text: /**
   * \file        lzma/index.h
   * \brief       Handling of .xz Index and related information
   */
  
  /*
   * Author: Lasse Collin
   *
   * This file has been put into the public domain.
   * You can do whatever you want with this file.
   *
   * See ../lzma.h for information about liblzma as a whole.
   */
  
  #ifndef LZMA_H_INTERNAL
  #	error Never include this file directly. Use <lzma.h> instead.
  #endif
  
  
  /**
   * \brief       Opaque data type to hold the Index(es) and other information
   *
   * lzma_index often holds just one .xz Index and possibly the Stream Flags
   * of the same Stream and size of the Stream Padding field. However,
   * multiple lzma_indexes can be concatenated with lzma_index_cat() and then
   * there may be information about multiple Streams in the same lzma_index.
   *
   * Notes about thread safety: Only one thread may modify lzma_index at
   * a time. All functions that take non-const pointer to lzma_index
   * modify it. As long as no thread is modifying the lzma_index, getting
   * information from the same lzma_index can be done from multiple threads
   * at the same time with functions that take a const pointer to
   * lzma_index or use lzma_index_iter. The same iterator must be used
   * only by one thread at a time, of course, but there can be as many
   * iterators for the same lzma_index as needed.
   */
  typedef struct lzma_index_s lzma_index;
  
  
  /**
   * \brief       Iterator to get information about Blocks and Streams
   */
  typedef struct {
  	struct {
  		/**
  		 * \brief       Pointer to Stream Flags
  		 *
  		 * This is NULL if Stream Flags have not been set for
  		 * this Stream with lzma_index_stream_flags().
  		 */
  		const lzma_stream_flags *flags;
  
  		const void *reserved_ptr1;
  		const void *reserved_ptr2;
  		const void *reserved_ptr3;
  
  		/**
  		 * \brief       Stream number in the lzma_index
  		 *
  		 * The first Stream is 1.
  		 */
  		lzma_vli number;
  
  		/**
  		 * \brief       Number of Blocks in the Stream
  		 *
  		 * If this is zero, the block structure below has
  		 * undefined values.
  		 */
  		lzma_vli block_count;
  
  		/**
  		 * \brief       Compressed start offset of this Stream
  		 *
  		 * The offset is relative to the beginning of the lzma_index
  		 * (i.e. usually the beginning of the .xz file).
  		 */
  		lzma_vli compressed_offset;
  
  		/**
  		 * \brief       Uncompressed start offset of this Stream
  		 *
  		 * The offset is relative to the beginning of the lzma_index
  		 * (i.e. usually the beginning of the .xz file).
  		 */
  		lzma_vli uncompressed_offset;
  
  		/**
  		 * \brief       Compressed size of this Stream
  		 *
  		 * This includes all headers except the possible
  		 * Stream Padding after this Stream.
  		 */
  		lzma_vli compressed_size;
  
  		/**
  		 * \brief       Uncompressed size of this Stream
  		 */
  		lzma_vli uncompressed_size;
  
  		/**
  		 * \brief       Size of Stream Padding after this Stream
  		 *
  		 * If it hasn't been set with lzma_index_stream_padding(),
  		 * this defaults to zero. Stream Padding is always
  		 * a multiple of four bytes.
  		 */
  		lzma_vli padding;
  
  		lzma_vli reserved_vli1;
  		lzma_vli reserved_vli2;
  		lzma_vli reserved_vli3;
  		lzma_vli reserved_vli4;
  	} stream;
  
  	struct {
  		/**
  		 * \brief       Block number in the file
  		 *
  		 * The first Block is 1.
  		 */
  		lzma_vli number_in_file;
  
  		/**
  		 * \brief       Compressed start offset of this Block
  		 *
  		 * This offset is relative to the beginning of the
  		 * lzma_index (i.e. usually the beginning of the .xz file).
  		 * Normally this is where you should seek in the .xz file
  		 * to start decompressing this Block.
  		 */
  		lzma_vli compressed_file_offset;
  
