307 lines
8.7 KiB
C
307 lines
8.7 KiB
C
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///////////////////////////////////////////////////////////////////////////////
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//
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/// \file lz_decoder.c
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/// \brief LZ out window
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///
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// Authors: Igor Pavlov
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// Lasse Collin
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//
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// This file has been put into the public domain.
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// You can do whatever you want with this file.
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//
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///////////////////////////////////////////////////////////////////////////////
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// liblzma supports multiple LZ77-based filters. The LZ part is shared
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// between these filters. The LZ code takes care of dictionary handling
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// and passing the data between filters in the chain. The filter-specific
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// part decodes from the input buffer to the dictionary.
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#include "lz_decoder.h"
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typedef struct {
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/// Dictionary (history buffer)
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lzma_dict dict;
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/// The actual LZ-based decoder e.g. LZMA
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lzma_lz_decoder lz;
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/// Next filter in the chain, if any. Note that LZMA and LZMA2 are
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/// only allowed as the last filter, but the long-range filter in
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/// future can be in the middle of the chain.
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lzma_next_coder next;
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/// True if the next filter in the chain has returned LZMA_STREAM_END.
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bool next_finished;
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/// True if the LZ decoder (e.g. LZMA) has detected end of payload
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/// marker. This may become true before next_finished becomes true.
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bool this_finished;
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/// Temporary buffer needed when the LZ-based filter is not the last
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/// filter in the chain. The output of the next filter is first
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/// decoded into buffer[], which is then used as input for the actual
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/// LZ-based decoder.
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struct {
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size_t pos;
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size_t size;
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uint8_t buffer[LZMA_BUFFER_SIZE];
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} temp;
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} lzma_coder;
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static void
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lz_decoder_reset(lzma_coder *coder)
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{
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coder->dict.pos = 0;
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coder->dict.full = 0;
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coder->dict.buf[coder->dict.size - 1] = '\0';
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coder->dict.need_reset = false;
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return;
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}
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static lzma_ret
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decode_buffer(lzma_coder *coder,
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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)
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{
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while (true) {
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// Wrap the dictionary if needed.
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if (coder->dict.pos == coder->dict.size)
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coder->dict.pos = 0;
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// Store the current dictionary position. It is needed to know
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// where to start copying to the out[] buffer.
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const size_t dict_start = coder->dict.pos;
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// Calculate how much we allow coder->lz.code() to decode.
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// It must not decode past the end of the dictionary
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// buffer, and we don't want it to decode more than is
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// actually needed to fill the out[] buffer.
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coder->dict.limit = coder->dict.pos
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+ my_min(out_size - *out_pos,
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coder->dict.size - coder->dict.pos);
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// Call the coder->lz.code() to do the actual decoding.
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const lzma_ret ret = coder->lz.code(
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coder->lz.coder, &coder->dict,
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in, in_pos, in_size);
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// Copy the decoded data from the dictionary to the out[]
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// buffer.
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const size_t copy_size = coder->dict.pos - dict_start;
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assert(copy_size <= out_size - *out_pos);
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memcpy(out + *out_pos, coder->dict.buf + dict_start,
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copy_size);
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*out_pos += copy_size;
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// Reset the dictionary if so requested by coder->lz.code().
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if (coder->dict.need_reset) {
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lz_decoder_reset(coder);
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// Since we reset dictionary, we don't check if
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// dictionary became full.
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if (ret != LZMA_OK || *out_pos == out_size)
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return ret;
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} else {
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// Return if everything got decoded or an error
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// occurred, or if there's no more data to decode.
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//
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// Note that detecting if there's something to decode
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// is done by looking if dictionary become full
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// instead of looking if *in_pos == in_size. This
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// is because it is possible that all the input was
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// consumed already but some data is pending to be
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// written to the dictionary.
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if (ret != LZMA_OK || *out_pos == out_size
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|| coder->dict.pos < coder->dict.size)
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return ret;
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}
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}
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}
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static lzma_ret
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lz_decode(void *coder_ptr,
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const lzma_allocator *allocator lzma_attribute((__unused__)),
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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,
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lzma_action action)
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{
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lzma_coder *coder = coder_ptr;
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if (coder->next.code == NULL)
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return decode_buffer(coder, in, in_pos, in_size,
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out, out_pos, out_size);
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// We aren't the last coder in the chain, we need to decode
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// our input to a temporary buffer.
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while (*out_pos < out_size) {
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// Fill the temporary buffer if it is empty.
