xref: /freebsd/contrib/xz/src/liblzma/simple/simple_coder.c (revision a91a246563dffa876a52f53a98de4af9fa364c52)
1 // SPDX-License-Identifier: 0BSD
2 
3 ///////////////////////////////////////////////////////////////////////////////
4 //
5 /// \file       simple_coder.c
6 /// \brief      Wrapper for simple filters
7 ///
8 /// Simple filters don't change the size of the data i.e. number of bytes
9 /// in equals the number of bytes out.
10 //
11 //  Author:     Lasse Collin
12 //
13 ///////////////////////////////////////////////////////////////////////////////
14 
15 #include "simple_private.h"
16 
17 
18 /// Copied or encodes/decodes more data to out[].
19 static lzma_ret
20 copy_or_code(lzma_simple_coder *coder, const lzma_allocator *allocator,
21 		const uint8_t *restrict in, size_t *restrict in_pos,
22 		size_t in_size, uint8_t *restrict out,
23 		size_t *restrict out_pos, size_t out_size, lzma_action action)
24 {
25 	assert(!coder->end_was_reached);
26 
27 	if (coder->next.code == NULL) {
28 		lzma_bufcpy(in, in_pos, in_size, out, out_pos, out_size);
29 
30 		// Check if end of stream was reached.
31 		if (coder->is_encoder && action == LZMA_FINISH
32 				&& *in_pos == in_size)
33 			coder->end_was_reached = true;
34 
35 	} else {
36 		// Call the next coder in the chain to provide us some data.
37 		const lzma_ret ret = coder->next.code(
38 				coder->next.coder, allocator,
39 				in, in_pos, in_size,
40 				out, out_pos, out_size, action);
41 
42 		if (ret == LZMA_STREAM_END) {
43 			assert(!coder->is_encoder
44 					|| action == LZMA_FINISH);
45 			coder->end_was_reached = true;
46 
47 		} else if (ret != LZMA_OK) {
48 			return ret;
49 		}
50 	}
51 
52 	return LZMA_OK;
53 }
54 
55 
56 static size_t
57 call_filter(lzma_simple_coder *coder, uint8_t *buffer, size_t size)
58 {
59 	const size_t filtered = coder->filter(coder->simple,
60 			coder->now_pos, coder->is_encoder,
61 			buffer, size);
62 	coder->now_pos += filtered;
63 	return filtered;
64 }
65 
66 
67 static lzma_ret
68 simple_code(void *coder_ptr, const lzma_allocator *allocator,
69 		const uint8_t *restrict in, size_t *restrict in_pos,
70 		size_t in_size, uint8_t *restrict out,
71 		size_t *restrict out_pos, size_t out_size, lzma_action action)
72 {
73 	lzma_simple_coder *coder = coder_ptr;
74 
75 	// TODO: Add partial support for LZMA_SYNC_FLUSH. We can support it
76 	// in cases when the filter is able to filter everything. With most
77 	// simple filters it can be done at offset that is a multiple of 2,
78 	// 4, or 16. With x86 filter, it needs good luck, and thus cannot
79 	// be made to work predictably.
80 	if (action == LZMA_SYNC_FLUSH)
81 		return LZMA_OPTIONS_ERROR;
82 
83 	// Flush already filtered data from coder->buffer[] to out[].
84 	if (coder->pos < coder->filtered) {
85 		lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
86 				out, out_pos, out_size);
87 
88 		// If we couldn't flush all the filtered data, return to
89 		// application immediately.
90 		if (coder->pos < coder->filtered)
91 			return LZMA_OK;
92 
93 		if (coder->end_was_reached) {
94 			assert(coder->filtered == coder->size);
95 			return LZMA_STREAM_END;
96 		}
97 	}
98 
99 	// If we get here, there is no filtered data left in the buffer.
100 	coder->filtered = 0;
101 
102 	assert(!coder->end_was_reached);
103 
104 	// If there is more output space left than there is unfiltered data
105 	// in coder->buffer[], flush coder->buffer[] to out[], and copy/code
106 	// more data to out[] hopefully filling it completely. Then filter
107 	// the data in out[]. This step is where most of the data gets
108 	// filtered if the buffer sizes used by the application are reasonable.
109 	const size_t out_avail = out_size - *out_pos;
110 	const size_t buf_avail = coder->size - coder->pos;
111 	if (out_avail > buf_avail || buf_avail == 0) {
112 		// Store the old position so that we know from which byte
113 		// to start filtering.
114 		const size_t out_start = *out_pos;
115 
116 		// Flush data from coder->buffer[] to out[], but don't reset
117 		// coder->pos and coder->size yet. This way the coder can be
118 		// restarted if the next filter in the chain returns e.g.
119 		// LZMA_MEM_ERROR.
120 		//
121 		// Do the memcpy() conditionally because out can be NULL
122 		// (in which case buf_avail is always 0). Calling memcpy()
123 		// with a null-pointer is undefined even if the third
124 		// argument is 0.
125 		if (buf_avail > 0)
126 			memcpy(out + *out_pos, coder->buffer + coder->pos,
127 					buf_avail);
128 
129 		*out_pos += buf_avail;
130 
131 		// Copy/Encode/Decode more data to out[].
132 		{
133 			const lzma_ret ret = copy_or_code(coder, allocator,
134 					in, in_pos, in_size,
135 					out, out_pos, out_size, action);
136 			assert(ret != LZMA_STREAM_END);
137 			if (ret != LZMA_OK)
138 				return ret;
139 		}
140 
141 		// Filter out[] unless there is nothing to filter.
142 		// This way we avoid null pointer + 0 (undefined behavior)
143 		// when out == NULL.
