From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <01b44d51cc3bf724b4857f2e167b3825@plan9.bell-labs.com>
From: "Russ Cox" <rsc@plan9.bell-labs.com>
To: 9fans@cse.psu.edu
Subject: Re: [9fans] fidtab revisited
In-Reply-To: <20030217073038.BCFD19653.mta2-rme.xtra.co.nz@[210.54.206.123]>
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Date: Mon, 17 Feb 2003 09:32:49 -0500
Topicbox-Message-UUID: 64dfd8d2-eacb-11e9-9e20-41e7f4b1d025

Pack and unpack were inspired by my 1998 attempts
at writing an SMB client for Plan 9.  The packets are
these grotesque little blobs that have a certain amount
of reason to them internally but not enough to make it
easy to parse.  The little mini-language made the code a lot
shorter but in the end, a lot harder to understand and debug.
I've since tossed it out and written traditional packet
routines, though even that hasn't been enough to salvage
the project (yet).

The minilanguage for smb was nice mainly because there
are redundant count fields scattered throughout
the packet, and the assembler takes care of those automatically.

9P doesn't really need a packet assembler because things are
so simple.  The packet assembler would be just as long
as the simple implementation.  There's also something therapeutic
about how direct that code is.  (I've been playing with an
Sun RPC compiler recently; trust me on this.)

Here are some examples from the 1998 SMB code.  The #
separates request from reply formats.  Inside each half,
the | separates the "word" section from the "data" section.
of the packet.  *X and *D variable sized data in various
guises.  A appears to be a string.

Russ


static int
PCsession(void)
{
	ushort action;
	int l;

	l = strlen(smb.passwd);
	if(dosmb(SmbSessionX, Niltid, 1, "hhhhhlhl|*Xaaaa#hhh|",
		0xff, 0, 7000, 1, 0, 0, l,
		0, l, smb.passwd, "rsc", "rsc-land", "plan9", "plan9",
		nil, nil, &action) < 0)
		return -1;
	chat("action=%x...", action);
	return 0;
}

static int
PCtreecon(char *tree)
{
	ushort tid;
	char str[1024];
	smb.tree = strdup(tree);	/* FIXME */
	snprint(str, sizeof str, "\\\\%s\\%s", smb.servername, tree);
	strupr(str);

	chat("treecon(%s)...", str);
	if(dosmb(SmbTreeConn, Niltid, 1, "|AAA#hh|", str, smb.passwd, "A:", nil, &tid) < 0)
		return -1;
	return tid;
}

static int
PCopen(char *fname, int mode)
{
	char str[1024];
	int fd;

	mode = (4<<4)|mode;	/* no locking */
	snprint(str, sizeof str, "%s", fname);	/* FIXME XXX estrdup */
	strupr(str);

	chat("\nopen(%s, 0x%x)...", str, mode);
	if(dosmb(SmbOpen, smb.tid, 1, "hh|A#hhllh|", mode, 0, str, &fd, nil, nil, nil, nil) < 0)
		return -1;
	return fd;
}

static int
PCread(int fd, void *v, int off, int n)
{
	if(dosmb(SmbRead, smb.tid, 1, "hhlh|#hll|*D", fd, n, off, 0, nil, nil, nil, &n, v) < 0)
		return -1;
	return n;
}

static int
PCwrite(int fd, void *v, int off, int n)
{
	if(dosmb(SmbWrite, smb.tid, 1, "hhlh|*D#h|", fd, n, off, 0, n, v, &n) < 0)
		return -1;
	return n;
}

static int
PCcreate(char *fname, int mode, int perm)
{
	int t, fd;

	USED(mode);
	t = time(0);
	perm = (perm & 0200) ? 0x20: 0x21;
	if(dosmb(SmbCreate, smb.tid, 1, "hl|A#h|", perm, t, fname, &fd) < 0)
		return -1;
	return fd;
}