X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~mdw/git/mLib/blobdiff_plain/dd3c57bc8cac59e0d657ee665ce462988d27d714..18c831dcd0ae4d660c70ccac69d27ed2a97851be:/struct/assoc.c

diff --git a/struct/assoc.c b/struct/assoc.c
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+/* -*-c-*-
+ *
+ * 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.
+ */
+
+/*----- 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);
+    if (!p)
+      break;
+    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, ATOM_HASH(a)), **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->a = a;
+  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 -------------------------------------------------*/