  		/**
  		 * \brief       Uncompressed start offset of this Block
  		 *
  		 * This offset is relative to the beginning of the lzma_index
  		 * (i.e. usually the beginning of the .xz file).
  		 *
  		 * When doing random-access reading, it is possible that
  		 * the target offset is not exactly at Block boundary. One
  		 * will need to compare the target offset against
  		 * uncompressed_file_offset or uncompressed_stream_offset,
  		 * and possibly decode and throw away some amount of data
  		 * before reaching the target offset.
  		 */
  		lzma_vli uncompressed_file_offset;
  
  		/**
  		 * \brief       Block number in this Stream
  		 *
  		 * The first Block is 1.
  		 */
  		lzma_vli number_in_stream;
  
  		/**
  		 * \brief       Compressed start offset of this Block
  		 *
  		 * This offset is relative to the beginning of the Stream
  		 * containing this Block.
  		 */
  		lzma_vli compressed_stream_offset;
  
  		/**
  		 * \brief       Uncompressed start offset of this Block
  		 *
  		 * This offset is relative to the beginning of the Stream
  		 * containing this Block.
  		 */
  		lzma_vli uncompressed_stream_offset;
  
  		/**
  		 * \brief       Uncompressed size of this Block
  		 *
  		 * You should pass this to the Block decoder if you will
  		 * decode this Block. It will allow the Block decoder to
  		 * validate the uncompressed size.
  		 */
  		lzma_vli uncompressed_size;
  
  		/**
  		 * \brief       Unpadded size of this Block
  		 *
  		 * You should pass this to the Block decoder if you will
  		 * decode this Block. It will allow the Block decoder to
  		 * validate the unpadded size.
  		 */
  		lzma_vli unpadded_size;
  
  		/**
  		 * \brief       Total compressed size
  		 *
  		 * This includes all headers and padding in this Block.
  		 * This is useful if you need to know how many bytes
  		 * the Block decoder will actually read.
  		 */
  		lzma_vli total_size;
  
  		lzma_vli reserved_vli1;
  		lzma_vli reserved_vli2;
  		lzma_vli reserved_vli3;
  		lzma_vli reserved_vli4;
  
  		const void *reserved_ptr1;
  		const void *reserved_ptr2;
  		const void *reserved_ptr3;
  		const void *reserved_ptr4;
  	} block;
  
  	/*
  	 * Internal data which is used to store the state of the iterator.
  	 * The exact format may vary between liblzma versions, so don't
  	 * touch these in any way.
  	 */
  	union {
  		const void *p;
  		size_t s;
  		lzma_vli v;
  	} internal[6];
  } lzma_index_iter;
  
  
  /**
   * \brief       Operation mode for lzma_index_iter_next()
   */
  typedef enum {
  	LZMA_INDEX_ITER_ANY             = 0,
  		/**<
  		 * \brief       Get the next Block or Stream
  		 *
  		 * Go to the next Block if the current Stream has at least
  		 * one Block left. Otherwise go to the next Stream even if
  		 * it has no Blocks. If the Stream has no Blocks
  		 * (lzma_index_iter.stream.block_count == 0),
  		 * lzma_index_iter.block will have undefined values.
  		 */
  
  	LZMA_INDEX_ITER_STREAM          = 1,
  		/**<
  		 * \brief       Get the next Stream
  		 *
  		 * Go to the next Stream even if the current Stream has
  		 * unread Blocks left. If the next Stream has at least one
  		 * Block, the iterator will point to the first Block.
  		 * If there are no Blocks, lzma_index_iter.block will have
  		 * undefined values.
  		 */
  
  	LZMA_INDEX_ITER_BLOCK           = 2,
  		/**<
  		 * \brief       Get the next Block
  		 *
  		 * Go to the next Block if the current Stream has at least
  		 * one Block left. If the current Stream has no Blocks left,
  		 * the next Stream with at least one Block is located and
  		 * the iterator will be made to point to the first Block of
  		 * that Stream.
  		 */
  
  	LZMA_INDEX_ITER_NONEMPTY_BLOCK  = 3
  		/**<
  		 * \brief       Get the next non-empty Block
  		 *
  		 * This is like LZMA_INDEX_ITER_BLOCK except that it will
  		 * skip Blocks whose Uncompressed Size is zero.
  		 */
  
