blocks|key|1686502|text|使用Boost+C%2B%2B+libraries。其中包含了一个CRC，并且license很好。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1686503|entityMap|0|LINK|mutability|MUTABLE|url|http://www.boost.org/|1|http://www.boost.org/doc/libs/release/libs/crc/index.html|2|http://www.boost.org/LICENSE_1_0.txt^0|2|J|0|T|3|1|Z|7|2|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]|$A|T|B|U|1|V]|$A|W|B|X|1|Y]]|C|$]]|$1|D|3|-4|5|6|7|Z|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]|N|$5|G|H|I|C|$J|O]]]]

Use the <a href="http://www.boost.org/" rel="noreferrer">Boost C++ libraries</a>. There is a <a href="http://www.boost.org/doc/libs/release/libs/crc/index.html" rel="noreferrer">CRC</a> included there and the <a href="http://www.boost.org/LICENSE_1_0.txt" rel="noreferrer">license</a> is good.

blocks|key|1471378|text|SNIPPETS+C+Source+Code+Archive有一个可自由使用的CRC32+implementation：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1471379|/*+Copyright+(C)+1986+Gary+S.+Brown.++You+may+use+this+program,+or
+++code+or+tables+extracted+from+it,+as+desired+without+restriction.*/|code-block|syntax|javascript|1471380|(不幸的是，c.snippets.org似乎已经死了。幸运的是，Wayback+Machine已经将其存档。)|1471381|为了能够编译代码，您需要将BYTE的typedefs添加为无符号的8位整数，将DWORD添加为无符号的32位整数，以及头文件crc.h+&+sniptype.h。|style|CODE|1471382|标题中唯一关键的一项是这个宏(它可以很容易地放入CRC_32.c本身：|1471383|#define+UPDC32(octet,+crc)+(crc_32_tab[((crc)+%5E+(octet))+&+0xff]+%5E+((crc)+>>+8))|1471384|entityMap|0|LINK|mutability|MUTABLE|url|http://web.archive.org/web/20080217222203/http://c.snippets.org/|1|http://web.archive.org/web/20080303102530/http://c.snippets.org/snip_lister.php?fname=crc_32.c|2|http://web.archive.org/|3|http://web.archive.org/web/20080303093609/http://c.snippets.org/snip_lister.php?fname=crc.h|4|http://web.archive.org/web/20080303103500/http://c.snippets.org/snip_lister.php?fname=sniptype.h^0|0|U|0|13|K|1|0|0|W|F|2|0|D|4|13|5|1Q|5|3|1Y|A|4|0|0|0^^$0|@$1|2|3|4|5|6|7|18|8|@]|9|@$A|19|B|1A|1|1B]|$A|1C|B|1D|1|1E]]|C|$]]|$1|D|3|E|5|F|7|1F|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|1G|8|@]|9|@$A|1H|B|1I|1|1J]]|C|$]]|$1|K|3|L|5|6|7|1K|8|@$A|1L|B|1M|M|N]|$A|1N|B|1O|M|N]]|9|@$A|1P|B|1Q|1|1R]|$A|1S|B|1T|1|1U]]|C|$]]|$1|O|3|P|5|6|7|1V|8|@]|9|@]|C|$]]|$1|Q|3|R|5|F|7|1W|8|@]|9|@]|C|$G|H]]|$1|S|3|-4|5|6|7|1X|8|@]|9|@]|C|$]]]|T|$U|$5|V|W|X|C|$Y|Z]]|10|$5|V|W|X|C|$Y|11]]|12|$5|V|W|X|C|$Y|13]]|14|$5|V|W|X|C|$Y|15]]|16|$5|V|W|X|C|$Y|17]]]]

The <a href="http://web.archive.org/web/20080217222203/http://c.snippets.org/" rel="noreferrer">SNIPPETS C Source Code Archive</a> has a <a href="http://web.archive.org/web/20080303102530/http://c.snippets.org/snip_lister.php?fname=crc_32.c" rel="noreferrer">CRC32 implementation</a> that is freely usable:

<pre><code>/* Copyright (C) 1986 Gary S. Brown. You may use this program, or
 code or tables extracted from it, as desired without restriction.*/
</code></pre>

(Unfortunately, c.snippets.org seems to have died. Fortunately, the <a href="http://web.archive.org/" rel="noreferrer">Wayback Machine</a> has it archived.)

