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DEFINITIONS
This source file includes following definitions.
- stream_decoder_reset
- stream_decode
- stream_decoder_end
- stream_decoder_get_check
- stream_decoder_memconfig
- lzma_stream_decoder_init
- LZMA_API
///////////////////////////////////////////////////////////////////////////////
//
/// \file stream_decoder.c
/// \brief Decodes .xz Streams
//
// Author: Lasse Collin
//
// This file has been put into the public domain.
// You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////
#include "stream_decoder.h"
#include "block_decoder.h"
struct lzma_coder_s {
enum {
SEQ_STREAM_HEADER,
SEQ_BLOCK_HEADER,
SEQ_BLOCK,
SEQ_INDEX,
SEQ_STREAM_FOOTER,
SEQ_STREAM_PADDING,
} sequence;
/// Block or Metadata decoder. This takes little memory and the same
/// data structure can be used to decode every Block Header, so it's
/// a good idea to have a separate lzma_next_coder structure for it.
lzma_next_coder block_decoder;
/// Block options decoded by the Block Header decoder and used by
/// the Block decoder.
lzma_block block_options;
/// Stream Flags from Stream Header
lzma_stream_flags stream_flags;
/// Index is hashed so that it can be compared to the sizes of Blocks
/// with O(1) memory usage.
lzma_index_hash *index_hash;
/// Memory usage limit
uint64_t memlimit;
/// Amount of memory actually needed (only an estimate)
uint64_t memusage;
/// If true, LZMA_NO_CHECK is returned if the Stream has
/// no integrity check.
bool tell_no_check;
/// If true, LZMA_UNSUPPORTED_CHECK is returned if the Stream has
/// an integrity check that isn't supported by this liblzma build.
bool tell_unsupported_check;
/// If true, LZMA_GET_CHECK is returned after decoding Stream Header.
bool tell_any_check;
/// If true, we will decode concatenated Streams that possibly have
/// Stream Padding between or after them. LZMA_STREAM_END is returned
/// once the application isn't giving us any new input, and we aren't
/// in the middle of a Stream, and possible Stream Padding is a
/// multiple of four bytes.
bool concatenated;
/// When decoding concatenated Streams, this is true as long as we
/// are decoding the first Stream. This is needed to avoid misleading
/// LZMA_FORMAT_ERROR in case the later Streams don't have valid magic
/// bytes.
bool first_stream;
/// Write position in buffer[] and position in Stream Padding
size_t pos;
/// Buffer to hold Stream Header, Block Header, and Stream Footer.
/// Block Header has biggest maximum size.
uint8_t buffer[LZMA_BLOCK_HEADER_SIZE_MAX];
};
static lzma_ret
stream_decoder_reset(lzma_coder *coder, lzma_allocator *allocator)
{
// Initialize the Index hash used to verify the Index.
coder->index_hash = lzma_index_hash_init(coder->index_hash, allocator);
if (coder->index_hash == NULL)
return LZMA_MEM_ERROR;
// Reset the rest of the variables.
coder->sequence = SEQ_STREAM_HEADER;
coder->pos = 0;
return LZMA_OK;
}
static lzma_ret
stream_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,
size_t *restrict out_pos, size_t out_size, lzma_action action)
{
// When decoding the actual Block, it may be able to produce more
// output even if we don't give it any new input.
while (true)
switch (coder->sequence) {
case SEQ_STREAM_HEADER: {
// Copy the Stream Header to the internal buffer.
lzma_bufcpy(in, in_pos, in_size, coder->buffer, &coder->pos,
LZMA_STREAM_HEADER_SIZE);
// Return if we didn't get the whole Stream Header yet.
if (coder->pos < LZMA_STREAM_HEADER_SIZE)
return LZMA_OK;
coder->pos = 0;
// Decode the Stream Header.
const lzma_ret ret = lzma_stream_header_decode(
&coder->stream_flags, coder->buffer);
if (ret != LZMA_OK)
return ret == LZMA_FORMAT_ERROR && !coder->first_stream
? LZMA_DATA_ERROR : ret;
// If we are decoding concatenated Streams, and the later
// Streams have invalid Header Magic Bytes, we give
// LZMA_DATA_ERROR instead of LZMA_FORMAT_ERROR.
coder->first_stream = false;
// Copy the type of the Check so that Block Header and Block
// decoders see it.
coder->block_options.check = coder->stream_flags.check;
// Even if we return LZMA_*_CHECK below, we want
// to continue from Block Header decoding.
