Add string table implementation

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

1 files changed, 76 insertions, 0 deletions

diff --git a/include/str_table.h b/include/str_table.h
new file mode 100644
index 0000000..b0d83f1
--- /dev/null
+++ b/include/str_table.h
@@ -0,0 +1,76 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#ifndef STR_TABLE_H
+#define STR_TABLE_H
+
+typedef struct str_bucket_t {
+	struct str_bucket_t *next;
+	char *str;
+	size_t index;
+} str_bucket_t;
+
+/**
+ * @struct str_table_t
+ *
+ * @brief A data structure that manages incremental, unique IDs for strings
+ *
+ * A string table allocates IDs for strings, and provides fast lookup for ID by
+ * string and string by ID.
+ */
+typedef struct {
+	str_bucket_t **buckets;
+	size_t num_buckets;
+
+	char **strings;
+	size_t num_strings;
+	size_t max_strings;
+} str_table_t;
+
+/**
+ * @brief Initialize a string table
+ *
+ * @memberof str_table_t
+ *
+ * @param size The number of hash table buckets to use internally
+ *
+ * @return Zero on success, -1 on failure (reports error to stderr)
+ */
+int str_table_init(str_table_t *table, size_t size);
+
+/**
+ * @brief Free all memory used by a string table
+ *
+ * @memberof str_table_t
+ *
+ * @param table A pointer to a string table object
+ */
+void str_table_cleanup(str_table_t *table);
+
+/**
+ * @brief Resolve a string to an incremental, unique ID
+ *
+ * @memberof str_table_t
+ *
+ * If the string is passed to this function for the first time, a new ID
+ * is allocated for the string.
+ *
+ * @param table A pointer to a string table object
+ * @param str   A pointer to a string to resolve
+ * @param idx   Returns the unique ID of the string
+ *
+ * @return Zero on success, -1 on failure (reports error to stderr)
+ */
+int str_table_get_index(str_table_t *table, const char *str, size_t *idx);
+
+/**
+ * @brief Resolve a unique ID to the string it represents
+ *
+ * @memberof str_table_t
+ *
+ * @param table A pointer to a string table object
+ * @param index The ID to resolve
+ *
+ * @return A pointer to the string or NULL if it hasn't been added yet
+ */
+const char *str_table_get_string(str_table_t *table, size_t index);
+
+#endif /* STR_TABLE_H */