From 19e69366177799f7ccff75b6f4a1850ff0ca8d09 Mon Sep 17 00:00:00 2001
From: Eric Wong <e@80x24.org>
Date: Wed, 2 Dec 2015 11:11:06 +0000
Subject: dtas-mpd-emu: beginning of the MPD emulation proxy

Get basic commands and output buffering (in-memory) working.
The original mpd buffers large responses into memory, too,
so there probably isn't much concern for DoS-ing with slow
clients like a typical web server has.
---
 lib/dtas/mpd_emu_client.rb | 108 +++++++++++++++++++++++++++++++++++++++++++++
 lib/dtas/server_loop.rb    |  55 +++++++++++++++++++++++
 2 files changed, 163 insertions(+)
 create mode 100644 lib/dtas/mpd_emu_client.rb
 create mode 100644 lib/dtas/server_loop.rb

(limited to 'lib')

diff --git a/lib/dtas/mpd_emu_client.rb b/lib/dtas/mpd_emu_client.rb
new file mode 100644
index 0000000..01258d1
--- /dev/null
+++ b/lib/dtas/mpd_emu_client.rb
@@ -0,0 +1,108 @@
+# Copyright (C) 2015 all contributors <dtas-all@nongnu.org>
+# License: GPLv3 or later (https://www.gnu.org/licenses/gpl-3.0.txt)
+
+# emulate the MPD protocol
+require_relative '../dtas'
+require 'shellwords'
+
+class DTAS::MpdEmuClient # :nodoc:
+  attr_reader :to_io
+
+  # protocol version we support
+  SERVER = 'MPD 0.13.0'
+  MAX_RBUF = 8192
+  ACK = {
+    ERROR_NOT_LIST: 1,
+    ERROR_ARG: 2,
+    ERROR_PASSWORD: 3,
+    ERROR_PERMISSION: 4,
+    ERROR_UNKNOWN: 5,
+    ERROR_NO_EXIST: 50,
+    ERROR_PLAYLIST_MAX: 51,
+    ERROR_SYSTEM: 52,
+    ERROR_PLAYLIST_LOAD: 53,
+    ERROR_UPDATE_ALREADY: 54,
+    ERROR_PLAYER_SYNC: 55,
+    ERROR_EXIST: 56,
+  }
+
+  def initialize(io)
+    @to_io = io
+    @rbuf = ''.b
+    @wbuf = nil
+    @cmd_listnum = 0
+    out("OK #{SERVER}\n")
+  end
+
+  def dispatch_loop(rbuf)
+    while rbuf.sub!(/\A([^\r\n]+)\r?\n/n, '')
+      rv = dispatch(Shellwords.split($1))
+      next if rv == true
+      return rv
+    end
+    rbuf.size >= MAX_RBUF ? nil : :wait_readable
+  end
+
+  def dispatch(argv)
+    cmd = argv.shift or return err(:ERROR_UNKNOWN)
+    cmd = "mpdcmd_#{cmd}"
+    respond_to?(cmd) ? __send__(cmd, argv) : err(:ERROR_UNKNOWN)
+  end
+
+  def err(sym)
+    "[#{ACK[sym]}@#@cmd_listnum {}"
+  end
+
+  def mpdcmd_ping(argv)
+    out("OK\n")
+  end
+
+  # returns true on complete, :wait_writable when blocked, or nil on error
+  def out(buf)
+    buf = buf.b
+    if @wbuf
+      @wbuf << buf
+      :wait_writable
+    else
+      tot = buf.size
+      case rv = @to_io.write_nonblock(buf, exception: false)
+      when Integer
+        return true if rv == tot
+        buf.slice!(0, rv).clear
+        tot -= rv
+      when :wait_writable
+        @wbuf = buf
+        return rv
+      end while tot > 0
+      true # all done
+    end
+  rescue
+    nil # signal EOF up the chain
+  end
+
+  def dispatch_rd(buf)
+    case rv = @to_io.read_nonblock(MAX_RBUF, buf, exception: false)
+    when String then dispatch_loop(@rbuf << rv)
+    when :wait_readable, nil then rv
+    end
+  rescue
+    nil
+  end
+
+  def dispatch_wr
+    tot = @wbuf.size
+    case rv = @to_io.write_nonblock(@wbuf, exception: false)
+    when Integer
+      @wbuf.slice!(0, rv).clear
+      tot -= rv
+      return :wait_readable if tot == 0
+    when :wait_writable then return rv
+    end while true
+  rescue
+    nil
+  end
+
+  def hash
+    @to_io.fileno
+  end
+end
diff --git a/lib/dtas/server_loop.rb b/lib/dtas/server_loop.rb
new file mode 100644
index 0000000..f0936aa
--- /dev/null
+++ b/lib/dtas/server_loop.rb
@@ -0,0 +1,55 @@
+# Copyright (C) 2015 all contributors <dtas-all@nongnu.org>
+# License: GPLv3 or later (https://www.gnu.org/licenses/gpl-3.0.txt)
+
+require_relative '../dtas'
+
+# Used for mpd emulation currently, but dtas-player might use this eventually
+class DTAS::ServerLoop
+  def initialize(listeners, client_class)
+    @rd = {}
+    @wr = {}
+    @rbuf = ''
+    @client_class = client_class
+    listeners.each { |l| @rd[l] = true }
+  end
+
+  def run_forever
+    begin
+      r = IO.select(@rd.keys, @wr.keys) or next
+      r[0].each { |rd| do_read(rd) }
+      r[1].each { |wr| do_write(wr) }
+    end while true
+  end
+
+  def do_write(wr)
+    case wr.dispatch_wr
+    when :wait_readable
+      @wr.delete(wr)
+      @rd[wr] = true
+    when nil
+      @wr.delete(wr)
+      wr.to_io.close
+    # when :wait_writable # do nothing
+    end
+  end
+
+  def do_read(rd)
+    case rd
+    when @client_class
+      case rd.dispatch_rd(@rbuf)
+      when :wait_writable
+        @rd.delete(rd)
+        @wr[rd] = true
+      when nil
+        @rd.delete(rd)
+        rd.to_io.close
+      # when :wait_readable : do nothing
+      end
+    else
+      case io = rd.accept_nonblock(exception: false)
+      when :wait_readable then break
+      when IO then @rd[@client_class.new(io)] = true
+      end while true
+    end
+  end
+end
-- 
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