path: root/doc/lzlib.texi

\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename lzlib.info
@documentencoding ISO-8859-15
@settitle Lzlib Manual
@finalout
@c %**end of header

@set UPDATED 30 January 2014
@set VERSION 1.6-pre2

@dircategory Data Compression
@direntry
* Lzlib: (lzlib).               Compression library for the lzip format
@end direntry


@ifnothtml
@titlepage
@title Lzlib
@subtitle Compression library for the lzip format
@subtitle for Lzlib version @value{VERSION}, @value{UPDATED}
@author by Antonio Diaz Diaz

@page
@vskip 0pt plus 1filll
@end titlepage

@contents
@end ifnothtml

@node Top
@top

This manual is for Lzlib (version @value{VERSION}, @value{UPDATED}).

@menu
* Introduction::                Purpose and features of Lzlib
* Library version::             Checking library version
* Buffering::                   Sizes of Lzlib's buffers
* Parameter limits::            Min / max values for some parameters
* Compression functions::       Descriptions of the compression functions
* Decompression functions::     Descriptions of the decompression functions
* Error codes::                 Meaning of codes returned by functions
* Error messages::              Error messages corresponding to error codes
* Data format::                 Detailed format of the compressed data
* Examples::                    A small tutorial with examples
* Problems::                    Reporting bugs
* Concept index::               Index of concepts
@end menu

@sp 1
Copyright @copyright{} 2009, 2010, 2011, 2012, 2013, 2014
Antonio Diaz Diaz.

This manual is free documentation: you have unlimited permission
to copy, distribute and modify it.


@node Introduction
@chapter Introduction
@cindex introduction

Lzlib is a data compression library providing in-memory LZMA compression
and decompression functions, including integrity checking of the
decompressed data. The compressed data format used by the library is the
lzip format. Lzlib is written in C.

The lzip file format is designed for long-term data archiving. It is
clean, provides very safe 4 factor integrity checking, and is backed by
the recovery capabilities of lziprecover.

The functions and variables forming the interface of the compression
library are declared in the file @samp{lzlib.h}. Usage examples of the
library are given in the files @samp{main.c} and @samp{bbexample.c} from
the source distribution.

Compression/decompression is done by repeatedly calling a couple of
read/write functions until all the data has been processed by the
library. This interface is safer and less error prone than the
traditional zlib interface.

Compression/decompression is done when the read function is called. This
means the value returned by the position functions will not be updated
until some data is read, even if you write a lot of data. If you want
the data to be compressed in advance, just call the read function with a
@var{size} equal to 0.

Lzlib will correctly decompress a data stream which is the concatenation
of two or more compressed data streams. The result is the concatenation
of the corresponding decompressed data streams. Integrity testing of
concatenated compressed data streams is also supported.

All the library functions are thread safe. The library does not install
any signal handler. The decoder checks the consistency of the compressed
data, so the library should never crash even in case of corrupted input.

Lzlib implements a simplified version of the LZMA (Lempel-Ziv-Markov
chain-Algorithm) algorithm. The high compression of LZMA comes from
combining two basic, well-proven compression ideas: sliding dictionaries
(LZ77/78) and markov models (the thing used by every compression
algorithm that uses a range encoder or similar order-0 entropy coder as
its last stage) with segregation of contexts according to what the bits
are used for.

The ideas embodied in lzlib are due to (at least) the following people:
Abraham Lempel and Jacob Ziv (for the LZ algorithm), Andrey Markov (for
the definition of Markov chains), G.N.N. Martin (for the definition of
range encoding), Igor Pavlov (for putting all the above together in
LZMA), and Julian Seward (for bzip2's CLI).


@node Library version
@chapter Library version
@cindex library version

@deftypefun {const char *} LZ_version ( void )
Returns the library version as a string.
@end deftypefun

@deftypevr Constant {const char *} LZ_version_string
This constant is defined in the header file @samp{lzlib.h}.
@end deftypevr

The application should compare LZ_version and LZ_version_string for
consistency. If the first character differs, the library code actually
used may be incompatible with the @samp{lzlib.h} header file used by the
application.

