1 ///////////////////////////////////////////////////////////////////////////////
2 //
3 /// \file       simple_coder.c
4 /// \brief      Wrapper for simple filters
5 ///
6 /// Simple filters don't change the size of the data i.e. number of bytes
7 /// in equals the number of bytes out.
8 //
9 //  Author:     Lasse Collin
10 //
11 //  This file has been put into the public domain.
12 //  You can do whatever you want with this file.
13 //
14 ///////////////////////////////////////////////////////////////////////////////
15 
16 #include "simple_private.h"
17 
18 
19 /// Copied or encodes/decodes more data to out[].
20 static lzma_ret
21 copy_or_code(lzma_simple_coder *coder, const lzma_allocator *allocator,
22 		const uint8_t *restrict in, size_t *restrict in_pos,
23 		size_t in_size, uint8_t *restrict out,
24 		size_t *restrict out_pos, size_t out_size, lzma_action action)
25 {
26 	assert(!coder->end_was_reached);
27 
28 	if (coder->next.code == NULL) {
29 		lzma_bufcpy(in, in_pos, in_size, out, out_pos, out_size);
30 
31 		// Check if end of stream was reached.
32 		if (coder->is_encoder && action == LZMA_FINISH
33 				&& *in_pos == in_size)
34 			coder->end_was_reached = true;
35 
36 	} else {
37 		// Call the next coder in the chain to provide us some data.
38 		const lzma_ret ret = coder->next.code(
39 				coder->next.coder, allocator,
40 				in, in_pos, in_size,
41 				out, out_pos, out_size, action);
42 
43 		if (ret == LZMA_STREAM_END) {
44 			assert(!coder->is_encoder
45 					|| action == LZMA_FINISH);
46 			coder->end_was_reached = true;
47 
48 		} else if (ret != LZMA_OK) {
49 			return ret;
50 		}
51 	}
52 
53 	return LZMA_OK;
54 }
55 
56 
57 static size_t
58 call_filter(lzma_simple_coder *coder, uint8_t *buffer, size_t size)
59 {
60 	const size_t filtered = coder->filter(coder->simple,
61 			coder->now_pos, coder->is_encoder,
62 			buffer, size);
63 	coder->now_pos += filtered;
64 	return filtered;
65 }
66 
67 
68 static lzma_ret
69 simple_code(void *coder_ptr, const lzma_allocator *allocator,
70 		const uint8_t *restrict in, size_t *restrict in_pos,
71 		size_t in_size, uint8_t *restrict out,
72 		size_t *restrict out_pos, size_t out_size, lzma_action action)
73 {
74 	lzma_simple_coder *coder = coder_ptr;
75 
76 	// TODO: Add partial support for LZMA_SYNC_FLUSH. We can support it
77 	// in cases when the filter is able to filter everything. With most
78 	// simple filters it can be done at offset that is a multiple of 2,
79 	// 4, or 16. With x86 filter, it needs good luck, and thus cannot
80 	// be made to work predictably.
81 	if (action == LZMA_SYNC_FLUSH)
82 		return LZMA_OPTIONS_ERROR;
83 
84 	// Flush already filtered data from coder->buffer[] to out[].
85 	if (coder->pos < coder->filtered) {
86 		lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
87 				out, out_pos, out_size);
88 
89 		// If we couldn't flush all the filtered data, return to
90 		// application immediately.
91 		if (coder->pos < coder->filtered)
92 			return LZMA_OK;
93 
94 		if (coder->end_was_reached) {
95 			assert(coder->filtered == coder->size);
96 			return LZMA_STREAM_END;
97 		}
98 	}
99 
100 	// If we get here, there is no filtered data left in the buffer.
101 	coder->filtered = 0;
102 
103 	assert(!coder->end_was_reached);
104 
105 	// If there is more output space left than there is unfiltered data
106 	// in coder->buffer[], flush coder->buffer[] to out[], and copy/code
107 	// more data to out[] hopefully filling it completely. Then filter
108 	// the data in out[]. This step is where most of the data gets
109 	// filtered if the buffer sizes used by the application are reasonable.
110 	const size_t out_avail = out_size - *out_pos;
111 	const size_t buf_avail = coder->size - coder->pos;
112 	if (out_avail > buf_avail || buf_avail == 0) {
113 		// Store the old position so that we know from which byte
114 		// to start filtering.
115 		const size_t out_start = *out_pos;
116 
117 		// Flush data from coder->buffer[] to out[], but don't reset
118 		// coder->pos and coder->size yet. This way the coder can be
119 		// restarted if the next filter in the chain returns e.g.
120 		// LZMA_MEM_ERROR.
121 		//
122 		// Do the memcpy() conditionally because out can be NULL
123 		// (in which case buf_avail is always 0). Calling memcpy()
124 		// with a null-pointer is undefined even if the third
125 		// argument is 0.
126 		if (buf_avail > 0)
127 			memcpy(out + *out_pos, coder->buffer + coder->pos,
128 					buf_avail);
129 
130 		*out_pos += buf_avail;
131 
132 		// Copy/Encode/Decode more data to out[].
133 		{
134 			const lzma_ret ret = copy_or_code(coder, allocator,
135 					in, in_pos, in_size,
136 					out, out_pos, out_size, action);
137 			assert(ret != LZMA_STREAM_END);
138 			if (ret != LZMA_OK)
139 				return ret;
140 		}
141 
142 		// Filter out[] unless there is nothing to filter.
143 		// This way we avoid null pointer + 0 (undefined behavior)
144 		// when out == NULL.
