crc | 易学教程

tricky crc algorithm

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问题 I am trying to find the crc that works with the following results. The byte string consists of 2 bytes (ie. 0xCE1E) and the crc is an single byte (ie. 0x03) byte crc CE1E 03 CE20 45 CE22 6F 0000 C0 0001 D4 FFFF 95 Can anyone help? 回答1: First, 4 hex digits aren't 4 bytes. Since all your examples show 4 hex digits -- 2 bytes -- I'll assume you mean 2 bytes. There are only 65,536 distinct hash values, here's what you do. Execute the hash function for all 65,536 values from 0000 to FFFF. Tabulate

Shorter GUID using CRC

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问题 I am making a website in ASP.NET and want to be able to have a user profile which can be accessed via a URL with the users id at the end. Unique identifier is obviously a bad choice as it is long and (correct me if i am wrong) not really URL friendly. I was wondering if i produced a unique idnetifier on the ASP page then hashed it using CRC (or something similar) if it would still be as unique (or even unique at all) as just a GUID. For example: The GUID 6f1a7841-190b-4c7a-9f23-98709b6f8848

Matching CRC32 from STM32F0 and zlib

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问题 I'm working on a communication link between a computer running Linux and a STM32F0. I want to use some kind of error detection for my packets and since the STM32F0 has CRC32 hw and I have zlib with CRC32 on Linux I thought it would be a good idea to use CRC32 for my project. The problem is that I won't get the same CRC value for the same data on the different platforms. #include <inttypes.h> #include <stdint.h> #include <stdio.h> #include <stdlib.h> #include <zlib.h> int main(void) { uint8_t

Implementing CRC8 on Arduino to write to MLX90614

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UPDATE: I can't even get this calculator to reproduce the SMBus PECs illustrated in figures 8 and 9 of this datasheet ! So I'm interfacing an arduino with a Melexis temperature sensor, and it's going okay--aside from the fact that I can't seem to get the CRC check to work. I've gotten read operations to complete successfully (although my software ignores the packet error code) but I have tried a lot of implementations of CRC8 to check the PEC byte to no avail. The code block I am using now came from OneWire: uint8_t OneWire::crc8(const uint8_t *addr, uint8_t len) { uint8_t crc = 0; while (len-

Understanding two different ways of implementing CRC generation with LFSR

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There are two ways of implementing CRC generation with linear feedback shift registers (LFSR), as shown in this figure . The coefficients of generator polynomial in this picture are 100111, and the red "+" circles are exclusive-or operators. The initialization register values are 00000 for both. For example, if the input data bit stream is 10010011, both A and B will give CRC checksum of 1010. The difference is A finishes with 8 shifts, while B with 8+5=13 shifts because of the 5 zeros appended to the input data. I can understand B very easily since it closely mimics the modulo-2 division.

how to calculate CRC value for a file in C#.net?

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问题 i want to calculate the CRC value for a file using 32-bit algorithm in C#.net.... 回答1: Algorithm is straightforward (rewritten from c++) class Crc32 { public static uint CountCrc(byte[] pBuf) { // Table of CRC-32's of all single byte values uint[] crctab = new uint[] { 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148,

Find out CRC or CHECKSUM of RS232 data

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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 80 42 00 00 00 00 00 00 00 00 00 00 00 03 0F 01 80 42 00 00 00 00 00 00 00 00 00 00 00 04 8C 01 80 42

CRC checks for files

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问题 I'm working with a small FAT16 filesystem, and I want to generate CRC values for indidual XML files which store configuration information. In case the data changes or is corrupted, I want to be able to check the CRC to determine that the file is still in it's original state. The question is, how do I put the CRC value into the file, without changing the CRC value of the file itself? I can think of a couple solutions, but I think there must be a fairly standard solution for this issue. 回答1:

Expected collisions for perfect 32bit crc

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问题 I'm trying to determine how my crc compares to an " ideal " 32bit crc. So I ran my crc over 1 million completely random samples of data and collected the amount of collisions, I want to compare this number to the number of collisions I could expect from the " ideal " crc. Does anyone know how to calculate the expected collision for an " ideal " 32bit crc? 回答1: Compare your own CRC with 0x1EDC6F41 as your "ideal" reference. Having said that, there is no ideal 32-bit CRC. Different polynomials

How to calculate 32 bit CRC in Ruby on rails?

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问题 i want to calculate 32 bit CRC value for 'input field value" in Ruby on rails. need the sample code , please help me anyone. 回答1: You could use Ruby's Zlib module. require 'zlib' crc32 = Zlib::crc32('input field value') 来源： https://stackoverflow.com/questions/4273281/how-to-calculate-32-bit-crc-in-ruby-on-rails