  } lzma_index_iter_mode;
  
  
  /**
   * \brief       Calculate memory usage of lzma_index
   *
   * On disk, the size of the Index field depends on both the number of Records
   * stored and how big values the Records store (due to variable-length integer
   * encoding). When the Index is kept in lzma_index structure, the memory usage
   * depends only on the number of Records/Blocks stored in the Index(es), and
   * in case of concatenated lzma_indexes, the number of Streams. The size in
   * RAM is almost always significantly bigger than in the encoded form on disk.
   *
   * This function calculates an approximate amount of memory needed hold
   * the given number of Streams and Blocks in lzma_index structure. This
   * value may vary between CPU architectures and also between liblzma versions
   * if the internal implementation is modified.
   */
  extern LZMA_API(uint64_t) lzma_index_memusage(
  		lzma_vli streams, lzma_vli blocks) lzma_nothrow;
  
  
  /**
   * \brief       Calculate the memory usage of an existing lzma_index
   *
   * This is a shorthand for lzma_index_memusage(lzma_index_stream_count(i),
   * lzma_index_block_count(i)).
   */
  extern LZMA_API(uint64_t) lzma_index_memused(const lzma_index *i)
  		lzma_nothrow;
  
  
  /**
   * \brief       Allocate and initialize a new lzma_index structure
   *
   * \return      On success, a pointer to an empty initialized lzma_index is
   *              returned. If allocation fails, NULL is returned.
   */
  extern LZMA_API(lzma_index *) lzma_index_init(const lzma_allocator *allocator)
  		lzma_nothrow;
  
  
  /**
   * \brief       Deallocate lzma_index
   *
   * If i is NULL, this does nothing.
   */
  extern LZMA_API(void) lzma_index_end(
  		lzma_index *i, const lzma_allocator *allocator) lzma_nothrow;
  
  
  /**
   * \brief       Add a new Block to lzma_index
   *
   * \param       i                 Pointer to a lzma_index structure
   * \param       allocator         Pointer to lzma_allocator, or NULL to
   *                                use malloc()
   * \param       unpadded_size     Unpadded Size of a Block. This can be
   *                                calculated with lzma_block_unpadded_size()
   *                                after encoding or decoding the Block.
   * \param       uncompressed_size Uncompressed Size of a Block. This can be
   *                                taken directly from lzma_block structure
   *                                after encoding or decoding the Block.
   *
   * Appending a new Block does not invalidate iterators. For example,
   * if an iterator was pointing to the end of the lzma_index, after
   * lzma_index_append() it is possible to read the next Block with
   * an existing iterator.
   *
   * \return      - LZMA_OK
   *              - LZMA_MEM_ERROR
   *              - LZMA_DATA_ERROR: Compressed or uncompressed size of the
   *                Stream or size of the Index field would grow too big.
   *              - LZMA_PROG_ERROR
   */
  extern LZMA_API(lzma_ret) lzma_index_append(
  		lzma_index *i, const lzma_allocator *allocator,
  		lzma_vli unpadded_size, lzma_vli uncompressed_size)
  		lzma_nothrow lzma_attr_warn_unused_result;
  
  
  /**
   * \brief       Set the Stream Flags
   *
   * Set the Stream Flags of the last (and typically the only) Stream
   * in lzma_index. This can be useful when reading information from the
   * lzma_index, because to decode Blocks, knowing the integrity check type
   * is needed.
   *
   * The given Stream Flags are copied into internal preallocated structure
   * in the lzma_index, thus the caller doesn't need to keep the *stream_flags
   * available after calling this function.
   *
   * \return      - LZMA_OK
   *              - LZMA_OPTIONS_ERROR: Unsupported stream_flags->version.
   *              - LZMA_PROG_ERROR
   */
  extern LZMA_API(lzma_ret) lzma_index_stream_flags(
  		lzma_index *i, const lzma_stream_flags *stream_flags)
  		lzma_nothrow lzma_attr_warn_unused_result;
  