@example
if( LZ_version()[0] != LZ_version_string[0] )
  error( "bad library version" );
@end example


@node Buffering
@chapter Buffering
@cindex buffering

Lzlib internal functions need access to a memory chunk at least as large
as the dictionary size (sliding window). For efficiency reasons, the
input buffer for compression is twice as large as the dictionary size.
Finally, for security reasons, lzlib uses two more internal buffers.

These are the four buffers used by lzlib, and their guaranteed minimum
sizes:

@itemize @bullet
@item Input compression buffer. Written to by the
@samp{LZ_compress_write} function. Its size is two times the dictionary
size set with the @samp{LZ_compress_open} function or 64 KiB, whichever
is larger.

@item Output compression buffer. Read from by the
@samp{LZ_compress_read} function. Its size is 64 KiB.

@item Input decompression buffer. Written to by the
@samp{LZ_decompress_write} function. Its size is 64 KiB.

@item Output decompression buffer. Read from by the
@samp{LZ_decompress_read} function. Its size is the dictionary size set
in the header of the member currently being decompressed or 64 KiB,
whichever is larger.
@end itemize


@node Parameter limits
@chapter Parameter limits
@cindex parameter limits

These functions provide minimum and maximum values for some parameters.
Current values are shown in square brackets.

@deftypefun int LZ_min_dictionary_bits ( void )
Returns the base 2 logarithm of the smallest valid dictionary size [12].
@end deftypefun

@deftypefun int LZ_min_dictionary_size ( void )
Returns the smallest valid dictionary size [4 KiB].
@end deftypefun

@deftypefun int LZ_max_dictionary_bits ( void )
Returns the base 2 logarithm of the largest valid dictionary size [29].
@end deftypefun

@deftypefun int LZ_max_dictionary_size ( void )
Returns the largest valid dictionary size [512 MiB].
@end deftypefun

@deftypefun int LZ_min_match_len_limit ( void )
Returns the smallest valid match length limit [5].
@end deftypefun

@deftypefun int LZ_max_match_len_limit ( void )
Returns the largest valid match length limit [273].
@end deftypefun


@node Compression functions
@chapter Compression functions
@cindex compression functions

These are the functions used to compress data. In case of error, all of
them return -1 or 0, for signed and unsigned return values respectively,
except @samp{LZ_compress_open} whose return value must be verified by
calling @samp{LZ_compress_errno} before using it.


@deftypefun {struct LZ_Encoder *} LZ_compress_open ( const int @var{dictionary_size}, const int @var{match_len_limit}, const unsigned long long @var{member_size} )
Initializes the internal stream state for compression and returns a
pointer that can only be used as the @var{encoder} argument for the
other LZ_compress functions, or a null pointer if the encoder could not
be allocated.

The returned pointer must be verified by calling
@samp{LZ_compress_errno} before using it. If @samp{LZ_compress_errno}
does not return @samp{LZ_ok}, the returned pointer must not be used and
should be freed with @samp{LZ_compress_close} to avoid memory leaks.

@var{dictionary_size} sets the dictionary size to be used, in bytes.
Valid values range from 4 KiB to 512 MiB. Note that dictionary sizes are
quantized. If the specified size does not match one of the valid sizes,
it will be rounded upwards by adding up to (@var{dictionary_size} / 16)
to it.

@var{match_len_limit} sets the match length limit in bytes. Valid values
range from 5 to 273. Larger values usually give better compression
ratios but longer compression times.

