From mboxrd@z Thu Jan  1 00:00:00 1970
Message-ID: <b3e03fdd438a70a90540e544ce2bebaa@collyer.net>
To: 9fans@cse.psu.edu
Date: Mon,  9 Aug 2004 18:52:07 -0700
From: geoff@collyer.net
MIME-Version: 1.0
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Subject: [9fans] 9P1 clients?
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Topicbox-Message-UUID: d386bf9c-eacd-11e9-9e20-41e7f4b1d025

Hmm, no answer on plan9dev, so I'll try here=E2=8B=AF

Does anybody still have 9P1 clients (other than drawterm, which we
have 9P2000 versions of now)?  I ask because I've got a version of
Ken's file server that uses 64-bit file sizes, offsets and block
numbers.  It works just fine, but 9P1 isn't a great fit, since some of
the relevant fields are only 32 bits wide (e.g., qid.path).

Incidentally, here's a program to find the largest file size possible
on a given file system empirically.  With a 4kB block size and
triple-indirect blocks on my 63-bit file server, it prints

	542,811,039,744 (5.42811e+11)

which matches the theoretical limit.  Quadruple-indirect blocks may be
called for to reach 2=E2=81=B6=E2=81=B3 bytes.


# To unbundle, run this file
echo 9fslimit.c
sed 's/^X//' >9fslimit.c <<'!'
X/* 9fslimit >tempfile - perform a binary search to find largest file siz=
e */

X#include <u.h>
X#include <libc.h>

static int
iswritablebyte(vlong offset)
X{
X	char c;

X	return seek(1, offset, 0) >=3D 0 && write(1, &c, 1) =3D=3D 1;
X}

static int
islastbyte(vlong offset)
X{
X	return iswritablebyte(offset) && !iswritablebyte(offset+1);
X}

X/*
X * sometimes limits are near powers of 2, but sometimes they are
X * determined by file system structure (e.g., indirect blocks).
X */
void
main(int argc, char **argv)
X{
X	int verbose =3D 0;
X	uvlong low =3D 0, high =3D ~0ULL, new =3D 0;

X	ARGBEGIN {
X	case 'v':
X		verbose =3D 1;
X		break;
X	default:
X		fprint(2, "usage: %s >junkfile\n", argv0);
X		exits("usage");
X	} ARGEND;
X	while (low <=3D high){
X		new =3D (high + low)/2;
X		if (verbose)
X			fprint(2, "new guess: %,lld\n", new);
X		if (islastbyte(new))
X			break;
X		if (iswritablebyte(new))
X			low =3D new + 1;
X		else
X			high =3D new - 1;
X	}
X	if (low > high)
X		fprint(2, "failed to converge\n");
X	else {
X		/*
X		 * new is last possible offset with zero-origin, so add 1 to
X		 * get size.
X		 */
X		++new;
X		fprint(2, "%,lld (%g)\n", new, (double)new);
X	}
X	exits(0);
X}
!