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diff --git a/doc/lzlib.info b/doc/lzlib.info new file mode 100644 index 0000000..28aea4d --- /dev/null +++ b/doc/lzlib.info @@ -0,0 +1,487 @@ +This is lzlib.info, produced by makeinfo version 4.13 from +lzlib.texinfo. + +INFO-DIR-SECTION Data Compression +START-INFO-DIR-ENTRY +* Lzlib: (lzlib). A compression library for lzip files +END-INFO-DIR-ENTRY + + +File: lzlib.info, Node: Top, Next: Introduction, Up: (dir) + +Lzlib +***** + +This manual is for Lzlib (version 0.3, 3 May 2009). + +* Menu: + +* Introduction:: Purpose and features of Lzlib +* Library Version:: Checking library version +* Compression Functions:: Descriptions of the compression functions +* Decompression Functions:: Descriptions of the decompression functions +* Error Codes:: Meaning of codes returned by functions +* Data Format:: Detailed format of the compressed data +* Examples:: A small tutorial with examples +* Problems:: Reporting bugs +* Concept Index:: Index of concepts + + + Copyright (C) 2009 Antonio Diaz Diaz. + + This manual is free documentation: you have unlimited permission to +copy, distribute and modify it. + + +File: lzlib.info, Node: Introduction, Next: Library Version, Prev: Top, Up: Top + +1 Introduction +************** + +The lzlib compression library provides in-memory LZMA compression and +decompression functions, including integrity checking of the +uncompressed data. The compressed data format used by the library is the +lzip format. + + The functions and variables forming the interface of the compression +library are declared in the file `lzlib.h'. An usage example of the +library is given in the file main.cc. + + Compression/decompression is done by repeteadly 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. + + 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 uncompressed 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 original LZMA algorithm was designed by +Igor Pavlov. For a description of the LZMA algorithm, see the Lzip +manual. + + +File: lzlib.info, Node: Library Version, Next: Compression Functions, Prev: Introduction, Up: Top + +2 Library Version +***************** + + -- Function: const char * LZ_version ( void ) + Returns the library version as a string. + + -- Constant: const char * LZ_version_string + This constant is defined in the header file `lzlib.h'. + + 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 `lzlib.h' header file used by the +application. + + if( LZ_version()[0] != LZ_version_string[0] ) + error( "bad library version" ); + + +File: lzlib.info, Node: Compression Functions, Next: Decompression Functions, Prev: Library Version, Up: Top + +3 Compression Functions +*********************** + +These are the functions used to compress data. In case of error, all of +them return -1, except `LZ_compress_open' whose return value must be +verified by calling `LZ_compress_errno' before using it. + + -- Function: void * LZ_compress_open ( const int DICTIONARY_SIZE, + const int MATCH_LEN_LIMIT, const long long MEMBER_SIZE ) + Initializes the internal stream state for compression and returns a + pointer that can only be used as the ENCODER argument for the + other LZ_compress functions. + + The returned pointer must be verified by calling + `LZ_compress_errno' before using it. If `LZ_compress_errno' does + not return `LZ_ok', the returned pointer must not be used and + should be freed with `LZ_compress_close' to avoid memory leaks. + + DICTIONARY_SIZE sets the dictionary size to be used, in bytes. + Valid values range from 4KiB to 512MiB. Note that dictionary sizes + are quantized. If the specified size does not match one of the + valid sizes, it will be rounded upwards. + + 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. + + MEMBER_SIZE sets the member size limit in bytes. Minimum member + size limit is 100kB. Small member size may degrade compression + ratio, so use it only when needed. To produce a single member data + stream, give MEMBER_SIZE a value larger than the amount of data to + be produced, for example LLONG_MAX. + + -- Function: int LZ_compress_close ( void * const 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 `LZ_compress_close', ENCODER + can no more be used as an argument to any LZ_compress function. + + -- Function: int LZ_compress_finish ( void * const ENCODER ) + Use this function to tell `lzlib' that all the data for this stream + has already been written (with the `LZ_compress_write' function). + + -- Function: int LZ_compress_finish_member ( void * const ENCODER ) + Use this function to tell `lzlib' that all the data for the current + member, in a multimember data stream, has already been written + (with the `LZ_compress_write' function). + + -- Function: int LZ_compress_restart_member ( void * const ENCODER, + const long long MEMBER_SIZE ) + Use this function to start a new member, in a multimember data + stream. Call this function only after + `LZ_compress_member_finished' indicates that the current member + has been fully read (with the `LZ_compress_read' function). + + -- Function: int LZ_compress_read ( void * const ENCODER, uint8_t * + const BUFFER, const int SIZE ) + The `LZ_compress_read' function reads up to SIZE bytes