@var{member_size} sets the member size limit in bytes. Minimum member
size limit is 100 kB. Small member size may degrade compression ratio, so
use it only when needed. To produce a single-member data stream, give
@var{member_size} a value larger than the amount of data to be produced,
for example INT64_MAX.
@end deftypefun


@deftypefun int LZ_compress_close ( struct LZ_Encoder * const @var{encoder} )
Frees all dynamically allocated data structures for this stream. This
function discards any unprocessed input and does not flush any pending
output. After a call to @samp{LZ_compress_close}, @var{encoder} can no
more be used as an argument to any LZ_compress function.
@end deftypefun


@deftypefun int LZ_compress_finish ( struct LZ_Encoder * const @var{encoder} )
Use this function to tell @samp{lzlib} that all the data for this member
has already been written (with the @samp{LZ_compress_write} function).
After all the produced compressed data has been read with
@samp{LZ_compress_read} and @samp{LZ_compress_member_finished} returns
1, a new member can be started with @samp{LZ_compress_restart_member}.
@end deftypefun


@deftypefun int LZ_compress_restart_member ( struct LZ_Encoder * const @var{encoder}, const unsigned long long @var{member_size} )
Use this function to start a new member, in a multi-member data stream.
Call this function only after @samp{LZ_compress_member_finished}
indicates that the current member has been fully read (with the
@samp{LZ_compress_read} function).
@end deftypefun


@deftypefun int LZ_compress_sync_flush ( struct LZ_Encoder * const @var{encoder} )
Use this function to make available to @samp{LZ_compress_read} all the
data already written with the @samp{LZ_compress_write} function.
Repeated use of @samp{LZ_compress_sync_flush} may degrade compression
ratio, so use it only when needed.
@end deftypefun


@deftypefun int LZ_compress_read ( struct LZ_Encoder * const @var{encoder}, uint8_t * const @var{buffer}, const int @var{size} )
The @samp{LZ_compress_read} function reads up to @var{size} bytes from
the stream pointed to by @var{encoder}, storing the results in
@var{buffer}.

The return value is the number of bytes actually read. This might be
less than @var{size}; for example, if there aren't that many bytes left
in the stream or if more bytes have to be yet written with the
@samp{LZ_compress_write} function. Note that reading less than
@var{size} bytes is not an error.
@end deftypefun


@deftypefun int LZ_compress_write ( struct LZ_Encoder * const @var{encoder}, uint8_t * const @var{buffer}, const int @var{size} )
The @samp{LZ_compress_write} function writes up to @var{size} bytes from
@var{buffer} to the stream pointed to by @var{encoder}.

The return value is the number of bytes actually written. This might be
less than @var{size}. Note that writing less than @var{size} bytes is
not an error.
@end deftypefun


@deftypefun int LZ_compress_write_size ( struct LZ_Encoder * const @var{encoder} )
The @samp{LZ_compress_write_size} function returns the maximum number of
bytes that can be immediately written through the @samp{LZ_compress_write}
function.

It is guaranteed that an immediate call to @samp{LZ_compress_write} will
accept a @var{size} up to the returned number of bytes.
@end deftypefun


@deftypefun {enum LZ_Errno} LZ_compress_errno ( struct LZ_Encoder * const @var{encoder} )
Returns the current error code for @var{encoder} (@pxref{Error codes}).
@end deftypefun


@deftypefun int LZ_compress_finished ( struct LZ_Encoder * const @var{encoder} )
Returns 1 if all the data has been read and @samp{LZ_compress_close} can
be safely called. Otherwise it returns 0.
@end deftypefun


@deftypefun int LZ_compress_member_finished ( struct LZ_Encoder * const @var{encoder} )
Returns 1 if the current member, in a multi-member data stream, has been
fully read and @samp{LZ_compress_restart_member} can be safely called.
Otherwise it returns 0.
@end deftypefun


@deftypefun {unsigned long long} LZ_compress_data_position ( struct LZ_Encoder * const @var{encoder} )
Returns the number of input bytes already compressed in the current
member.
@end deftypefun


@deftypefun {unsigned long long} LZ_compress_member_position ( struct LZ_Encoder * const @var{encoder} )
Returns the number of compressed bytes already produced, but perhaps not
yet read, in the current member.
@end deftypefun


@deftypefun {unsigned long long} LZ_compress_total_in_size ( struct LZ_Encoder * const @var{encoder} )
Returns the total number of input bytes already compressed.
@end deftypefun


@deftypefun {unsigned long long} LZ_compress_total_out_size ( struct LZ_Encoder * const @var{encoder} )
Returns the total number of compressed bytes already produced, but
perhaps not yet read.
@end deftypefun


@node Decompression functions
@chapter Decompression functions
@cindex decompression functions

These are the functions used to decompress data. In case of error, all
of them return -1 or 0, for signed and unsigned return values
respectively, except @samp{LZ_decompress_open} whose return value must
be verified by calling @samp{LZ_decompress_errno} before using it.


