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algorithm fnv-1 is hash := FNV_offset_basis for each byte_of_data to be hashed do hash := hash × FNV_prime hash := hash XOR byte_of_data return hash. In the above pseudocode, all variables are unsigned integers. All variables, except for byte_of_data, have the same number of bits as the FNV hash. The variable, byte_of_data, is an 8-bit ...
Logical shifts can be useful as efficient ways to perform multiplication or division of unsigned integers by powers of two. Shifting left by n bits on a signed or unsigned binary number has the effect of multiplying it by 2 n. Shifting right by n bits on an unsigned binary number has the effect of dividing it by 2 n (rounding towards 0).
For unsigned integers, the bitwise complement of a number is the "mirror reflection" of the number across the half-way point of the unsigned integer's range. For example, for 8-bit unsigned integers, NOT x = 255 - x , which can be visualized on a graph as a downward line that effectively "flips" an increasing range from 0 to 255, to a ...
algorithm Murmur3_32 is // Note: In this version, all arithmetic is performed with unsigned 32-bit integers. // In the case of overflow, the result is reduced modulo 2 32. input: key, len, seed c1 ← 0xcc9e2d51 c2 ← 0x1b873593 r1 ← 15 r2 ← 13 m ← 5 n ← 0xe6546b64 hash ← seed for each fourByteChunk of key do k ← fourByteChunk k ...
However, the implementation of AddSwap above in the C programming language always works even in case of integer overflow, since, according to the C standard, addition and subtraction of unsigned integers follow the rules of modular arithmetic, i. e. are done in the cyclic group / where is the number of bits of unsigned int.
If blocks are extracted from the data word in memory by a simple read of a 16-bit unsigned integer, then the values of the blocks will be different in the two systems, due to the reversal of the byte order of 16-bit data elements in memory, and the checksum result will be different as a consequence.
Adding an integer to a sequence number is simple unsigned integer addition, followed by unsigned modulo operation to bring the result back into range (usually implicit in the unsigned addition, on most architectures): s' = (s + n) modulo 2 SERIAL_BITS. Addition of a value below 0 or above 2 SERIAL_BITS−1 − 1 is undefined. Basically, adding ...
Thus, the algorithm runs at a "rate" of one multiplication per word of input. The same scheme can also be used for hashing integers, by interpreting their bits as vectors of bytes. In this variant, the vector technique is known as tabulation hashing and it provides a practical alternative to multiplication-based universal hashing schemes. [14]