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+# TODO list
+
+## Release v0.6
+
+1. Review encoder and check for lzma improvements under xz.
+2. Fix binary tree matcher.
+3. Compare compression ratio with xz tool using comparable parameters
+   and optimize parameters
+4. Do some optimizations
+    - rename operation action and make it a simple type of size 8
+    - make maxMatches, wordSize parameters
+    - stop searching after a certain length is found (parameter sweetLen)
+
+## Release v0.7
+
+1. Optimize code
+2. Do statistical analysis to get linear presets.
+3. Test sync.Pool compatability for xz and lzma Writer and Reader
+3. Fuzz optimized code.
+
+## Release v0.8
+
+1. Support parallel go routines for writing and reading xz files.
+2. Support a ReaderAt interface for xz files with small block sizes.
+3. Improve compatibility between gxz and xz
+4. Provide manual page for gxz
+
+## Release v0.9
+
+1. Improve documentation
+2. Fuzz again
+
+## Release v1.0
+
+1. Full functioning gxz
+2. Add godoc URL to README.md (godoc.org)
+3. Resolve all issues.
+4. Define release candidates.
+5. Public announcement.
+
+## Package lzma
+
+### Release v0.6
+
+- Rewrite Encoder into a simple greedy one-op-at-a-time encoder
+  including
+    + simple scan at the dictionary head for the same byte
+    + use the killer byte (requiring matches to get longer, the first
+      test should be the byte that would make the match longer)
+
+
+## Optimizations
+
+- There may be a lot of false sharing in lzma.State; check whether this
+  can be improved by reorganizing the internal structure of it.
+- Check whether batching encoding and decoding improves speed.
+
+### DAG optimizations
+
+- Use full buffer to create minimal bit-length above range encoder.
+- Might be too slow (see v0.4)
+
+### Different match finders
+
+- hashes with 2, 3 characters additional to 4 characters
+- binary trees with 2-7 characters (uint64 as key, use uint32 as
+  pointers into a an array)
+- rb-trees with 2-7 characters (uint64 as key, use uint32 as pointers
+  into an array with bit-steeling for the colors)
+
+## Release Procedure
+
+- execute goch -l for all packages; probably with lower param like 0.5.
+- check orthography with gospell
+- Write release notes in doc/relnotes.
+- Update README.md
+- xb copyright . in xz directory to ensure all new files have Copyright
+  header
+- VERSION=<version> go generate github.com/ulikunitz/xz/... to update
+  version files
+- Execute test for Linux/amd64, Linux/x86 and Windows/amd64.
+- Update TODO.md - write short log entry
+- git checkout master && git merge dev
+- git tag -a <version>
+- git push
+
+## Log
+
+### 2018-10-28
+
+Release v0.5.5 fixes issues #19 observing ErrLimit outputs.
+
+### 2017-06-05
+
+Release v0.5.4 fixes issues #15 of another problem with the padding size
+check for the xz block header. I removed the check completely.
+
+### 2017-02-15
+
+Release v0.5.3 fixes issue #12 regarding the decompression of an empty
+XZ stream. Many thanks to Tomasz Kłak, who reported the issue.
+
+### 2016-12-02
+
+Release v0.5.2 became necessary to allow the decoding of xz files with
+4-byte padding in the block header. Many thanks to Greg, who reported
+the issue.
+
+### 2016-07-23
+
+Release v0.5.1 became necessary to fix problems with 32-bit platforms.
+Many thanks to Bruno Brigas, who reported the issue.
+
+### 2016-07-04
+
+Release v0.5 provides improvements to the compressor and provides support for
+the decompression of xz files with multiple xz streams.
+
+### 2016-01-31
+
+Another compression rate increase by checking the byte at length of the
+best match first, before checking the whole prefix. This makes the
+compressor even faster. We have now a large time budget to beat the
+compression ratio of the xz tool. For enwik8 we have now over 40 seconds
+to reduce the compressed file size for another 7 MiB.
+
+### 2016-01-30
+
+I simplified the encoder. Speed and compression rate increased
+dramatically. A high compression rate affects also the decompression
+speed. The approach with the buffer and optimizing for operation
+compression rate has not been successful. Going for the maximum length
+appears to be the best approach.
+
+### 2016-01-28
+
+The release v0.4 is ready. It provides a working xz implementation,
+which is rather slow, but works and is interoperable with the xz tool.
+It is an important milestone.
+
+### 2016-01-10
+
+I have the first working implementation of an xz reader and writer. I'm
+happy about reaching this milestone.
+
+### 2015-12-02
+
+I'm now ready to implement xz because, I have a working LZMA2
+implementation. I decided today that v0.4 will use the slow encoder
+using the operations buffer to be able to go back, if I intend to do so.
+
+### 2015-10-21
+
+I have restarted the work on the library. While trying to implement
+LZMA2, I discovered that I need to resimplify the encoder and decoder
+functions. The option approach is too complicated. Using a limited byte
+writer and not caring for written bytes at all and not to try to handle
+uncompressed data simplifies the LZMA encoder and decoder much.
