tapefs from plan9

src/cmd/tapefs/v6fs.c

@@ -0,0 +1,213 @@
+/*
+ * old (V6 and before) PDP-11 Unix filesystem
+ */
+#include <u.h>
+#include <libc.h>
+#include <auth.h>
+#include <fcall.h>
+#include "tapefs.h"
+
+/*
+ * v6 disk inode
+ */
+#define	V6NADDR	8
+#define	V6FMT	0160000
+#define	V6IFREG	0100000
+#define	V6IFDIR	0140000
+#define	V6IFCHR	0120000
+#define	V6IFBLK	0160000
+#define	V6MODE	0777
+#define	V6LARGE	010000
+#define	V6SUPERB	1
+#define	V6ROOT		1	/* root inode */
+#define	V6NAMELEN	14
+#define	BLSIZE	512
+#define	LINOPB	(BLSIZE/sizeof(struct v6dinode))
+#define	LNINDIR	(BLSIZE/sizeof(unsigned short))
+
+struct v6dinode {
+	unsigned char flags[2];
+	unsigned char nlinks;
+	unsigned char uid;
+	unsigned char gid;
+	unsigned char hisize;
+	unsigned char losize[2];
+	unsigned char addr[V6NADDR][2];
+	unsigned char atime[4];	/* pdp-11 order */
+	unsigned char mtime[4];	/* pdp-11 order */
+};
+
+struct	v6dir {
+	uchar	ino[2];
+	char	name[V6NAMELEN];
+};
+
+int	tapefile;
+Fileinf	iget(int ino);
+long	bmap(Ram *r, long bno);
+void	getblk(Ram *r, long bno, char *buf);
+
+void
+populate(char *name)
+{
+	Fileinf f;
+
+	replete = 0;
+	tapefile = open(name, OREAD);
+	if (tapefile<0)
+		error("Can't open argument file");
+	f = iget(V6ROOT);
+	ram->perm = f.mode;
+	ram->mtime = f.mdate;
+	ram->addr = f.addr;
+	ram->data = f.data;
+	ram->ndata = f.size;
+}
+
+void
+popdir(Ram *r)
+{
+	int i, ino;
+	char *cp;
+	struct v6dir *dp;
+	Fileinf f;
+	char name[V6NAMELEN+1];
+
+	cp = 0;
+	for (i=0; i<r->ndata; i+=sizeof(struct v6dir)) {
+		if (i%BLSIZE==0)
+			cp = doread(r, i, BLSIZE);
+		dp = (struct v6dir *)(cp+i%BLSIZE);
+		ino = dp->ino[0] + (dp->ino[1]<<8);
+		if (strcmp(dp->name, ".")==0 || strcmp(dp->name, "..")==0)
+			continue;
+		if (ino==0)
+			continue;
+		f = iget(ino);
+		strncpy(name, dp->name, V6NAMELEN);
+		name[V6NAMELEN+1] = '\0';
+		f.name = name;
+		popfile(r, f);
+	}
+	r->replete = 1;
+}
+
+void
+dotrunc(Ram *r)
+{
+	USED(r);
+}
+
+void
+docreate(Ram *r)
+{
+	USED(r);
+}
+
+char *
+doread(Ram *r, vlong off, long cnt)
+{
+	static char buf[Maxbuf+BLSIZE];
+	int bno, i;
+
+	bno = off/BLSIZE;
+	off -= bno*BLSIZE;
+	if (cnt>Maxbuf)
+		error("count too large");
+	if (off)
+		cnt += off;
+	i = 0;
+	while (cnt>0) {
+		getblk(r, bno, &buf[i*BLSIZE]);
+		cnt -= BLSIZE;
+		bno++;
+		i++;
+	}
+	return buf;
+}
+
+void
+dowrite(Ram *r, char *buf, long off, long cnt)
+{
+	USED(r); USED(buf); USED(off); USED(cnt);
+}
+
+int
+dopermw(Ram *r)
+{
+	USED(r);
+	return 0;
+}
+
+/*
+ * fetch an i-node
+ * -- no sanity check for now
+ * -- magic inode-to-disk-block stuff here
+ */
+
+Fileinf
+iget(int ino)
+{
+	char buf[BLSIZE];
+	struct v6dinode *dp;
+	long flags, i;
+	Fileinf f;
+
+	seek(tapefile, BLSIZE*((ino-1)/LINOPB + V6SUPERB + 1), 0);
+	if (read(tapefile, buf, BLSIZE) != BLSIZE)
+		error("Can't read inode");
+	dp = ((struct v6dinode *)buf) + ((ino-1)%LINOPB);
+	flags = (dp->flags[1]<<8) + dp->flags[0];
+	f.size = (dp->hisize << 16) + (dp->losize[1]<<8) + dp->losize[0];
+	if ((flags&V6FMT)==V6IFCHR || (flags&V6FMT)==V6IFBLK)
+		f.size = 0;
+	f.data = emalloc(V6NADDR*sizeof(ushort));
+	for (i = 0; i < V6NADDR; i++)
+		((ushort*)f.data)[i] = (dp->addr[i][1]<<8) + dp->addr[i][0];
+	f.mode = flags & V6MODE;
+	if ((flags&V6FMT)==V6IFDIR)
+		f.mode |= DMDIR;
+	f.uid = dp->uid;
+	f.gid = dp->gid;	
+	f.mdate = (dp->mtime[2]<<0) + (dp->mtime[3]<<8)
+	     +(dp->mtime[0]<<16) + (dp->mtime[1]<<24);
+	return f;
+}
+
+void
+getblk(Ram *r, long bno, char *buf)
+{
+	long dbno;
+
+	if ((dbno = bmap(r, bno)) == 0) {
+		memset(buf, 0, BLSIZE);
+		return;
+	}
+	seek(tapefile, dbno*BLSIZE, 0);
+	if (read(tapefile, buf, BLSIZE) != BLSIZE)
+		error("bad read");
+}
+
+/*
+ * logical to physical block
+ * only singly-indirect files for now
+ */
+
+long
+bmap(Ram *r, long bno)
+{
+	unsigned char indbuf[LNINDIR][2];
+
+	if (r->ndata <= V6NADDR*BLSIZE) {	/* assume size predicts largeness of file */
+		if (bno < V6NADDR)
+			return ((ushort*)r->data)[bno];
+		return 0;
+	}
+	if (bno < V6NADDR*LNINDIR) {
+		seek(tapefile, ((ushort *)r->data)[bno/LNINDIR]*BLSIZE, 0);
+		if (read(tapefile, (char *)indbuf, BLSIZE) != BLSIZE)
+			return 0;
+		return ((indbuf[bno%LNINDIR][1]<<8) + indbuf[bno%LNINDIR][0]);
+	}
+	return 0;
+}