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diff --git a/doc/lzlib.texi b/doc/lzlib.texi new file mode 100644 index 0000000..88f0b16 --- /dev/null +++ b/doc/lzlib.texi @@ -0,0 +1,812 @@ +\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 |