checksum

问题 I am trying to calculate a GS1 check digit and have come up with the following code. The algorithm for calculating a check digit is: Reverse the barcode Drop the last digit (calculated check digit) Add the digits together with first, third, fifth, e.t.c. digit multiplied by 3 and even digits multiplied by 1. Subtract the sum from nearest equal or higher multiple of ten It sounds simple typed out but the solution I came up with seemed a bit inelegant. It does work but I want to know if there

问题 Still learning how to use Maven , and I was wondering if there is a way to do a checksum on the generated WAR file. The Maven goal is package , and what I'm trying to achieve is to get a checksum value (of the packaged WAR file) put into a text file alongside the packaged file. Thanks in advance! 回答1: Got it working with the below pom code and changing my Maven goal to verify <dependency> ... <!-- CheckSum --> <dependency> <groupId>net.ju-n.maven.plugins</groupId> <artifactId>checksum-maven

问题 I need to communicate with a RS232 device, I have no specs or information available. I send a 16 byte command and get a 16 byte result back. The last byte looks like some kind of crc or checksum, I have tried using this http://miscel.dk/MiscEl/miscelCRCandChecksum.html with no luck. Anyone can reverse engineer the crc/checksum algorithm? here is some data captured with an RS-232 monitor program: 01 80 42 00 00 00 00 00 00 00 00 00 00 00 01 B3 01 80 42 00 00 00 00 00 00 00 00 00 00 00 02 51 01

问题 I need to calculate a CCITT 16 bit checksum value for data passed as a parameter together with the length. If I fill my array TempStr with the test data "123456789", use the polynomial 0x8408 with the length excluding the null termination character, I get the result string 6E90(Hex). Together with the null termination char I get 907A. When I swap out the polynomial to 0x1201 then I get results 29E2(Hex) and EFE8(Hex) with and without termination character. My questions are: Do I need to

问题 I would like to make a hash / signature of MySQL database schema (without data), in order to have a checksum of it, to ensure it is not modified by others. How can I achieve it ? 回答1: You need table checksum as far as I understand your question: checksum table `table` so, just make a checksum of an empty table, I guess 来源： https://stackoverflow.com/questions/12831918/hash-mysql-database-schema

问题 I wonder how reliable the adler32 checksum is, compared to e.g. md5 checksums? It was told on wikipedia that adler32 is "much less reliable" than md5, so I wonder how much, and in which way? More specifically, I'm wondering if it is reliable enough as a consistency check for long-time archiving of (tar) files of size 20GB+? 回答1: For details on the error-checking capabilities of the Adler-32 checksum, see for example Revisiting Fletcher and Adler Checksums. Maxino, 2006. This paper contains an

问题 When I run "mysql> CHECKSUM TABLE mytable;", I got the following result: +------------------+------------+ | Table | Checksum | +------------------+------------+ | mydb.mytable | 1679935596 | +------------------+------------+ How to select and return only the Checksum (not Table) in the above result in one mysql statement? Something like "SELECT Checksum FROM (CHECKSUM TABLE mytable);"??? Tried several times, but no idea. What I want is: +------------+ | Checksum | +------------+ | 1679935596

问题 I've tried the example from wikipedia: http://en.wikipedia.org/wiki/Longitudinal_redundancy_check This is the code for lrc (C#): /// <summary> /// Longitudinal Redundancy Check (LRC) calculator for a byte array. /// ex) DATA (hex 6 bytes): 02 30 30 31 23 03 /// LRC (hex 1 byte ): EC /// </summary> public static byte calculateLRC(byte[] bytes) { byte LRC = 0x00; for (int i = 0; i < bytes.Length; i++) { LRC = (LRC + bytes[i]) & 0xFF; } return ((LRC ^ 0xFF) + 1) & 0xFF; } It said the result is

问题 GCC's vector extensions offer a nice, reasonably portable way of accessing some SIMD instructions on different hardware architectures without resorting to hardware specific intrinsics (or auto-vectorization). A real use case, is calculating a simple additive checksum. The one thing that isn't clear is how to safely load data into a vector. typedef char v16qi __attribute__ ((vector_size(16))); static uint8_t checksum(uint8_t *buf, size_t size) { assert(size%16 == 0); uint8_t sum = 0; vec16qi

问题 We perform checksums of some data in sql server as follows: declare @cs int; select @cs = CHECKSUM_AGG(CHECKSUM(someid, position)) from SomeTable where userid = @userId group by userid; This data is then shared with clients. We'd like to be able to repeat the checksum at the client end... however there doesn't seem to be any info about how the checksums in the functions above are calculated. Can anyone enlighten me? 回答1: On SQL Server Forum, at this page, it's stated: The built-in CHECKSUM