xavriley · October 4, 2015 19:42 · Oct 4, 2015
diff --git a/README.md b/README.md
@@ -0,0 +1,6 @@
+This doesn't currently work because the OSC spec calls for the ints to be packed with a "twos complement" which basically means they are packed unsigned and converted when they get decoded.
+
+```
+[-1].pack('N').unpack('N') # => 16777216
+[-1].pack('N').unpack('N').pack('V').unpack('l') # => -1
+```
diff --git a/oscdecode.rb b/oscdecode.rb
@@ -0,0 +1,119 @@
+#--
+# This file is part of Sonic Pi: http://sonic-pi.net
+# Full project source: https://github.com/samaaron/sonic-pi
+# License: https://github.com/samaaron/sonic-pi/blob/master/LICENSE.md
+#
+# Copyright 2013, 2014, 2015 by Sam Aaron (http://sam.aaron.name).
+# All rights reserved.
+#
+# Permission is granted for use, copying, modification, and
+# distribution of modified versions of this work as long as this
+# notice is included.
+#++
+require 'strscan'
+
+module SonicPi
+  class OscDecode
+
+    def initialize(use_cache = false, cache_size=1000)
+      @float_cache = {}
+      @integer_cache = {}
+      @cache_size = cache_size
+
+      @num_cached_integers = 0
+      @num_cached_floats = 0
+      @string_terminator = Regexp.new("\x00")
+      @tag_separator = ','
+      @args = []
+      @i_tag = "i"
+      @f_tag = "f"
+      @s_tag = "s"
+      @d_tag = "d"
+      @h_tag = "h"
+      @b_tag = "b"
+
+      @cap_n = 'N'
+      @cap_g = 'G'
+      @low_g = 'g'
+      @low_l = 'l'
+      @q_lt = 'q>'
+      @binary_encoding = "BINARY"
+    end
+
+    def decode_single_message(msg)
+      ## Note everything is inlined here for effienciency to remove the
+      ## cost of method dispatch. Apologies if this makes it harder to
+      ## read & understand. See http://opensoundcontrol.org for spec.
+
+      m = StringScanner.new(msg)
+
+      pack_string = ""
+
+      # Get OSC address e.g. /foo
+      m.skip_until(@string_terminator)
+      m.pos = 4 * ((m.pos + 0.01)/4).ceil
+      pack_string << "Z#{m.pos}"
+
+      # Let's see if we have some args..
+      # check the next char to see if it's a comma
+      if m.peek(1) == @tag_separator
+        # Get type tags
+        orig_idx = m.pos
+        tags = m.scan_until(@string_terminator)
+        m.pos = 4 * ((m.pos + 0.01)/4).ceil
+        if tags.length > 1
+          pack_string << "Z#{m.pos - orig_idx}"
+        end
+
+        # skip the comma
+        tags.each_char do |t|
+          case t
+          when @tag_separator
+            # skip the comma
+            nil
+          when @string_terminator
+            # skip the null bytes
+            nil
+          when @i_tag
+            # int32
+            m.pos = m.pos+4
+            pack_string << @cap_n
+          when @f_tag
+            # float32
+            m.pos = m.pos+4
+            pack_string << @low_g
+          when @s_tag
+            # string
+            orig_idx = m.pos
+            m.skip_until(@string_terminator)
+            m.pos = 4 * ((m.pos + 0.01)/4).ceil
+            pack_string << "Z#{m.pos - orig_idx}"
+          when @d_tag
+            # double64
+            m.pos = m.pos+8
+            pack_string << @cap_g
+          when @h_tag
+            # int64
+            m.pos = m.pos+8
+            pack_string << @q_lt
+          when @b_tag
+            # binary blob
+            orig_idx = m.pos
+            pack_string << @cap_n
+            blob_length = m.getch.unpack(@cap_n)[0]
+            m.skip(Regexp.new(".#{blob_length}"))
+            pack_string << "Z#{m.pos - orig_idx}"
+
+            m.pos = 4 * ((m.pos + 0.01)/4).ceil
+          else
+            raise "Unknown OSC type #{t}"
+          end
+        end
+      end
+
+      address, tags, *args = msg.unpack(pack_string)
+      [address, args]
+    end
+
+  end
+end
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