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CPM OPERATING SYSTEMS/CPM 8000 (CPM8K)/P-CP M-Z8K SOURCES/as8000/alook.c

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+#include "stdio.h"
+/*
+ * Changed to use the Standard I/O library  9/13/82  FZ
+ */
+#include "acom.h"
+
+/*
+ * Version 3.2, 8/19/82.  Added initialization of the sy_val field
+ * when adding a new symbol to the symbol table.  It sometimes
+ * came up nonzero, giving undefined externals nonzero values in
+ * the object output.
+ */
+static	char	ident[] = "@(#)a.look.c	3.2";
+
+/*
+ * oclook - Returns a pointer to the operation table entry for the
+ * specified opcode symbol.  Creates a new entry in the operation
+ * table if necessary.
+ */
+struct octab *
+oclook(s) char *s; {
+
+struct	octab	*p, *q, *r;
+uns	h;
+int	cmp;
+
+	h = hash(s)>>(16-OHSHLOG)&(1<<OHSHLOG)-1;
+	p = 0;
+	q = ochtab[h];
+	while(q && (cmp=symcmp(s,q->oc_str))>0) {  /* follow hash chain */
+		p = q;
+		q = q->oc_lnk;
+	}
+	if(q && cmp==0) return(q);  /* found */
+	/*
+	 * Add a new entry to the table.
+	 */
+	if((uns)phytop&01) phytop++;  /* force integer alignment */
+	r = (struct octab *)palloc(sizeof(struct octab));
+	symcpy(r->oc_str,s);
+	r->oc_typ = 0;
+	r->oc_lnk = q;
+	if(p) p->oc_lnk = r; else ochtab[h] = r;
+	return(r);
+}
+
+/*
+ * hash - Given a string, computes a partial hashing function of the string,
+ * and returns its value.
+ */
+uns
+hash(s) char *s; {
+
+uns	h;
+
+	h = 0;
+	while(*s) h = (h<<1)+*s++;
+	return(h*40143);
+}
+
+/*
+ * sylook - Returns a virtual memory pointer to the symbol table entry
+ * for the specified symbol.  Creates a new entry in the symbol table
+ * if necessary.
+ */
+vmadr
+sylook(s) char *s; {
+
+struct	aside	*apt, **lpt;
+vmadr	p, q, r;
+struct	sytab	*qp, *rp;
+uns	h;
+int	cmp;
+
+#ifdef	STATS
+	sylct++;
+#endif
+	/*
+	 * Check the lookaside table to see if the symbol is in it.
+	 */
+	lpt = &ashead;  apt = ashead;
+	while((cmp = symcmp(apt->as_str,s)) && apt->as_lnk) {
+		apt = *(lpt = &apt->as_lnk);
+	}
+	/*
+	 * Whether we found a hit or not, move the entry to the front of the
+	 * lru chain.
+	 */
+	*lpt = apt->as_lnk;  apt->as_lnk = ashead;  ashead = apt;
+	if(cmp == 0) {  /* hit */
+#ifdef	STATS
+		ashct++;
+#endif
+		return(apt->as_sym);
+	}
+	/*
+	 * No luck in the lookaside table, so search the hash chains in
+	 * the customary manner.
+	 */
+	symcpy(ashead->as_str,s);  /* update lookaside table */
+	h = hash(s)>>(16-SHSHLOG)&(1<<SHSHLOG)-1;
+	p = 0;
+	q = syhtab[h];
+	while(q && (cmp=symcmp(s,(qp=(struct sytab *)rfetch(q))->sy_str))>0) {
+		p = q;
+		q = qp->sy_lnk;
+#ifdef	STATS
+		chnct++;
+#endif
+	}
+	if(q && cmp==0) return(ashead->as_sym = q);  /* found */
+	/*
+	 * Add a new entry to the table.
+	 */
+#ifdef	STATS
+	symct++;
+#endif
+	if((uns)virtop&01) virtop++;  /* force integer alignment */
+	rp = (struct sytab *)wfetch(r=valloc(sizeof(struct sytab)));
+	symcpy(rp->sy_str,s);
+	rp->sy_typ = rp->sy_atr = rp->sy_xlk = rp->sy_val = 0;
+	rp->sy_lnk = q;
+	if(p) ((struct sytab *)wfetch(p))->sy_lnk = r; else syhtab[h] = r;
+	return(ashead->as_sym = r);
+}