Need an algorithm to generate an integer hash value for a String in C

Question

I am using uthash.h for hash implementation in C. I am using the hash-table for a basic word count exercise. I have a file containing words and I have to count frequency of each word. The implementation of uthash.h requires me to generate an integer id for each entry, and I wanted to calculate a unique integer corresponding to each string. I tried using md5 hash algorithm, but it generates strings with digits and alphabets, so its no use.Can anybody suggest me such an algorithm.

A good implementation of the md5 hash should be able to give you the raw 16-byte array. Split this into 4 32bit integers and xor them together. That alphanumeric string is just a convent representation for displaying the hash. — Gareth A. Lloyd
– Gareth A. Lloyd, Commented Feb 20, 2015 at 21:43
See stackoverflow.com/questions/16521148/… and stackoverflow.com/questions/1010875/…. — Mihai8
– Mihai8, Commented Feb 20, 2015 at 21:44
@user1929959, the second link that you mentioned has hashing functions that return unsigned long values, but in uthash.h implementation the id needs to be integer. I am not wether this will work or not. I will try this approach and post my results once done. In the mean time if you have any more suggestion, please post them. — Love Bisaria
– Love Bisaria, Commented Feb 20, 2015 at 21:56
And please don't use md5 or any other cryptographic hash function for this. Their computation is much slower than good non-cryptographic hash functions. — Niklas B.
– Niklas B., Commented Feb 20, 2015 at 22:19

mprivat · Accepted Answer · 2015-02-20 21:50:28Z

Use Robert Sedgewick's algorithm for hashing

unsigned int GenerateHash(char* str, unsigned int len) { unsigned int result = 0; unsigned int b = 378551; unsigned int a = 63689; unsigned int i = 0; for(i=0; i<len; str++, i++) { result = result*a + (*str); a = a*b; } return result; }

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