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 }