144 		const size_t size = *out_pos - out_start;
145 		const size_t filtered = size == 0 ? 0 : call_filter(
146 				coder, out + out_start, size);
147 
148 		const size_t unfiltered = size - filtered;
149 		assert(unfiltered <= coder->allocated / 2);
150 
151 		// Now we can update coder->pos and coder->size, because
152 		// the next coder in the chain (if any) was successful.
153 		coder->pos = 0;
154 		coder->size = unfiltered;
155 
156 		if (coder->end_was_reached) {
157 			// The last byte has been copied to out[] already.
158 			// They are left as is.
159 			coder->size = 0;
160 
161 		} else if (unfiltered > 0) {
162 			// There is unfiltered data left in out[]. Copy it to
163 			// coder->buffer[] and rewind *out_pos appropriately.
164 			*out_pos -= unfiltered;
165 			memcpy(coder->buffer, out + *out_pos, unfiltered);
166 		}
167 	} else if (coder->pos > 0) {
168 		memmove(coder->buffer, coder->buffer + coder->pos, buf_avail);
169 		coder->size -= coder->pos;
170 		coder->pos = 0;
171 	}
172 
173 	assert(coder->pos == 0);
174 
175 	// If coder->buffer[] isn't empty, try to fill it by copying/decoding
176 	// more data. Then filter coder->buffer[] and copy the successfully
177 	// filtered data to out[]. It is probable, that some filtered and
178 	// unfiltered data will be left to coder->buffer[].
179 	if (coder->size > 0) {
180 		{
181 			const lzma_ret ret = copy_or_code(coder, allocator,
182 					in, in_pos, in_size,
183 					coder->buffer, &coder->size,
184 					coder->allocated, action);
185 			assert(ret != LZMA_STREAM_END);
186 			if (ret != LZMA_OK)
187 				return ret;
188 		}
189 
190 		coder->filtered = call_filter(
191 				coder, coder->buffer, coder->size);
192 
193 		// Everything is considered to be filtered if coder->buffer[]
194 		// contains the last bytes of the data.
195 		if (coder->end_was_reached)
196 			coder->filtered = coder->size;
197 
198 		// Flush as much as possible.
199 		lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
200 				out, out_pos, out_size);
201 	}
202 
203 	// Check if we got everything done.
204 	if (coder->end_was_reached && coder->pos == coder->size)
205 		return LZMA_STREAM_END;
206 
207 	return LZMA_OK;
208 }
209 
210 
211 static void
212 simple_coder_end(void *coder_ptr, const lzma_allocator *allocator)
213 {
214 	lzma_simple_coder *coder = coder_ptr;
215 	lzma_next_end(&coder->next, allocator);
216 	lzma_free(coder->simple, allocator);
217 	lzma_free(coder, allocator);
218 	return;
219 }
220 
221 
222 static lzma_ret
223 simple_coder_update(void *coder_ptr, const lzma_allocator *allocator,
224 		const lzma_filter *filters_null lzma_attribute((__unused__)),
225 		const lzma_filter *reversed_filters)
226 {
227 	lzma_simple_coder *coder = coder_ptr;
228 
229 	// No update support, just call the next filter in the chain.
230 	return lzma_next_filter_update(
231 			&coder->next, allocator, reversed_filters + 1);
232 }
233 
234 
235 extern lzma_ret
236 lzma_simple_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
237 		const lzma_filter_info *filters,
238 		size_t (*filter)(void *simple, uint32_t now_pos,
239 			bool is_encoder, uint8_t *buffer, size_t size),
240 		size_t simple_size, size_t unfiltered_max,
241 		uint32_t alignment, bool is_encoder)
242 {
243 	// Allocate memory for the lzma_simple_coder structure if needed.
244 	lzma_simple_coder *coder = next->coder;
245 	if (coder == NULL) {
246 		// Here we allocate space also for the temporary buffer. We
247 		// need twice the size of unfiltered_max, because then it
248 		// is always possible to filter at least unfiltered_max bytes
249 		// more data in coder->buffer[] if it can be filled completely.
250 		coder = lzma_alloc(sizeof(lzma_simple_coder)
251 				+ 2 * unfiltered_max, allocator);
252 		if (coder == NULL)
253 			return LZMA_MEM_ERROR;
254 
255 		next->coder = coder;
256 		next->code = &simple_code;
257 		next->end = &simple_coder_end;
258 		next->update = &simple_coder_update;
259 
260 		coder->next = LZMA_NEXT_CODER_INIT;
261 		coder->filter = filter;
262 		coder->allocated = 2 * unfiltered_max;
263 
264 		// Allocate memory for filter-specific data structure.
265 		if (simple_size > 0) {
266 			coder->simple = lzma_alloc(simple_size, allocator);
267 			if (coder->simple == NULL)
268 				return LZMA_MEM_ERROR;
269 		} else {
270 			coder->simple = NULL;
271 		}
272 	}
273 
274 	if (filters[0].options != NULL) {
275 		const lzma_options_bcj *simple = filters[0].options;
276 		coder->now_pos = simple->start_offset;
277 		if (coder->now_pos & (alignment - 1))
278 			return LZMA_OPTIONS_ERROR;
279 	} else {
280 		coder->now_pos = 0;
281 	}
282 
283 	// Reset variables.
284 	coder->is_encoder = is_encoder;
285 	coder->end_was_reached = false;
286 	coder->pos = 0;
287 	coder->filtered = 0;
288 	coder->size = 0;
289 
290 	return lzma_next_filter_init(&coder->next, allocator, filters + 1);
291 }
292