  
  /**
   * \brief       Get the types of integrity Checks
   *
   * If lzma_index_stream_flags() is used to set the Stream Flags for
   * every Stream, lzma_index_checks() can be used to get a bitmask to
   * indicate which Check types have been used. It can be useful e.g. if
   * showing the Check types to the user.
   *
   * The bitmask is 1 << check_id, e.g. CRC32 is 1 << 1 and SHA-256 is 1 << 10.
   */
  extern LZMA_API(uint32_t) lzma_index_checks(const lzma_index *i)
  		lzma_nothrow lzma_attr_pure;
  
  
  /**
   * \brief       Set the amount of Stream Padding
   *
   * Set the amount of Stream Padding of the last (and typically the only)
   * Stream in the lzma_index. This is needed when planning to do random-access
   * reading within multiple concatenated Streams.
   *
   * By default, the amount of Stream Padding is assumed to be zero bytes.
   *
   * \return      - LZMA_OK
   *              - LZMA_DATA_ERROR: The file size would grow too big.
   *              - LZMA_PROG_ERROR
   */
  extern LZMA_API(lzma_ret) lzma_index_stream_padding(
  		lzma_index *i, lzma_vli stream_padding)
  		lzma_nothrow lzma_attr_warn_unused_result;
  
  
  /**
   * \brief       Get the number of Streams
   */
  extern LZMA_API(lzma_vli) lzma_index_stream_count(const lzma_index *i)
  		lzma_nothrow lzma_attr_pure;
  
  
  /**
   * \brief       Get the number of Blocks
   *
   * This returns the total number of Blocks in lzma_index. To get number
   * of Blocks in individual Streams, use lzma_index_iter.
   */
  extern LZMA_API(lzma_vli) lzma_index_block_count(const lzma_index *i)
  		lzma_nothrow lzma_attr_pure;
  
  
  /**
   * \brief       Get the size of the Index field as bytes
   *
   * This is needed to verify the Backward Size field in the Stream Footer.
   */
  extern LZMA_API(lzma_vli) lzma_index_size(const lzma_index *i)
  		lzma_nothrow lzma_attr_pure;
  
  
  /**
   * \brief       Get the total size of the Stream
   *
   * If multiple lzma_indexes have been combined, this works as if the Blocks
   * were in a single Stream. This is useful if you are going to combine
   * Blocks from multiple Streams into a single new Stream.
   */
  extern LZMA_API(lzma_vli) lzma_index_stream_size(const lzma_index *i)
  		lzma_nothrow lzma_attr_pure;
  
  
  /**
   * \brief       Get the total size of the Blocks
   *
   * This doesn't include the Stream Header, Stream Footer, Stream Padding,
   * or Index fields.
   */
  extern LZMA_API(lzma_vli) lzma_index_total_size(const lzma_index *i)
  		lzma_nothrow lzma_attr_pure;
  
  
  /**
   * \brief       Get the total size of the file
   *
   * When no lzma_indexes have been combined with lzma_index_cat() and there is
   * no Stream Padding, this function is identical to lzma_index_stream_size().
   * If multiple lzma_indexes have been combined, this includes also the headers
   * of each separate Stream and the possible Stream Padding fields.
   */
  extern LZMA_API(lzma_vli) lzma_index_file_size(const lzma_index *i)
  		lzma_nothrow lzma_attr_pure;
  
  
  /**
   * \brief       Get the uncompressed size of the file
   */
  extern LZMA_API(lzma_vli) lzma_index_uncompressed_size(const lzma_index *i)
  		lzma_nothrow lzma_attr_pure;
  
