Zlib - Revision history

Sembiance: Added sample files

2023-12-28T15:06:13Z

Added sample files

Jsummers at 18:29, 21 August 2022

2022-08-21T18:29:16Z

Jsummers: /* Identification */

2022-08-18T16:27:07Z

‎Identification

Jsummers: /* Identification */

2022-08-18T16:12:39Z

‎Identification

Jsummers: /* Specifications */

2022-08-18T16:10:01Z

‎Specifications

Jsummers: /* Software */

2020-01-25T15:18:34Z

‎Software

Jsummers: /* Software */

2020-01-25T14:54:51Z

‎Software

Polluks: /* Software */ Deark

2019-12-12T00:52:46Z

‎Software: Deark

Jsummers: /* Software */

2019-11-03T14:39:09Z

‎Software

Jsummers: Rewrote the intro

2019-08-29T14:24:32Z

Rewrote the intro

@@ Line 40: / Line 40: @@
 See also [[DEFLATE#Software]].
 == Links ==
 * [[Wikipedia:Zlib|Wikipedia article]]

@@ Line 6: / Line 6: @@
 }}
 {{DISPLAYTITLE:zlib}}
-'''zlib''' format is a variant of the [[DEFLATE]] compressed data format. It adds a lightweight container, a small amount of configurability, and error checking.
+'''zlib''' format is a container and extension of the [[DEFLATE]] compressed data format. It adds a lightweight container, a small amount of configurability, and error checking.
 zlib is also the name of a software library that supports the zlib format, and other formats related to DEFLATE.
-There are ''many'' formats and protocols that use, or may use, zlib format. A notable example is [[PNG]].
+There are many formats and protocols that use, or may use, zlib format. A notable example is [[PNG]].
 == See also ==
@@ Line 20: / Line 20: @@
 * If the first two bytes are interpreted as a [[Endianness|big-endian]] integer, it is always a multiple of 31. (Always true)
-* The first byte has eight possible values: 0x08, 0x18, 0x28, ..., 0x78. (Always true, unless the zlib format has been extended to support compression methods other than Deflate.)
+* The first byte has eight possible values: <code>0x08</code>, <code>0x18</code>, <code>0x28</code>, ..., <code>0x78</code>. (Always true, unless the zlib format has been extended to support compression methods other than Deflate.)
-* The 0x20 bit of the second byte is 0. (A value of 1 is legal in zlib v3.3+, but indicates use of a preset dictionary, so the zlib stream is not as portable.)
+* Almost always, the <code>0x20</code> bit of the second byte is 0. (A value of 1 is legal in zlib v3.3+, but indicates use of a preset dictionary, so the zlib stream is not as portable.)
-* The first byte is exactly 0x78. (Any other value from the above list means the Deflate decompressor can use a window size less than the standard 32K. The extent to which this feature has been used is unclear.)
+* Most often, the Deflate window size is 32K, and there is no preset dictionary. With these assumptions, the first byte is <code>0x78</code>, and the second is <code>0x01</code> (if using fastest compression), <code>0x5e</code> (fast), <code>0x9c</code> (default), or <code>0xda</code> (max), with <code>0x9c</code> and <code>0xda</code> being the most common.
 == Specifications ==

@@ Line 17: / Line 17: @@
 == Identification ==
-The first two bytes can help to identify a zlib datastream. The following tests are ordered from most reliable to least reliable.
+The first two bytes can help to identify a zlib datastream. The following tests are ordered starting with those that are most certain to be true.
 * If the first two bytes are interpreted as a [[Endianness|big-endian]] integer, it is always a multiple of 31. (Always true)
 * The first byte has eight possible values: 0x08, 0x18, 0x28, ..., 0x78. (Always true, unless the zlib format has been extended to support compression methods other than Deflate.)
-* The 0x20 bit of the second byte is 0. (A value of 1 is legal in zlib v3.3+, but indicates use of a preset dictionary, so the zlib stream is not portable.)
+* The 0x20 bit of the second byte is 0. (A value of 1 is legal in zlib v3.3+, but indicates use of a preset dictionary, so the zlib stream is not as portable.)
-* The first byte is exactly 0x78. (Any other value from the list above means the Deflate decompressor can use a window size less than the standard 32K. The extent to which this feature has been used is unclear.)
+* The first byte is exactly 0x78. (Any other value from the above list means the Deflate decompressor can use a window size less than the standard 32K. The extent to which this feature has been used is unclear.)
 == Specifications ==

