implement reference counted strings

- on glib >=2.58, use the implementation provided by glib
- otherwise, a hash table will contain the strings

src/core/refstrings.c

@@ -0,0 +1,94 @@
+#include <string.h>
+
+#include <irssi/src/core/refstrings.h>
+
+#if GLIB_CHECK_VERSION(2, 58, 0)
+/* nothing */
+#else
+
+GHashTable *i_refstr_table;
+
+void i_refstr_init(void)
+{
+	i_refstr_table = g_hash_table_new(g_str_hash, g_str_equal);
+}
+
+char *i_refstr_intern(const char *str)
+{
+	char *ret;
+	gpointer rc_p, ret_p;
+	size_t rc;
+
+	if (str == NULL)
+		return NULL;
+
+	if (g_hash_table_lookup_extended(i_refstr_table, str, &ret_p, &rc_p)) {
+		rc = GPOINTER_TO_SIZE(rc_p);
+		ret = ret_p;
+	} else {
+		rc = 0;
+		ret = g_strdup(str);
+	}
+
+	if (rc + 1 <= G_MAXSIZE) {
+		g_hash_table_insert(i_refstr_table, ret, GSIZE_TO_POINTER(rc + 1));
+		return ret;
+	} else {
+		return g_strdup(str);
+	}
+}
+
+void i_refstr_release(char *str)
+{
+	char *ret;
+	gpointer rc_p, ret_p;
+	size_t rc;
+
+	if (str == NULL)
+		return;
+
+	if (g_hash_table_lookup_extended(i_refstr_table, str, &ret_p, &rc_p)) {
+		rc = GPOINTER_TO_SIZE(rc_p);
+		ret = ret_p;
+	} else {
+		rc = 0;
+		ret = NULL;
+	}
+
+	if (ret == str) {
+		if (rc > 1) {
+			g_hash_table_insert(i_refstr_table, ret, GSIZE_TO_POINTER(rc - 1));
+		} else {
+			g_hash_table_remove(i_refstr_table, ret);
+			g_free(ret);
+		}
+	} else {
+		g_free(str);
+	}
+}
+
+void i_refstr_deinit(void)
+{
+	g_hash_table_foreach(i_refstr_table, (GHFunc) g_free, NULL);
+	g_hash_table_destroy(i_refstr_table);
+}
+
+char *i_refstr_table_size_info(void)
+{
+	GHashTableIter iter;
+	void *k_p, *v_p;
+	size_t count, mem;
+	count = 0;
+	mem = 0;
+	g_hash_table_iter_init(&iter, i_refstr_table);
+	while (g_hash_table_iter_next(&iter, &k_p, &v_p)) {
+		char *key = k_p;
+		count++;
+		mem += sizeof(char) * (strlen(key) + 1) + 2 * sizeof(void *);
+	}
+
+	return g_strdup_printf("Shared strings: %ld, %dkB of data", count,
+	          (int) (mem / 1024));
+}
+
+#endif