| /////////////////////////////////////////////////////////////////////////////// |
| // |
| /// \file delta_coder.c |
| /// \brief Encoder and decoder for the Delta filter |
| // |
| // Copyright (C) 2007 Lasse Collin |
| // |
| // This library is free software; you can redistribute it and/or |
| // modify it under the terms of the GNU Lesser General Public |
| // License as published by the Free Software Foundation; either |
| // version 2.1 of the License, or (at your option) any later version. |
| // |
| // This library is distributed in the hope that it will be useful, |
| // but WITHOUT ANY WARRANTY; without even the implied warranty of |
| // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| // Lesser General Public License for more details. |
| // |
| /////////////////////////////////////////////////////////////////////////////// |
| |
| #include "delta_coder.h" |
| |
| |
| struct lzma_coder_s { |
| /// Next coder in the chain |
| lzma_next_coder next; |
| |
| /// Uncompressed size - This is needed when we are the last |
| /// filter in the chain. |
| lzma_vli uncompressed_size; |
| |
| /// Delta distance |
| size_t distance; |
| |
| /// True if we are encoding; false if decoding |
| bool is_encoder; |
| |
| /// Position in history[] |
| uint8_t pos; |
| |
| /// Buffer to hold history of the original data |
| uint8_t history[LZMA_DELTA_DISTANCE_MAX]; |
| }; |
| |
| |
| static void |
| encode_buffer(lzma_coder *coder, uint8_t *buffer, size_t size) |
| { |
| const size_t distance = coder->distance; |
| |
| for (size_t i = 0; i < size; ++i) { |
| const uint8_t tmp = coder->history[ |
| (distance + coder->pos) & 0xFF]; |
| coder->history[coder->pos--] = buffer[i]; |
| buffer[i] -= tmp; |
| } |
| |
| return; |
| } |
| |
| |
| static void |
| decode_buffer(lzma_coder *coder, uint8_t *buffer, size_t size) |
| { |
| const size_t distance = coder->distance; |
| |
| for (size_t i = 0; i < size; ++i) { |
| buffer[i] += coder->history[(distance + coder->pos) & 0xFF]; |
| coder->history[coder->pos--] = buffer[i]; |
| } |
| |
| return; |
| } |
| |
| |
| static lzma_ret |
| delta_code(lzma_coder *coder, lzma_allocator *allocator, |
| const uint8_t *restrict in, size_t *restrict in_pos, |
| size_t in_size, uint8_t *restrict out, |
| size_t *restrict out_pos, size_t out_size, lzma_action action) |
| { |
| const size_t out_start = *out_pos; |
| size_t size; |
| lzma_ret ret; |
| |
| if (coder->next.code == NULL) { |
| const size_t in_avail = in_size - *in_pos; |
| |
| if (coder->is_encoder) { |
| // Check that we don't have too much input. |
| if ((lzma_vli)(in_avail) > coder->uncompressed_size) |
| return LZMA_DATA_ERROR; |
| |
| // Check that once LZMA_FINISH has been given, the |
| // amount of input matches uncompressed_size if it |
| // is known. |
| if (action == LZMA_FINISH && coder->uncompressed_size |
| != LZMA_VLI_VALUE_UNKNOWN |
| && coder->uncompressed_size |
| != (lzma_vli)(in_avail)) |
| return LZMA_DATA_ERROR; |
| |
| } else { |
| // Limit in_size so that we don't copy too much. |
| if ((lzma_vli)(in_avail) > coder->uncompressed_size) |
| in_size = *in_pos + (size_t)( |
| coder->uncompressed_size); |
| } |
| |
| size = bufcpy(in, in_pos, in_size, out, out_pos, out_size); |
| |
| if (coder->uncompressed_size != LZMA_VLI_VALUE_UNKNOWN) |
| coder->uncompressed_size -= size; |
| |
| // action can be LZMA_FINISH only in the encoder. |
| ret = (action == LZMA_FINISH && *in_pos == in_size) |
| || coder->uncompressed_size == 0 |
| ? LZMA_STREAM_END : LZMA_OK; |
| |
| } else { |
| ret = coder->next.code(coder->next.coder, allocator, |
| in, in_pos, in_size, out, out_pos, out_size, |
| action); |
| if (ret != LZMA_OK && ret != LZMA_STREAM_END) |
| return ret; |
| |
| size = *out_pos - out_start; |
| } |
| |
| if (coder->is_encoder) |
| encode_buffer(coder, out + out_start, size); |
| else |
| decode_buffer(coder, out + out_start, size); |
| |
| return ret; |
| } |
| |
| |
| static void |
| delta_coder_end(lzma_coder *coder, lzma_allocator *allocator) |
| { |
| lzma_next_coder_end(&coder->next, allocator); |
| lzma_free(coder, allocator); |
| return; |
| } |
| |
| |
| static lzma_ret |
| delta_coder_init(lzma_next_coder *next, lzma_allocator *allocator, |
| const lzma_filter_info *filters, bool is_encoder) |
| { |
| // Allocate memory for the decoder if needed. |
| if (next->coder == NULL) { |
| next->coder = lzma_alloc(sizeof(lzma_coder), allocator); |
| if (next->coder == NULL) |
| return LZMA_MEM_ERROR; |
| |
| next->code = &delta_code; |
| next->end = &delta_coder_end; |
| next->coder->next = LZMA_NEXT_CODER_INIT; |
| } |
| |
| // Copy Uncompressed Size which is used to limit the output size. |
| next->coder->uncompressed_size = filters[0].uncompressed_size; |
| |
| // The coder acts slightly differently as encoder and decoder. |
| next->coder->is_encoder = is_encoder; |
| |
| // Set the delta distance. |
| if (filters[0].options == NULL) |
| return LZMA_PROG_ERROR; |
| next->coder->distance = ((lzma_options_delta *)(filters[0].options)) |
| ->distance; |
| if (next->coder->distance < LZMA_DELTA_DISTANCE_MIN |
| || next->coder->distance > LZMA_DELTA_DISTANCE_MAX) |
| return LZMA_HEADER_ERROR; |
| |
| // Initialize the rest of the variables. |
| next->coder->pos = 0; |
| memzero(next->coder->history, LZMA_DELTA_DISTANCE_MAX); |
| |
| // Initialize the next decoder in the chain, if any. |
| return lzma_next_filter_init(&next->coder->next, |
| allocator, filters + 1); |
| } |
| |
| |
| #ifdef HAVE_ENCODER |
| extern lzma_ret |
| lzma_delta_encoder_init(lzma_next_coder *next, lzma_allocator *allocator, |
| const lzma_filter_info *filters) |
| { |
| return delta_coder_init(next, allocator, filters, true); |
| } |
| #endif |
| |
| |
| #ifdef HAVE_DECODER |
| extern lzma_ret |
| lzma_delta_decoder_init(lzma_next_coder *next, lzma_allocator *allocator, |
| const lzma_filter_info *filters) |
| { |
| return delta_coder_init(next, allocator, filters, false); |
| } |
| #endif |