1///////////////////////////////////////////////////////////////////////////////
2//
3/// \file       index_encoder.c
4/// \brief      Encodes the Index field
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 "index_encoder.h"
14#include "index.h"
15#include "check.h"
16
17
18typedef struct {
19	enum {
20		SEQ_INDICATOR,
21		SEQ_COUNT,
22		SEQ_UNPADDED,
23		SEQ_UNCOMPRESSED,
24		SEQ_NEXT,
25		SEQ_PADDING,
26		SEQ_CRC32,
27	} sequence;
28
29	/// Index being encoded
30	const lzma_index *index;
31
32	/// Iterator for the Index being encoded
33	lzma_index_iter iter;
34
35	/// Position in integers
36	size_t pos;
37
38	/// CRC32 of the List of Records field
39	uint32_t crc32;
40} lzma_index_coder;
41
42
43static lzma_ret
44index_encode(void *coder_ptr,
45		const lzma_allocator *allocator lzma_attribute((__unused__)),
46		const uint8_t *restrict in lzma_attribute((__unused__)),
47		size_t *restrict in_pos lzma_attribute((__unused__)),
48		size_t in_size lzma_attribute((__unused__)),
49		uint8_t *restrict out, size_t *restrict out_pos,
50		size_t out_size,
51		lzma_action action lzma_attribute((__unused__)))
52{
53	lzma_index_coder *coder = coder_ptr;
54
55	// Position where to start calculating CRC32. The idea is that we
56	// need to call lzma_crc32() only once per call to index_encode().
57	const size_t out_start = *out_pos;
58
59	// Return value to use if we return at the end of this function.
60	// We use "goto out" to jump out of the while-switch construct
61	// instead of returning directly, because that way we don't need
62	// to copypaste the lzma_crc32() call to many places.
63	lzma_ret ret = LZMA_OK;
64
65	while (*out_pos < out_size)
66	switch (coder->sequence) {
67	case SEQ_INDICATOR:
68		out[*out_pos] = 0x00;
69		++*out_pos;
70		coder->sequence = SEQ_COUNT;
71		break;
72
73	case SEQ_COUNT: {
74		const lzma_vli count = lzma_index_block_count(coder->index);
75		ret = lzma_vli_encode(count, &coder->pos,
76				out, out_pos, out_size);
77		if (ret != LZMA_STREAM_END)
78			goto out;
79
80		ret = LZMA_OK;
81		coder->pos = 0;
82		coder->sequence = SEQ_NEXT;
83		break;
84	}
85
86	case SEQ_NEXT:
87		if (lzma_index_iter_next(
88				&coder->iter, LZMA_INDEX_ITER_BLOCK)) {
89			// Get the size of the Index Padding field.
90			coder->pos = lzma_index_padding_size(coder->index);
91			assert(coder->pos <= 3);
92			coder->sequence = SEQ_PADDING;
93			break;
94		}
95
96		coder->sequence = SEQ_UNPADDED;
97
98	// Fall through
99
100	case SEQ_UNPADDED:
101	case SEQ_UNCOMPRESSED: {
102		const lzma_vli size = coder->sequence == SEQ_UNPADDED
103				? coder->iter.block.unpadded_size
104				: coder->iter.block.uncompressed_size;
105
106		ret = lzma_vli_encode(size, &coder->pos,
107				out, out_pos, out_size);
108		if (ret != LZMA_STREAM_END)
109			goto out;
110
111		ret = LZMA_OK;
112		coder->pos = 0;
113
114		// Advance to SEQ_UNCOMPRESSED or SEQ_NEXT.
115		++coder->sequence;
116		break;
117	}
118
119	case SEQ_PADDING:
120		if (coder->pos > 0) {
121			--coder->pos;
122			out[(*out_pos)++] = 0x00;
123			break;
124		}
125
126		// Finish the CRC32 calculation.
127		coder->crc32 = lzma_crc32(out + out_start,
128				*out_pos - out_start, coder->crc32);
129
130		coder->sequence = SEQ_CRC32;
131
132	// Fall through
133
134	case SEQ_CRC32:
135		// We don't use the main loop, because we don't want
136		// coder->crc32 to be touched anymore.
137		do {
138			if (*out_pos == out_size)
139				return LZMA_OK;
140
141			out[*out_pos] = (coder->crc32 >> (coder->pos * 8))
142					& 0xFF;
143			++*out_pos;
144
145		} while (++coder->pos < 4);
146
147		return LZMA_STREAM_END;
148
149	default:
150		assert(0);
151		return LZMA_PROG_ERROR;
152	}
153
154out:
155	// Update the CRC32.
156	coder->crc32 = lzma_crc32(out + out_start,
157			*out_pos - out_start, coder->crc32);
158
159	return ret;
160}
161
162
163static void
164index_encoder_end(void *coder, const lzma_allocator *allocator)
165{
166	lzma_free(coder, allocator);
167	return;
168}
169
170
171static void
172index_encoder_reset(lzma_index_coder *coder, const lzma_index *i)
173{
174	lzma_index_iter_init(&coder->iter, i);
175
176	coder->sequence = SEQ_INDICATOR;
177	coder->index = i;
178	coder->pos = 0;
179	coder->crc32 = 0;
180
181	return;
182}
183
184
185extern lzma_ret
186lzma_index_encoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
187		const lzma_index *i)
188{
189	lzma_next_coder_init(&lzma_index_encoder_init, next, allocator);
190
191	if (i == NULL)
192		return LZMA_PROG_ERROR;
193
194	if (next->coder == NULL) {
195		next->coder = lzma_alloc(sizeof(lzma_index_coder), allocator);
196		if (next->coder == NULL)
197			return LZMA_MEM_ERROR;
198
199		next->code = &index_encode;
200		next->end = &index_encoder_end;
201	}
202
203	index_encoder_reset(next->coder, i);
204
205	return LZMA_OK;
206}
207
208
209extern LZMA_API(lzma_ret)
210lzma_index_encoder(lzma_stream *strm, const lzma_index *i)
211{
212	lzma_next_strm_init(lzma_index_encoder_init, strm, i);
213
214	strm->internal->supported_actions[LZMA_RUN] = true;
215	strm->internal->supported_actions[LZMA_FINISH] = true;
216
217	return LZMA_OK;
218}
219
220
221extern LZMA_API(lzma_ret)
222lzma_index_buffer_encode(const lzma_index *i,
223		uint8_t *out, size_t *out_pos, size_t out_size)
224{
225	// Validate the arguments.
226	if (i == NULL || out == NULL || out_pos == NULL || *out_pos > out_size)
227		return LZMA_PROG_ERROR;
228
229	// Don't try to encode if there's not enough output space.
230	if (out_size - *out_pos < lzma_index_size(i))
231		return LZMA_BUF_ERROR;
232
233	// The Index encoder needs just one small data structure so we can
234	// allocate it on stack.
235	lzma_index_coder coder;
236	index_encoder_reset(&coder, i);
237
238	// Do the actual encoding. This should never fail, but store
239	// the original *out_pos just in case.
240	const size_t out_start = *out_pos;
241	lzma_ret ret = index_encode(&coder, NULL, NULL, NULL, 0,
242			out, out_pos, out_size, LZMA_RUN);
243
244	if (ret == LZMA_STREAM_END) {
245		ret = LZMA_OK;
246	} else {
247		// We should never get here, but just in case, restore the
248		// output position and set the error accordingly if something
249		// goes wrong and debugging isn't enabled.
250		assert(0);
251		*out_pos = out_start;
252		ret = LZMA_PROG_ERROR;
253	}
254
255	return ret;
256}
257