Class: Rumai::IXP::Agent

Inherits:
Object show all
Defined in:
lib/rumai/ixp/transport.rb

Overview

A thread-safe channel that multiplexes many threads onto a single 9P2000 connection.

The send/recv implementation is based on the XCB cookie approach: www.x.org/releases/X11R7.5/doc/libxcb/tutorial/#requestsreplies

Defined Under Namespace

Classes: FidStream, RangedPool

Constant Summary

MODES =
{
  'r' => Topen::OREAD,
  'w' => Topen::OWRITE,
  't' => Topen::ORCLOSE,
  '+' => Topen::ORDWR,
}

Instance Attribute Summary (collapse)

Instance Method Summary (collapse)

Constructor Details

- (Agent) initialize(stream)

A new instance of Agent

Parameters:

  • stream

    I/O stream on which a 9P2000 server is listening.



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# File 'lib/rumai/ixp/transport.rb', line 22

def initialize stream
  @stream = stream

  @recv_buf = {} # tag => message
  @recv_lock = Mutex.new

  @tag_pool = RangedPool.new(0...BYTE2_MASK)
  @fid_pool = RangedPool.new(0...BYTE4_MASK)

  # establish connection with 9P2000 server
  req = Tversion.new(
    :tag     => Fcall::NOTAG,
    :msize   => Tversion::MSIZE,
    :version => Tversion::VERSION
  )
  rsp = talk(req)

  unless req.version == rsp.version
    raise Error, "protocol mismatch: self=#{req.version.inspect} server=#{rsp.version.inspect}"
  end

  @msize = rsp.msize

  # authenticate the connection (not necessary for wmii)
  @auth_fid = Fcall::NOFID

  # attach to filesystem root
  @root_fid = @fid_pool.obtain
  attach @root_fid, @auth_fid
end

Instance Attribute Details

- (Object) msize (readonly)

Returns the value of attribute msize



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# File 'lib/rumai/ixp/transport.rb', line 16

def msize
  @msize
end

Instance Method Details

- (Object) attach(root_fid, auth_fid = Fcall::NOFID, auth_name = ENV['USER'])

Associates the given FID with the FS root.



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# File 'lib/rumai/ixp/transport.rb', line 458

def attach root_fid, auth_fid = Fcall::NOFID, auth_name = ENV['USER']
  talk Tattach.new(
    :fid    => root_fid,
    :afid   => auth_fid,
    :uname  => ENV['USER'],
    :aname  => auth_name
  )
end

- (Object) clunk(fid)

Retires the given FID from use.



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# File 'lib/rumai/ixp/transport.rb', line 470

def clunk fid
  talk Tclunk.new(:fid => fid)
  @fid_pool.release fid
end

- (Object) create(path, mode = 'rw', perm = 0644)

Creates a new file at the given path that is accessible using the given modes for a user having the given permission bits.



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# File 'lib/rumai/ixp/transport.rb', line 383

def create path, mode = 'rw', perm = 0644
  prefix = File.dirname(path)
  target = File.basename(path)

  with_fid do |prefix_fid|
    walk_fid prefix_fid, prefix

    # create the file
    talk Tcreate.new(
      :fid => prefix_fid,
      :name => target,
      :perm => perm,
      :mode => MODES.parse(mode)
    )
  end
end

- (Object) entries(path)

Returns the basenames of all files inside the directory at the given path.

See Also:

  • Dir::entries


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# File 'lib/rumai/ixp/transport.rb', line 363

def entries path
  unless stat(path).directory?
    raise ArgumentError, "#{path.inspect} is not a directory"
  end

  read(path).map! {|t| t.name }
end

- (Object) open(path, mode = 'r')

Opens the given path for I/O access through a FidStream object. If a block is given, it is invoked with a FidStream object and the stream is closed afterwards.

