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In a polynomial code over () with code length and generator polynomial () of degree , there will be exactly code words. Indeed, by definition, p ( x ) {\displaystyle p(x)} is a code word if and only if it is of the form p ( x ) = g ( x ) ⋅ q ( x ) {\displaystyle p(x)=g(x)\cdot q(x)} , where q ( x ) {\displaystyle q(x)} (the quotient ) is of ...
The advantage of choosing a primitive polynomial as the generator for a CRC code is that the resulting code has maximal total block length in the sense that all 1-bit errors within that block length have different remainders (also called syndromes) and therefore, since the remainder is a linear function of the block, the code can detect all 2 ...
In computing, the modulo operation returns the remainder or signed remainder of a division, after one number is divided by another, called the modulus of the operation. Given two positive numbers a and n, a modulo n (often abbreviated as a mod n) is the remainder of the Euclidean division of a by n, where a is the dividend and n is the divisor. [1]
The long division may begin with a non-zero remainder. The remainder is generally computed using an -bit shift register holding the current remainder, while message bits are added and reduction modulo () is performed. Normal division initializes the shift register to zero, but it may instead be initialized to a non-zero value.
and −2 is the least absolute remainder. In the division of 42 by 5, we have: 42 = 8 × 5 + 2, and since 2 < 5/2, 2 is both the least positive remainder and the least absolute remainder. In these examples, the (negative) least absolute remainder is obtained from the least positive remainder by subtracting 5, which is d. This holds in general.
You will note that the code corresponds to the lsbit-first byte-at-a-time algorithm presented here, and the table is generated using the bit-at-a-time code. Function CRC32 Input: data: Bytes // Array of bytes Output: crc32: UInt32 // 32-bit unsigned CRC-32 value // Initialize CRC-32 to starting value crc32 ← 0xFFFFFFFF
The block length of a block code is the number of symbols in a block. Hence, the elements c {\displaystyle c} of Σ n {\displaystyle \Sigma ^{n}} are strings of length n {\displaystyle n} and correspond to blocks that may be received by the receiver.
Unfortunately, most programming languages make the latter much easier to write (X % r), so it is very commonly used. The generator is not sensitive to the choice of c, as long as it is relatively prime to the modulus (e.g. if m is a power of 2, then c must be odd), so the value c=1 is commonly chosen.