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if (!coder->next_finished
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&& coder->temp.pos == coder->temp.size) {
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coder->temp.pos = 0;
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coder->temp.size = 0;
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const lzma_ret ret = coder->next.code(
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coder->next.coder,
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allocator, in, in_pos, in_size,
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coder->temp.buffer, &coder->temp.size,
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LZMA_BUFFER_SIZE, action);
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if (ret == LZMA_STREAM_END)
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coder->next_finished = true;
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else if (ret != LZMA_OK || coder->temp.size == 0)
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return ret;
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}
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if (coder->this_finished) {
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if (coder->temp.size != 0)
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return LZMA_DATA_ERROR;
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if (coder->next_finished)
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return LZMA_STREAM_END;
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return LZMA_OK;
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}
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const lzma_ret ret = decode_buffer(coder, coder->temp.buffer,
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&coder->temp.pos, coder->temp.size,
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out, out_pos, out_size);
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if (ret == LZMA_STREAM_END)
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coder->this_finished = true;
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else if (ret != LZMA_OK)
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return ret;
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else if (coder->next_finished && *out_pos < out_size)
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return LZMA_DATA_ERROR;
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}
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return LZMA_OK;
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}
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static void
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lz_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
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{
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lzma_coder *coder = coder_ptr;
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lzma_next_end(&coder->next, allocator);
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lzma_free(coder->dict.buf, allocator);
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if (coder->lz.end != NULL)
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coder->lz.end(coder->lz.coder, allocator);
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else
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lzma_free(coder->lz.coder, allocator);
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lzma_free(coder, allocator);
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return;
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}
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extern lzma_ret
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lzma_lz_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
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const lzma_filter_info *filters,
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lzma_ret (*lz_init)(lzma_lz_decoder *lz,
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const lzma_allocator *allocator, const void *options,
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lzma_lz_options *lz_options))
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{
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// Allocate the base structure if it isn't already allocated.
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lzma_coder *coder = next->coder;
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if (coder == NULL) {
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coder = lzma_alloc(sizeof(lzma_coder), allocator);
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if (coder == NULL)
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return LZMA_MEM_ERROR;
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next->coder = coder;
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next->code = &lz_decode;
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next->end = &lz_decoder_end;
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coder->dict.buf = NULL;
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coder->dict.size = 0;
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coder->lz = LZMA_LZ_DECODER_INIT;
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coder->next = LZMA_NEXT_CODER_INIT;
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}
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// Allocate and initialize the LZ-based decoder. It will also give
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// us the dictionary size.
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lzma_lz_options lz_options;
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return_if_error(lz_init(&coder->lz, allocator,
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filters[0].options, &lz_options));
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// If the dictionary size is very small, increase it to 4096 bytes.
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// This is to prevent constant wrapping of the dictionary, which
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// would slow things down. The downside is that since we don't check
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// separately for the real dictionary size, we may happily accept
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// corrupt files.
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if (lz_options.dict_size < 4096)
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lz_options.dict_size = 4096;
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// Make dictionary size a multipe of 16. Some LZ-based decoders like
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// LZMA use the lowest bits lzma_dict.pos to know the alignment of the
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// data. Aligned buffer is also good when memcpying from the
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// dictionary to the output buffer, since applications are
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// recommended to give aligned buffers to liblzma.
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//
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// Avoid integer overflow.
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if (lz_options.dict_size > SIZE_MAX - 15)
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return LZMA_MEM_ERROR;
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lz_options.dict_size = (lz_options.dict_size + 15) & ~((size_t)(15));
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// Allocate and initialize the dictionary.
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if (coder->dict.size != lz_options.dict_size) {
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lzma_free(coder->dict.buf, allocator);
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coder->dict.buf
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= lzma_alloc(lz_options.dict_size, allocator);
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if (coder->dict.buf == NULL)
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return LZMA_MEM_ERROR;
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coder->dict.size = lz_options.dict_size;
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}
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lz_decoder_reset(next->coder);
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// Use the preset dictionary if it was given to us.
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if (lz_options.preset_dict != NULL
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&& lz_options.preset_dict_size > 0) {
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// If the preset dictionary is bigger than the actual
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// dictionary, copy only the tail.
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const size_t copy_size = my_min(lz_options.preset_dict_size,
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lz_options.dict_size);
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const size_t offset = lz_options.preset_dict_size - copy_size;
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memcpy(coder->dict.buf, lz_options.preset_dict + offset,
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copy_size);
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coder->dict.pos = copy_size;
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coder->dict.full = copy_size;
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}
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// Miscellaneous initializations
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coder->next_finished = false;
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coder->this_finished = false;
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coder->temp.pos = 0;
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coder->temp.size = 0;
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// Initialize the next filter in the chain, if any.
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return lzma_next_filter_init(&coder->next, allocator, filters + 1);
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}
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extern uint64_t
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lzma_lz_decoder_memusage(size_t dictionary_size)
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{
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return sizeof(lzma_coder) + (uint64_t)(dictionary_size);
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}
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extern void
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lzma_lz_decoder_uncompressed(void *coder_ptr, lzma_vli uncompressed_size)
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{
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lzma_coder *coder = coder_ptr;
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coder->lz.set_uncompressed(coder->lz.coder, uncompressed_size);
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}
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