See Also:

  • File::open


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# File 'lib/rumai/ixp/transport.rb', line 208

def open path, mode = 'r'
  # open the file
  path_fid = walk(path)
  talk Topen.new(
    :fid  => path_fid,
    :mode => MODES.parse(mode)
  )
  stream = FidStream.new(self, path_fid, @msize)

  # return the file stream
  if block_given?
    begin
      yield stream
    ensure
      stream.close
    end
  else
    stream
  end
end

- (Object) read(path, *args)

Returns the content of the file/directory at the given path.



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# File 'lib/rumai/ixp/transport.rb', line 353

def read path, *args
  open(path) {|f| f.read(*args) }
end

- (Object) recv(tag)

Returns the reply for the given ticket, which was previously given to you when you sent the corresponding request Fcall.



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# File 'lib/rumai/ixp/transport.rb', line 120

def recv tag
  loop do
    reply = @recv_lock.synchronize do
      if @recv_buf.key? tag
        @recv_buf.delete tag
      else
        # reply was not in receive buffer, so read
        # the next reply... hoping that it is ours

        next_reply_available =
          @recv_buf.empty? || begin
            # check (in a non-blocking fashion) if
            # the stream has reply for us right now
            @stream.ungetc @stream.read_nonblock(1).unpack('C').first
            true
          rescue Errno::EAGAIN
            # the stream is empty
          end

        if next_reply_available
          msg = Fcall.from_9p(@stream)

          if msg.tag == tag
            msg
          else
            # we got someone else's reply, so buffer
            # it (for them to receive) and try again
            @recv_buf[msg.tag] = msg
            nil
          end
        end
      end
    end

    if reply
      @tag_pool.release tag

      if reply.is_a? Rerror
        raise Error, reply.ename
      end

      return reply
    else
      # give other threads a chance to receive
      Thread.pass
    end
  end
end

- (Object) remove(path)

Deletes the file at the given path.



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# File 'lib/rumai/ixp/transport.rb', line 403

def remove path
  path_fid = walk(path)
  remove_fid path_fid # remove also does clunk
end

- (Object) remove_fid(path_fid)

Deletes the file corresponding to the given FID and clunks the given FID.



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# File 'lib/rumai/ixp/transport.rb', line 412

def remove_fid path_fid
  talk Tremove.new(:fid => path_fid)
end

- (Object) send(request)

Sends the given request Fcall and returns a ticket that you can use later to receive the reply.



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# File 'lib/rumai/ixp/transport.rb', line 107

def send request
  tag = @tag_pool.obtain

  request.tag = tag
  @stream << request.to_9p

  tag
end

- (Object) stat(path)

Returns information about the file at the given path.



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# File 'lib/rumai/ixp/transport.rb', line 419

def stat path
  with_fid do |path_fid|
    walk_fid path_fid, path
    stat_fid path_fid
  end
end

- (Object) stat_fid(path_fid)

Returns information about the file referenced by the given FID.



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# File 'lib/rumai/ixp/transport.rb', line 429

def stat_fid path_fid
  req = Tstat.new(:fid => path_fid)
  rsp = talk(req)
  rsp.stat
end

- (Object) talk(request)

Sends the given request Fcall and returns its reply.



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# File 'lib/rumai/ixp/transport.rb', line 172

def talk request
  tag = send(request)

  begin
    recv tag
  rescue Error => e
    e.message << " -- in reply to #{request.inspect}"
    raise
  end
end

- (Object) walk(path)

Returns an FID corresponding to the given path.



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# File 'lib/rumai/ixp/transport.rb', line 438

def walk path
  fid = @fid_pool.obtain
  walk_fid fid, path
  fid
end

- (Object) walk_fid(path_fid, path)

Associates the given FID to the given path.



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# File 'lib/rumai/ixp/transport.rb', line 447

def walk_fid path_fid, path
  talk Twalk.new(
    :fid    => @root_fid,
    :newfid => path_fid,
    :wname  => path.to_s.split(%r{/+}).reject {|s| s.empty? }
  )
end

- (Object) write(path, content)

Writes the given content to the file at the given path.



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# File 'lib/rumai/ixp/transport.rb', line 375

def write path, content
  open(path, 'w') {|f| f.write content }
end