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 //  Copyright (C) 2007 Lasse Collin
  10 //
  11 //  This library is free software; you can redistribute it and/or
  12 //  modify it under the terms of the GNU Lesser General Public
  13 //  License as published by the Free Software Foundation; either
  14 //  version 2.1 of the License, or (at your option) any later version.
  15 //
  16 //  This library is distributed in the hope that it will be useful,
  17 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  19 //  Lesser General Public License for more details.
  20 //
  21 ///////////////////////////////////////////////////////////////////////////////
  22
  23 #include "simple_private.h"
  24
  25
  26 /// Copied or encodes/decodes more data to out[].
  27 static lzma_ret
  28 copy_or_code(lzma_coder *coder, lzma_allocator *allocator,
  29                 const uint8_t *restrict in, size_t *restrict in_pos,
  30                 size_t in_size, uint8_t *restrict out,
  31                 size_t *restrict out_pos, size_t out_size, lzma_action action)
  32 {
  33         assert(!coder->end_was_reached);
  34
  35         if (coder->next.code == NULL) {
  36                 lzma_bufcpy(in, in_pos, in_size, out, out_pos, out_size);
  37
  38                 // Check if end of stream was reached.
  39                 if (coder->is_encoder && action == LZMA_FINISH
  40                                 && *in_pos == in_size)
  41                         coder->end_was_reached = true;
  42
  43         } else {
  44                 // Call the next coder in the chain to provide us some data.
  45                 // We don't care about uncompressed_size here, because
  46                 // the next filter in the chain will do it for us (since
  47                 // we don't change the size of the data).
  48                 const lzma_ret ret = coder->next.code(
  49                                 coder->next.coder, allocator,
  50                                 in, in_pos, in_size,
  51                                 out, out_pos, out_size, action);
  52
  53                 if (ret == LZMA_STREAM_END) {
  54                         assert(!coder->is_encoder
  55                                         || action == LZMA_FINISH);
  56                         coder->end_was_reached = true;
  57
  58                 } else if (ret != LZMA_OK) {
  59                         return ret;
  60                 }
  61         }
  62
  63         return LZMA_OK;
  64 }
  65
  66
  67 static size_t
  68 call_filter(lzma_coder *coder, uint8_t *buffer, size_t size)
  69 {
  70         const size_t filtered = coder->filter(coder->simple,
  71                         coder->now_pos, coder->is_encoder,
  72                         buffer, size);
  73         coder->now_pos += filtered;
  74         return filtered;
  75 }
  76
  77
  78 static lzma_ret
  79 simple_code(lzma_coder *coder, lzma_allocator *allocator,
  80                 const uint8_t *restrict in, size_t *restrict in_pos,
  81                 size_t in_size, uint8_t *restrict out,
  82                 size_t *restrict out_pos, size_t out_size, lzma_action action)
  83 {
  84         // TODO: Add partial support for LZMA_SYNC_FLUSH. We can support it
  85         // in cases when the filter is able to filter everything. With most
  86         // simple filters it can be done at offset that is a multiple of 2,
  87         // 4, or 16. With x86 filter, it needs good luck, and thus cannot
  88         // be made to work predictably.
  89         if (action == LZMA_SYNC_FLUSH)
  90                 return LZMA_OPTIONS_ERROR;
  91
  92         // Flush already filtered data from coder->buffer[] to out[].
  93         if (coder->pos < coder->filtered) {
  94                 lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
  95                                 out, out_pos, out_size);
  96
  97                 // If we couldn't flush all the filtered data, return to
  98                 // application immediatelly.
  99                 if (coder->pos < coder->filtered)
 100                         return LZMA_OK;
 101
 102                 if (coder->end_was_reached) {
 103                         assert(coder->filtered == coder->size);
 104                         return LZMA_STREAM_END;
 105                 }
 106         }
 107
 108         // If we get here, there is no filtered data left in the buffer.
 109         coder->filtered = 0;
 110
 111         assert(!coder->end_was_reached);
 112
 113         // If there is more output space left than there is unfiltered data
 114         // in coder->buffer[], flush coder->buffer[] to out[], and copy/code
 115         // more data to out[] hopefully filling it completely. Then filter
 116         // the data in out[]. This step is where most of the data gets
 117         // filtered if the buffer sizes used by the application are reasonable.
 118         const size_t out_avail = out_size - *out_pos;
 119         const size_t buf_avail = coder->size - coder->pos;
 120         if (out_avail > buf_avail) {
 121                 // Store the old position so that we know from which byte
 122                 // to start filtering.
 123                 const size_t out_start = *out_pos;
 124
 125                 // Flush data from coder->buffer[] to out[], but don't reset
 126                 // coder->pos and coder->size yet. This way the coder can be
 127                 // restarted if the next filter in the chain returns e.g.
 128                 // LZMA_MEM_ERROR.
 129                 memcpy(out + *out_pos, coder->buffer + coder->pos, buf_avail);
 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[].