@deftypefun {struct LZ_Decoder *} LZ_decompress_open ( void )
Initializes the internal stream state for decompression and returns a
pointer that can only be used as the @var{decoder} argument for the
other LZ_decompress functions, or a null pointer if the decoder could
not be allocated.

The returned pointer must be verified by calling
@samp{LZ_decompress_errno} before using it. If
@samp{LZ_decompress_errno} does not return @samp{LZ_ok}, the returned
pointer must not be used and should be freed with
@samp{LZ_decompress_close} to avoid memory leaks.
@end deftypefun


@deftypefun int LZ_decompress_close ( struct LZ_Decoder * const @var{decoder} )
Frees all dynamically allocated data structures for this stream. This
function discards any unprocessed input and does not flush any pending
output. After a call to @samp{LZ_decompress_close}, @var{decoder} can no
more be used as an argument to any LZ_decompress function.
@end deftypefun


@deftypefun int LZ_decompress_finish ( struct LZ_Decoder * const @var{decoder} )
Use this function to tell @samp{lzlib} that all the data for this stream
has already been written (with the @samp{LZ_decompress_write} function).
@end deftypefun


@deftypefun int LZ_decompress_reset ( struct LZ_Decoder * const @var{decoder} )
Resets the internal state of @var{decoder} as it was just after opening
it with the @samp{LZ_decompress_open} function. Data stored in the
internal buffers is discarded. Position counters are set to 0.
@end deftypefun


@deftypefun int LZ_decompress_sync_to_member ( struct LZ_Decoder * const @var{decoder} )
Resets the error state of @var{decoder} and enters a search state that
lasts until a new member header (or the end of the stream) is found.
After a successful call to @samp{LZ_decompress_sync_to_member}, data
written with @samp{LZ_decompress_write} will be consumed and
@samp{LZ_decompress_read} will return 0 until a header is found.

This function is useful to discard any data preceding the first member,
or to discard the rest of the current member, for example in case of a
data error. If the decoder is already at the beginning of a member, this
function does nothing.
@end deftypefun


@deftypefun int LZ_decompress_read ( struct LZ_Decoder * const @var{decoder}, uint8_t * const @var{buffer}, const int @var{size} )
The @samp{LZ_decompress_read} function reads up to @var{size} bytes from
the stream pointed to by @var{decoder}, storing the results in
@var{buffer}.

The return value is the number of bytes actually read. This might be
less than @var{size}; for example, if there aren't that many bytes left
in the stream or if more bytes have to be yet written with the
@samp{LZ_decompress_write} function. Note that reading less than
@var{size} bytes is not an error.
@end deftypefun


@deftypefun int LZ_decompress_write ( struct LZ_Decoder * const @var{decoder}, uint8_t * const @var{buffer}, const int @var{size} )
The @samp{LZ_decompress_write} function writes up to @var{size} bytes from
@var{buffer} to the stream pointed to by @var{decoder}.

The return value is the number of bytes actually written. This might be
less than @var{size}. Note that writing less than @var{size} bytes is
not an error.
@end deftypefun


@deftypefun int LZ_decompress_write_size ( struct LZ_Decoder * const @var{decoder} )
The @samp{LZ_decompress_write_size} function returns the maximum number
of bytes that can be immediately written through the
@samp{LZ_decompress_write} function.

