Merging upstream version 1.7~pre1.
Signed-off-by: Daniel Baumann <daniel@debian.org>
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101
doc/lzlib.info
101
doc/lzlib.info
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@ -11,7 +11,7 @@ File: lzlib.info, Node: Top, Next: Introduction, Up: (dir)
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Lzlib Manual
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************
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This manual is for Lzlib (version 1.6, 27 August 2014).
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This manual is for Lzlib (version 1.7-pre1, 24 February 2015).
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* Menu:
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@ -29,7 +29,7 @@ This manual is for Lzlib (version 1.6, 27 August 2014).
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* Concept index:: Index of concepts
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Copyright (C) 2009-2014 Antonio Diaz Diaz.
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Copyright (C) 2009-2015 Antonio Diaz Diaz.
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This manual is free documentation: you have unlimited permission to
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copy, distribute and modify it.
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@ -45,8 +45,9 @@ and decompression functions, including integrity checking of the
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decompressed data. The compressed data format used by the library is the
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lzip format. Lzlib is written in C.
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The lzip file format is designed for long-term data archiving, taking
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into account both data integrity and decoder availability:
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The lzip file format is designed for data sharing and long-term
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archiving, taking into account both data integrity and decoder
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availability:
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* The lzip format provides very safe integrity checking and some data
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recovery means. The lziprecover program can repair bit-flip errors
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@ -61,8 +62,8 @@ into account both data integrity and decoder availability:
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archaeologist to extract the data from a lzip file long after
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quantum computers eventually render LZMA obsolete.
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* Additionally lzip is copylefted, which guarantees that it will
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remain free forever.
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* Additionally the lzip reference implementation is copylefted, which
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guarantees that it will remain free forever.
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A nice feature of the lzip format is that a corrupt byte is easier to
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repair the nearer it is from the beginning of the file. Therefore, with
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@ -75,15 +76,21 @@ library are given in the files 'main.c' and 'bbexample.c' from the
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source distribution.
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Compression/decompression is done by repeatedly calling a couple of
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read/write functions until all the data has been processed by the
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read/write functions until all the data have been processed by the
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library. This interface is safer and less error prone than the
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traditional zlib interface.
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Compression/decompression is done when the read function is called.
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This means the value returned by the position functions will not be
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updated until some data is read, even if you write a lot of data. If
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you want the data to be compressed in advance, just call the read
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function with a SIZE equal to 0.
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updated until a read call, even if a lot of data is written. If you
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want the data to be compressed in advance, just call the read function
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with a SIZE equal to 0.
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If all the data to be compressed are written in advance, lzlib will
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automatically adjust the header of the compressed data to use the
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smallest possible dictionary size. This feature reduces the amount of
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memory needed for decompression and allows minilzip to produce identical
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compressed output as lzip.
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Lzlib will correctly decompress a data stream which is the
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concatenation of two or more compressed data streams. The result is the
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@ -103,9 +110,9 @@ elaborated way of finding coding sequences of minimum price than the one
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currently used by lzip could be developed, and the resulting sequence
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could also be coded using the LZMA coding scheme.
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Lzip currently implements two variants of the LZMA algorithm; fast
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(used by option -0) and normal (used by all other compression levels).
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Lzlib just implements the "normal" variant.
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Lzlib currently implements two variants of the LZMA algorithm; fast
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(used by option -0 of minilzip) and normal (used by all other
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compression levels).
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The high compression of LZMA comes from combining two basic,
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well-proven compression ideas: sliding dictionaries (LZ77/78) and
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@ -147,15 +154,18 @@ File: lzlib.info, Node: Buffering, Next: Parameter limits, Prev: Library vers
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Lzlib internal functions need access to a memory chunk at least as large
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as the dictionary size (sliding window). For efficiency reasons, the
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input buffer for compression is twice as large as the dictionary size.
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Finally, for safety reasons, lzlib uses two more internal buffers.
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input buffer for compression is twice or sixteen times as large as the
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dictionary size.
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Finally, for safety reasons, lzlib uses two more internal buffers.
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These are the four buffers used by lzlib, and their guaranteed
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minimum sizes:
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* Input compression buffer. Written to by the 'LZ_compress_write'
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function. Its size is two times the dictionary size set with the
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'LZ_compress_open' function or 64 KiB, whichever is larger.
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function. For the normal variant of LZMA, its size is two times
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the dictionary size set with the 'LZ_compress_open' function or 64
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KiB, whichever is larger. For the fast variant, its size is 1 MiB.
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* Output compression buffer. Read from by the 'LZ_compress_read'
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function. Its size is 64 KiB.
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@ -230,6 +240,11 @@ calling 'LZ_compress_errno' before using it.
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range from 5 to 273. Larger values usually give better compression
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ratios but longer compression times.
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If DICTIONARY_SIZE is 65535 and MATCH_LEN_LIMIT is 16, the fast
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variant of LZMA is chosen, which produces identical compressed
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output as 'lzip -0'. (The DICTIONARY_SIZE used will be rounded
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upwards to 64 KiB).
