diff --git a/lib/mongo/util/bson_c.rb b/lib/mongo/util/bson_c.rb
new file mode 100644
index 0000000..4c3d640
--- /dev/null
+++ b/lib/mongo/util/bson_c.rb
@@ -0,0 +1,45 @@
+# A thin wrapper for the CBson class
+class BSON_C
+
+  if RUBY_VERSION >= '1.9'
+    def self.to_utf8(str)
+      str.encode("utf-8")
+    end
+  else
+    def self.to_utf8(str)
+      begin
+      str.unpack("U*")
+      rescue => ex
+        raise InvalidStringEncoding, "String not valid utf-8: #{str}"
+      end
+      str
+    end
+  end
+
+  def self.serialize_cstr(buf, val)
+    buf.put_array(to_utf8(val.to_s).unpack("C*") + [0])
+  end
+
+  def self.serialize(obj, check_keys=false)
+    ByteBuffer.new(CBson.serialize(obj, check_keys))
+  end
+
+  def self.deserialize(buf=nil)
+    if buf.is_a? String
+      to_deserialize = ByteBuffer.new(buf) if buf
+    else
+      buf = ByteBuffer.new(buf.to_a) if buf
+    end
+    buf.rewind
+    CBson.deserialize(buf.to_s)
+  end
+
+  def deserialize(buf=nil)
+    self.class.deserialize(buf)
+  end
+
+  def serialize(buf, check_keys=false)
+    self.class.serialize(buf, check_keys)
+  end
+
+end
diff --git a/lib/mongo/util/bson_ruby.rb b/lib/mongo/util/bson_ruby.rb
new file mode 100644
index 0000000..6c1f5d4
--- /dev/null
+++ b/lib/mongo/util/bson_ruby.rb
@@ -0,0 +1,547 @@
+# --
+# Copyright (C) 2008-2009 10gen Inc.
+#
+# This program is free software: you can redistribute it and/or modify it
+# under the terms of the GNU Affero General Public License, version 3, as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Affero General Public License
+# for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+# ++
+
+require 'base64'
+require 'mongo/util/byte_buffer'
+require 'mongo/util/ordered_hash'
+require 'mongo/types/binary'
+require 'mongo/types/dbref'
+require 'mongo/types/objectid'
+require 'mongo/types/regexp_of_holding'
+
+# A BSON seralizer/deserializer in pure Ruby.
+class BSON_RUBY
+
+  include Mongo
+
+  MINKEY = -1
+  EOO = 0
+  NUMBER = 1
+  STRING = 2
+  OBJECT = 3
+  ARRAY = 4
+  BINARY = 5
+  UNDEFINED = 6
+  OID = 7
+  BOOLEAN = 8
+  DATE = 9
+  NULL = 10
+  REGEX = 11
+  REF = 12
+  CODE = 13
+  SYMBOL = 14
+  CODE_W_SCOPE = 15
+  NUMBER_INT = 16
+  TIMESTAMP = 17
+  NUMBER_LONG = 18
+  MAXKEY = 127
+
+  def initialize
+    @buf = ByteBuffer.new
+  end
+
+  if RUBY_VERSION >= '1.9'
+    def self.to_utf8(str)
+      str.encode("utf-8")
+    end
+  else
+    def self.to_utf8(str)
+      begin
+      str.unpack("U*")
+      rescue => ex
+        raise InvalidStringEncoding, "String not valid utf-8: #{str}"
+      end
+      str
+    end
+  end
+
+  def self.serialize_cstr(buf, val)
+    buf.put_array(to_utf8(val.to_s).unpack("C*") + [0])
+  end
+
+  def to_a
+    @buf.to_a
+  end
+
+  # Serializes an object.
+  # Implemented to ensure an API compatible with BSON extension. 
