155 lines
4.6 KiB
C++
155 lines
4.6 KiB
C++
/*
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* Copyright 2013 (c) Anna Schumaker.
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*
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* Databases are a generic store for information used by Ocarina. Users must
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* provide a struct db_ops when initializing a database.
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*
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* When writing a database to disk, databases will store their size in additon
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* to valid bits and values at each index. For example, let's say we have a
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* database with the following values: { 1, 2, NULL, 4 }. The resulting file
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* would look like:
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*
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* 4
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* 1 1
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* 1 2
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* 0
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* 1 4
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* <valid> <data>
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*
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* The database class will add a newline after each struct db_entry.
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*/
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#ifndef OCARINA_CORE_CONTAINERS_DATABASE_H
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#define OCARINA_CORE_CONTAINERS_DATABASE_H
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#include <core/file.h>
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struct db_entry {
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unsigned int dbe_index; /* The db_entry's position in the database. */
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gchar *dbe_key; /* The db_entry's hash key. */
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void *dbe_data; /* The db_entry's private data. */
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};
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static inline void dbe_init(struct db_entry *dbe, void *data)
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{
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dbe->dbe_index = 0;
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dbe->dbe_key = NULL;
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dbe->dbe_data = data;
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}
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static inline void *DBE_DATA(struct db_entry *dbe)
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{
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if (dbe)
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return dbe->dbe_data;
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return NULL;
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}
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struct db_ops {
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/* Allocate a new struct db_entry from a given key. */
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struct db_entry *(*dbe_alloc)(const gchar *, unsigned int);
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/* Free a struct db_entry. */
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void (*dbe_free)(struct db_entry *);
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/* Return a unique string representing a single struct db_entry. */
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gchar *(*dbe_key)(struct db_entry *);
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/* Read a single struct db_entry from disk. */
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struct db_entry *(*dbe_read)(struct file *, unsigned int);
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/* Write a single struct db_entry to disk. */
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void (*dbe_write)(struct file *, struct db_entry *);
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};
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struct database {
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unsigned int db_size; /* The database's count of valid entries. */
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bool db_autosave; /* The database's automatic save setting. */
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struct file db_file; /* The database's associated file object. */
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GPtrArray *db_entries; /* The database's backing array. */
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GHashTable *db_keys; /* The database's mapping of key -> value. */
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const struct db_ops *db_ops; /* The database's operations vector. */
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};
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#define DB_INIT(fname, autosave, ops, fmin) \
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{ \
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.db_size = 0, \
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.db_autosave = autosave, \
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.db_file = FILE_INIT_DATA("", fname, fmin), \
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.db_entries = g_ptr_array_new(), \
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.db_keys = g_hash_table_new(g_str_hash, g_str_equal), \
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.db_ops = ops, \
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}
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/*
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* Initialize a database using filepath as a location on disk to store data
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* and autosave as a hint for if this database should be automatically saved.
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*/
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void db_init(struct database *, const char *, bool, const struct db_ops *,
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unsigned int);
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/* Called to prevent memory leaks by freeing all remaining database entries. */
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void db_deinit(struct database *);
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/* Called to write the database to disk. */
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void db_save(struct database *);
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/* Save the database to disk iff database->db_autosave is set to True */
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void db_autosave(struct database *);
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/* Called to read the database from disk. */
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void db_load(struct database *);
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/* Returns the size of the backing std::vector. */
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unsigned int db_actual_size(const struct database *);
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/*
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* Called to add a new item to the database. The caller MUST check if the
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* database already contains a similar item before calling this function.
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*/
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struct db_entry *db_insert(struct database *, const gchar *);
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/* Called to remove an item from the database. */
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void db_remove(struct database *, struct db_entry *);
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/*
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* Called to shrink the database by removing any NULL pointers without
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* changing the order of items in the database.
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* Returns true if the database has been modified.
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*/
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bool db_defrag(struct database *);
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/* Called to change the key of a database entry. */
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void db_rekey(struct database *, struct db_entry *);
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/* Returns the database item at the requested index. */
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struct db_entry *db_at(const struct database *, unsigned int);
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/* Returns the database item with the specified key. */
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struct db_entry *db_get(struct database *, const gchar *);
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/*
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* Similar to db_get(), but allocate and return a new item if the
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* database doesn't contain an item with the specified key.
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*/
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struct db_entry *db_find(struct database *, const gchar *);
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/* Returns the first valid database item. */
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struct db_entry *db_first(const struct database *);
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/* Returns the next valid database item. */
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struct db_entry *db_next(const struct database *, struct db_entry *);
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#define db_for_each(ent, next, db) \
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for (ent = db_first(db), next = db_next(db, ent); \
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ent != NULL; \
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ent = next, next = db_next(db, ent))
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#endif /* OCARINA_CORE_CONTAINERS_DATABASE_H */
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