It is guaranteed that an immediate call to @samp{LZ_decompress_write}
will accept a @var{size} up to the returned number of bytes.
@end deftypefun


@deftypefun {enum LZ_Errno} LZ_decompress_errno ( struct LZ_Decoder * const @var{decoder} )
Returns the current error code for @var{decoder} (@pxref{Error codes}).
@end deftypefun


@deftypefun int LZ_decompress_finished ( struct LZ_Decoder * const @var{decoder} )
Returns 1 if all the data has been read and @samp{LZ_decompress_close}
can be safely called. Otherwise it returns 0.
@end deftypefun


@deftypefun int LZ_decompress_member_finished ( struct LZ_Decoder * const @var{decoder} )
Returns 1 if the previous call to @samp{LZ_decompress_read} finished
reading the current member, indicating that final values for member are
available through @samp{LZ_decompress_data_crc},
@samp{LZ_decompress_data_position}, and
@samp{LZ_decompress_member_position}. Otherwise it returns 0.
@end deftypefun


@deftypefun int LZ_decompress_member_version ( struct LZ_Decoder * const @var{decoder} )
Returns the version of current member from member header.
@end deftypefun


@deftypefun int LZ_decompress_dictionary_size ( struct LZ_Decoder * const @var{decoder} )
Returns the dictionary size of current member from member header.
@end deftypefun


@deftypefun {unsigned} LZ_decompress_data_crc ( struct LZ_Decoder * const @var{decoder} )
Returns the 32 bit Cyclic Redundancy Check of the data decompressed from
the current member. The returned value is valid only when
@samp{LZ_decompress_member_finished} returns 1.
@end deftypefun


@deftypefun {unsigned long long} LZ_decompress_data_position ( struct LZ_Decoder * const @var{decoder} )
Returns the number of decompressed bytes already produced, but perhaps
not yet read, in the current member.
@end deftypefun


@deftypefun {unsigned long long} LZ_decompress_member_position ( struct LZ_Decoder * const @var{decoder} )
Returns the number of input bytes already decompressed in the current
member.
@end deftypefun


@deftypefun {unsigned long long} LZ_decompress_total_in_size ( struct LZ_Decoder * const @var{decoder} )
Returns the total number of input bytes already decompressed.
@end deftypefun


@deftypefun {unsigned long long} LZ_decompress_total_out_size ( struct LZ_Decoder * const @var{decoder} )
Returns the total number of decompressed bytes already produced, but
perhaps not yet read.
@end deftypefun


@node Error codes
@chapter Error codes
@cindex error codes

Most library functions return -1 to indicate that they have failed. But
this return value only tells you that an error has occurred. To find out
what kind of error it was, you need to verify the error code by calling
@samp{LZ_(de)compress_errno}.

Library functions do not change the value returned by
@samp{LZ_(de)compress_errno} when they succeed; thus, the value returned
by @samp{LZ_(de)compress_errno} after a successful call is not
necessarily LZ_ok, and you should not use @samp{LZ_(de)compress_errno}
to determine whether a call failed. If the call failed, then you can
examine @samp{LZ_(de)compress_errno}.

The error codes are defined in the header file @samp{lzlib.h}.

@deftypevr Constant {enum LZ_Errno} LZ_ok
The value of this constant is 0 and is used to indicate that there is no
error.
@end deftypevr

@deftypevr Constant {enum LZ_Errno} LZ_bad_argument
At least one of the arguments passed to the library function was
invalid.
@end deftypevr

@deftypevr Constant {enum LZ_Errno} LZ_mem_error
No memory available. The system cannot allocate more virtual memory
because its capacity is full.
@end deftypevr

@deftypevr Constant {enum LZ_Errno} LZ_sequence_error
A library function was called in the wrong order. For example
@samp{LZ_compress_restart_member} was called before
@samp{LZ_compress_member_finished} indicates that the current member is
finished.
@end deftypevr

@deftypevr Constant {enum LZ_Errno} LZ_header_error
Reading of member header failed. If this happens at the end of the data
stream it may indicate trailing garbage.
@end deftypevr

@deftypevr Constant {enum LZ_Errno} LZ_unexpected_eof
The end of the data stream was reached in the middle of a member.
@end deftypevr

