Zlib 1.2.8 Download ((HOT))
Yvone Rollman
The examples given below are drastically simplified to show the basic concept.Using zlib encoding can be expensive, and the results ought to be cached.See Memory usage tuning for more information on the speed/memory/compressiontradeoffs involved in zlib usage.
By default, the zlib methods will throw an error when decompressingtruncated data. However, if it is known that the data is incomplete, orthe desire is to inspect only the beginning of a compressed file, it ispossible to suppress the default error handling by changing the flushingmethod that is used to decompress the last chunk of input data:
The speed of zlib compression is affected most dramatically by thelevel setting. A higher level will result in better compression, butwill take longer to complete. A lower level will result in lesscompression, but will be much faster.
In general, greater memory usage options will mean that Node.js has to makefewer calls to zlib because it will be able to process more data oneach write operation. So, this is another factor that affects thespeed, at the cost of memory usage.
Calling .flush() on a compression stream will make zlib return as muchoutput as currently possible. This may come at the cost of degraded compressionquality, but can be useful when data needs to be available as soon as possible.
All of the constants defined in zlib.h are also defined onrequire('node:zlib').constants. In the normal course of operations, it willnot be necessary to use these constants. They are documented so that theirpresence is not surprising. This section is taken almost directly from thezlib documentation.
Previously, the constants were available directly from require('node:zlib'),for instance zlib.Z_NO_FLUSH. Accessing the constants directly from the moduleis currently still possible but is deprecated.
Deprecated alias for zlib.bytesWritten. This original name was chosenbecause it also made sense to interpret the value as the number of bytesread by the engine, but is inconsistent with other streams in Node.js thatexpose values under these names.
Calling this only flushes data from the internal zlib state, and does notperform flushing of any kind on the streams level. Rather, it behaves like anormal call to .write(), i.e. it will be queued up behind other pendingwrites and will only produce output when data is being read from the stream.
An upgrade of zlib from 1.2.8 to 1.2.11 changed behavior when windowBitsis set to 8 for raw deflate streams. zlib would automatically set windowBitsto 9 if was initially set to 8. Newer versions of zlib will throw an exception,so Node.js restored the original behavior of upgrading a value of 8 to 9,since passing windowBits = 9 to zlib actually results in a compressed streamthat effectively uses an 8-bit window only.
All of these take a Buffer, TypedArray, DataView,ArrayBuffer or string as the first argument, an optional second argumentto supply options to the zlib classes and will call the supplied callbackwith callback(error, result).
For applications that require data compression, the functions in this moduleallow compression and decompression, using the zlib library. The zlib libraryhas its own home page at There are knownincompatibilities between the Python module and versions of the zlib libraryearlier than 1.1.3; 1.1.3 has a security vulnerability, so we recommend using1.1.4 or later.
+9 to +15: The base-two logarithm of the window size, whichtherefore ranges between 512 and 32768. Larger values producebetter compression at the expense of greater memory usage. Theresulting output will include a zlib-specific header and trailer.
When decompressing a stream, the window size must not be smallerthan the size originally used to compress the stream; using a too-smallvalue may result in an error exception. The default wbits valuecorresponds to the largest window size and requires a zlib header andtrailer to be included.
All pending input is processed, and a bytes object containing the remaining compressedoutput is returned. mode can be selected from the constantsZ_NO_FLUSH, Z_PARTIAL_FLUSH, Z_SYNC_FLUSH,Z_FULL_FLUSH, Z_BLOCK (zlib 1.2.3.4), or Z_FINISH,defaulting to Z_FINISH. Except Z_FINISH, all constantsallow compressing further bytestrings of data, while Z_FINISH finishes thecompressed stream and prevents compressing any more data. After calling flush()with mode set to Z_FINISH, the compress() method cannot be called again;the only realistic action is to delete the object.
A bytes object that contains any data that was not consumed by the lastdecompress() call because it exceeded the limit for the uncompressed databuffer. This data has not yet been seen by the zlib machinery, so you must feedit (possibly with further data concatenated to it) back to a subsequentdecompress() method call in order to get correct output.
