Initial revision

lang/pc/libpc/dis.c

@@ -0,0 +1,86 @@
+/*
+ * (c) copyright 1983 by the Vrije Universiteit, Amsterdam, The Netherlands.
+ *
+ *          This product is part of the Amsterdam Compiler Kit.
+ *
+ * Permission to use, sell, duplicate or disclose this software must be
+ * obtained in writing. Requests for such permissions may be sent to
+ *
+ *      Dr. Andrew S. Tanenbaum
+ *      Wiskundig Seminarium
+ *      Vrije Universiteit
+ *      Postbox 7161
+ *      1007 MC Amsterdam
+ *      The Netherlands
+ *
+ */
+
+/* Author: J.W. Stevenson */
+
+#include	<pc_err.h>
+
+#define assert()	/* nothing */
+
+/*
+ * use circular list of free blocks from low to high addresses
+ * _highp points to free block with highest address
+ */
+struct adm {
+	struct adm	*next;
+	int		size;
+};
+
+extern struct adm	*_lastp;
+extern struct adm	*_highp;
+extern			_trp();
+
+static int merge(p1,p2) struct adm *p1,*p2; {
+	struct adm *p;
+
+	p = (struct adm *)((char *)p1 + p1->size);
+	if (p > p2)
+		_trp(EFREE);
+	if (p != p2)
+		return(0);
+	p1->size += p2->size;
+	p1->next = p2->next;
+	return(1);
+}
+
+_dis(n,pp) int n; struct adm **pp; {
+	struct adm *p1,*p2;
+
+	/*
+	 * NOTE: dispose only objects whose size is a multiple of sizeof(*pp).
+	 *       this is always true for objects allocated by _new()
+	 */
+	n = ((n+sizeof(*p1)-1) / sizeof(*p1)) * sizeof(*p1);
+	if (n == 0)
+		return;
+	if ((p1= *pp) == (struct adm *) 0)
+		_trp(EFREE);
+	p1->size = n;
+	if ((p2 = _highp) == 0)  /*p1 is the only free block*/
+		p1->next = p1;
+	else {
+		if (p2 > p1) {
+			/*search for the preceding free block*/
+			if (_lastp < p1)  /*reduce search*/
+				p2 = _lastp;
+			while (p2->next < p1)
+				p2 = p2->next;
+		}
+		/* if p2 preceeds p1 in the circular list,
+		 * try to merge them			*/
+		p1->next = p2->next; p2->next = p1;
+		if (p2 <= p1 && merge(p2,p1))
+			p1 = p2;
+		p2 = p1->next;
+		/* p1 preceeds p2 in the circular list */
+		if (p2 > p1) merge(p1,p2);
+	}
+	if (p1 >= p1->next)
+		_highp = p1;
+	_lastp = p1;
+	*pp = (struct adm *) 0;
+}