 143                 const size_t size = *out_pos - out_start;
 144                 const size_t filtered = call_filter(
 145                                 coder, out + out_start, size);
 146
 147                 const size_t unfiltered = size - filtered;
 148                 assert(unfiltered <= coder->allocated / 2);
 149
 150                 // Now we can update coder->pos and coder->size, because
 151                 // the next coder in the chain (if any) was successful.
 152                 coder->pos = 0;
 153                 coder->size = unfiltered;
 154
 155                 if (coder->end_was_reached) {
 156                         // The last byte has been copied to out[] already.
 157                         // They are left as is.
 158                         coder->size = 0;
 159
 160                 } else if (unfiltered > 0) {
 161                         // There is unfiltered data left in out[]. Copy it to
 162                         // coder->buffer[] and rewind *out_pos appropriately.
 163                         *out_pos -= unfiltered;
 164                         memcpy(coder->buffer, out + *out_pos, unfiltered);
 165                 }
 166         } else if (coder->pos > 0) {
 167                 memmove(coder->buffer, coder->buffer + coder->pos, buf_avail);
 168                 coder->size -= coder->pos;
 169                 coder->pos = 0;
 170         }
 171
 172         assert(coder->pos == 0);
 173
 174         // If coder->buffer[] isn't empty, try to fill it by copying/decoding
 175         // more data. Then filter coder->buffer[] and copy the successfully
 176         // filtered data to out[]. It is probable, that some filtered and
 177         // unfiltered data will be left to coder->buffer[].
 178         if (coder->size > 0) {
 179                 {
 180                         const lzma_ret ret = copy_or_code(coder, allocator,
 181                                         in, in_pos, in_size,
 182                                         coder->buffer, &coder->size,
 183                                         coder->allocated, action);
 184                         assert(ret != LZMA_STREAM_END);
 185                         if (ret != LZMA_OK)
 186                                 return ret;
 187                 }
 188
 189                 coder->filtered = call_filter(
 190                                 coder, coder->buffer, coder->size);
 191
 192                 // Everything is considered to be filtered if coder->buffer[]
 193                 // contains the last bytes of the data.
 194                 if (coder->end_was_reached)
 195                         coder->filtered = coder->size;
 196
 197                 // Flush as much as possible.
 198                 lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
 199                                 out, out_pos, out_size);
 200         }
 201
 202         // Check if we got everything done.
 203         if (coder->end_was_reached && coder->pos == coder->size)
 204                 return LZMA_STREAM_END;
 205
 206         return LZMA_OK;
 207 }
 208
 209
 210 static void
 211 simple_coder_end(lzma_coder *coder, lzma_allocator *allocator)
 212 {
 213         lzma_next_end(&coder->next, allocator);
 214         lzma_free(coder->simple, allocator);
 215         lzma_free(coder, allocator);
 216         return;
 217 }
 218
 219
 220 extern lzma_ret
 221 lzma_simple_coder_init(lzma_next_coder *next, lzma_allocator *allocator,
 222                 const lzma_filter_info *filters,
 223                 size_t (*filter)(lzma_simple *simple, uint32_t now_pos,
 224                         bool is_encoder, uint8_t *buffer, size_t size),
 225                 size_t simple_size, size_t unfiltered_max, bool is_encoder)
 226 {
 227         // Allocate memory for the lzma_coder structure if needed.
 228         if (next->coder == NULL) {
 229                 // Here we allocate space also for the temporary buffer. We
 230                 // need twice the size of unfiltered_max, because then it
 231                 // is always possible to filter at least unfiltered_max bytes
 232                 // more data in coder->buffer[] if it can be filled completely.
 233                 next->coder = lzma_alloc(sizeof(lzma_coder)
 234                                 + 2 * unfiltered_max, allocator);
 235                 if (next->coder == NULL)
 236                         return LZMA_MEM_ERROR;
 237
 238                 next->code = &simple_code;
 239                 next->end = &simple_coder_end;
 240
 241                 next->coder->next = LZMA_NEXT_CODER_INIT;
 242                 next->coder->filter = filter;
 243                 next->coder->allocated = 2 * unfiltered_max;
 244
 245                 // Allocate memory for filter-specific data structure.
 246                 if (simple_size > 0) {
 247                         next->coder->simple = lzma_alloc(
 248                                         simple_size, allocator);
 249                         if (next->coder->simple == NULL)
 250                                 return LZMA_MEM_ERROR;
 251                 } else {
 252                         next->coder->simple = NULL;
 253                 }
 254         }
 255
 256         if (filters[0].options != NULL) {
 257                 const lzma_options_bcj *simple = filters[0].options;
 258                 next->coder->now_pos = simple->start_offset;
 259         } else {
 260                 next->coder->now_pos = 0;
 261         }
 262
 263         // Reset variables.
 264         next->coder->is_encoder = is_encoder;
 265         next->coder->end_was_reached = false;
 266         next->coder->pos = 0;
 267         next->coder->filtered = 0;
 268         next->coder->size = 0;
 269
 270         return lzma_next_filter_init(
 271                         &next->coder->next, allocator, filters + 1);
 272 }