#081 a Dictionary
An example of using struct-based C to implement a somewhat object-oriented dictionary.
Notes
This is based on an example from 21st Century C Chapter 11: Object-Oriented Programming in C, Implementing a Dictionary, p210.
It is not intended to be ready for prime-time; this problem has been solved before and there a re reliable implementations available such as GHashTable.
A dictionary (aka hash table) is an easy structure to generate, given what we have in struct-based C. It represents associations between keys and values so that given a key the value can be found quickly.
Design
keyval.{h,c} implements the core key-value data structure and some supporting manipulation methods.
It just stores the name and a pointer to the value:
typedef struct keyval {
char *key;
void *value;
} keyval;
dict.{h,c} is the dictionary implementation. It holds the list of keyval and keeps track of the list length:
typedef struct dictionary {
keyval **pairs;
int length;
} dictionary;
dict_use.c demonstrates the use. The basics:
int zero = 0;
dictionary *d = dictionary_new();
dictionary_add(d, "an int", &zero);
printf("The integer I recorded was: %i\n", *(int*)dictionary_find(d, "an int"));
Building with Make
I’ve added a Makefile that builds the project with minimal fuss. It produces two binaries: dict_test and dict_use.
$ make all
$ ./dict_test
/set1/new test: OK
/set1/copy test: OK
/set2/fail test: OK
$ ./dict_use
Finding: 'key1' (int) .. found: 1
Finding: 'key2' (float) .. found: 2.000000
Finding: 'key3' (string) .. found: three
Finding: 'bogative' .. not found
Building with Automake
The build_with_automake.sh script wraps up the commands to build with Automake. This will copy and re-generate the project in a sub-folder called hash.
$ ./build_with_automake.sh
...
...
ALL DONE! Trying it out...
The integer I recorded was: 0
The string was: two