contrib/xz/src/liblzma/simple/simple_coder.c

   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_coder *coder, 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_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(lzma_coder *coder, 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         // TODO: Add partial support for LZMA_SYNC_FLUSH. We can support it
  75         // in cases when the filter is able to filter everything. With most
  76         // simple filters it can be done at offset that is a multiple of 2,
  77         // 4, or 16. With x86 filter, it needs good luck, and thus cannot
  78         // be made to work predictably.
  79         if (action == LZMA_SYNC_FLUSH)
  80                 return LZMA_OPTIONS_ERROR;
  81
  82         // Flush already filtered data from coder->buffer[] to out[].
  83         if (coder->pos < coder->filtered) {
  84                 lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
  85                                 out, out_pos, out_size);
  86
  87                 // If we couldn't flush all the filtered data, return to
  88                 // application immediately.
  89                 if (coder->pos < coder->filtered)
  90                         return LZMA_OK;
  91
  92                 if (coder->end_was_reached) {
  93                         assert(coder->filtered == coder->size);
  94                         return LZMA_STREAM_END;
  95                 }
  96         }
  97
  98         // If we get here, there is no filtered data left in the buffer.
  99         coder->filtered = 0;
 100
 101         assert(!coder->end_was_reached);
 102
 103         // If there is more output space left than there is unfiltered data
 104         // in coder->buffer[], flush coder->buffer[] to out[], and copy/code
 105         // more data to out[] hopefully filling it completely. Then filter
 106         // the data in out[]. This step is where most of the data gets
 107         // filtered if the buffer sizes used by the application are reasonable.
 108         const size_t out_avail = out_size - *out_pos;
 109         const size_t buf_avail = coder->size - coder->pos;
 110         if (out_avail > buf_avail || buf_avail == 0) {
 111                 // Store the old position so that we know from which byte
 112                 // to start filtering.
 113                 const size_t out_start = *out_pos;
 114
 115                 // Flush data from coder->buffer[] to out[], but don't reset
 116                 // coder->pos and coder->size yet. This way the coder can be
 117                 // restarted if the next filter in the chain returns e.g.
 118                 // LZMA_MEM_ERROR.
 119                 memcpy(out + *out_pos, coder->buffer + coder->pos, buf_avail);
 120                 *out_pos += buf_avail;
 121
 122                 // Copy/Encode/Decode more data to out[].
 123                 {
 124                         const lzma_ret ret = copy_or_code(coder, allocator,
 125                                         in, in_pos, in_size,
 126                                         out, out_pos, out_size, action);
 127                         assert(ret != LZMA_STREAM_END);
 128                         if (ret != LZMA_OK)
 129                                 return ret;
 130                 }
 131
 132                 // Filter out[].
 133                 const size_t size = *out_pos - out_start;
 134                 const size_t filtered = call_filter(
 135                                 coder, out + out_start, size);
 136
 137                 const size_t unfiltered = size - filtered;
 138                 assert(unfiltered <= coder->allocated / 2);
 139
 140                 // Now we can update coder->pos and coder->size, because
 141                 // the next coder in the chain (if any) was successful.
 142                 coder->pos = 0;
 143                 coder->size = unfiltered;
 144
 145                 if (coder->end_was_reached) {
 146                         // The last byte has been copied to out[] already.
 147                         // They are left as is.
 148                         coder->size = 0;
 149
 150                 } else if (unfiltered > 0) {
 151                         // There is unfiltered data left in out[]. Copy it to
 152                         // coder->buffer[] and rewind *out_pos appropriately.
 153                         *out_pos -= unfiltered;
 154                         memcpy(coder->buffer, out + *out_pos, unfiltered);
 155                 }
 156         } else if (coder->pos > 0) {
 157                 memmove(coder->buffer, coder->buffer + coder->pos, buf_avail);
 158                 coder->size -= coder->pos;
 159                 coder->pos = 0;
 160         }
 161
 162         assert(coder->pos == 0);
 163
 164         // If coder->buffer[] isn't empty, try to fill it by copying/decoding
 165         // more data. Then filter coder->buffer[] and copy the successfully
 166         // filtered data to out[]. It is probable, that some filtered and
 167         // unfiltered data will be left to coder->buffer[].
