dictionary/map/key-value pairs data structure in C

Question

How does one construct and access a set of key-value pairs in C? To use a silly simple example, let\'s say I want to create a table which translates between an integer and i

Answer 1

You can use map implemented as part of clib library

Answer 2

You could consider hash implementation in C language to achieve this. For basics of hash refer to Wikipedia. Refer to this question for more details and links.

This link gives good overview and implementation details.

Answer 3

There is no built-in way to do this unless you count initializing an array like this in C99:

double squareRoots[] =
{
     [4] = 2.0,
     [9] = 3.0,
    [16] = 4.0,
    [25] = 5.0,
};

However, this allocates 26 elements in the array; the other values are all zeroes.

Assuming you didn't mean this, then look at C Interfaces and Implementations by D R Hanson; it shows a way of implementing associative arrays (aka hashes or dictionaries).

Answer 4

You could also use the libghthash for general purpose hashes. They are quite easy to use, and incorporate in your application. However, it is a third party API - so if that's a problem, you would have to implement your own.

There's no built in associate array/hash tables in C.

The array initialization (C99) is probably the best way to go unless you have non-numeric keys:

T hash[] = {
    [1] = tObj,
    [255] = tObj2,
};