In order to be able to compile the code, you'll need to add typedefs for <code>BYTE</code> as an unsigned 8-bit integer and <code>DWORD</code> as an unsigned 32-bit integer, along with the header files <a href="http://web.archive.org/web/20080303093609/http://c.snippets.org/snip_lister.php?fname=crc.h" rel="noreferrer">crc.h</a> &amp; <a href="http://web.archive.org/web/20080303103500/http://c.snippets.org/snip_lister.php?fname=sniptype.h" rel="noreferrer">sniptype.h</a>.

The only critical item in the header is this macro (which could just as easily go in CRC_32.c itself:

<pre><code>#define UPDC32(octet, crc) (crc_32_tab[((crc) ^ (octet)) &amp; 0xff] ^ ((crc) &gt;&gt; 8))
</code></pre>

blocks|key|1471411|text|我是指定链接的源代码的作者。虽然源代码许可证的意图还不清楚(将在今天晚些时候)，但代码实际上是开放的，可以在您的免费或商业应用程序中免费使用，没有附加任何条件。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1471412|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

I am the author of the source code at the specified link. While the intention of the source code license is not clear (it will be later today), the code is in fact open and free for use in your free or commercial applications with no strings attached.

blocks|key|1686643|text|zlib+(http://zlib.net/)中的crc代码是最快的代码之一，并且具有非常自由的开源许可证。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1686644|而且您不应该使用adler-32，除非在特殊应用程序中，速度比错误检测性能更重要。|1686645|entityMap|0|LINK|mutability|MUTABLE|url|http://zlib.net/^0|6|G|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

The crc code in zlib (http://zlib.net/) is among the fastest there is, and has a very liberal open source license.

And you should not use adler-32 except for special applications where speed is more important than error detection performance.

blocks|key|1686714|text|使用zlib.h+(http://refspecs.linuxbase.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/zlib-crc32-1.html)：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1686715|#include+<zlib.h>
unsigned+long++crc+=+crc32(0L,+Z_NULL,+0);
crc+=+crc32(crc,+(const+unsigned+char*)data_address,+data_len);|code-block|syntax|javascript|1686716|entityMap|0|LINK|mutability|MUTABLE|url|http://refspecs.linuxbase.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/zlib-crc32-1.html^0|A|2J|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

using zlib.h (<a href="http://refspecs.linuxbase.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/zlib-crc32-1.html">http://refspecs.linuxbase.org/LSB_3.0.0/LSB-Core-generic/LSB-Core-generic/zlib-crc32-1.html</a>):

<pre><code>#include &lt;zlib.h&gt;
unsigned long crc = crc32(0L, Z_NULL, 0);
crc = crc32(crc, (const unsigned char*)data_address, data_len);
</code></pre>

blocks|key|1471584|text|我找到的最简单、最直接的C/C%2B%2B实现是在这个页面底部的一个链接中：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1471585|网页：http://www.barrgroup.com/Embedded-Systems/How-To/CRC-Calculation-C-Code|offset|length|1471586|代码下载链接：https://barrgroup.com/code/crc.zip|1471587|它是一个简单的独立实现，只有一个.h和一个.c文件。通过使用定义，可以支持CRC32、CRC16和CRC_CCITT。此外，代码还允许用户更改参数设置，如CRC多项式、初始/最终XOR值和反射选项。|1471588|许可证没有明确地定义为LGPL或类似的许可证。然而，该网站确实表示，他们将代码放在公共领域，以供任何用途。实际的代码文件也是这样说的。|1471589|希望它能帮上忙！|1471590|entityMap|0|LINK|mutability|MUTABLE|url|http://www.barrgroup.com/Embedded-Systems/How-To/CRC-Calculation-C-Code|1|https://barrgroup.com/code/crc.zip^0|0|3|1Z|0|0|7|Y|1|0|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Y|8|@]|9|@$D|Z|E|10|1|11]]|A|$]]|$1|F|3|G|5|6|7|12|8|@]|9|@$D|13|E|14|1|15]]|A|$]]|$1|H|3|I|5|6|7|16|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|17|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|18|8|@]|9|@]|A|$]]|$1|N|3|-4|5|6|7|19|8|@]|9|@]|A|$]]]|O|$P|$5|Q|R|S|A|$T|U]]|V|$5|Q|R|S|A|$T|W]]]]