coder->sequence = SEQ_BLOCK_HEADER;
// Detect if there's no integrity check or if it is
// unsupported if those were requested by the application.
if (coder->tell_no_check && coder->stream_flags.check
== LZMA_CHECK_NONE)
return LZMA_NO_CHECK;
if (coder->tell_unsupported_check
&& !lzma_check_is_supported(
coder->stream_flags.check))
return LZMA_UNSUPPORTED_CHECK;
if (coder->tell_any_check)
return LZMA_GET_CHECK;
}
// Fall through
case SEQ_BLOCK_HEADER: {
if (*in_pos >= in_size)
return LZMA_OK;
if (coder->pos == 0) {
// Detect if it's Index.
if (in[*in_pos] == 0x00) {
coder->sequence = SEQ_INDEX;
break;
}
// Calculate the size of the Block Header. Note that
// Block Header decoder wants to see this byte too
// so don't advance *in_pos.
coder->block_options.header_size
= lzma_block_header_size_decode(
in[*in_pos]);
}
// Copy the Block Header to the internal buffer.
lzma_bufcpy(in, in_pos, in_size, coder->buffer, &coder->pos,
coder->block_options.header_size);
// Return if we didn't get the whole Block Header yet.
if (coder->pos < coder->block_options.header_size)
return LZMA_OK;
coder->pos = 0;
// Version 0 is currently the only possible version.
coder->block_options.version = 0;
// Set up a buffer to hold the filter chain. Block Header
// decoder will initialize all members of this array so
// we don't need to do it here.
lzma_filter filters[LZMA_FILTERS_MAX + 1];
coder->block_options.filters = filters;
// Decode the Block Header.
return_if_error(lzma_block_header_decode(&coder->block_options,
allocator, coder->buffer));
// Check the memory usage limit.
const uint64_t memusage = lzma_raw_decoder_memusage(filters);
lzma_ret ret;
if (memusage == UINT64_MAX) {
// One or more unknown Filter IDs.
ret = LZMA_OPTIONS_ERROR;
} else {
// Now we can set coder->memusage since we know that
// the filter chain is valid. We don't want
// lzma_memusage() to return UINT64_MAX in case of
// invalid filter chain.
coder->memusage = memusage;
if (memusage > coder->memlimit) {
// The chain would need too much memory.
ret = LZMA_MEMLIMIT_ERROR;
} else {
// Memory usage is OK.
// Initialize the Block decoder.
ret = lzma_block_decoder_init(
&coder->block_decoder,
allocator,
&coder->block_options);
}
}
// Free the allocated filter options since they are needed
// only to initialize the Block decoder.
for (size_t i = 0; i < LZMA_FILTERS_MAX; ++i)
lzma_free(filters[i].options, allocator);
coder->block_options.filters = NULL;
// Check if memory usage calculation and Block enocoder
// initialization succeeded.
if (ret != LZMA_OK)
return ret;
coder->sequence = SEQ_BLOCK;
}
// Fall through
case SEQ_BLOCK: {
const lzma_ret ret = coder->block_decoder.code(
coder->block_decoder.coder, allocator,
in, in_pos, in_size, out, out_pos, out_size,
action);
if (ret != LZMA_STREAM_END)
return ret;
// Block decoded successfully. Add the new size pair to
// the Index hash.
return_if_error(lzma_index_hash_append(coder->index_hash,
lzma_block_unpadded_size(
&coder->block_options),
coder->block_options.uncompressed_size));
coder->sequence = SEQ_BLOCK_HEADER;
break;
}
case SEQ_INDEX: {
// If we don't have any input, don't call
// lzma_index_hash_decode() since it would return
// LZMA_BUF_ERROR, which we must not do here.
if (*in_pos >= in_size)
return LZMA_OK;
// Decode the Index and compare it to the hash calculated
// from the sizes of the Blocks (if any).
const lzma_ret ret = lzma_index_hash_decode(coder->index_hash,
in, in_pos, in_size);
if (ret != LZMA_STREAM_END)
return ret;
coder->sequence = SEQ_STREAM_FOOTER;
}
// Fall through
case SEQ_STREAM_FOOTER: {
// Copy the Stream Footer to the internal buffer.
lzma_bufcpy(in, in_pos, in_size, coder->buffer, &coder->pos,
LZMA_STREAM_HEADER_SIZE);
// Return if we didn't get the whole Stream Footer yet.
