1// Copyright 2014-2019 Ulrich Kunitz. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5// Package lzma supports the decoding and encoding of LZMA streams.
6// Reader and Writer support the classic LZMA format. Reader2 and
7// Writer2 support the decoding and encoding of LZMA2 streams.
8//
9// The package is written completely in Go and doesn't rely on any external
10// library.
11package lzma
12
13import (
14	"errors"
15	"io"
16)
17
18// ReaderConfig stores the parameters for the reader of the classic LZMA
19// format.
20type ReaderConfig struct {
21	DictCap int
22}
23
24// fill converts the zero values of the configuration to the default values.
25func (c *ReaderConfig) fill() {
26	if c.DictCap == 0 {
27		c.DictCap = 8 * 1024 * 1024
28	}
29}
30
31// Verify checks the reader configuration for errors. Zero values will
32// be replaced by default values.
33func (c *ReaderConfig) Verify() error {
34	c.fill()
35	if !(MinDictCap <= c.DictCap && int64(c.DictCap) <= MaxDictCap) {
36		return errors.New("lzma: dictionary capacity is out of range")
37	}
38	return nil
39}
40
41// Reader provides a reader for LZMA files or streams.
42type Reader struct {
43	lzma io.Reader
44	h    header
45	d    *decoder
46}
47
48// NewReader creates a new reader for an LZMA stream using the classic
49// format. NewReader reads and checks the header of the LZMA stream.
50func NewReader(lzma io.Reader) (r *Reader, err error) {
51	return ReaderConfig{}.NewReader(lzma)
52}
53
54// NewReader creates a new reader for an LZMA stream in the classic
55// format. The function reads and verifies the the header of the LZMA
56// stream.
57func (c ReaderConfig) NewReader(lzma io.Reader) (r *Reader, err error) {
58	if err = c.Verify(); err != nil {
59		return nil, err
60	}
61	data := make([]byte, HeaderLen)
62	if _, err := io.ReadFull(lzma, data); err != nil {
63		if err == io.EOF {
64			return nil, errors.New("lzma: unexpected EOF")
65		}
66		return nil, err
67	}
68	r = &Reader{lzma: lzma}
69	if err = r.h.unmarshalBinary(data); err != nil {
70		return nil, err
71	}
72	if r.h.dictCap < MinDictCap {
73		return nil, errors.New("lzma: dictionary capacity too small")
74	}
75	dictCap := r.h.dictCap
76	if c.DictCap > dictCap {
77		dictCap = c.DictCap
78	}
79
80	state := newState(r.h.properties)
81	dict, err := newDecoderDict(dictCap)
82	if err != nil {
83		return nil, err
84	}
85	r.d, err = newDecoder(ByteReader(lzma), state, dict, r.h.size)
86	if err != nil {
87		return nil, err
88	}
89	return r, nil
90}
91
92// EOSMarker indicates that an EOS marker has been encountered.
93func (r *Reader) EOSMarker() bool {
94	return r.d.eosMarker
95}
96
97// Read returns uncompressed data.
98func (r *Reader) Read(p []byte) (n int, err error) {
99	return r.d.Read(p)
100}
101