
return n, nil
}
// countingReader is a reader that counts the bytes read.
type countingReader struct {
r io.Reader
n int64
}
// Read reads data from the wrapped reader and adds it to the n field.
func (lr *countingReader) Read(p []byte) (n int, err error) {
n, err = lr.r.Read(p)
lr.n += int64(n)
return n, err
}
// blockReader supports the reading of a block.
type blockReader struct {
lxz countingReader
header *blockHeader
headerLen int
n int64
hash hash.Hash
r io.Reader
err error
}
// newBlockReader creates a new block reader.
func (c *ReaderConfig) newBlockReader(xz io.Reader, h *blockHeader,
hlen int, hash hash.Hash) (br *blockReader, err error) {
br = &blockReader{
lxz: countingReader{r: xz},
header: h,
headerLen: hlen,
hash: hash,
}
fr, err := c.newFilterReader(&br.lxz, h.filters)
if err != nil {
return nil, err
}
br.r = io.TeeReader(fr, br.hash)
return br, nil
}
// uncompressedSize returns the uncompressed size of the block.
func (br *blockReader) uncompressedSize() int64 {
return br.n
}
// compressedSize returns the compressed size of the block.
func (br *blockReader) compressedSize() int64 {
return br.lxz.n
}
// unpaddedSize computes the unpadded size for the block.
func (br *blockReader) unpaddedSize() int64 {
n := int64(br.headerLen)
n += br.compressedSize()
n += int64(br.hash.Size())
return n
}
// record returns the index record for the current block.
func (br *blockReader) record() record {
return record{br.unpaddedSize(), br.uncompressedSize()}
}
// errBlockSize indicates that the size of the block in the block header
// is wrong.
var errBlockSize = errors.New("xz: wrong uncompressed size for block")
// Read reads data from the block.
func (br *blockReader) Read(p []byte) (n int, err error) {
n, err = br.r.Read(p)
br.n += int64(n)
u := br.header.uncompressedSize
if u >= 0 && br.uncompressedSize() > u {
return n, errors.New("xz: wrong uncompressed size for block")
}
c := br.header.compressedSize
if c >= 0 && br.compressedSize() > c {
return n, errors.New("xz: wrong compressed size for block")
}
if err != io.EOF {
return n, err
}
if br.uncompressedSize() < u || br.compressedSize() < c {
return n, io.ErrUnexpectedEOF
}
s := br.hash.Size()
k := padLen(br.lxz.n)
q := make([]byte, k+s, k+2*s)
if _, err = io.ReadFull(br.lxz.r, q); err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return n, err
}
if !allZeros(q[:k]) {
return n, errors.New("xz: non-zero block padding")
}
checkSum := q[k:]
computedSum := br.hash.Sum(checkSum[s:])
if !bytes.Equal(checkSum, computedSum) {
return n, errors.New("xz: checksum error for block")
}
return n, io.EOF
}
func (c *ReaderConfig) newFilterReader(r io.Reader, f []filter) (fr io.Reader,
err error) {
if err = verifyFilters(f); err != nil {
return nil, err
}
fr = r
for i := len(f) - 1; i >= 0; i-- {
fr, err = f[i].reader(fr, c)
if err != nil {
return nil, err
}
}
return fr, nil
}
