The mother of all programming languages, that is of course C! Everyone knows, of course, that C itself does not have many data structures, such as a hash map for example. In addition, of course, it also has no hash function. For this reason, this repository provides an implementation of several hash functions, in this case Fowler-Noll-Vo 1A (also called FNV-1A) and the dbj2 hash functions.

So: do you want a better insight into various hash functions, with an implementation within the C programming language? Then you've come to the right place! And 👀 no further!

It is very easy to create a hash, just by calling the function hash_fnv_string, in this case generating a representative hash of a string. To give an example of a corresponding hash, this can be done as follows:

#include <stdio.h>
#include "hash.h"

int main() {
    const char* str = "Do you want a hash?";
    printf("Hashed value: %u", hash_fnv_string(str)); // This creates the hash, following FNV-1A, 1097005601 (using 32-bits). 

    return 0;
}

You can see that the hash 1097005601 has been generated from the relevant string, but note that in this case 32-bits have been used. Of course, you can also call other functions, from which just a hash can be generated, since for example void* is used to allow various types. If you want to generate a hash of a string, this string must exist, because const char used_string [static 1] is used in the implementation.

In this project you can work with different hash sizes, which are given in bits. Support is provided for both 32-bit and 64-bit. You can change this in the corresponding CMakeLists.txt of this project. Within this is a specific variable, which is applied to the corresponding target. If you specify values other than 32-bit or 64-bit it will roughly not compile. To change the size you need to change the following variable in the CMakeLists.txt:

# The available hash sizes are in the case 32 bits or 64 bits.
# Within this project are 32-bits hash sizes used!
set(HASH_SIZE_SUPPORT 32) # Change this value to either 32-bits, or 64 bits!

target_compile_definitions(HASH PRIVATE HASH_BITS=${HASH_SIZE_SUPPORT})

You can see that in the above code snippet the variable set(HASH_SIZE_SUPPORT 32) needs to be changed. Based on this, the program will compile.