from the + stream pointed to by ENCODER, storing the results in BUFFER. + + The return value is the number of bytes actually read. This might + be less than 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 + `LZ_compress_write' function. Note that reading less than SIZE + bytes is not an error. + + -- Function: int LZ_compress_write ( void * const ENCODER, uint8_t * + const BUFFER, const int SIZE ) + The `LZ_compress_write' function writes up to SIZE bytes from + BUFFER to the stream pointed to by ENCODER. + + The return value is the number of bytes actually written. This + might be less than SIZE. Note that writing less than SIZE bytes is + not an error. + + -- Function: enum LZ_errno LZ_compress_errno ( void * const ENCODER ) + Returns the current error code for ENCODER (*note Error Codes::) + + -- Function: int LZ_compress_finished ( void * const ENCODER ) + Returns 1 if all the data has been read and `LZ_compress_close' can + be safely called. Otherwise it returns 0. + + -- Function: int LZ_compress_member_finished ( void * const ENCODER ) + Returns 1 if the current member, in a multimember data stream, has + been fully read and `LZ_compress_restart_member' can be safely + called. Otherwise it returns 0. + + -- Function: long long LZ_compress_data_position ( void * const + ENCODER ) + Returns the number of input bytes already compressed in the current + member. + + -- Function: long long LZ_compress_member_position ( void * const + ENCODER ) + Returns the number of compressed bytes already produced, but + perhaps not yet read, in the current member. + + -- Function: long long LZ_compress_total_in_size ( void * const + ENCODER ) + Returns the total number of input bytes already compressed. + + -- Function: long long LZ_compress_total_out_size ( void * const + ENCODER ) + Returns the total number of compressed bytes already produced, but + perhaps not yet read. + + +File: lzlib.info, Node: Decompression Functions, Next: Error Codes, Prev: Compression Functions, Up: Top + +4 Decompression Functions +************************* + +These are the functions used to decompress data. In case of error, all +of them return -1, except `LZ_decompress_open' whose return value must +be verified by calling `LZ_decompress_errno' before using it. + + -- Function: void * LZ_decompress_open ( void ) + Initializes the internal stream state for decompression and + returns a pointer that can only be used as the DECODER argument + for the other LZ_decompress functions. + + The returned pointer must be verified by calling + `LZ_decompress_errno' before using it. If `LZ_decompress_errno' + does not return `LZ_ok', the returned pointer must not be used and + should be freed with `LZ_decompress_close' to avoid memory leaks. + + -- Function: int LZ_decompress_close ( void * const 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 `LZ_decompress_close', DECODER + can no more be used as an argument to any LZ_decompress function. + + -- Function: int LZ_decompress_finish ( void * const DECODER ) + Use this function to tell `lzlib' that all the data for this stream + has already been written (with the `LZ_decompress_write' function). + + -- Function: int LZ_decompress_read ( void * const DECODER, uint8_t * + const BUFFER, const int SIZE ) + The `LZ_decompress_read' function reads up to SIZE bytes from the + stream pointed to by DECODER, storing the results in BUFFER. + + The return value is the number of bytes actually read. This might + be less than 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 + `LZ_decompress_write' function. Note that reading less than SIZE + bytes is not an error. + + -- Function: int LZ_decompress_write ( void * const DECODER, uint8_t * + const BUFFER, const int SIZE ) + The `LZ_decompress_write' function writes up to SIZE bytes from + BUFFER to the stream pointed to by DECODER. + + The return value is the number of bytes actually written. This + might be less than SIZE. Note that writing less than SIZE bytes is + not an error. + + -- Function: enum LZ_errno LZ_decompress_errno ( void * const DECODER ) + Returns the current error code for DECODER (*note Error Codes::) + + -- Function: int LZ_decompress_finished ( void * const DECODER ) + Returns 1 if all the data has been read and `LZ_decompress_close' + can be safely called. Otherwise it returns 0. + + -- Function: long long LZ_decompress_data_position ( void * const + DECODER ) + Returns the number of decompressed bytes already produced, but + perhaps not yet read, in the current member. + + -- Function: long long LZ_decompress_member_position ( void * const + DECODER ) + Returns the number of input bytes already decompressed in the + current member. + + -- Function: long long LZ_decompress_total_in_size ( void * const + DECODER ) + Returns the total number of input bytes already decompressed. + + -- Function: long long LZ_decompress_total_out_size ( void * const + DECODER ) + Returns the total number of decompressed bytes already produced, + but perhaps not yet read. + + +File: lzlib.info, Node: Error Codes, Next: Data Format, Prev: Decompression Functions, Up: Top + +5 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 +`LZ_(de)compress_errno'. + + Library functions do not change