@@ Line 17: / Line 17: @@
 == Identification ==
-The first byte of a zlib datastream has eight possible values: 0x08, 0x18, 0x28, ..., 0x78.
+The first two bytes can help to identify a zlib datastream. The following tests are ordered from most reliable to least reliable.
-If the first two bytes are interpreted as a [[Endianness|big-endian]] integer, it is always a multiple of 31.
+* If the first two bytes are interpreted as a [[Endianness|big-endian]] integer, it is always a multiple of 31. (Always true)
 == Specifications ==

← Older revision		Revision as of 16:10, 18 August 2022
Line 22:		Line 22:

	== Specifications ==		== Specifications ==
		+	* ZLIB Specification v3.1 - ''No copy found. There are dead links to it in e.g. the [https://zlib.net/fossils/zlib-0.95.tar.gz zlib 0.95] README file.''
		+	* [https://web.archive.org/web/20030426211434/http://mirror.cs.wisc.edu/pub/mirrors/ghost/gzip_doc/zlib-3.2.doc ZLIB Specification v3.2] (from archive.org)
	* RFC 1950: ZLIB Compressed Data Format Specification version 3.3		* RFC 1950: ZLIB Compressed Data Format Specification version 3.3

@@ Line 26: / Line 26: @@
 == Software ==
 * [https://zlib.net zlib data compression library]
-** [https://github.com/cloudflare/zlib CloudFlare fork of zlib]
+* [https://github.com/cloudflare/zlib CloudFlare fork of zlib]
-** [https://github.com/zlib-ng/zlib-ng zlib-ng]
+* [https://github.com/zlib-ng/zlib-ng zlib-ng]
 * [https://github.com/richgel999/miniz miniz]
 * [https://github.com/google/zopfli zopfli] - zlib compressor highly optimized for file size

@@ Line 1: / Line 1: @@
 {{FormatInfo
 |formattype=electronic
 |subcat=Compression
 }}
 {{DISPLAYTITLE:zlib}}
-'''zlib''' is a data compression library, and a general-purpose data compression format.
+'''zlib''' format is a variant of the [[DEFLATE]] compressed data format. It adds a lightweight container, a small amount of configurability, and error checking.
-The data format uses [[DEFLATE]] compression. It is used in many other file formats, and sometimes on its own as a file format. It is defined in [http://tools.ietf.org/html/rfc1950 RFC 1950].
+zlib is also the name of a software library that supports the zlib format, and other formats related to DEFLATE.
-The zlib format is not the same as [[gzip]] format, but they are fairly similar, and both are supported by the zlib library.
+There are ''many'' formats and protocols that use, or may use, zlib format. A notable example is [[PNG]].
 == See also ==
 * [[Adler-32]]
 == Identification ==
@@ Line 17: / Line 20: @@
 If the first two bytes are interpreted as a [[Endianness|big-endian]] integer, it is always a multiple of 31.
 == Software ==
-* [http://zlib.net/ zlib data compression library]
+* [https://zlib.net/ zlib data compression library]
 ** [https://github.com/cloudflare/zlib CloudFlare fork of zlib]
 * [https://github.com/richgel999/miniz miniz]
@@ Line 25: / Line 31: @@
 * [http://aluigi.altervista.org/mytoolz.htm#offzip Offzip]
-== Specifications ==
+== Links ==
-* [http://tools.ietf.org/html/rfc1950 RFC 1950]
-−
-== External links ==
 * [[Wikipedia:Zlib|Wikipedia article]]