@deftypevr Constant {enum LZ_Errno} LZ_data_error
The data stream is corrupt.
@end deftypevr

@deftypevr Constant {enum LZ_Errno} LZ_library_error
A bug was detected in the library. Please, report it (@pxref{Problems}).
@end deftypevr


@node Error messages
@chapter Error messages
@cindex error messages

@deftypefun {const char *} LZ_strerror ( const enum LZ_Errno @var{lz_errno} )
Returns the standard error message for a given error code. The messages
are fairly short; there are no multi-line messages or embedded newlines.
This function makes it easy for your program to report informative error
messages about the failure of a library call.

The value of @var{lz_errno} normally comes from a call to
@samp{LZ_(de)compress_errno}.
@end deftypefun


@node Data format
@chapter Data format
@cindex data format

Perfection is reached, not when there is no longer anything to add, but
when there is no longer anything to take away.@*
--- Antoine de Saint-Exupery

@sp 1
In the diagram below, a box like this:
@verbatim
+---+
|   | <-- the vertical bars might be missing
+---+
@end verbatim

represents one byte; a box like this:
@verbatim
+==============+
|              |
+==============+
@end verbatim

represents a variable number of bytes.

@sp 1
A lzip data stream consists of a series of "members" (compressed data
sets). The members simply appear one after another in the data stream,
with no additional information before, between, or after them.

Each member has the following structure:
@verbatim
+--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID string | VN | DS | Lzma stream | CRC32 |   Data size   |  Member size  |
+--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
@end verbatim

All multibyte values are stored in little endian order.

@table @samp
@item ID string
A four byte string, identifying the lzip format, with the value "LZIP"
(0x4C, 0x5A, 0x49, 0x50).

@item VN (version number, 1 byte)
Just in case something needs to be modified in the future. 1 for now.

@item DS (coded dictionary size, 1 byte)
Lzip divides the distance between any two powers of 2 into 8 equally
spaced intervals, named "wedges". The dictionary size is calculated by
taking a power of 2 (the base size) and substracting from it a number of
wedges between 0 and 7. The size of a wedge is (base_size / 16).@*
Bits 4-0 contain the base 2 logarithm of the base size (12 to 29).@*
Bits 7-5 contain the number of wedges (0 to 7) to substract from the
base size to obtain the dictionary size.@*
Example: 0xD3 = 2^19 - 6 * 2^15 = 512 KiB - 6 * 32 KiB = 320 KiB@*
Valid values for dictionary size range from 4 KiB to 512 MiB.

@item Lzma stream
The lzma stream, finished by an end of stream marker. Uses default
values for encoder properties. See the lzip manual for a full
description.@*
Lzip only uses the LZMA marker @samp{2} ("End Of Stream" marker). Lzlib
also uses the LZMA marker @samp{3} ("Sync Flush" marker).

@item CRC32 (4 bytes)
CRC of the uncompressed original data.

@item Data size (8 bytes)
Size of the uncompressed original data.

@item Member size (8 bytes)
Total size of the member, including header and trailer. This field acts
as a distributed index, allows the verification of stream integrity, and
facilitates safe recovery of undamaged members from multi-member files.

@end table


@node Examples
@chapter A small tutorial with examples
@cindex examples

This chapter shows the order in which the library functions should be
called depending on what kind of data stream you want to compress or
decompress. See the file @samp{bbexample.c} in the source distribution
for an example of how buffer-to-buffer compression/decompression can be
implemented using lzlib.

Note that lzlib's interface is symmetrical. That is, the code for normal
compression and decompression is identical except because one calls
LZ_compress* functions while the other calls LZ_decompress* functions.

@sp 1
@noindent
Example 1: Normal compression (@var{member_size} > total output).

@example
1) LZ_compress_open
2) LZ_compress_write
3) LZ_compress_read
4) go back to step 2 until all input data has been written
5) LZ_compress_finish
6) LZ_compress_read
7) go back to step 6 until LZ_compress_finished returns 1
8) LZ_compress_close
@end example

@sp 1
@noindent
Example 2: Normal compression using LZ_compress_write_size.

