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101 lines
2.6 KiB
101 lines
2.6 KiB
// 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 supports the decoding and encoding of LZMA streams.
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// Reader and Writer support the classic LZMA format. Reader2 and
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// Writer2 support the decoding and encoding of LZMA2 streams.
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//
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// The package is written completely in Go and doesn't rely on any external
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// library.
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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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)
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// ReaderConfig stores the parameters for the reader of the classic LZMA
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// format.
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type ReaderConfig 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 *ReaderConfig) 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 values will
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// be replaced by default values.
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func (c *ReaderConfig) 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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// Reader provides a reader for LZMA files or streams.
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type Reader struct {
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lzma io.Reader
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h header
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d *decoder
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}
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// NewReader creates a new reader for an LZMA stream using the classic
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// format. NewReader reads and checks the header of the LZMA stream.
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func NewReader(lzma io.Reader) (r *Reader, err error) {
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return ReaderConfig{}.NewReader(lzma)
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}
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// NewReader creates a new reader for an LZMA stream in the classic
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// format. The function reads and verifies the the header of the LZMA
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// stream.
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func (c ReaderConfig) NewReader(lzma io.Reader) (r *Reader, 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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data := make([]byte, HeaderLen)
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if _, err := io.ReadFull(lzma, data); err != nil {
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if err == io.EOF {
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return nil, errors.New("lzma: unexpected EOF")
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}
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return nil, err
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}
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r = &Reader{lzma: lzma}
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if err = r.h.unmarshalBinary(data); err != nil {
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return nil, err
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}
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if r.h.dictCap < MinDictCap {
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return nil, errors.New("lzma: dictionary capacity too small")
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}
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dictCap := r.h.dictCap
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if c.DictCap > dictCap {
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dictCap = c.DictCap
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}
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state := newState(r.h.properties)
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dict, err := newDecoderDict(dictCap)
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if err != nil {
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return nil, err
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}
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r.d, err = newDecoder(ByteReader(lzma), state, dict, r.h.size)
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if err != nil {
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return nil, err
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}
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return r, nil
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}
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// EOSMarker indicates that an EOS marker has been encountered.
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func (r *Reader) EOSMarker() bool {
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return r.d.eosMarker
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}
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// Read returns uncompressed data.
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func (r *Reader) Read(p []byte) (n int, err error) {
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return r.d.Read(p)
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}
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