Bzip2 Download Windows
Bertha Simmons
so i found this nice batch for window that would compress every file of the same extension in the same directory into bzip2 by dragging and dropping any of the files into it but i would like to take it further and make it that when i drag and drop a folder into it. it would compress all the files in it, including the sub-folders until it reaches the end. obviously i would guess it has something to do with looping with using %%d but i could not exactly figure it out.
Files that have the BZ2 extension have been created using the open source compression software bzip2, which is typically used on UNIX or Linux systems. Th BZ2 format is used to compress single files only and is not able to archive a group of files. That means you need to assemble the group of files you want to compress into an archive first, then apply bzip2 compression to that archive file. On UNIX/Linux, this file archiving is commonly done with the TAR utility. If you receive a .bz2 file, you can decompress bz2 with WinZip by following the steps below.
bz2/bzip2 is a free and open-source file compression program that uses the BurrowsCWheeler algorithm. It only compresses single files and is not a file archiver. It is developed and maintained by Julian Seward. Seward made the first public release of bzip2, version 0.15, in July 1996. The compressor's stability and popularity grew over the next several years, and Seward released version 1.0 in late 2000.
bzip2 compresses most files more effectively than the older LZW (.Z) and Deflate (.zip and .gz) compression algorithms, but is considerably slower. LZMA is generally more space-efficient than bzip2 at the expense of slower compression speed, while having much faster decompression.
bzip2 compresses data in blocks of size between 100 and 900 kB and uses the BurrowsCWheeler transform to convert frequently-recurring character sequences into strings of identical letters. It then applies move-to-front transform and Huffman coding. bzip2's ancestor bzip used arithmetic coding instead of Huffman. The change was made because of a software patent restriction.
A .bz2 stream consists of a 4-byte header, followed by zero or more compressed blocks, immediately followed by an end-of-stream marker containing a 32-bit CRC for the plaintext whole stream processed. The compressed blocks are bit-aligned and no padding occurs.
To open/extract bz2/bzip2 file on Mac, you can use Mac OS built-in utility Archive Utility, or third-part freeware. For example: GUI Tar, The Unarchiver, Nmap, or B1 Free Archiver. B1 Free Archiver is recommended. B1 Free Archiver is a free software for creating archive folder and extracting archive file. B1 Archiver works on all platforms - Windows, Linux, Mac and Android. The freeware supports most popular formats including bz2/bzip2.
You need to install bzip2. bunzip2 (or bzip2 -d) decompresses bz/bzip2 file. Files which were not created by bzip2 will be detected and ignored, and a warning issued. bzip2 attempts to guess the filename for the decompressed file from that of the compressed file as follows:
The algorithm has gone through multiple maintainers since its initial release, with Micah Snyder being the maintainer since June 2021. There have been some modifications to the algorithm, such as pbzip2, which uses multi-threading to improve compression speed on multi-CPU and multi-core computers.
Seward made the first public release of bzip2, version 0.15, in July 1996. The compressor's stability and popularity grew over the next several years, and Seward released version 1.0 in late 2000.[not verified in body] Following a nine-year hiatus of updates for the project since 2010, on 4 June 2019 Federico Mena accepted maintainership of the bzip2 project.[4] Since June 2021, the maintainer is Micah Snyder.[5]
Any sequence of 4 to 255 consecutive duplicate symbols is replaced by the first 4 symbols and a repeat length between 0 and 251. Thus the sequence AAAAAAABBBBCCCD is replaced with AAAA\3BBBB\0CCCD, where \3 and \0 represent byte values 3 and 0 respectively. Runs of symbols are always transformed after 4 consecutive symbols, even if the run-length is set to zero, to keep the transformation reversible.
The move-to-front transform again does not alter the size of the processed block. Each of the symbols in use in the document is placed in an array. When a symbol is processed, it is replaced by its location (index) in the array and that symbol is shuffled to the front of the array. The effect is that immediately recurring symbols are replaced by zero symbols (long runs of any arbitrary symbol thus become runs of zero symbols), while other symbols are remapped according to their local frequency.
Much "natural" data contains identical symbols that recur within a limited range (text is a good example). As the MTF transform assigns low values to symbols that reappear frequently, this results in a data stream containing many symbols in the low integer range, many of them being identical (different recurring input symbols can actually map to the same output symbol). Such data can be very efficiently encoded by any legacy compression method.
