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///////////////////////////////////////////////////////////////////////////////
//
/// \file index_decoder.c
/// \brief Decodes the Index field
//
// Copyright (C) 2008 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 "index.h"
#include "check.h"
struct lzma_coder_s {
enum {
SEQ_INDICATOR,
SEQ_COUNT,
SEQ_TOTAL,
SEQ_UNCOMPRESSED,
SEQ_PADDING_INIT,
SEQ_PADDING,
SEQ_CRC32,
} sequence;
/// Target Index
lzma_index *index;
/// Number of Records left to decode.
lzma_vli count;
/// The most recent Total Size field
lzma_vli total_size;
/// The most recent Uncompressed Size field
lzma_vli uncompressed_size;
/// Position in integers
size_t pos;
/// CRC32 of the List of Records field
uint32_t crc32;
};
static lzma_ret
index_decode(lzma_coder *coder, lzma_allocator *allocator,
const uint8_t *restrict in, size_t *restrict in_pos,
size_t in_size, uint8_t *restrict out lzma_attribute((unused)),
size_t *restrict out_pos lzma_attribute((unused)),
size_t out_size lzma_attribute((unused)),
lzma_action action lzma_attribute((unused)))
{
// Similar optimization as in index_encoder.c
const size_t in_start = *in_pos;
lzma_ret ret = LZMA_OK;
while (*in_pos < in_size)
switch (coder->sequence) {
case SEQ_INDICATOR:
// Return LZMA_DATA_ERROR instead of e.g. LZMA_PROG_ERROR or
// LZMA_FORMAT_ERROR, because a typical usage case for Index
// decoder is when parsing the Stream backwards. If seeking
// backward from the Stream Footer gives us something that
// doesn't begin with Index Indicator, the file is considered
// corrupt, not "programming error" or "unrecognized file
// format". One could argue that the application should
// verify the Index Indicator before trying to decode the
// Index, but well, I suppose it is simpler this way.
if (in[(*in_pos)++] != 0x00)
return LZMA_DATA_ERROR;
coder->sequence = SEQ_COUNT;
break;
case SEQ_COUNT: {
ret = lzma_vli_decode(&coder->count, &coder->pos,
in, in_pos, in_size);
if (ret != LZMA_STREAM_END)
goto out;
ret = LZMA_OK;
coder->pos = 0;
coder->sequence = coder->count == 0
? SEQ_PADDING_INIT : SEQ_TOTAL;
break;
}
case SEQ_TOTAL:
case SEQ_UNCOMPRESSED: {
lzma_vli *size = coder->sequence == SEQ_TOTAL
? &coder->total_size
: &coder->uncompressed_size;
ret = lzma_vli_decode(size, &coder->pos,
in, in_pos, in_size);
if (ret != LZMA_STREAM_END)
goto out;
ret = LZMA_OK;
coder->pos = 0;
if (coder->sequence == SEQ_TOTAL) {
// Validate that encoded Total Size isn't too big.
if (coder->total_size > TOTAL_SIZE_ENCODED_MAX)
return LZMA_DATA_ERROR;
// Convert the encoded Total Size to the real
// Total Size.
coder->total_size = total_size_decode(
coder->total_size);
coder->sequence = SEQ_UNCOMPRESSED;
} else {
// Add the decoded Record to the Index.
return_if_error(lzma_index_append(
coder->index, allocator,
coder->total_size,
coder->uncompressed_size));
// Check if this was the last Record.
coder->sequence = --coder->count == 0
? SEQ_PADDING_INIT
: SEQ_TOTAL;
}
break;
}
case SEQ_PADDING_INIT:
coder->pos = lzma_index_padding_size(coder->index);
coder->sequence = SEQ_PADDING;
// Fall through
case SEQ_PADDING:
if (coder->pos > 0) {
--coder->pos;
if (in[(*in_pos)++] != 0x00)
return LZMA_DATA_ERROR;
break;
}
// Finish the CRC32 calculation.
coder->crc32 = lzma_crc32(in + in_start,
*in_pos - in_start, coder->crc32);
coder->sequence = SEQ_CRC32;
// Fall through
case SEQ_CRC32:
do {
if (*in_pos == in_size)
return LZMA_OK;
if (((coder->crc32 >> (coder->pos * 8)) & 0xFF)
!= in[(*in_pos)++])
return LZMA_DATA_ERROR;
} while (++coder->pos < 4);
// Make index NULL so we don't free it unintentionally.
coder->index = NULL;
return LZMA_STREAM_END;
default:
assert(0);
return LZMA_PROG_ERROR;
}
out:
// Update the CRC32,
coder->crc32 = lzma_crc32(in + in_start,
*in_pos - in_start, coder->crc32);
return ret;
}
static void
index_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
{
lzma_index_end(coder->index, allocator);
lzma_free(coder, allocator);
return;
}
static lzma_ret
index_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
lzma_index **i)
{
lzma_next_coder_init(index_decoder_init, next, allocator);
if (i == NULL)
return LZMA_PROG_ERROR;
if (next->coder == NULL) {
next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
if (next->coder == NULL)
return LZMA_MEM_ERROR;
next->code = &index_decode;
next->end = &index_decoder_end;
next->coder->index = NULL;
} else {
lzma_index_end(next->coder->index, allocator);
}
// We always allocate a new lzma_index.
*i = lzma_index_init(NULL, allocator);
if (*i == NULL)
return LZMA_MEM_ERROR;
// Initialize the rest.
next->coder->sequence = SEQ_INDICATOR;
next->coder->index = *i;
next->coder->pos = 0;
next->coder->crc32 = 0;
return LZMA_OK;
}
extern LZMA_API lzma_ret
lzma_index_decoder(lzma_stream *strm, lzma_index **i)
{
lzma_next_strm_init(index_decoder_init, strm, i);
strm->internal->supported_actions[LZMA_RUN] = true;
return LZMA_OK;
}
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