+  def self.serialize(obj, check_keys=false)
+    new.serialize(obj, check_keys)
+  end
+
+  def self.deserialize(buf=nil)
+    new.deserialize(buf)
+  end
+
+  def serialize(obj, check_keys=false)
+    raise "Document is null" unless obj
+
+    @buf.rewind
+    # put in a placeholder for the total size
+    @buf.put_int(0)
+
+    # Write key/value pairs. Always write _id first if it exists.
+    if obj.has_key? '_id'
+      serialize_key_value('_id', obj['_id'], check_keys)
+    elsif obj.has_key? :_id
+      serialize_key_value('_id', obj[:_id], check_keys)
+    end
+
+    obj.each {|k, v| serialize_key_value(k, v, check_keys) unless k == '_id' || k == :_id }
+
+    serialize_eoo_element(@buf)
+    @buf.put_int(@buf.size, 0)
+    self
+  end
+
+  # Returns the array stored in the buffer.
+  # Implemented to ensure an API compatible with BSON extension. 
+  def unpack(arg)
+    @buf.to_a
+  end
+
+  def serialize_key_value(k, v, check_keys)
+    k = k.to_s
+    if check_keys
+      if k[0] == ?$
+        raise InvalidName.new("key #{k} must not start with '$'")
+      end
+      if k.include? ?.
+        raise InvalidName.new("key #{k} must not contain '.'")
+      end
+    end
+    type = bson_type(v)
+    case type
+    when STRING, SYMBOL
+      serialize_string_element(@buf, k, v, type)
+    when NUMBER, NUMBER_INT
+      serialize_number_element(@buf, k, v, type)
+    when OBJECT
+      serialize_object_element(@buf, k, v, check_keys)
+    when OID
+      serialize_oid_element(@buf, k, v)
+    when ARRAY
+      serialize_array_element(@buf, k, v, check_keys)
+    when REGEX
+      serialize_regex_element(@buf, k, v)
+    when BOOLEAN
+      serialize_boolean_element(@buf, k, v)
+    when DATE
+      serialize_date_element(@buf, k, v)
+    when NULL
+      serialize_null_element(@buf, k)
+    when REF
+      serialize_dbref_element(@buf, k, v)
+    when BINARY
+      serialize_binary_element(@buf, k, v)
+    when UNDEFINED
+      serialize_null_element(@buf, k)
+    when CODE_W_SCOPE
+      serialize_code_w_scope(@buf, k, v)
+    else
+      raise "unhandled type #{type}"
+    end
+  end
+
+  def deserialize(buf=nil)
+    # If buf is nil, use @buf, assumed to contain already-serialized BSON.
+    # This is only true during testing.
+    if buf.is_a? String
+      @buf = ByteBuffer.new(buf) if buf
+    else
+      @buf = ByteBuffer.new(buf.to_a) if buf
+    end
+    @buf.rewind
+    @buf.get_int                # eat message size
+    doc = OrderedHash.new
+    while @buf.more?
+      type = @buf.get
+      case type
+      when STRING, CODE
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_string_data(@buf)
+      when SYMBOL
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_string_data(@buf).intern
+      when NUMBER
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_number_data(@buf)
+      when NUMBER_INT
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_number_int_data(@buf)
+      when NUMBER_LONG
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_number_long_data(@buf)
+      when OID
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_oid_data(@buf)
+      when ARRAY
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_array_data(@buf)
+      when REGEX
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_regex_data(@buf)
+      when OBJECT
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_object_data(@buf)
+      when BOOLEAN
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_boolean_data(@buf)
+      when DATE
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_date_data(@buf)
+      when NULL
+        key = deserialize_cstr(@buf)
+        doc[key] = nil
+      when UNDEFINED
+        key = deserialize_cstr(@buf)
+        doc[key] = nil
+      when REF
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_dbref_data(@buf)
+      when BINARY
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_binary_data(@buf)
+      when CODE_W_SCOPE
+        key = deserialize_cstr(@buf)
+        doc[key] = deserialize_code_w_scope_data(@buf)
+      when TIMESTAMP
+        key = deserialize_cstr(@buf)
+        doc[key] = [deserialize_number_int_data(@buf),
+                    deserialize_number_int_data(@buf)]
+      when EOO
+        break
+      else
+        raise "Unknown type #{type}, key = #{key}"
+      end
+    end
+    @buf.rewind
+    doc
+  end
+
+  # For debugging.
