1///////////////////////////////////////////////////////////////////////////////
2//
3/// \file       alone_decoder.c
4/// \brief      Decoder for LZMA_Alone files
5//
6//  Author:     Lasse Collin
7//
8//  This file has been put into the public domain.
9//  You can do whatever you want with this file.
10//
11///////////////////////////////////////////////////////////////////////////////
12
13#include "alone_decoder.h"
14#include "lzma_decoder.h"
15#include "lz_decoder.h"
16
17
18struct lzma_coder_s {
19	lzma_next_coder next;
20
21	enum {
22		SEQ_PROPERTIES,
23		SEQ_DICTIONARY_SIZE,
24		SEQ_UNCOMPRESSED_SIZE,
25		SEQ_CODER_INIT,
26		SEQ_CODE,
27	} sequence;
28
29	/// Position in the header fields
30	size_t pos;
31
32	/// Uncompressed size decoded from the header
33	lzma_vli uncompressed_size;
34
35	/// Memory usage limit
36	uint64_t memlimit;
37
38	/// Amount of memory actually needed (only an estimate)
39	uint64_t memusage;
40
41	/// Options decoded from the header needed to initialize
42	/// the LZMA decoder
43	lzma_options_lzma options;
44};
45
46
47static lzma_ret
48alone_decode(lzma_coder *coder,
49		lzma_allocator *allocator lzma_attribute((__unused__)),
50		const uint8_t *restrict in, size_t *restrict in_pos,
51		size_t in_size, uint8_t *restrict out,
52		size_t *restrict out_pos, size_t out_size,
53		lzma_action action)
54{
55	while (*out_pos < out_size
56			&& (coder->sequence == SEQ_CODE || *in_pos < in_size))
57	switch (coder->sequence) {
58	case SEQ_PROPERTIES:
59		if (lzma_lzma_lclppb_decode(&coder->options, in[*in_pos]))
60			return LZMA_FORMAT_ERROR;
61
62		coder->sequence = SEQ_DICTIONARY_SIZE;
63		++*in_pos;
64		break;
65
66	case SEQ_DICTIONARY_SIZE:
67		coder->options.dict_size
68				|= (size_t)(in[*in_pos]) << (coder->pos * 8);
69
70		if (++coder->pos == 4) {
71			if (coder->options.dict_size != UINT32_MAX) {
72				// A hack to ditch tons of false positives:
73				// We allow only dictionary sizes that are
74				// 2^n or 2^n + 2^(n-1). LZMA_Alone created
75				// only files with 2^n, but accepts any
76				// dictionary size. If someone complains, this
77				// will be reconsidered.
78				uint32_t d = coder->options.dict_size - 1;
79				d |= d >> 2;
80				d |= d >> 3;
81				d |= d >> 4;
82				d |= d >> 8;
83				d |= d >> 16;
84				++d;
85
86				if (d != coder->options.dict_size)
87					return LZMA_FORMAT_ERROR;
88			}
89
90			coder->pos = 0;
91			coder->sequence = SEQ_UNCOMPRESSED_SIZE;
92		}
93
94		++*in_pos;
95		break;
96
97	case SEQ_UNCOMPRESSED_SIZE:
98		coder->uncompressed_size
99				|= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);
100		++*in_pos;
101		if (++coder->pos < 8)
102			break;
103
104		// Another hack to ditch false positives: Assume that
105		// if the uncompressed size is known, it must be less
106		// than 256 GiB. Again, if someone complains, this
107		// will be reconsidered.
108		if (coder->uncompressed_size != LZMA_VLI_UNKNOWN
109				&& coder->uncompressed_size
110					>= (LZMA_VLI_C(1) << 38))
111			return LZMA_FORMAT_ERROR;
112
113		// Calculate the memory usage so that it is ready
114		// for SEQ_CODER_INIT.
115		coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
116				+ LZMA_MEMUSAGE_BASE;
117
118		coder->pos = 0;
119		coder->sequence = SEQ_CODER_INIT;
120
121	// Fall through
122
123	case SEQ_CODER_INIT: {
124		if (coder->memusage > coder->memlimit)
125			return LZMA_MEMLIMIT_ERROR;
126
127		lzma_filter_info filters[2] = {
128			{
129				.init = &lzma_lzma_decoder_init,
130				.options = &coder->options,
131			}, {
132				.init = NULL,
133			}
134		};
135
136		const lzma_ret ret = lzma_next_filter_init(&coder->next,
137				allocator, filters);
138		if (ret != LZMA_OK)
139			return ret;
140
141		// Use a hack to set the uncompressed size.
142		lzma_lz_decoder_uncompressed(coder->next.coder,
143				coder->uncompressed_size);
144
145		coder->sequence = SEQ_CODE;
146		break;
147	}
148
149	case SEQ_CODE: {
150		return coder->next.code(coder->next.coder,
151				allocator, in, in_pos, in_size,
152				out, out_pos, out_size, action);
153	}
154
155	default:
156		return LZMA_PROG_ERROR;
157	}
158
159	return LZMA_OK;
160}
161
162
163static void
164alone_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
165{
166	lzma_next_end(&coder->next, allocator);
167	lzma_free(coder, allocator);
168	return;
169}
170
171
172static lzma_ret
173alone_decoder_memconfig(lzma_coder *coder, uint64_t *memusage,
174		uint64_t *old_memlimit, uint64_t new_memlimit)
175{
176	*memusage = coder->memusage;
177	*old_memlimit = coder->memlimit;
178
179	if (new_memlimit != 0) {
180		if (new_memlimit < coder->memusage)
181			return LZMA_MEMLIMIT_ERROR;
182
183		coder->memlimit = new_memlimit;
184	}
185
186	return LZMA_OK;
187}
188
189
190extern lzma_ret
191lzma_alone_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
192		uint64_t memlimit)
193{
194	lzma_next_coder_init(&lzma_alone_decoder_init, next, allocator);
195
196	if (memlimit == 0)
197		return LZMA_PROG_ERROR;
198
199	if (next->coder == NULL) {
200		next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
201		if (next->coder == NULL)
202			return LZMA_MEM_ERROR;
203
204		next->code = &alone_decode;
205		next->end = &alone_decoder_end;
206		next->memconfig = &alone_decoder_memconfig;
207		next->coder->next = LZMA_NEXT_CODER_INIT;
208	}
209
210	next->coder->sequence = SEQ_PROPERTIES;
211	next->coder->pos = 0;
212	next->coder->options.dict_size = 0;
213	next->coder->options.preset_dict = NULL;
214	next->coder->options.preset_dict_size = 0;
215	next->coder->uncompressed_size = 0;
216	next->coder->memlimit = memlimit;
217	next->coder->memusage = LZMA_MEMUSAGE_BASE;
218
219	return LZMA_OK;
220}
221
222
223extern LZMA_API(lzma_ret)
224lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit)
225{
226	lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit);
227
228	strm->internal->supported_actions[LZMA_RUN] = true;
229	strm->internal->supported_actions[LZMA_FINISH] = true;
230
231	return LZMA_OK;
232}
233