if (coder->pos < LZMA_STREAM_HEADER_SIZE)
return LZMA_OK;
coder->pos = 0;
// Decode the Stream Footer. The decoder gives
// LZMA_FORMAT_ERROR if the magic bytes don't match,
// so convert that return code to LZMA_DATA_ERROR.
lzma_stream_flags footer_flags;
const lzma_ret ret = lzma_stream_footer_decode(
&footer_flags, coder->buffer);
if (ret != LZMA_OK)
return ret == LZMA_FORMAT_ERROR
? LZMA_DATA_ERROR : ret;
// Check that Index Size stored in the Stream Footer matches
// the real size of the Index field.
if (lzma_index_hash_size(coder->index_hash)
!= footer_flags.backward_size)
return LZMA_DATA_ERROR;
// Compare that the Stream Flags fields are identical in
// both Stream Header and Stream Footer.
return_if_error(lzma_stream_flags_compare(
&coder->stream_flags, &footer_flags));
if (!coder->concatenated)
return LZMA_STREAM_END;
coder->sequence = SEQ_STREAM_PADDING;
}
// Fall through
case SEQ_STREAM_PADDING:
assert(coder->concatenated);
// Skip over possible Stream Padding.
while (true) {
if (*in_pos >= in_size) {
// Unless LZMA_FINISH was used, we cannot
// know if there's more input coming later.
if (action != LZMA_FINISH)
return LZMA_OK;
// Stream Padding must be a multiple of
// four bytes.
return coder->pos == 0
? LZMA_STREAM_END
: LZMA_DATA_ERROR;
}
// If the byte is not zero, it probably indicates
// beginning of a new Stream (or the file is corrupt).
if (in[*in_pos] != 0x00)
break;
++*in_pos;
coder->pos = (coder->pos + 1) & 3;
}
// Stream Padding must be a multiple of four bytes (empty
// Stream Padding is OK).
if (coder->pos != 0) {
++*in_pos;
return LZMA_DATA_ERROR;
}
// Prepare to decode the next Stream.
return_if_error(stream_decoder_reset(coder, allocator));
break;
default:
assert(0);
return LZMA_PROG_ERROR;
}
// Never reached
}
static void
stream_decoder_end(lzma_coder *coder, lzma_allocator *allocator)
{
lzma_next_end(&coder->block_decoder, allocator);
lzma_index_hash_end(coder->index_hash, allocator);
lzma_free(coder, allocator);
return;
}
static lzma_check
stream_decoder_get_check(const lzma_coder *coder)
{
return coder->stream_flags.check;
}
static lzma_ret
stream_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_stream_decoder_init(lzma_next_coder *next, lzma_allocator *allocator,
uint64_t memlimit, uint32_t flags)
{
lzma_next_coder_init(&lzma_stream_decoder_init, next, allocator);
if (memlimit == 0)
return LZMA_PROG_ERROR;
if (flags & ~LZMA_SUPPORTED_FLAGS)
return LZMA_OPTIONS_ERROR;
if (next->coder == NULL) {
next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
if (next->coder == NULL)
return LZMA_MEM_ERROR;
next->code = &stream_decode;
next->end = &stream_decoder_end;
next->get_check = &stream_decoder_get_check;
next->memconfig = &stream_decoder_memconfig;
next->coder->block_decoder = LZMA_NEXT_CODER_INIT;
next->coder->index_hash = NULL;
}
next->coder->memlimit = memlimit;
next->coder->memusage = LZMA_MEMUSAGE_BASE;
next->coder->tell_no_check = (flags & LZMA_TELL_NO_CHECK) != 0;
next->coder->tell_unsupported_check
= (flags & LZMA_TELL_UNSUPPORTED_CHECK) != 0;
next->coder->tell_any_check = (flags & LZMA_TELL_ANY_CHECK) != 0;
next->coder->concatenated = (flags & LZMA_CONCATENATED) != 0;
next->coder->first_stream = true;
return stream_decoder_reset(next->coder, allocator);
}
extern LZMA_API(lzma_ret)
lzma_stream_decoder(lzma_stream *strm, uint64_t memlimit, uint32_t flags)
{
lzma_next_strm_init(lzma_stream_decoder_init, strm, memlimit, flags);
strm->internal->supported_actions[LZMA_RUN] = true;
strm->internal->supported_actions[LZMA_FINISH] = true;
return LZMA_OK;
}