+Processing uncompressed data and handling limits is a feature of the
+LZMA2 format not of LZMA.
+
+I learned an interesting method from the LZO format. If the last copy is
+too far away they are moving the head one 2 bytes and not 1 byte to
+reduce processing times.
+
+### 2015-08-26
+
+I have now reimplemented the lzma package. The code is reasonably fast,
+but can still be optimized. The next step is to implement LZMA2 and then
+xz.
+
+### 2015-07-05
+
+Created release v0.3. The version is the foundation for a full xz
+implementation that is the target of v0.4.
+
+### 2015-06-11
+
+The gflag package has been developed because I couldn't use flag and
+pflag for a fully compatible support of gzip's and lzma's options. It
+seems to work now quite nicely.
+
+### 2015-06-05
+
+The overflow issue was interesting to research, however Henry S. Warren
+Jr. Hacker's Delight book was very helpful as usual and had the issue
+explained perfectly. Fefe's information on his website was based on the
+C FAQ and quite bad, because it didn't address the issue of -MININT ==
+MININT.
+
+### 2015-06-04
+
+It has been a productive day. I improved the interface of lzma.Reader
+and lzma.Writer and fixed the error handling.
+
+### 2015-06-01
+
+By computing the bit length of the LZMA operations I was able to
+improve the greedy algorithm implementation. By using an 8 MByte buffer
+the compression rate was not as good as for xz but already better then
+gzip default.
+
+Compression is currently slow, but this is something we will be able to
+improve over time.
+
+### 2015-05-26
+
+Checked the license of ogier/pflag. The binary lzmago binary should
+include the license terms for the pflag library.
+
+I added the endorsement clause as used by Google for the Go sources the
+LICENSE file.
+
+### 2015-05-22
+
+The package lzb contains now the basic implementation for creating or
+reading LZMA byte streams. It allows the support for the implementation
+of the DAG-shortest-path algorithm for the compression function.
+
+### 2015-04-23
+
+Completed yesterday the lzbase classes. I'm a little bit concerned that
+using the components may require too much code, but on the other hand
+there is a lot of flexibility.
+
+### 2015-04-22
+
+Implemented Reader and Writer during the Bayern game against Porto. The
+second half gave me enough time.
+
+### 2015-04-21
+
+While showering today morning I discovered that the design for OpEncoder
+and OpDecoder doesn't work, because encoding/decoding might depend on
+the current status of the dictionary. This is not exactly the right way
+to start the day.
+
+Therefore we need to keep the Reader and Writer design. This time around
+we simplify it by ignoring size limits. These can be added by wrappers
+around the Reader and Writer interfaces. The Parameters type isn't
+needed anymore.
+
+However I will implement a ReaderState and WriterState type to use
+static typing to ensure the right State object is combined with the
+right lzbase.Reader and lzbase.Writer.
+
+As a start I have implemented ReaderState and WriterState to ensure
+that the state for reading is only used by readers and WriterState only
+used by Writers.
+
+### 2015-04-20
+
+Today I implemented the OpDecoder and tested OpEncoder and OpDecoder.
+
+### 2015-04-08
+
+Came up with a new simplified design for lzbase. I implemented already
+the type State that replaces OpCodec.
+
+### 2015-04-06
+
+The new lzma package is now fully usable and lzmago is using it now. The
+old lzma package has been completely removed.
+
+### 2015-04-05
+
+Implemented lzma.Reader and tested it.
+
+### 2015-04-04
+
+Implemented baseReader by adapting code form lzma.Reader.
+
+### 2015-04-03
+
+The opCodec has been copied yesterday to lzma2. opCodec has a high
+number of dependencies on other files in lzma2. Therefore I had to copy
+almost all files from lzma.
+
+### 2015-03-31
+
+Removed only a TODO item.
+
+However in Francesco Campoy's presentation "Go for Javaneros
+(Javaïstes?)" is the the idea that using an embedded field E, all the
+methods of E will be defined on T. If E is an interface T satisfies E.
+
+https://talks.golang.org/2014/go4java.slide#51
+
+I have never used this, but it seems to be a cool idea.
+
+### 2015-03-30
+
+Finished the type writerDict and wrote a simple test.
+
+### 2015-03-25
+
+I started to implement the writerDict.
+
+### 2015-03-24
+
+After thinking long about the LZMA2 code and several false starts, I
+have now a plan to create a self-sufficient lzma2 package that supports
+the classic LZMA format as well as LZMA2. The core idea is to support a
+baseReader and baseWriter type that support the basic LZMA stream
+without any headers. Both types must support the reuse of dictionaries
+and the opCodec.
+
+### 2015-01-10
+
+1. Implemented simple lzmago tool
+2. Tested tool against large 4.4G file
+    - compression worked correctly; tested decompression with lzma
+    - decompression hits a full buffer condition
+3. Fixed a bug in the compressor and wrote a test for it
+4. Executed full cycle for 4.4 GB file; performance can be improved ;-)
+
+### 2015-01-11
+
+- Release v0.2 because of the working LZMA encoder and decoder