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MEMBER_SIZE sets the member size limit in bytes. Minimum member
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size limit is 100 kB. Small member size may degrade compression
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ratio, so use it only when needed. To produce a single-member data
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@ -246,8 +261,8 @@ calling 'LZ_compress_errno' before using it.
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-- Function: int LZ_compress_finish ( struct LZ_Encoder * const
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ENCODER )
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Use this function to tell 'lzlib' that all the data for this member
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has already been written (with the 'LZ_compress_write' function).
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After all the produced compressed data has been read with
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have already been written (with the 'LZ_compress_write' function).
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After all the produced compressed data have been read with
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'LZ_compress_read' and 'LZ_compress_member_finished' returns 1, a
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new member can be started with 'LZ_compress_restart_member'.
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@ -262,9 +277,8 @@ calling 'LZ_compress_errno' before using it.
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ENCODER )
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Use this function to make available to 'LZ_compress_read' all the
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data already written with the 'LZ_compress_write' function. First
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call 'LZ_compress_read' until it returns 0. Then call
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'LZ_compress_sync_flush'. Finally, call 'LZ_compress_read' again
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to read the remaining data.
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call 'LZ_compress_sync_flush'. Then call 'LZ_compress_read' until
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it returns 0.
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Repeated use of 'LZ_compress_sync_flush' may degrade compression
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ratio, so use it only when needed.
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@ -304,8 +318,8 @@ calling 'LZ_compress_errno' before using it.
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-- Function: int LZ_compress_finished ( struct LZ_Encoder * const
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ENCODER )
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Returns 1 if all the data has been read and 'LZ_compress_close' can
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be safely called. Otherwise it returns 0.
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Returns 1 if all the data have been read and 'LZ_compress_close'
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can be safely called. Otherwise it returns 0.
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-- Function: int LZ_compress_member_finished ( struct LZ_Encoder *
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const ENCODER )
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@ -364,7 +378,8 @@ verified by calling 'LZ_decompress_errno' before using it.
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-- Function: int LZ_decompress_finish ( struct LZ_Decoder * const
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DECODER )
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Use this function to tell 'lzlib' that all the data for this stream
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has already been written (with the 'LZ_decompress_write' function).
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have already been written (with the 'LZ_decompress_write'
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function).
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-- Function: int LZ_decompress_reset ( struct LZ_Decoder * const
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DECODER )
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@ -420,7 +435,7 @@ verified by calling 'LZ_decompress_errno' before using it.
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-- Function: int LZ_decompress_finished ( struct LZ_Decoder * const
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DECODER )
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Returns 1 if all the data has been read and 'LZ_decompress_close'
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Returns 1 if all the data have been read and 'LZ_decompress_close'
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can be safely called. Otherwise it returns 0.
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-- Function: int LZ_decompress_member_finished ( struct LZ_Decoder *
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@ -589,8 +604,8 @@ with no additional information before, between, or after them.
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'Lzma stream'
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The lzma stream, finished by an end of stream marker. Uses default
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values for encoder properties. See the lzip manual for a full
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description.
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values for encoder properties. *Note Stream format: (lzip)Stream
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format, for a complete description.
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Lzip only uses the LZMA marker '2' ("End Of Stream" marker). Lzlib
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also uses the LZMA marker '3' ("Sync Flush" marker).
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@ -630,7 +645,7 @@ Example 1: Normal compression (MEMBER_SIZE > total output).
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1) LZ_compress_open
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2) LZ_compress_write
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3) LZ_compress_read
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4) go back to step 2 until all input data has been written
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4) go back to step 2 until all input data have been written
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5) LZ_compress_finish
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6) LZ_compress_read
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7) go back to step 6 until LZ_compress_finished returns 1
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@ -653,7 +668,7 @@ Example 3: Decompression.
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1) LZ_decompress_open
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2) LZ_decompress_write
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3) LZ_decompress_read
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4) go back to step 2 until all input data has been written
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4) go back to step 2 until all input data have been written
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5) LZ_decompress_finish
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6) LZ_decompress_read
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7) go back to step 6 until LZ_decompress_finished returns 1
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@ -697,7 +712,7 @@ Example 6: Multi-member compression (user-restarted members).
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6) LZ_compress_read
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7) go back to step 6 until LZ_compress_member_finished returns 1
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8) verify that LZ_compress_finished returns 1
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9) go to step 12 if all input data has been written
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9) go to step 12 if all input data have been written
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10) LZ_compress_restart_member
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11) go back to step 2
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12) LZ_compress_close
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@ -770,18 +785,18 @@ Concept index
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Tag Table:
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Node: Top220
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Node: Introduction1304
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Node: Library version5487
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Node: Buffering6132
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Node: Parameter limits7253
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Node: Compression functions8212
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Node: Decompression functions14594
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Node: Error codes20755
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Node: Error messages22694
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Node: Data format23273
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Node: Examples25922
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Node: Problems30005
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Node: Concept index30577
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Node: Introduction1311
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Node: Library version5808
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Node: Buffering6453
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Node: Parameter limits7673
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Node: Compression functions8632
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Node: Decompression functions15176
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Node: Error codes21344
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Node: Error messages23283
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Node: Data format23862
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Node: Examples26538
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Node: Problems30624
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Node: Concept index31196
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End Tag Table
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