lib9p

commit 6b0f642ec2992f334e5d33bf334dfb88972181e2
parent f1ef31934f6a1eff05525b52c119ce811481cd72
Author: Matsuda Kenji <info@mtkn.jp>
Date:   Wed, 17 Jan 2024 08:36:21 +0900

add comment

Diffstat:
M
cmd/semfs/fs.go
 | 
12
------------
M
cmd/semfs/main.go
 | 
39
+++++++++++++++++++++++++++++++++++++++

2 files changed, 39 insertions(+), 12 deletions(-)
diff --git a/cmd/semfs/fs.go b/cmd/semfs/fs.go
@@ -38,18 +38,6 @@ func (fsys *semFS) OpenFile(name string, _ int) (lib9p.File, error) {
 	}
 }
 
-// This function assumes that group and uid both exist and
-// the leader of group has the same name as group itself.
-func (fsys *semFS) IsGroupLeader(group, uid string) bool {
-	return group == uid
-}
-
-// This function assumes that group and uid both exists and
-// only the member of group has the same name as group itself.
-func (fsys *semFS) IsGroupMember(group, uid string) bool {
-	return group == uid
-}
-
 func (fsys *semFS) Create(name string, uid string, mode lib9p.OpenMode, perm lib9p.FileMode) (lib9p.File, error) {
 	for _, f := range fsys.semfiles {
 		if f.name == name {
diff --git a/cmd/semfs/main.go b/cmd/semfs/main.go
@@ -1,3 +1,42 @@
+/*
+Semfs is a semaphore file system.
+The original idea is from this book ([Ballesteros 2006]).
+
+You can mount this file system via 9P using 9pfuse for example.
+The file system is initially empty, and you can make files on it.
+Each file represents a semaphore length of which is the number of tickets.
+To add tickets to an file, write the number of tickets to be added to the file.
+To consume a ticket, read the file.
+
+	$ 9pfuse localhost:5640 /mnt
+	$ echo 1 > /mnt/sem
+	$ ls -l /mnt/sem
+	-rw-rw-rw- 1 kenji kenji 1 Jan 17 08:16 /mnt/sem
+	$ cat /mnt/sem
+	$ ls -l /mnt/sem
+	-rw-rw-rw- 1 kenji kenji 0 Jan 17 08:17 /mnt/sem
+
+Reading a file with length 0 blocks until someone adds tickets to
+the file.
+
+	$ ls -l /mnt/sem
+	-rw-rw-rw- 1 kenji kenji 0 Jan 17 08:17 /mnt/sem
+	$ (cat /mnt/sem; echo done) & sleep 1; echo write; echo 1 > /mnt/sem
+	[2] 42872
+	write
+	$ done
+
+Usage:
+
+	semfs [-D]
+
+The Flags are:
+
+	-D
+		print very chatty 9P conversation dialogue to the standard output.
+
+[Ballesteros 2006]: http://doc.cat-v.org/plan_9/9.intro.pdf
+*/
 package main
 
 import (