@example
1) LZ_compress_open
2) go to step 5 if LZ_compress_write_size returns 0
3) LZ_compress_write
4) if no more data to write, call LZ_compress_finish
5) LZ_compress_read
6) go back to step 2 until LZ_compress_finished returns 1
7) LZ_compress_close
@end example

@sp 1
@noindent
Example 3: Decompression.

@example
1) LZ_decompress_open
2) LZ_decompress_write
3) LZ_decompress_read
4) go back to step 2 until all input data has been written
5) LZ_decompress_finish
6) LZ_decompress_read
7) go back to step 6 until LZ_decompress_finished returns 1
8) LZ_decompress_close
@end example

@sp 1
@noindent
Example 4: Decompression using LZ_decompress_write_size.

@example
1) LZ_decompress_open
2) go to step 5 if LZ_decompress_write_size returns 0
3) LZ_decompress_write
4) if no more data to write, call LZ_decompress_finish
5) LZ_decompress_read
5a) optionally, if LZ_decompress_member_finished returns 1, read
    final values for member with LZ_decompress_data_crc, etc.
6) go back to step 2 until LZ_decompress_finished returns 1
7) LZ_decompress_close
@end example

@sp 1
@noindent
Example 5: Multi-member compression (@var{member_size} < total output).

@example
 1) LZ_compress_open
 2) go to step 5 if LZ_compress_write_size returns 0
 3) LZ_compress_write
 4) if no more data to write, call LZ_compress_finish
 5) LZ_compress_read
 6) go back to step 2 until LZ_compress_member_finished returns 1
 7) go to step 10 if LZ_compress_finished() returns 1
 8) LZ_compress_restart_member
 9) go back to step 2
10) LZ_compress_close
@end example

@sp 1
@noindent
Example 6: Multi-member compression (user-restarted members).

@example
 1) LZ_compress_open
 2) LZ_compress_write
 3) LZ_compress_read
 4) go back to step 2 until member termination is desired
 5) LZ_compress_finish
 6) LZ_compress_read
 7) go back to step 6 until LZ_compress_member_finished returns 1
 8) verify that LZ_compress_finished returns 1
 9) go to step 12 if all input data has been written
10) LZ_compress_restart_member
11) go back to step 2
12) LZ_compress_close
@end example

@sp 1
@noindent
Example 7: Decompression with automatic removal of leading garbage.

@example
1) LZ_decompress_open
2) LZ_decompress_sync_to_member
3) go to step 6 if LZ_decompress_write_size returns 0
4) LZ_decompress_write
5) if no more data to write, call LZ_decompress_finish
6) LZ_decompress_read
7) go back to step 3 until LZ_decompress_finished returns 1
8) LZ_decompress_close
@end example

@sp 1
@noindent
Example 8: Streamed decompression with automatic resynchronization to
next member in case of data error.

@example
1) LZ_decompress_open
2) go to step 5 if LZ_decompress_write_size returns 0
3) LZ_decompress_write
4) if no more data to write, call LZ_decompress_finish
5) if LZ_decompress_read produces LZ_header_error or LZ_data_error,
   call LZ_decompress_sync_to_member
6) go back to step 2 until LZ_decompress_finished returns 1
7) LZ_decompress_close
@end example


@node Problems
@chapter Reporting bugs
@cindex bugs
@cindex getting help

There are probably bugs in Lzlib. There are certainly errors and
omissions in this manual. If you report them, they will get fixed. If
you don't, no one will ever know about them and they will remain unfixed
for all eternity, if not longer.

If you find a bug in Lzlib, please send electronic mail to
@email{lzip-bug@@nongnu.org}. Include the version number, which you can
find by running @w{@samp{minilzip --version}} or in
@samp{LZ_version_string} from @samp{lzlib.h}.


@node Concept index
@unnumbered Concept index

@printindex cp

@bye