///////////////////////////////////////////////////////////////////////////////

//

/// \file alone_decoder.c

/// \brief Decoder for LZMA_Alone files

//

// Author: Lasse Collin

//

// This file has been put into the public domain.

// You can do whatever you want with this file.

//

///////////////////////////////////////////////////////////////////////////////

#include "alone_decoder.h"

#include "lzma_decoder.h"

#include "lz_decoder.h"

struct lzma_coder_s {

lzma_next_coder next;

enum {

SEQ_PROPERTIES,

SEQ_DICTIONARY_SIZE,

SEQ_UNCOMPRESSED_SIZE,

SEQ_CODER_INIT,

SEQ_CODE,

} sequence;

/// Position in the header fields

size_t pos;

/// Uncompressed size decoded from the header

lzma_vli uncompressed_size;

/// Memory usage limit

uint64_t memlimit;

/// Amount of memory actually needed (only an estimate)

uint64_t memusage;

/// Options decoded from the header needed to initialize

/// the LZMA decoder

lzma_options_lzma options;

};

static lzma_ret

alone_decode(lzma_coder *coder,

lzma_allocator *allocator lzma_attribute((unused)),

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)

{

while (*out_pos < out_size

&& (coder->sequence == SEQ_CODE || *in_pos < in_size))

switch (coder->sequence) {

case SEQ_PROPERTIES:

if (lzma_lzma_lclppb_decode(&coder->options, in[*in_pos]))

return LZMA_FORMAT_ERROR;

coder->sequence = SEQ_DICTIONARY_SIZE;

++*in_pos;

break;

case SEQ_DICTIONARY_SIZE:

coder->options.dict_size

|= (size_t)(in[*in_pos]) << (coder->pos * 8);

if (++coder->pos == 4) {

if (coder->options.dict_size != UINT32_MAX) {

// A hack to ditch tons of false positives:

// We allow only dictionary sizes that are

// 2^n or 2^n + 2^(n-1). LZMA_Alone created

// only files with 2^n, but accepts any

// dictionary size. If someone complains, this

// will be reconsidered.

uint32_t d = coder->options.dict_size - 1;

d |= d >> 2;

d |= d >> 3;

d |= d >> 4;

d |= d >> 8;

d |= d >> 16;

++d;

if (d != coder->options.dict_size)

return LZMA_FORMAT_ERROR;

}

coder->pos = 0;

coder->sequence = SEQ_UNCOMPRESSED_SIZE;

}

++*in_pos;

break;

case SEQ_UNCOMPRESSED_SIZE:

coder->uncompressed_size

|= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);

++*in_pos;

if (++coder->pos < 8)

break;

// Another hack to ditch false positives: Assume that

// if the uncompressed size is known, it must be less

// than 256 GiB. Again, if someone complains, this

// will be reconsidered.

if (coder->uncompressed_size != LZMA_VLI_UNKNOWN

&& coder->uncompressed_size

>= (LZMA_VLI_C(1) << 38))

return LZMA_FORMAT_ERROR;

// Calculate the memory usage so that it is ready

// for SEQ_CODER_INIT.

coder->memusage = lzma_lzma_decoder_memusage(&coder->options)

+ LZMA_MEMUSAGE_BASE;

coder->pos = 0;

coder->sequence = SEQ_CODER_INIT;

// Fall through

case SEQ_CODER_INIT: {

if (coder->memusage > coder->memlimit)

return LZMA_MEMLIMIT_ERROR;

lzma_filter_info filters[2] = {

{

.init = &lzma_lzma_decoder_init,

.options = &coder->options,

}, {

.init = NULL,

}

};

const lzma_ret ret = lzma_next_filter_init(&coder->next,

allocator, filters);

if (ret != LZMA_OK)

return ret;

// Use a hack to set the uncompressed size.

lzma_lz_decoder_uncompressed(coder->next.coder,

coder->uncompressed_size);

coder->sequence = SEQ_CODE;

break;

}

case SEQ_CODE: {

return coder->next.code(coder->next.coder,

allocator, in, in_pos, in_size,

out, out_pos, out_size, action);

}

default:

return LZMA_PROG_ERROR;

}

return LZMA_OK;

}

static void

alone_decoder_end(lzma_coder *coder, lzma_allocator *allocator)

{

lzma_next_end(&coder->next, allocator);

lzma_free(coder, allocator);

return;

}

static lzma_ret

alone_decoder_memconfig(lzma_coder *coder, uint64_t *memusage,

uint64_t *old_memlimit, uint64_t new_memlimit)

{

*memusage = coder->memusage;

*old_memlimit = coder->memlimit;

if (new_memlimit != 0) {

if (new_memlimit < coder->memusage)

return LZMA_MEMLIMIT_ERROR;

coder->memlimit = new_memlimit;

}

return LZMA_OK;

}

extern lzma_ret

lzma_alone_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,

uint64_t memlimit)

{

lzma_next_coder_init(&lzma_alone_decoder_init, next, allocator);

if (memlimit == 0)

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 = &alone_decode;

next->end = &alone_decoder_end;

next->memconfig = &alone_decoder_memconfig;

next->coder->next = LZMA_NEXT_CODER_INIT;

}

next->coder->sequence = SEQ_PROPERTIES;

next->coder->pos = 0;

next->coder->options.dict_size = 0;

next->coder->options.preset_dict = NULL;

next->coder->options.preset_dict_size = 0;

next->coder->uncompressed_size = 0;

next->coder->memlimit = memlimit;

next->coder->memusage = LZMA_MEMUSAGE_BASE;

return LZMA_OK;

}

extern LZMA_API(lzma_ret)

lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit)

{

lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit);

strm->internal->supported_actions[LZMA_RUN] = true;

strm->internal->supported_actions[LZMA_FINISH] = true;

return LZMA_OK;

}