Do you want a hash?

Pay attention! This repository is currently under construction! Functions will be added to it. Extra notice: this project is on the long run. When school projects are finished, this project will be continued.

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!

Creating a hash

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.

Supported hash sizes

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.