145 		const size_t size = *out_pos - out_start;
146 		const size_t filtered = size == 0 ? 0 : call_filter(
147 				coder, out + out_start, size);
148 
149 		const size_t unfiltered = size - filtered;
150 		assert(unfiltered <= coder->allocated / 2);
151 
152 		// Now we can update coder->pos and coder->size, because
153 		// the next coder in the chain (if any) was successful.
154 		coder->pos = 0;
155 		coder->size = unfiltered;
156 
157 		if (coder->end_was_reached) {
158 			// The last byte has been copied to out[] already.
159 			// They are left as is.
160 			coder->size = 0;
161 
162 		} else if (unfiltered > 0) {
163 			// There is unfiltered data left in out[]. Copy it to
164 			// coder->buffer[] and rewind *out_pos appropriately.
165 			*out_pos -= unfiltered;
166 			memcpy(coder->buffer, out + *out_pos, unfiltered);
167 		}
168 	} else if (coder->pos > 0) {
169 		memmove(coder->buffer, coder->buffer + coder->pos, buf_avail);
170 		coder->size -= coder->pos;
171 		coder->pos = 0;
172 	}
173 
174 	assert(coder->pos == 0);
175 
176 	// If coder->buffer[] isn't empty, try to fill it by copying/decoding
177 	// more data. Then filter coder->buffer[] and copy the successfully
178 	// filtered data to out[]. It is probable, that some filtered and
179 	// unfiltered data will be left to coder->buffer[].
180 	if (coder->size > 0) {
181 		{
182 			const lzma_ret ret = copy_or_code(coder, allocator,
183 					in, in_pos, in_size,
184 					coder->buffer, &coder->size,
185 					coder->allocated, action);
186 			assert(ret != LZMA_STREAM_END);
187 			if (ret != LZMA_OK)
188 				return ret;
189 		}
190 
191 		coder->filtered = call_filter(
192 				coder, coder->buffer, coder->size);
193 
194 		// Everything is considered to be filtered if coder->buffer[]
195 		// contains the last bytes of the data.
196 		if (coder->end_was_reached)
197 			coder->filtered = coder->size;
198 
199 		// Flush as much as possible.
200 		lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
201 				out, out_pos, out_size);
202 	}
203 
204 	// Check if we got everything done.
205 	if (coder->end_was_reached && coder->pos == coder->size)
206 		return LZMA_STREAM_END;
207 
208 	return LZMA_OK;
209 }
210 
211 
212 static void
213 simple_coder_end(void *coder_ptr, const lzma_allocator *allocator)
214 {
215 	lzma_simple_coder *coder = coder_ptr;
216 	lzma_next_end(&coder->next, allocator);
217 	lzma_free(coder->simple, allocator);
218 	lzma_free(coder, allocator);
219 	return;
220 }
221 
222 
223 static lzma_ret
224 simple_coder_update(void *coder_ptr, const lzma_allocator *allocator,
225 		const lzma_filter *filters_null lzma_attribute((__unused__)),
226 		const lzma_filter *reversed_filters)
227 {
228 	lzma_simple_coder *coder = coder_ptr;
229 
230 	// No update support, just call the next filter in the chain.
231 	return lzma_next_filter_update(
232 			&coder->next, allocator, reversed_filters + 1);
233 }
234 
235 
236 extern lzma_ret
237 lzma_simple_coder_init(lzma_next_coder *next, const lzma_allocator *allocator,
238 		const lzma_filter_info *filters,
239 		size_t (*filter)(void *simple, uint32_t now_pos,
240 			bool is_encoder, uint8_t *buffer, size_t size),
241 		size_t simple_size, size_t unfiltered_max,
242 		uint32_t alignment, bool is_encoder)
243 {
244 	// Allocate memory for the lzma_simple_coder structure if needed.
245 	lzma_simple_coder *coder = next->coder;
246 	if (coder == NULL) {
247 		// Here we allocate space also for the temporary buffer. We
248 		// need twice the size of unfiltered_max, because then it
249 		// is always possible to filter at least unfiltered_max bytes
250 		// more data in coder->buffer[] if it can be filled completely.
251 		coder = lzma_alloc(sizeof(lzma_simple_coder)
252 				+ 2 * unfiltered_max, allocator);
253 		if (coder == NULL)
254 			return LZMA_MEM_ERROR;
255 
256 		next->coder = coder;
257 		next->code = &simple_code;
258 		next->end = &simple_coder_end;
259 		next->update = &simple_coder_update;
260 
261 		coder->next = LZMA_NEXT_CODER_INIT;
262 		coder->filter = filter;
263 		coder->allocated = 2 * unfiltered_max;
264 
265 		// Allocate memory for filter-specific data structure.
266 		if (simple_size > 0) {
267 			coder->simple = lzma_alloc(simple_size, allocator);
268 			if (coder->simple == NULL)
269 				return LZMA_MEM_ERROR;
270 		} else {
271 			coder->simple = NULL;
272 		}
273 	}
274 
275 	if (filters[0].options != NULL) {
276 		const lzma_options_bcj *simple = filters[0].options;
277 		coder->now_pos = simple->start_offset;
278 		if (coder->now_pos & (alignment - 1))
279 			return LZMA_OPTIONS_ERROR;
280 	} else {
281 		coder->now_pos = 0;
282 	}
283 
284 	// Reset variables.
285 	coder->is_encoder = is_encoder;
286 	coder->end_was_reached = false;
287 	coder->pos = 0;
288 	coder->filtered = 0;
289 	coder->size = 0;
290 
291 	return lzma_next_filter_init(&coder->next, allocator, filters + 1);
292 }
293