the value returned by +`LZ_(de)compress_errno' when they succeed; thus, the value returned by +`LZ_(de)compress_errno' after a successful call is not necessarily +zero, and you should not use `LZ_(de)compress_errno' to determine +whether a call failed. If the call failed, then you can examine +`LZ_(de)compress_errno'. + + The error codes are defined in the header file `lzlib.h'. + + -- Constant: enum LZ_errno LZ_ok + The value of this constant is 0 and is used to indicate that there + is no error. + + -- Constant: enum LZ_errno LZ_bad_argument + At least one of the arguments passed to the library function was + invalid. + + -- Constant: enum LZ_errno LZ_mem_error + No memory available. The system cannot allocate more virtual memory + because its capacity is full. + + -- Constant: enum LZ_errno LZ_sequence_error + A library function was called in the wrong order. For example + `LZ_compress_restart_member' was called before + `LZ_compress_member_finished' indicates that the current member is + finished. + + -- 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. + + -- Constant: enum LZ_errno LZ_unexpected_eof + The end of the data stream was reached in the middle of a member. + + -- Constant: enum LZ_errno LZ_data_error + The data stream is corrupt. + + -- Constant: enum LZ_errno LZ_library_error + A bug was detected in the library. Please, report it (*note + Problems::). + + +File: lzlib.info, Node: Data Format, Next: Examples, Prev: Error Codes, Up: Top + +6 Data Format +************* + +In the diagram below, a box like this: ++---+ +| | <-- the vertical bars might be missing ++---+ + + represents one byte; a box like this: ++==============+ +| | ++==============+ + + represents a variable number of bytes. + + + 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: ++--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +| ID string | VN | DS | Lzma stream | CRC32 | Data size | Member size | ++--+--+--+--+----+----+=============+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + + All multibyte values are stored in little endian order. + +`ID string' + A four byte string, identifying the member type, with the value + "LZIP". + +`VN (version number, 1 byte)' + Just in case something needs to be modified in the future. Valid + values are 0 and 1. Version 0 files have only one member and lack + `Member size'. + +`DS (coded dictionary size, 1 byte)' + Bits 4-0 contain the base 2 logarithm of the base dictionary size. + Bits 7-5 contain the number of "wedges" to substract from the base + dictionary size to obtain the dictionary size. The size of a wedge + is (base dictionary size / 16). + Valid values for dictionary size range from 4KiB to 512MiB. + +`Lzma stream' + The lzma stream, finished by an end of stream marker. Uses default + values for encoder properties. + +`CRC32 (4 bytes)' + CRC of the uncompressed original data. + +`Data size (8 bytes)' + Size of the uncompressed original data. + +`Member size (8 bytes)' + Total size of the member, including header and trailer. This + facilitates safe recovery of undamaged members from multimember + files. + + + +File: lzlib.info, Node: Examples, Next: Problems, Prev: Data Format, Up: Top + +7 A small tutorial with examples +******************************** + +This chaper shows the order in which the library functions should be +called depending on what kind of data stream you want to compress or +decompress. + + +Example 1: Normal compression (MEMBER_SIZE > total output). + + 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_read returns 0 + 8) LZ_compress_close + + +Example 2: Decompression. + + 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_read returns 0 + 8) LZ_decompress_close + + +Example 3: Multimember compression (MEMBER_SIZE < total output). + + 1) LZ_compress_open + 2) LZ_compress_write + 3) LZ_compress_read + 4) go back to step 2 until LZ_compress_member_finished returns 1 + 5) LZ_compress_restart_member + 6) go back to step 2 until all input data has been written + 7) LZ_compress_finish + 8) LZ_compress_read + 9) go back to step 8 until LZ_compress_read returns 0 + 10) LZ_compress_close + + +File: lzlib.info, Node: Problems, Next: Concept Index, Prev: Examples, Up: Top + +8 Reporting Bugs +**************** + +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 +<lzip-bug@nongnu.org>. Include the version number, which you can find +by running `minilzip --version' or in `LZ_version_string' from +`lzlib.h'. + + +File: lzlib.info, Node: Concept Index, Prev: Problems, Up: Top + +Concept Index +************* + + +* Menu: + +* bugs: Problems. (line 6) +* compression functions: Compression Functions. (line 6) +* data format: Data Format. (line 6) +* decompression functions: Decompression Functions. + (line 6) +* error codes: Error Codes. (line 6) +* examples: Examples. (line 6) +* getting help: Problems. (line 6) +* introduction: Introduction. (line 6) +* library version: Library Version. (line 6) + + + +Tag Table: +Node: Top219 +Node: Introduction968 +Node: Library Version2428 +Node: Compression Functions3085 +Node: Decompression Functions8178 +Node: Error Codes11616 +Node: Data Format13551 +Node: Examples15518 +Node: Problems16940 +Node: Concept Index17510 + +End Tag Table |