/* -*-c-*-
*
- * $Id: sym.h,v 1.11 2000/06/17 10:37:39 mdw Exp $
+ * $Id: sym.h,v 1.12 2001/01/20 11:49:37 mdw Exp $
*
* Symbol table management
*
/*----- Revision history --------------------------------------------------*
*
* $Log: sym.h,v $
+ * Revision 1.12 2001/01/20 11:49:37 mdw
+ * Export tuning parameters from header file, for the benefit of other
+ * hashtable implementations. Change the storage of symbol names: store
+ * the name after the allocated symbol block in all cases. This replaces
+ * the previous complicated and slightly wasteful arrangement.
+ *
* Revision 1.11 2000/06/17 10:37:39 mdw
* Add support for arena management.
*
# include "sub.h"
#endif
+/*----- Tuning parameters -------------------------------------------------*/
+
+/* --- Initial hash table size --- *
+ *
+ * This is the initial @mask@ value. It must be of the form %$2^n - 1$%,
+ * so that it can be used to mask of the bottom bits of a hash value.
+ */
+
+#define SYM_INITSZ 32 /* Size of a new hash table */
+
+/* --- Maximum load factor --- *
+ *
+ * This parameter controls how much the table has to be loaded before the
+ * table is extended. The number of elements %$n$%, the number of bins %$b$%
+ * and the limit %$l$% satisfy the relation %$n < bl$%; if a new item is
+ * added to the table and this relation is found to be false, the table is
+ * doubled in size.
+ */
+
+#define SYM_LIMIT(n) ((n) * 2) /* Load factor for growing table */
+
/*----- Type definitions --------------------------------------------------*/
/* --- Symbol table --- *
* sufficient to allow me to manipulate such objects.
*/
-#define SYM_BUFSZ 16 /* Size of local string buffer */
-
typedef struct sym_base {
- hash_base b;
- union {
- char *p; /* Pointer to name string */
- char b[SYM_BUFSZ]; /* Buffer containing a short name */
- } name; /* Name of this symbol */
+ hash_base b; /* Base structure */
+ char *name; /* Pointer to name string */
size_t len; /* Length of the symbol's name */
} sym_base;
-/* --- A macro to pick a symbol's name out from the mess --- */
+/* --- Macros for picking out useful information --- *
+ *
+ * Note that @SYM_LEN@ returns the size of the symbol key. For textual keys,
+ * this will include the terminating null.
+ */
-#define SYM_NAME(sy) \
- (((sym_base *)(sy))->len > SYM_BUFSZ ? \
- ((sym_base *)(sy))->name.p : \
- ((sym_base *)(sy))->name.b)
+#define SYM_NAME(sy) ((const char *)(((sym_base *)(sy))->name))
+#define SYM_LEN(sy) (((sym_base *)(sy))->len + 0)
+#define SYM_HASH(sy) (((sym_base *)(sy))->b.hash + 0)
/* --- An iterator block --- */