Hash tables indexed by atoms, to avoid expense of hashing keys on each

[mLib] / assoc.h

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+/* -*-c-*-
+ *
+ * $Id: assoc.h,v 1.1 2001/01/20 11:50:58 mdw Exp $
+ *
+ * Assocation tables
+ *
+ * (c) 2000 Straylight/Edgeware
+ */
+
+/*----- Licensing notice --------------------------------------------------* 
+ *
+ * This file is part of the mLib utilities library.
+ *
+ * mLib is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Library General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ * 
+ * mLib is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Library General Public License for more details.
+ * 
+ * You should have received a copy of the GNU Library General Public
+ * License along with mLib; if not, write to the Free
+ * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
+ * MA 02111-1307, USA.
+ */
+
+/*----- Revision history --------------------------------------------------* 
+ *
+ * $Log: assoc.h,v $
+ * Revision 1.1  2001/01/20 11:50:58  mdw
+ * Hash tables indexed by atoms, to avoid expense of hashing keys on each
+ * lookup, and to reduce storage used by key texts.
+ *
+ */
+
+#ifndef MLIB_ASSOC_H
+#define MLIB_ASSOC_H
+
+#ifdef __cplusplus
+  extern "C" {
+#endif
+
+/*----- Header files ------------------------------------------------------*/
+
+#ifndef MLIB_ATOM_H
+#  include "atom.h"
+#endif
+
+#ifndef MLIB_HASH_H
+#  include "hash.h"
+#endif
+
+/*----- Data structures ---------------------------------------------------*/
+
+typedef struct assoc_table {
+  hash_table t;
+  size_t load;
+} assoc_table;
+
+typedef struct assoc_base {
+  hash_base b;
+  atom *a;
+} assoc_base;
+
+typedef struct { hash_iter i; } assoc_iter;
+
+/*----- Functions provided ------------------------------------------------*/
+
+/* --- @assoc_create@ --- *
+ *
+ * Arguments:  @assoc_table *t@ = pointer to an association table
+ *
+ * Returns:    ---
+ *
+ * Use:                Creates a new association table.
+ */
+
+extern void assoc_create(assoc_table */*t*/);
+
+/* --- @assoc_destroy@ --- *
+ *
+ * Arguments:  @assoc_table *t@ = pointer to an association table
+ *
+ * Returns:    ---
+ *
+ * Use:                Destroys an association table.
+ */
+
+extern void assoc_destroy(assoc_table */*t*/);
+
+/* --- @assoc_find@ --- *
+ *
+ * Arguments:  @assoc_table *t@ = pointer to an association table
+ *             @atom *a@ = an atom to label the item
+ *             @size_t sz@ = size of block to allocate
+ *             @unsigned *f@ = pointer to `found' flag
+ *
+ * Returns:    A pointer to the item located or null.
+ *
+ * Use:                Looks up an atom in an association table.  If the atom is
+ *             found, the association is returned.  If not, and @sz@ is
+ *             zero, a null pointer is returned.  Otherwise, a block of size
+ *             @sz@ is allocated, its @assoc_base@ header is filled in, and
+ *             the pointer returned.  The flag @*f@ is cleared if the item
+ *             couldn't be found, or set if it was.
+ *
+ *             All the atoms used in a particular table should 
+ */
+
+extern void *assoc_find(assoc_table */*t*/, atom */*a*/,
+                       size_t /*sz*/, unsigned */*f*/);
+
+/* --- @assoc_remove@ --- *
+ *
+ * Arguments:  @assoc_table *t@ = pointer to an association table
+ *             @void *p@ = pointer to a block to remove
+ *
+ * Returns:    ---
+ *
+ * Use:                Removes an association from a table.
+ */
+
+extern void assoc_remove(assoc_table */*t*/, void */*p*/);
+
+/* --- @assoc_mkiter@, @assoc_next@ --- *
+ *
+ * Arguments:  @assoc_iter *i@ = pointer to an iterator
+ *             @assoc_table *t@ = pointer to an association table
+ *
+ * Returns:    Next association, or null, for @assoc_next@; nothing for
+ *             @assoc_mkiter@.
+ *
+ * Use:                Iterates over the associations in a table.
+ */
+
+#define ASSOC_MKITER(i_, t_) HASH_MKITER(&(i_)->i, &(t_)->t)
+
+#define ASSOC_NEXT(i_, p) do {                                         \
+  hash_base *_q;                                                       \
+  HASH_NEXT(&(i_)->i, _q);                                             \
+  (p) = (void *)_q;                                                    \
+} while (0)
+
+extern void assoc_mkiter(assoc_iter */*i*/, assoc_table */*t*/);
+extern void *assoc_next(assoc_iter */*i*/);
+
+/*----- That's all, folks -------------------------------------------------*/
+
+#ifdef __cplusplus
+  }
+#endif
+
+#endif