 168         if (coder->size > 0) {
 169                 {
 170                         const lzma_ret ret = copy_or_code(coder, allocator,
 171                                         in, in_pos, in_size,
 172                                         coder->buffer, &coder->size,
 173                                         coder->allocated, action);
 174                         assert(ret != LZMA_STREAM_END);
 175                         if (ret != LZMA_OK)
 176                                 return ret;
 177                 }
 178
 179                 coder->filtered = call_filter(
 180                                 coder, coder->buffer, coder->size);
 181
 182                 // Everything is considered to be filtered if coder->buffer[]
 183                 // contains the last bytes of the data.
 184                 if (coder->end_was_reached)
 185                         coder->filtered = coder->size;
 186
 187                 // Flush as much as possible.
 188                 lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
 189                                 out, out_pos, out_size);
 190         }
 191
 192         // Check if we got everything done.
 193         if (coder->end_was_reached && coder->pos == coder->size)
 194                 return LZMA_STREAM_END;
 195
 196         return LZMA_OK;
 197 }
 198
 199
 200 static void
 201 simple_coder_end(lzma_coder *coder, lzma_allocator *allocator)
 202 {
 203         lzma_next_end(&coder->next, allocator);
 204         lzma_free(coder->simple, allocator);
 205         lzma_free(coder, allocator);
 206         return;
 207 }
 208
 209
 210 static lzma_ret
 211 simple_coder_update(lzma_coder *coder, lzma_allocator *allocator,
 212                 const lzma_filter *filters_null lzma_attribute((__unused__)),
 213                 const lzma_filter *reversed_filters)
 214 {
 215         // No update support, just call the next filter in the chain.
 216         return lzma_next_filter_update(
 217                         &coder->next, allocator, reversed_filters + 1);
 218 }
 219
 220
 221 extern lzma_ret
 222 lzma_simple_coder_init(lzma_next_coder *next, lzma_allocator *allocator,
 223                 const lzma_filter_info *filters,
 224                 size_t (*filter)(lzma_simple *simple, uint32_t now_pos,
 225                         bool is_encoder, uint8_t *buffer, size_t size),
 226                 size_t simple_size, size_t unfiltered_max,
 227                 uint32_t alignment, bool is_encoder)
 228 {
 229         // Allocate memory for the lzma_coder structure if needed.
 230         if (next->coder == NULL) {
 231                 // Here we allocate space also for the temporary buffer. We
 232                 // need twice the size of unfiltered_max, because then it
 233                 // is always possible to filter at least unfiltered_max bytes
 234                 // more data in coder->buffer[] if it can be filled completely.
 235                 next->coder = lzma_alloc(sizeof(lzma_coder)
 236                                 + 2 * unfiltered_max, allocator);
 237                 if (next->coder == NULL)
 238                         return LZMA_MEM_ERROR;
 239
 240                 next->code = &simple_code;
 241                 next->end = &simple_coder_end;
 242                 next->update = &simple_coder_update;
 243
 244                 next->coder->next = LZMA_NEXT_CODER_INIT;
 245                 next->coder->filter = filter;
 246                 next->coder->allocated = 2 * unfiltered_max;
 247
 248                 // Allocate memory for filter-specific data structure.
 249                 if (simple_size > 0) {
 250                         next->coder->simple = lzma_alloc(
 251                                         simple_size, allocator);
 252                         if (next->coder->simple == NULL)
 253                                 return LZMA_MEM_ERROR;
 254                 } else {
 255                         next->coder->simple = NULL;
 256                 }
 257         }
 258
 259         if (filters[0].options != NULL) {
 260                 const lzma_options_bcj *simple = filters[0].options;
 261                 next->coder->now_pos = simple->start_offset;
 262                 if (next->coder->now_pos & (alignment - 1))
 263                         return LZMA_OPTIONS_ERROR;
 264         } else {
 265                 next->coder->now_pos = 0;
 266         }
 267
 268         // Reset variables.
 269         next->coder->is_encoder = is_encoder;
 270         next->coder->end_was_reached = false;
 271         next->coder->pos = 0;
 272         next->coder->filtered = 0;
 273         next->coder->size = 0;
 274
 275         return lzma_next_filter_init(
 276                         &next->coder->next, allocator, filters + 1);
 277 }