Long strings of zeros in the output of the move-to-front transform (which come from repeated symbols in the output of the BWT) are replaced by a sequence of two special codes, RUNA and RUNB, which represent the run-length as a binary number. Actual zeros are never encoded in the output; a lone zero becomes RUNA. (This step in fact is done at the same time as MTF is; whenever MTF would produce zero, it instead increases a counter to then encode with RUNA and RUNB.)
The sequence 0, 0, 0, 0, 0, 1 would be represented as RUNA, RUNB, 1; RUNA, RUNB represents the value 5 as described below. The run-length code is terminated by reaching another normal symbol. This RLE process is more flexible than the initial RLE step, as it is able to encode arbitrarily long integers (in practice, this is usually limited by the block size, so that this step does not encode a run of more than 900000 bytes). The run-length is encoded in this fashion: assigning place values of 1 to the first bit, 2 to the second, 4 to the third, etc. in the sequence, multiply each place value in a RUNB spot by 2, and add all the resulting place values (for RUNA and RUNB values alike) together. This is similar to base-2 bijective numeration. Thus, the sequence RUNA, RUNB results in the value (1 + 2 2) = 5. As a more complicated example:
Several identically sized Huffman tables can be used with a block if the gain from using them is greater than the cost of including the extra table. At least 2 and up to 6 tables can be present, with the most appropriate table being reselected before every 50 symbols processed. This has the advantage of having very responsive Huffman dynamics without having to continuously supply new tables, as would be required in DEFLATE. Run-length encoding in the previous step is designed to take care of codes that have an inverse probability of use higher than the shortest code Huffman code in use.
If multiple Huffman tables are in use, the selection of each table (numbered 0 to 5) is done from a list by a zero-terminated bit run between 1 and 6 bits in length. The selection is into a MTF list of the tables. Using this feature results in a maximal expansion of around 1.015, but generally less. This expansion is likely to be greatly over-shadowed by the advantage of selecting more appropriate Huffman tables, and the common-case of continuing to use the same Huffman table is represented as a single bit. Rather than unary encoding, effectively this is an extreme form of a Huffman tree, where each code has half the probability of the previous code.
As an overview, a .bz2 stream consists of a 4-byte header, followed by zero or more compressed blocks, immediately followed by an end-of-stream marker containing a 32-bit CRC for the plaintext whole stream processed. The compressed blocks are bit-aligned and no padding occurs.
Because of the first-stage RLE compression (see above), the maximum length of plaintext that a single 900 kB bzip2 block can contain is around 46 MB (45,899,236 bytes). This can occur if the whole plaintext consists entirely of repeated values (the resulting .bz2 file in this case is 46 bytes long). An even smaller file of 40 bytes can be achieved by using an input containing entirely values of 251, an apparent compression ratio of 1147480.9:1.
A compressed block in bzip2 can be decompressed without having to process earlier blocks. This means that bzip2 files can be decompressed in parallel, making it a good format for use in big data applications with cluster computing frameworks like Hadoop and Apache Spark.[8]
bzip2 compresses most files more effectively than the older LZW (.Z) and Deflate (.zip and .gz) compression algorithms, but is considerably slower. LZMA is generally more space-efficient than bzip2 at the expense of even slower compression speed, while having much faster decompression.[9]
bzip2 performance is asymmetric, as decompression is relatively fast. Motivated by the long time required for compression, a modified version was created in 2003 called pbzip2 that used multi-threading to encode the file in multiple chunks, giving almost linear speedup on multi-CPU and multi-core computers.[12] As of May 2010[update], this functionality has not been incorporated into the main project.
Like gzip, bzip2 is only a data compressor. It is not an archiver like tar or ZIP; the bzip2 file format does not support storing the contents of multiple files in a single compressed file, and the program itself has no facilities for multiple files, encryption or archive-splitting. In the UNIX tradition, archiving could be done by a separate program producing an archive which is then compressed with bzip2, and un-archiving could be done by bzip2 uncompressing the compressed archive file and a separate program decompressing it. Some archivers have built-in support for compression and decompression, so that it is not necessary to use the bzip2 program to compress or decompress the archive. GnuPG also has built-in support for bzip2 compression and decompression.
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