lander/include/trie.h

#ifndef AD3_TERNARYTRIE
#define AD3_TERNARYTRIE

#define ALPHABET_SIZE 256
#define DELIMITER '\0'
#define MAX(x, y) (((x) > (y)) ? (x) : (y))

// Should not be higher than 254 or stuff will break
#define TRIE_MAX_SKIP_SIZE 8

/**
 * The implementation of a Ternary Trie.
 *
 * Each node should be represented by a binary tree in order to reduce the
 * memory usage.
 */

#include <stdbool.h>
#include <stddef.h>
#include <string.h>

static const char charset[] =
    "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
static const size_t charset_len = sizeof(charset) - 1;

// Length of randomly generated keys
#define RANDOM_KEY_LENGTH_SHORT 4
#define RANDOM_KEY_LENGTH_LONG 16

/**
 * Type definition for the struct representing the current Trie.
 *
 * You can (and should) redefine this in your c-file with the concrete fields.
 */
typedef struct ttrie Trie;

typedef enum entry_type { Redirect, Paste, Unknown } EntryType;

typedef struct entry {
  EntryType type;
  char *string;
} Entry;

Entry *entry_new(EntryType type, const char *string);

/**
 * Allocate and initialize an empty Trie.
 *
 * @return a pointer to an empty Trie struct
 */
Trie *trie_init();

/**
 * Populate trie with entries stored in the given file.
 *
 * @param trie
 * @param file_path path to file containing entries
 * @return amount of entries added; -1 if an error occured
 */
int trie_populate(Trie *trie, const char *file_path);

/**
 * De-allocate a trie by freeing the memory occupied by this trie.
 *
 * @param trie which should be freed
 */
void trie_free(Trie *trie);

/**
 * Search for an entry in the trie.
 *
 * @param trie
 * @param key key representing the entry
 * @return pointer to entry; NULL if not found
 */
Entry *trie_search(Trie *trie, const char *key);

/**
 * Add a string to this trie.
 *
 * @param trie
 * @param key key to represent entry with
 * @param entry entry to add
 * @return true if the trie was changed by this operation, false if it was
 * already present
 */
bool trie_add(Trie *trie, const char *key, Entry *entry);

bool trie_add_no_lock(Trie *trie, const char *key, Entry *entry);

/**
 * Add an entry by generating a random string as the key.
 *
 * @param trie
 * @param entry entry to add
 * @param secure whether to generate a longer, more secure random key
 * @return the generated key
 */
char *trie_add_random(Trie *trie, Entry *entry, bool secure);

/**
 * Remove an entry from this trie given its key.
 *
 * @param trie
 * @param key key representing entry
 * @return true if the entry was present and has been removed, false if it was
 * not present
 */
bool trie_remove(Trie *trie, const char *key);

/**
 * Returns the number of entries in this trie.
 *
 * @param trie
 * @return the number of entries in this trie
 */
size_t trie_size(Trie *trie);

#endif // AD3_TERNARYTRIE