Symbol table example

symbol_table.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define LEN 80
#define INIT_SIZE 30

typedef struct Entry {
    void* key;
    void* value;
} Entry;

typedef struct SymbolTable {
    Entry* entries;
    int size;
    int total;

    Entry (*make_entry)(void*, void*);
    int (*compare)(void*, void*);
} SymbolTable;

SymbolTable create_symbol_table(Entry (*make_entry_fn)(void*, void*), int (*compare_fn)(void*, void*)) {
    SymbolTable t;
    t.entries = (Entry*) malloc(INIT_SIZE * sizeof(Entry));
    t.total = 0;
    t.size = INIT_SIZE;
    t.make_entry = make_entry_fn;
    t.compare = compare_fn;

    return t;
}

void drop_symbol_table(SymbolTable* t) {
    free(t->entries);
}

void add_entry(void* key, void* value, SymbolTable* t) {
    if (t->total == t->size) {
        t->size += INIT_SIZE;
        t->entries = (Entry*) realloc(t->entries, t->size * sizeof(Entry));
    }

    t->entries[ t->total ] = t->make_entry(key, value);
    t->total += 1;
}

Entry make_phone(void* name, void* phone) {
    Entry res;

    res.key = strdup( (char*)name );
    res.value = malloc(sizeof(long));
    memcpy( res.value, phone, sizeof(long) );

    return res;
}

int get_entry(void* key, SymbolTable t) {
    int i;

    for (i = 0; i < t.total; i += 1) {
        if (t.compare(key, &t.entries[i]) == 0) return i;
    }

    return -1;
}

int compare_phone(void* m, void* n) {
    return strcmp((char*) m, (char*) n);
}

void print_phone(Entry e) {
    printf("Name: %s, Phone num: %ld\n", (char*) e.key, *((long*) e.value));
}

int main() {
    int i;
    SymbolTable p = create_symbol_table(make_phone, compare_phone);

    long num = 123456789;
    for (i = 0; i < 1000; i += 1) {
        add_entry("Tung", &num, &p);
    }

    for (i = 0; i < 1000; i += 1) {
        printf("%d: ", i);
        print_phone(p.entries[0]);
    }

    drop_symbol_table(&p);
    return 0;
}