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