  
  /**
   * \brief       Initialize an iterator
   *
   * \param       iter    Pointer to a lzma_index_iter structure
   * \param       i       lzma_index to which the iterator will be associated
   *
   * This function associates the iterator with the given lzma_index, and calls
   * lzma_index_iter_rewind() on the iterator.
   *
   * This function doesn't allocate any memory, thus there is no
   * lzma_index_iter_end(). The iterator is valid as long as the
   * associated lzma_index is valid, that is, until lzma_index_end() or
   * using it as source in lzma_index_cat(). Specifically, lzma_index doesn't
   * become invalid if new Blocks are added to it with lzma_index_append() or
   * if it is used as the destination in lzma_index_cat().
   *
   * It is safe to make copies of an initialized lzma_index_iter, for example,
   * to easily restart reading at some particular position.
   */
  extern LZMA_API(void) lzma_index_iter_init(
  		lzma_index_iter *iter, const lzma_index *i) lzma_nothrow;
  
  
  /**
   * \brief       Rewind the iterator
   *
   * Rewind the iterator so that next call to lzma_index_iter_next() will
   * return the first Block or Stream.
   */
  extern LZMA_API(void) lzma_index_iter_rewind(lzma_index_iter *iter)
  		lzma_nothrow;
  
  
  /**
   * \brief       Get the next Block or Stream
   *
   * \param       iter    Iterator initialized with lzma_index_iter_init()
   * \param       mode    Specify what kind of information the caller wants
   *                      to get. See lzma_index_iter_mode for details.
   *
   * \return      If next Block or Stream matching the mode was found, *iter
   *              is updated and this function returns false. If no Block or
   *              Stream matching the mode is found, *iter is not modified
   *              and this function returns true. If mode is set to an unknown
   *              value, *iter is not modified and this function returns true.
   */
  extern LZMA_API(lzma_bool) lzma_index_iter_next(
  		lzma_index_iter *iter, lzma_index_iter_mode mode)
  		lzma_nothrow lzma_attr_warn_unused_result;
  
  
  /**
   * \brief       Locate a Block
   *
   * If it is possible to seek in the .xz file, it is possible to parse
   * the Index field(s) and use lzma_index_iter_locate() to do random-access
   * reading with granularity of Block size.
   *
   * \param       iter    Iterator that was earlier initialized with
   *                      lzma_index_iter_init().
   * \param       target  Uncompressed target offset which the caller would
   *                      like to locate from the Stream
   *
   * If the target is smaller than the uncompressed size of the Stream (can be
   * checked with lzma_index_uncompressed_size()):
   *  - Information about the Stream and Block containing the requested
   *    uncompressed offset is stored into *iter.
   *  - Internal state of the iterator is adjusted so that
   *    lzma_index_iter_next() can be used to read subsequent Blocks or Streams.
   *  - This function returns false.
   *
   * If target is greater than the uncompressed size of the Stream, *iter
   * is not modified, and this function returns true.
   */
  extern LZMA_API(lzma_bool) lzma_index_iter_locate(
  		lzma_index_iter *iter, lzma_vli target) lzma_nothrow;
  
  
  /**
   * \brief       Concatenate lzma_indexes
   *
   * Concatenating lzma_indexes is useful when doing random-access reading in
   * multi-Stream .xz file, or when combining multiple Streams into single
   * Stream.
   *
   * \param       dest      lzma_index after which src is appended
   * \param       src       lzma_index to be appended after dest. If this
   *                        function succeeds, the memory allocated for src
   *                        is freed or moved to be part of dest, and all
   *                        iterators pointing to src will become invalid.
   * \param       allocator Custom memory allocator; can be NULL to use
   *                        malloc() and free().
   *
   * \return      - LZMA_OK: lzma_indexes were concatenated successfully.
   *                src is now a dangling pointer.
   *              - LZMA_DATA_ERROR: *dest would grow too big.
   *              - LZMA_MEM_ERROR
   *              - LZMA_PROG_ERROR
   */
  extern LZMA_API(lzma_ret) lzma_index_cat(lzma_index *dest, lzma_index *src,
  		const lzma_allocator *allocator)
  		lzma_nothrow lzma_attr_warn_unused_result;
  
  
  /**
   * \brief       Duplicate lzma_index
   *
   * \return      A copy of the lzma_index, or NULL if memory allocation failed.
   */
  extern LZMA_API(lzma_index *) lzma_index_dup(
  		const lzma_index *i, const lzma_allocator *allocator)
  		lzma_nothrow lzma_attr_warn_unused_result;
  