It seems to be you have to install zlib.If you are using Centos, install zlib by using yum install zlib-develIf you are using Debian, install zlib by using apt-get install zlib1g-dev.If you wanna get source grep it from and install it, if you do this sure you will have git in your system.Note: If you install git from the aptitude package manager or from repositories it will automatically install the dependencies.
But this is a restriction on distribution. You could comply with this term by never distributing your modified code or by adding such notices prior to distribution. But this would violate the zlib license.
So how is the zlib license GPL compatible when it contains a restriction on modification that is not like any restriction found in the GPL and the presence of additional restrictions is what makes a license not GPL compatible?
Note these Section 7 restrictions do not necessarily activate on distribution. A license term that applies only to private modification still fits within the definitions set forth in Section 7. I expect the allowances for additional restrictions are written in this broad way precisely to allow terms like the second term of the zlib license.
I recently noticed that some of the artifact registry images have been tagged with zlib vulnerability. I am not sure how to upgrade to newer version. I do not have much experience with this, any pointer?
zlib through 1.2.12 has a heap-based buffer over-read or buffer overflow in inflate in inflate.c via a large gzip header extra field. Note that only applications that call inflateGetHeader are affected. Some common applications bundle the affected zlib source code but may be unable to call inflateGetHeader (e.g., see the nodejs/node reference). You can find detailed information about this security vulnerability here: Out-of-bounds Write, CVE-2022-37434 Detail.
The Alpine Linux project has announced that releases 3.13.12, 3.14.8, 3.15.6, and 3.16.2 fix the zlib CVE-2022-37434 vulnerability. You can find more information here: -3.13.12-3.14.8-3.15.6-3.16.2-released.html
I want to install zlib on Debian 6. For this, I think I would use apt-get install, but I don't know which package to use. The package zlib doesn't exist, and if I install zlibc (which sounds most appropriate), running zlib -version brings up the error command not found. (I used apt-file search zlib to find zlibc.)
The decoder uses a table to look up bit-sequences and map them to their decoded values. The longest Huffman code allowed by the DEFLATE specification is 15-bits, which would require a 128kb table, so to fit tables comfortably in cache, zlib splits this into a root table and a number of (possibly nested) subtables.
The base two logarithm of the window size (the size of the history buffer). It is to be in the range 8 through 15. Larger values result in better compression at the expense of memory usage. Defaults to 15 if deflateInit/2 is used. A negative WindowBits value suppresses the zlib header (and checksum) from the stream. Notice that the zlib source mentions this only as a undocumented feature.
Due to a known bug in the underlying zlib library, WindowBits values 8 and -8do not work as expected. In zlib versions before 1.2.9 values8 and -8 are automatically changed to 9 and -9. From zlib version 1.2.9value -8 is rejected causing zlib:deflateInit/6 to fail(8 is still changed to 9). It also seem possible that future versionsof zlib may fix this bug and start accepting 8 and -8 as is.
The zlib format was designed to be compact and fast for use in memory and on communications channels. The gzip format was designed for single-file compression on file systems, has a larger header than zlib to maintain directory information, and uses a different, slower check method than zlib.
This directory: /usr/local/Zlib is not the one of default system to install software. The usual would be to Zlib to install on /usr/local/lib, /usr/local/include, /usr/local/share, etc. During its installation it seems it was executed ./configure --prefix=/usr/local/zlib that was used to create this dir and then install zlib components on it.
P.S: I used this to detect libraries, but your problem seems related to header files detection, so take it with a grain of salt. If it does not work, you could create symbolic links from zlib/include to /usr/local/include
Note: Versions mentioned in the description apply only to the upstream zlib package and not the zlib package as distributed by Debian.See How to fix? for Debian:11 relevant fixed versions and status.
zlib through 1.2.12 has a heap-based buffer over-read or buffer overflow in inflate in inflate.c via a large gzip header extra field. NOTE: only applications that call inflateGetHeader are affected. Some common applications bundle the affected zlib source code but may be unable to call inflateGetHeader (e.g., see the nodejs/node reference).
This is an implementation of the fast deflate algorithm for zlib (to be exact, here is a new implementation of the longest_match function). In my tests it works about 2.5-10x times faster than original method with neraly the same compression ratio (at keast it never compress worse than original zlib).
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