mirror of https://git.tukaani.org/xz.git
103 lines
2.9 KiB
C
103 lines
2.9 KiB
C
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///////////////////////////////////////////////////////////////////////////////
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//
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/// \file delta_decoder.c
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/// \brief Delta filter decoder
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//
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// Copyright (C) 2007, 2008 Lasse Collin
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Lesser General Public
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// License as published by the Free Software Foundation; either
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// version 2.1 of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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// Lesser General Public License for more details.
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//
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///////////////////////////////////////////////////////////////////////////////
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#include "delta_decoder.h"
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#include "delta_common.h"
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/// Copies and decodes the data at the same time. This is used when Delta
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/// is the last filter in the chain.
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static void
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copy_and_decode(lzma_coder *coder,
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const uint8_t *restrict in, uint8_t *restrict out, size_t size)
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{
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const size_t distance = coder->distance;
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for (size_t i = 0; i < size; ++i) {
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out[i] = in[i] + coder->history[
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(distance + coder->pos) & 0xFF];
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coder->history[coder->pos-- & 0xFF] = out[i];
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}
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}
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/// Decodes the data in place. This is used when we are not the last filter
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/// in the chain.
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static void
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decode_in_place(lzma_coder *coder, uint8_t *buffer, size_t size)
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{
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const size_t distance = coder->distance;
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for (size_t i = 0; i < size; ++i) {
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buffer[i] += coder->history[(distance + coder->pos) & 0xFF];
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coder->history[coder->pos-- & 0xFF] = buffer[i];
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}
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}
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static lzma_ret
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delta_decode(lzma_coder *coder, lzma_allocator *allocator,
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const uint8_t *restrict in, size_t *restrict in_pos,
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size_t in_size, uint8_t *restrict out,
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size_t *restrict out_pos, size_t out_size, lzma_action action)
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{
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lzma_ret ret;
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if (coder->next.code == NULL) {
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// Limit in_size so that we don't copy too much.
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if ((lzma_vli)(in_size - *in_pos) > coder->uncompressed_size)
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in_size = *in_pos + (size_t)(coder->uncompressed_size);
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const size_t in_avail = in_size - *in_pos;
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const size_t out_avail = out_size - *out_pos;
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const size_t size = MIN(in_avail, out_avail);
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copy_and_decode(coder, in + *in_pos, out + *out_pos, size);
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*in_pos += size;
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*out_pos += size;
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assert(coder->uncompressed_size <= LZMA_VLI_VALUE_MAX);
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coder->uncompressed_size -= size;
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ret = coder->uncompressed_size == 0
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? LZMA_STREAM_END : LZMA_OK;
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} else {
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const size_t out_start = *out_pos;
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ret = coder->next.code(coder->next.coder, allocator,
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in, in_pos, in_size, out, out_pos, out_size,
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action);
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decode_in_place(coder, out + out_start, *out_pos - out_start);
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}
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return ret;
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}
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extern lzma_ret
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lzma_delta_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
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const lzma_filter_info *filters)
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{
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return lzma_delta_coder_init(next, allocator, filters, &delta_decode);
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}
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