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

lookup, and to reduce storage used by key texts.

diff --git a/assoc.c b/assoc.c
new file mode 100644 (file)
index 0000000..26fe2c9
--- /dev/null
+++ b/assoc.c
@@ -0,0 +1,175 @@
+/* -*-c-*-
+ *
+ * $Id: assoc.c,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.c,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.
+ *
+ */
+
+/*----- Header files ------------------------------------------------------*/
+
+#include "alloc.h"
+#include "assoc.h"
+#include "atom.h"
+#include "hash.h"
+
+/*----- Main code ---------------------------------------------------------*/
+
+/* --- @assoc_create@ --- *
+ *
+ * Arguments:  @assoc_table *t@ = pointer to an association table
+ *
+ * Returns:    ---
+ *
+ * Use:                Creates a new association table.
+ */
+
+void assoc_create(assoc_table *t)
+{
+  hash_create(&t->t, SYM_INITSZ);
+  t->load = SYM_LIMIT(SYM_INITSZ);
+}
+
+/* --- @assoc_destroy@ --- *
+ *
+ * Arguments:  @assoc_table *t@ = pointer to an association table
+ *
+ * Returns:    ---
+ *
+ * Use:                Destroys an association table.
+ */
+
+void assoc_destroy(assoc_table *t)
+{
+  hash_iter i;
+
+  HASH_MKITER(&i, &t->t);
+  for (;;) {
+    hash_base *p;
+    HASH_NEXT(&i, p);
+    x_free(t->t.a, p);
+  }
+  hash_destroy(&t->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 
+ */
+
+void *assoc_find(assoc_table *t, atom *a, size_t sz, unsigned *f)
+{
+  hash_base **bin = HASH_BIN(&t->t, a->b.b.hash), **p;
+  assoc_base *q;
+
+  /* --- Try to find the association --- */
+
+  for (p = bin; *p; p = &(*p)->next) {
+    q = (assoc_base *)*p;
+    if (q->a == a) {
+      *p = q->b.next;
+      q->b.next = *bin;
+      *bin = &q->b;
+      if (f) *f = 1;
+      return (q);
+    }
+  }
+
+  /* --- Failed to find a match --- */
+
+  if (f) *f = 0;
+  if (!sz) return (0);
+
+  /* --- Make a new assoication --- */
+
+  q = x_alloc(t->t.a, sz);
+  q->b.next = *bin;
+  q->b.hash = ATOM_HASH(a);
+  *bin = &q->b;
+
+  /* --- Maybe extend the table --- */
+
+  if (t->load)
+    t->load--;
+  if (!t->load && hash_extend(&t->t))
+    t->load = SYM_LIMIT(t->t.mask + 1);
+  return (q);
+}
+
+/* --- @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.
+ */
+
+void assoc_remove(assoc_table *t, void *p)
+{
+  assoc_base *q = p;
+  hash_remove(&t->t, &q->b);
+  x_free(t->t.a, q);
+  t->load++;
+}
+
+/* --- @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.
+ */
+
+void assoc_mkiter(assoc_iter *i, assoc_table *t) { ASSOC_MKITER(i, t); }
+void *assoc_next(assoc_iter *i) { void *p; ASSOC_NEXT(i, p); return (p); }
+
+/*----- That's all, folks -------------------------------------------------*/

diff --git a/assoc.h b/assoc.h
new file mode 100644 (file)
index 0000000..6eea33a
--- /dev/null
+++ b/assoc.h
@@ -0,0 +1,156 @@
+/* -*-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