The most simple and straightforward C/C++ implementation that I found is in a link at the bottom of this page:

Web Page: <a href="http://www.barrgroup.com/Embedded-Systems/How-To/CRC-Calculation-C-Code" rel="nofollow noreferrer">http://www.barrgroup.com/Embedded-Systems/How-To/CRC-Calculation-C-Code</a>

Code Download Link: <a href="https://barrgroup.com/code/crc.zip" rel="nofollow noreferrer">https://barrgroup.com/code/crc.zip</a>

It is a simple standalone implementation with one .h and one .c file.
There is support for CRC32, CRC16 and CRC_CCITT thru the use of a define. Also, the code lets the user change parameter settings like the CRC polynomial, initial/final XOR value, and reflection options if you so desire.

The license is not explicitly defined ala LGPL or similar. However the site does say that they are placing the code in the public domain for any use. The actual code files also say this.

Hope it helps!

blocks|key|1686630|text|mhash+library对我来说工作得很好。它足够快，支持多种类型的散列(crc32，MD5，SHA-1，HAVAL，RIPEMD128，RIPEMD160，TIGER，GOST等)。要获取字符串的CRC32，您可以执行如下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1686631|+MHASH+td+=+mhash_init(MHASH_CRC32);

+if+(td+==+MHASH_FAILED)+return+-1;+//+handle+failure

+mhash(td,+s,+strlen(s));

+unsigned+int+digest+=+0;+//+crc32+will+be+stored+here

+mhash_deinit(td,+&digest);

+//+do+endian+swap+here+if+desired|code-block|syntax|javascript|1686632|entityMap|0|LINK|mutability|MUTABLE|url|http://mhash.sourceforge.net/^0|0|D|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

The <a href="http://mhash.sourceforge.net/" rel="nofollow">mhash library</a> works pretty good for me. It's fast enough, supports multiple types of hashing (crc32, MD5, SHA-1, HAVAL, RIPEMD128, RIPEMD160, TIGER, GOST, etc.). To get CRC32 of a string you would do something like this:

<pre><code> MHASH td = mhash_init(MHASH_CRC32);

 if (td == MHASH_FAILED) return -1; // handle failure

 mhash(td, s, strlen(s));

 unsigned int digest = 0; // crc32 will be stored here

 mhash_deinit(td, &amp;digest);

