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Pearson hashing is a way of producing random numbers. In 1990, Peter K. Pearson published a pseudo-random walk hash algorithm which produces integers from 0 to 255, using a combination of XOR and a 256-entry non-linear permutation table. Pearson hashing can often be used with a specially selected non-linear permutation table to make a perfect hash function: this combination is known as perfect Pearson hashing.
In the Python programming language, the hash algorithm can be implemented as follows (assuming that permutation_table is defined externally):
def hash(input):
hash_value = len(input) % 256
for character in input:
character = ord(character) # ord() gets the character's byte value
hash_value = permutation_table[hash_value ^ character]
return hash_value
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