Upload

Digital Research

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

@@ -0,0 +1,100 @@
+#include "stdio.h"
+/*
+ * Changed to use the Standard I/O library  9/13/82  FZ
+ */
+#include "acom.h"
+
+static	char	ident[] = "@(#)a.vm.c	3.1";
+
+/*
+ * getbuf - Returns a pointer to a buffer which contains the specified
+ * virtual address.  Pages the buffers on a LRU basis.
+ */
+struct vmbuf *
+getbuf(adr) vmadr adr; {
+
+static int limblk = 0;			/* file high water mark */
+reg struct vmbuf *cb, *pb;
+reg uns vbn;
+
+#ifdef	STATS
+	vmgct++;
+#endif
+	vbn = adr>>BLKLOG;
+	pb = &vmhead;  cb = vmhead;
+	while(cb->vm_blk!=vbn && cb->vm_lnk) {
+		pb = cb;  cb = cb->vm_lnk;
+	}
+	if(cb->vm_blk!=vbn) { /* must commandeer a buffer */
+		if(cb->vm_flg&VMDIR) { /* write out old contents */
+			lseek(vmfd,(long)cb->vm_blk<<BLKLOG,0);
+			write(vmfd,cb->vm_mem,1<<BLKLOG);
+			if(cb->vm_blk >= limblk) limblk = cb->vm_blk+1;
+			cb->vm_flg &= ~VMDIR;
+#ifdef	STATS
+			vmwct++;
+#endif
+		}
+		if(vbn < limblk) {  /* read from disk */
+			lseek(vmfd,(long)vbn<<BLKLOG,0);
+			read(vmfd,cb->vm_mem,1<<BLKLOG);
+#ifdef	STATS
+			vmrct++;
+#endif
+		}
+		cb->vm_blk = vbn;
+	}
+	pb->vm_lnk = cb->vm_lnk;  cb->vm_lnk = vmhead;  vmhead = cb;
+	return(cb);
+}
+
+/*
+ * rfetch - Fetches a specified virtual address for reading, and returns
+ * a pointer to the in-core copy of the address.
+ */
+char *
+rfetch(adr) vmadr adr; {
+
+	return(&getbuf(adr)->vm_mem[adr&(1<<BLKLOG)-1]);
+}
+
+/*
+ * valloc - Allocates a region of virtual memory of the specified size,
+ * and returns the vm address of it.  The region is guaranteed to reside
+ * entirely within a single block.
+ */
+vmadr
+valloc(size) uns size; {
+
+vmadr	base, blklim;
+
+	blklim = (virtop|(1<<BLKLOG)-1)+1;
+	if(virtop+size > blklim) virtop = blklim;
+	base = virtop;  virtop += size;
+	return(base);
+}
+
+/*
+ * vinit - Opens the virtual memory file.
+ */
+vinit() {
+
+	close(creatb("VM.TMP",0666));
+	if((vmfd=openb("VM.TMP",2)) == -1) {
+		fprintf(ERROR,"Cannot reopen vm file\n");
+		exit(1);
+	}
+}
+
+/*
+ * wfetch - Fetches a specified virtual address for writing, and returns
+ * a pointer to the in-core copy of the address.
+ */
+char *
+wfetch(adr) vmadr adr; {
+
+reg struct vmbuf *bp;
+
+	(bp=getbuf(adr))->vm_flg |= VMDIR;
+	return(&bp->vm_mem[adr&(1<<BLKLOG)-1]);
+}