mirror of
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232 lines
5.0 KiB
Go
Vendored
232 lines
5.0 KiB
Go
Vendored
// Copyright 2014-2021 Ulrich Kunitz. 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 lzma
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import (
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"errors"
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"io"
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"github.com/ulikunitz/xz/internal/xlog"
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)
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// Reader2Config stores the parameters for the LZMA2 reader.
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// format.
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type Reader2Config struct {
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DictCap int
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}
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// fill converts the zero values of the configuration to the default values.
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func (c *Reader2Config) fill() {
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if c.DictCap == 0 {
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c.DictCap = 8 * 1024 * 1024
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}
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}
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// Verify checks the reader configuration for errors. Zero configuration values
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// will be replaced by default values.
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func (c *Reader2Config) Verify() error {
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c.fill()
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if !(MinDictCap <= c.DictCap && int64(c.DictCap) <= MaxDictCap) {
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return errors.New("lzma: dictionary capacity is out of range")
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}
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return nil
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}
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// Reader2 supports the reading of LZMA2 chunk sequences. Note that the
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// first chunk should have a dictionary reset and the first compressed
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// chunk a properties reset. The chunk sequence may not be terminated by
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// an end-of-stream chunk.
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type Reader2 struct {
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r io.Reader
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err error
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dict *decoderDict
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ur *uncompressedReader
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decoder *decoder
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chunkReader io.Reader
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cstate chunkState
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}
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// NewReader2 creates a reader for an LZMA2 chunk sequence.
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func NewReader2(lzma2 io.Reader) (r *Reader2, err error) {
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return Reader2Config{}.NewReader2(lzma2)
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}
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// NewReader2 creates an LZMA2 reader using the given configuration.
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func (c Reader2Config) NewReader2(lzma2 io.Reader) (r *Reader2, err error) {
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if err = c.Verify(); err != nil {
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return nil, err
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}
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r = &Reader2{r: lzma2, cstate: start}
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r.dict, err = newDecoderDict(c.DictCap)
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if err != nil {
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return nil, err
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}
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if err = r.startChunk(); err != nil {
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r.err = err
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}
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return r, nil
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}
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// uncompressed tests whether the chunk type specifies an uncompressed
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// chunk.
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func uncompressed(ctype chunkType) bool {
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return ctype == cU || ctype == cUD
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}
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// startChunk parses a new chunk.
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func (r *Reader2) startChunk() error {
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r.chunkReader = nil
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header, err := readChunkHeader(r.r)
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if err != nil {
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if err == io.EOF {
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err = io.ErrUnexpectedEOF
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}
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return err
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}
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xlog.Debugf("chunk header %v", header)
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if err = r.cstate.next(header.ctype); err != nil {
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return err
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}
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if r.cstate == stop {
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return io.EOF
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}
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if header.ctype == cUD || header.ctype == cLRND {
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r.dict.Reset()
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}
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size := int64(header.uncompressed) + 1
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if uncompressed(header.ctype) {
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if r.ur != nil {
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r.ur.Reopen(r.r, size)
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} else {
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r.ur = newUncompressedReader(r.r, r.dict, size)
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}
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r.chunkReader = r.ur
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return nil
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}
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br := ByteReader(io.LimitReader(r.r, int64(header.compressed)+1))
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if r.decoder == nil {
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state := newState(header.props)
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r.decoder, err = newDecoder(br, state, r.dict, size)
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if err != nil {
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return err
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}
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r.chunkReader = r.decoder
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return nil
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}
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switch header.ctype {
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case cLR:
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r.decoder.State.Reset()
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case cLRN, cLRND:
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r.decoder.State = newState(header.props)
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}
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err = r.decoder.Reopen(br, size)
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if err != nil {
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return err
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}
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r.chunkReader = r.decoder
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return nil
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}
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// Read reads data from the LZMA2 chunk sequence.
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func (r *Reader2) Read(p []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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for n < len(p) {
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var k int
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k, err = r.chunkReader.Read(p[n:])
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n += k
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if err != nil {
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if err == io.EOF {
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err = r.startChunk()
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if err == nil {
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continue
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}
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}
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r.err = err
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return n, err
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}
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if k == 0 {
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r.err = errors.New("lzma: Reader2 doesn't get data")
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return n, r.err
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}
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}
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return n, nil
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}
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// EOS returns whether the LZMA2 stream has been terminated by an
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// end-of-stream chunk.
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func (r *Reader2) EOS() bool {
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return r.cstate == stop
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}
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// uncompressedReader is used to read uncompressed chunks.
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type uncompressedReader struct {
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lr io.LimitedReader
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Dict *decoderDict
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eof bool
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err error
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}
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// newUncompressedReader initializes a new uncompressedReader.
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func newUncompressedReader(r io.Reader, dict *decoderDict, size int64) *uncompressedReader {
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ur := &uncompressedReader{
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lr: io.LimitedReader{R: r, N: size},
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Dict: dict,
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}
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return ur
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}
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// Reopen reinitializes an uncompressed reader.
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func (ur *uncompressedReader) Reopen(r io.Reader, size int64) {
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ur.err = nil
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ur.eof = false
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ur.lr = io.LimitedReader{R: r, N: size}
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}
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// fill reads uncompressed data into the dictionary.
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func (ur *uncompressedReader) fill() error {
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if !ur.eof {
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n, err := io.CopyN(ur.Dict, &ur.lr, int64(ur.Dict.Available()))
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if err != io.EOF {
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return err
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}
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ur.eof = true
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if n > 0 {
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return nil
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}
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}
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if ur.lr.N != 0 {
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return io.ErrUnexpectedEOF
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}
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return io.EOF
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}
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// Read reads uncompressed data from the limited reader.
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func (ur *uncompressedReader) Read(p []byte) (n int, err error) {
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if ur.err != nil {
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return 0, ur.err
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}
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for {
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var k int
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k, err = ur.Dict.Read(p[n:])
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n += k
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if n >= len(p) {
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return n, nil
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}
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if err != nil {
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break
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}
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err = ur.fill()
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if err != nil {
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break
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}
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}
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ur.err = err
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return n, err
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}
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