  
  /**
   * \brief       Initialize .xz Index encoder
   *
   * \param       strm        Pointer to properly prepared lzma_stream
   * \param       i           Pointer to lzma_index which should be encoded.
   *
   * The valid `action' values for lzma_code() are LZMA_RUN and LZMA_FINISH.
   * It is enough to use only one of them (you can choose freely).
   *
   * \return      - LZMA_OK: Initialization succeeded, continue with lzma_code().
   *              - LZMA_MEM_ERROR
   *              - LZMA_PROG_ERROR
   */
  extern LZMA_API(lzma_ret) lzma_index_encoder(
  		lzma_stream *strm, const lzma_index *i)
  		lzma_nothrow lzma_attr_warn_unused_result;
  
  
  /**
   * \brief       Initialize .xz Index decoder
   *
   * \param       strm        Pointer to properly prepared lzma_stream
   * \param       i           The decoded Index will be made available via
   *                          this pointer. Initially this function will
   *                          set *i to NULL (the old value is ignored). If
   *                          decoding succeeds (lzma_code() returns
   *                          LZMA_STREAM_END), *i will be set to point
   *                          to a new lzma_index, which the application
   *                          has to later free with lzma_index_end().
   * \param       memlimit    How much memory the resulting lzma_index is
   *                          allowed to require. liblzma 5.2.3 and earlier
   *                          don't allow 0 here and return LZMA_PROG_ERROR;
   *                          later versions treat 0 as if 1 had been specified.
   *
   * Valid `action' arguments to lzma_code() are LZMA_RUN and LZMA_FINISH.
   * There is no need to use LZMA_FINISH, but it's allowed because it may
   * simplify certain types of applications.
   *
   * \return      - LZMA_OK: Initialization succeeded, continue with lzma_code().
   *              - LZMA_MEM_ERROR
   *              - LZMA_PROG_ERROR
   *
   *              liblzma 5.2.3 and older list also LZMA_MEMLIMIT_ERROR here
   *              but that error code has never been possible from this
   *              initialization function.
   */
  extern LZMA_API(lzma_ret) lzma_index_decoder(
  		lzma_stream *strm, lzma_index **i, uint64_t memlimit)
  		lzma_nothrow lzma_attr_warn_unused_result;
  
  
  /**
   * \brief       Single-call .xz Index encoder
   *
   * \param       i         lzma_index to be encoded
   * \param       out       Beginning of the output buffer
   * \param       out_pos   The next byte will be written to out[*out_pos].
   *                        *out_pos is updated only if encoding succeeds.
   * \param       out_size  Size of the out buffer; the first byte into
   *                        which no data is written to is out[out_size].
   *
   * \return      - LZMA_OK: Encoding was successful.
   *              - LZMA_BUF_ERROR: Output buffer is too small. Use
   *                lzma_index_size() to find out how much output
   *                space is needed.
   *              - LZMA_PROG_ERROR
   *
   * \note        This function doesn't take allocator argument since all
   *              the internal data is allocated on stack.
   */
  extern LZMA_API(lzma_ret) lzma_index_buffer_encode(const lzma_index *i,
  		uint8_t *out, size_t *out_pos, size_t out_size) lzma_nothrow;
  
  
  /**
   * \brief       Single-call .xz Index decoder
   *
   * \param       i           If decoding succeeds, *i will point to a new
   *                          lzma_index, which the application has to
   *                          later free with lzma_index_end(). If an error
   *                          occurs, *i will be NULL. The old value of *i
   *                          is always ignored and thus doesn't need to be
   *                          initialized by the caller.
   * \param       memlimit    Pointer to how much memory the resulting
   *                          lzma_index is allowed to require. The value
   *                          pointed by this pointer is modified if and only
   *                          if LZMA_MEMLIMIT_ERROR is returned.
   * \param       allocator   Pointer to lzma_allocator, or NULL to use malloc()
   * \param       in          Beginning of the input buffer
   * \param       in_pos      The next byte will be read from in[*in_pos].
   *                          *in_pos is updated only if decoding succeeds.
   * \param       in_size     Size of the input buffer; the first byte that
   *                          won't be read is in[in_size].
   *
   * \return      - LZMA_OK: Decoding was successful.
   *              - LZMA_MEM_ERROR
   *              - LZMA_MEMLIMIT_ERROR: Memory usage limit was reached.
   *                The minimum required memlimit value was stored to *memlimit.
   *              - LZMA_DATA_ERROR
   *              - LZMA_PROG_ERROR
   */
  extern LZMA_API(lzma_ret) lzma_index_buffer_decode(lzma_index **i,
  		uint64_t *memlimit, const lzma_allocator *allocator,
  		const uint8_t *in, size_t *in_pos, size_t in_size)
  		lzma_nothrow;
  
