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// Copyright 2014-2019 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 lzma
import (
"errors"
"io"
"github.com/ulikunitz/xz/internal/xlog"
)
// Reader2Config stores the parameters for the LZMA2 reader.
// format.
type Reader2Config struct {
DictCap int
}
// fill converts the zero values of the configuration to the default values.
func (c *Reader2Config) fill() {
if c.DictCap == 0 {
c.DictCap = 8 * 1024 * 1024
}
}
// Verify checks the reader configuration for errors. Zero configuration values
// will be replaced by default values.
func (c *Reader2Config) Verify() error {
c.fill()
if !(MinDictCap <= c.DictCap && int64(c.DictCap) <= MaxDictCap) {
return errors.New("lzma: dictionary capacity is out of range")
}
return nil
}
// Reader2 supports the reading of LZMA2 chunk sequences. Note that the
// first chunk should have a dictionary reset and the first compressed
// chunk a properties reset. The chunk sequence may not be terminated by
// an end-of-stream chunk.
type Reader2 struct {
r io.Reader
err error
dict *decoderDict
ur *uncompressedReader
decoder *decoder
chunkReader io.Reader
cstate chunkState
ctype chunkType
}
// NewReader2 creates a reader for an LZMA2 chunk sequence.
func NewReader2(lzma2 io.Reader) (r *Reader2, err error) {
return Reader2Config{}.NewReader2(lzma2)
}
// NewReader2 creates an LZMA2 reader using the given configuration.
func (c Reader2Config) NewReader2(lzma2 io.Reader) (r *Reader2, err error) {
if err = c.Verify(); err != nil {
return nil, err
}
r = &Reader2{r: lzma2, cstate: start}
r.dict, err = newDecoderDict(c.DictCap)
if err != nil {
return nil, err
}
if err = r.startChunk(); err != nil {
r.err = err
}
return r, nil
}
// uncompressed tests whether the chunk type specifies an uncompressed
// chunk.
func uncompressed(ctype chunkType) bool {
return ctype == cU || ctype == cUD
}
// startChunk parses a new chunk.
func (r *Reader2) startChunk() error {
r.chunkReader = nil
header, err := readChunkHeader(r.r)
if err != nil {
if err == io.EOF {
err = io.ErrUnexpectedEOF
}
return err
}
xlog.Debugf("chunk header %v", header)
if err = r.cstate.next(header.ctype); err != nil {
return err
}
if r.cstate == stop {
return io.EOF
}
if header.ctype == cUD || header.ctype == cLRND {
r.dict.Reset()
}
size := int64(header.uncompressed) + 1
if uncompressed(header.ctype) {
if r.ur != nil {
r.ur.Reopen(r.r, size)
} else {
r.ur = newUncompressedReader(r.r, r.dict, size)
}
r.chunkReader = r.ur
return nil
}
br := ByteReader(io.LimitReader(r.r, int64(header.compressed)+1))
if r.decoder == nil {
state := newState(header.props)
r.decoder, err = newDecoder(br, state, r.dict, size)
if err != nil {
return err
}
r.chunkReader = r.decoder
return nil
}
switch header.ctype {
case cLR:
r.decoder.State.Reset()
case cLRN, cLRND:
r.decoder.State = newState(header.props)
}
err = r.decoder.Reopen(br, size)
if err != nil {
return err
}
r.chunkReader = r.decoder
return nil
}
// Read reads data from the LZMA2 chunk sequence.
func (r *Reader2) Read(p []byte) (n int, err error) {
if r.err != nil {
return 0, r.err
}
for n < len(p) {
var k int
k, err = r.chunkReader.Read(p[n:])
n += k
if err != nil {
if err == io.EOF {
err = r.startChunk()
if err == nil {
continue
}
}
r.err = err
return n, err
}
if k == 0 {
r.err = errors.New("lzma: Reader2 doesn't get data")
return n, r.err
}
}
return n, nil
}
// EOS returns whether the LZMA2 stream has been terminated by an
// end-of-stream chunk.
func (r *Reader2) EOS() bool {
return r.cstate == stop
}
// uncompressedReader is used to read uncompressed chunks.
type uncompressedReader struct {
lr io.LimitedReader
Dict *decoderDict
eof bool
err error
}
// newUncompressedReader initializes a new uncompressedReader.
func newUncompressedReader(r io.Reader, dict *decoderDict, size int64) *uncompressedReader {
ur := &uncompressedReader{
lr: io.LimitedReader{R: r, N: size},
Dict: dict,
}
return ur
}
// Reopen reinitializes an uncompressed reader.
func (ur *uncompressedReader) Reopen(r io.Reader, size int64) {
ur.err = nil
ur.eof = false
ur.lr = io.LimitedReader{R: r, N: size}
}
// fill reads uncompressed data into the dictionary.
func (ur *uncompressedReader) fill() error {
if !ur.eof {
n, err := io.CopyN(ur.Dict, &ur.lr, int64(ur.Dict.Available()))
if err != io.EOF {
return err
}
ur.eof = true
if n > 0 {
return nil
}
}
if ur.lr.N != 0 {
return io.ErrUnexpectedEOF
}
return io.EOF
}
// Read reads uncompressed data from the limited reader.
func (ur *uncompressedReader) Read(p []byte) (n int, err error) {
if ur.err != nil {
return 0, ur.err
}
for {
var k int
k, err = ur.Dict.Read(p[n:])
n += k
if n >= len(p) {
return n, nil
}
if err != nil {
break
}
err = ur.fill()
if err != nil {
break
}
}
ur.err = err
return n, err
}
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