 // do endian swap here if desired
</code></pre>

blocks|key|1686701|text|rurban's+fork+of+SMHasher+(最初的SMHasher似乎已被废弃)支持硬件CRC32。这些更改是在初始提交之前添加的，但请尝试比较the+new+CMakeLists.txt和the+old+one+(根本没有提到SSE+)。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1686702|最好的选择可能是this+paper中描述的Intel's+zlib+fork+with+PCLMULQDQ+support。这个库also+has+the+SSE+4.2+optimizations。|1686703|如果您不需要可移植性，并且您使用的是Linux，那么您可以使用内核的实现(如果可用，它是硬件加速的)：https://stackoverflow.com/a/11156040/309483|1686704|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/rurban/smhasher|1|https://github.com/rurban/smhasher/blame/fbb0fda71354140899a9c347c3057d159d18537a/CMakeLists.txt#L35|2|https://code.google.com/p/smhasher/source/browse/trunk/CMakeLists.txt|3|http://www.intel.com/content/dam/www/public/us/en/documents/white-papers/fast-crc-computation-generic-polynomials-pclmulqdq-paper.pdf|4|https://github.com/jtkukunas/zlib|5|https://github.com/jtkukunas/zlib/blob/e176b3c23ace88d5ded5b8f8371bbab6d7b02ba8/deflate.c#L190|6|https://stackoverflow.com/a/11156040/309483^0|0|P|0|25|M|1|2S|B|2|0|8|A|3|M|14|4|1U|Y|5|0|1F|17|6|0^^$0|@$1|2|3|4|5|6|7|11|8|@]|9|@$A|12|B|13|1|14]|$A|15|B|16|1|17]|$A|18|B|19|1|1A]]|C|$]]|$1|D|3|E|5|6|7|1B|8|@]|9|@$A|1C|B|1D|1|1E]|$A|1F|B|1G|1|1H]|$A|1I|B|1J|1|1K]]|C|$]]|$1|F|3|G|5|6|7|1L|8|@]|9|@$A|1M|B|1N|1|1O]]|C|$]]|$1|H|3|-4|5|6|7|1P|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]|P|$5|K|L|M|C|$N|Q]]|R|$5|K|L|M|C|$N|S]]|T|$5|K|L|M|C|$N|U]]|V|$5|K|L|M|C|$N|W]]|X|$5|K|L|M|C|$N|Y]]|Z|$5|K|L|M|C|$N|10]]]]

<a href="https://github.com/rurban/smhasher" rel="nofollow noreferrer">rurban's fork of SMHasher</a> (the original SMHasher seems abandoned) has hardware CRC32 support. The changes were added before the initial commit, but try comparing <a href="https://github.com/rurban/smhasher/blame/fbb0fda71354140899a9c347c3057d159d18537a/CMakeLists.txt#L35" rel="nofollow noreferrer">the new CMakeLists.txt</a> and <a href="https://code.google.com/p/smhasher/source/browse/trunk/CMakeLists.txt" rel="nofollow noreferrer">the old one</a> (which doesn't mention SSE at all).

The best option is probably <a href="https://github.com/jtkukunas/zlib" rel="nofollow noreferrer">Intel's zlib fork with PCLMULQDQ support</a> described in <a href="http://www.intel.com/content/dam/www/public/us/en/documents/white-papers/fast-crc-computation-generic-polynomials-pclmulqdq-paper.pdf" rel="nofollow noreferrer">this paper</a>. This library <a href="https://github.com/jtkukunas/zlib/blob/e176b3c23ace88d5ded5b8f8371bbab6d7b02ba8/deflate.c#L190" rel="nofollow noreferrer">also has the SSE 4.2 optimizations</a>.

If you don't need portability and you're on Linux, you can use the kernel's implementation (which is hardware accelerated if available): <a href="https://stackoverflow.com/a/11156040/309483">https://stackoverflow.com/a/11156040/309483</a>

I'm looking for an implementation of CRC32 in C or C++ that is explicitly licensed as being no cost or public domain. The implementation <a href="http://www.networkdls.com/Software/View/CRC32" rel="noreferrer">here</a> seems nice, but the only thing it says about the license is "source code", which isn't good enough. I'd prefer non LGPL so I don't have to fool around with a DLL (my app is closed source). I saw the adler32 implementation in zlib, but I'm checking small chunks of data, which adler is not good for.

CRC32 C or C++ implementation

Linux

我正在寻找一种用C或C++实现的CRC32，它被明确授权为免费或公共领域。实现看起来不错，但它对许可证的唯一说明是“源代码”，这还不够好。我更喜欢非LGPL，这样我就不用浪费在DLL上了(我的应用是封闭源代码的)。我在zlib中看到了adler32实现，但我检查的是小块数据，这是adler不适合的。

问CRC32 C或C++实现
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