  
  /**
   * \brief       Initialize a .xz file information decoder
   *
   * \param       strm        Pointer to a properly prepared lzma_stream
   * \param       dest_index  Pointer to a pointer where the decoder will put
   *                          the decoded lzma_index. The old value
   *                          of *dest_index is ignored (not freed).
   * \param       memlimit    How much memory the resulting lzma_index is
   *                          allowed to require. Use UINT64_MAX to
   *                          effectively disable the limiter.
   * \param       file_size   Size of the input .xz file
   *
   * This decoder decodes the Stream Header, Stream Footer, Index, and
   * Stream Padding field(s) from the input .xz file and stores the resulting
   * combined index in *dest_index. This information can be used to get the
   * uncompressed file size with lzma_index_uncompressed_size(*dest_index) or,
   * for example, to implement random access reading by locating the Blocks
   * in the Streams.
   *
   * To get the required information from the .xz file, lzma_code() may ask
   * the application to seek in the input file by returning LZMA_SEEK_NEEDED
   * and having the target file position specified in lzma_stream.seek_pos.
   * The number of seeks required depends on the input file and how big buffers
   * the application provides. When possible, the decoder will seek backward
   * and forward in the given buffer to avoid useless seek requests. Thus, if
   * the application provides the whole file at once, no external seeking will
   * be required (that is, lzma_code() won't return LZMA_SEEK_NEEDED).
   *
   * The value in lzma_stream.total_in can be used to estimate how much data
   * liblzma had to read to get the file information. However, due to seeking
   * and the way total_in is updated, the value of total_in will be somewhat
   * inaccurate (a little too big). Thus, total_in is a good estimate but don't
   * expect to see the same exact value for the same file if you change the
   * input buffer size or switch to a different liblzma version.
   *
   * Valid `action' arguments to lzma_code() are LZMA_RUN and LZMA_FINISH.
   * You only need to use LZMA_RUN; LZMA_FINISH is only supported because it
   * might be convenient for some applications. If you use LZMA_FINISH and if
   * lzma_code() asks the application to seek, remember to reset `action' back
   * to LZMA_RUN unless you hit the end of the file again.
   *
   * Possible return values from lzma_code():
   *   - LZMA_OK: All OK so far, more input needed
   *   - LZMA_SEEK_NEEDED: Provide more input starting from the absolute
   *     file position strm->seek_pos
   *   - LZMA_STREAM_END: Decoding was successful, *dest_index has been set
   *   - LZMA_FORMAT_ERROR: The input file is not in the .xz format (the
   *     expected magic bytes were not found from the beginning of the file)
   *   - LZMA_OPTIONS_ERROR: File looks valid but contains headers that aren't
   *     supported by this version of liblzma
   *   - LZMA_DATA_ERROR: File is corrupt
   *   - LZMA_BUF_ERROR
   *   - LZMA_MEM_ERROR
   *   - LZMA_MEMLIMIT_ERROR
   *   - LZMA_PROG_ERROR
   *
   * \return      - LZMA_OK
   *              - LZMA_MEM_ERROR
   *              - LZMA_PROG_ERROR
   */
  extern LZMA_API(lzma_ret) lzma_file_info_decoder(
  		lzma_stream *strm, lzma_index **dest_index,
  		uint64_t memlimit, uint64_t file_size)
  		lzma_nothrow;
  