Comments on: Calculating CRC-32 in C# and .NET http://damieng.com/blog/2006/08/08/calculating_crc32_in_c_and_net A .NET developer in Redmond Tue, 06 Jan 2009 09:47:46 +0000 http://wordpress.org/?v=2.7 hourly 1 By: Alessio http://damieng.com/blog/2006/08/08/calculating_crc32_in_c_and_net/comment-page-1#comment-10410 Alessio Tue, 25 Nov 2008 11:27:34 +0000 http://damieng.com/blog/archive/2006/08/08/calculating_crc32_in_c_and_net.aspx#comment-10410 Hi, I tried to execute the program under Windows XP and the CRC-hash calculated for a file of 25MB wasn't correct, just because of in windows XP the CalculateHash was called more than once(it works with a lenght of 4096 byte at a time). I toke off the '~' from "return ~crc" of CalculateHash and put it on "byte[] hashBuffer = UInt32ToBigEndianBytes(~hash)" of HashFinal, so that step was made only once at the end of cycle (without modifying the intermediate values). In this way the algorithm worked corrctly. I hope I gived a hand, Alessio Hi,
I tried to execute the program under Windows XP and the CRC-hash calculated for a file of 25MB wasn't correct, just because of in windows XP the CalculateHash was called more than once(it works with a lenght of 4096 byte at a time). I toke off the '~' from "return ~crc" of CalculateHash and put it on "byte[] hashBuffer = UInt32ToBigEndianBytes(~hash)" of HashFinal, so that step was made only once at the end of cycle (without modifying the intermediate values).
In this way the algorithm worked corrctly.

I hope I gived a hand,
Alessio

]]> By: stefan http://damieng.com/blog/2006/08/08/calculating_crc32_in_c_and_net/comment-page-1#comment-9146 stefan Fri, 15 Aug 2008 15:06:20 +0000 http://damieng.com/blog/archive/2006/08/08/calculating_crc32_in_c_and_net.aspx#comment-9146 Did you fix the error in your code now? I would like to use it, with files longer than 4096 bytes. Did you fix the error in your code now? I would like to use it, with files longer than 4096 bytes.

]]> By: Damien Guard http://damieng.com/blog/2006/08/08/calculating_crc32_in_c_and_net/comment-page-1#comment-6461 Damien Guard Thu, 28 Feb 2008 13:43:44 +0000 http://damieng.com/blog/archive/2006/08/08/calculating_crc32_in_c_and_net.aspx#comment-6461 You're right, multiple calls to HashCore will carry on from the final complement instead of the actual current hash value. Removing the ~ complement from the CalculateHash function means you can't use that static method directly... I think complementing it in Initialize and inside HashCore might be a better approach. Will update the code once I've had chance to test it and check the other hashing algorithms I have up. Thanks! [)amien You're right, multiple calls to HashCore will carry on from the final complement instead of the actual current hash value.

Removing the ~ complement from the CalculateHash function means you can't use that static method directly... I think complementing it in Initialize and inside HashCore might be a better approach.

Will update the code once I've had chance to test it and check the other hashing algorithms I have up.

Thanks!

[)amien

]]> By: Mario http://damieng.com/blog/2006/08/08/calculating_crc32_in_c_and_net/comment-page-1#comment-6460 Mario Thu, 28 Feb 2008 13:26:37 +0000 http://damieng.com/blog/archive/2006/08/08/calculating_crc32_in_c_and_net.aspx#comment-6460 Nice code, but i found a bug if you compute values for streams larger than 4096 bytes (make textfile in sample code larger than 4096). In this case the HashCore function is called more than once but the complement is build in the CalculateHash function. So you don't get the complement for the final value but for each intermediate value which will result in a wrong value. The complement build should take place in the HashFinal function. Nice code, but i found a bug if you compute values for streams larger than 4096 bytes (make textfile in sample code larger than 4096). In this case the HashCore function is called more than once but the complement is build in the CalculateHash function. So you don't get the complement for the final value but for each intermediate value which will result in a wrong value. The complement build should take place in the HashFinal function.

]]> By: Gaurav http://damieng.com/blog/2006/08/08/calculating_crc32_in_c_and_net/comment-page-1#comment-5770 Gaurav Tue, 01 Jan 2008 16:30:26 +0000 http://damieng.com/blog/archive/2006/08/08/calculating_crc32_in_c_and_net.aspx#comment-5770 ]Dude, thanks a lot, i found a lot of dumb code out there and this is the best code written for this purpose. I wrote one my self but it was a conversion from Java to c# and i did not use at least some support which c# provides and there was some other code which generated wrong checksomes on a 64-bit processor. Although i have not tested your code on 64 bit processor but it seems it should work fine as far as my knowledge is concerned. ]Dude, thanks a lot, i found a lot of dumb code out there and this is the best code written for this purpose.

I wrote one my self but it was a conversion from Java to c# and i did not use at least some support which c# provides and there was some other code which generated wrong checksomes on a 64-bit processor.
Although i have not tested your code on 64 bit processor but it seems it should work fine as far as my knowledge is concerned.

]]> By: Calculating CRC-64 in C# and .NET » DamienG http://damieng.com/blog/2006/08/08/calculating_crc32_in_c_and_net/comment-page-1#comment-5195 Calculating CRC-64 in C# and .NET » DamienG Mon, 19 Nov 2007 12:53:43 +0000 http://damieng.com/blog/archive/2006/08/08/calculating_crc32_in_c_and_net.aspx#comment-5195 [...] how the CRC-32 C# class I posted some time ago continues to get lots of Google hits I thought I'd post a CRC-64 version which will no doubt be far [...] [...] how the CRC-32 C# class I posted some time ago continues to get lots of Google hits I thought I'd post a CRC-64 version which will no doubt be far [...]

]]> By: Damien Guard http://damieng.com/blog/2006/08/08/calculating_crc32_in_c_and_net/comment-page-1#comment-1547 Damien Guard Sun, 29 Oct 2006 11:40:37 +0000 http://damieng.com/blog/archive/2006/08/08/calculating_crc32_in_c_and_net.aspx#comment-1547 Updated to include usage sample. [)amien Updated to include usage sample.

[)amien

]]> By: Ronak http://damieng.com/blog/2006/08/08/calculating_crc32_in_c_and_net/comment-page-1#comment-1546 Ronak Sat, 28 Oct 2006 08:14:41 +0000 http://damieng.com/blog/archive/2006/08/08/calculating_crc32_in_c_and_net.aspx#comment-1546 But how do i use it in the Actual Code.<br />I want to calculate CRC of file...<br />How can i use this code to do it But how do i use it in the Actual Code.
I want to calculate CRC of file...
How can i use this code to do it

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