+  def hex_dump
+    str = ''
+    @buf.to_a.each_with_index { |b,i|
+      if (i % 8) == 0
+        str << "\n" if i > 0
+        str << '%4d:  ' % i
+      else
+        str << ' '
+      end
+      str << '%02X' % b
+    }
+    str
+  end
+
+  def deserialize_date_data(buf)
+    unsigned = buf.get_long()
+    # see note for deserialize_number_long_data below
+    milliseconds = unsigned >= 2 ** 64 / 2 ? unsigned - 2**64 : unsigned
+    Time.at(milliseconds.to_f / 1000.0).utc # at() takes fractional seconds
+  end
+
+  def deserialize_boolean_data(buf)
+    buf.get == 1
+  end
+
+  def deserialize_number_data(buf)
+    buf.get_double
+  end
+
+  def deserialize_number_int_data(buf)
+    # sometimes ruby makes me angry... why would the same code pack as signed
+    # but unpack as unsigned
+    unsigned = buf.get_int
+    unsigned >= 2**32 / 2 ? unsigned - 2**32 : unsigned
+  end
+
+  def deserialize_number_long_data(buf)
+    # same note as above applies here...
+    unsigned = buf.get_long
+    unsigned >= 2 ** 64 / 2 ? unsigned - 2**64 : unsigned
+  end
+
+  def deserialize_object_data(buf)
+    size = buf.get_int
+    buf.position -= 4
+    object = BSON.new().deserialize(buf.get(size))
+    if object.has_key? "$ref"
+      DBRef.new(object["$ref"], object["$id"])
+    else
+      object
+    end
+  end
+
+  def deserialize_array_data(buf)
+    h = deserialize_object_data(buf)
+    a = []
+    h.each { |k, v| a[k.to_i] = v }
+    a
+  end
+
+  def deserialize_regex_data(buf)
+    str = deserialize_cstr(buf)
+    options_str = deserialize_cstr(buf)
+    options = 0
+    options |= Regexp::IGNORECASE if options_str.include?('i')
+    options |= Regexp::MULTILINE if options_str.include?('m')
+    options |= Regexp::EXTENDED if options_str.include?('x')
+    options_str.gsub!(/[imx]/, '') # Now remove the three we understand
+    RegexpOfHolding.new(str, options, options_str)
+  end
+
+  def deserialize_string_data(buf)
+    len = buf.get_int
+    bytes = buf.get(len)
+    str = bytes[0..-2]
+    if str.respond_to? "pack"
+      str = str.pack("C*")
+    end
+    if RUBY_VERSION >= '1.9'
+      str.force_encoding("utf-8")
+    end
+    str
+  end
+
+  def deserialize_code_w_scope_data(buf)
+    buf.get_int
+    len = buf.get_int
+    code = buf.get(len)[0..-2]
+    if code.respond_to? "pack"
+      code = code.pack("C*")
+    end
+    if RUBY_VERSION >= '1.9'
+      code.force_encoding("utf-8")
+    end
+
+    scope_size = buf.get_int
+    buf.position -= 4
+    scope = BSON.new().deserialize(buf.get(scope_size))
+
+    Code.new(code, scope)
+  end
+
+  def deserialize_oid_data(buf)
+    ObjectID.new(buf.get(12))
+  end
+
+  def deserialize_dbref_data(buf)
+    ns = deserialize_string_data(buf)
+    oid = deserialize_oid_data(buf)
+    DBRef.new(ns, oid)
+  end
+
+  def deserialize_binary_data(buf)
+    len = buf.get_int
+    type = buf.get
+    len = buf.get_int if type == Binary::SUBTYPE_BYTES
+    Binary.new(buf.get(len), type)
+  end
+
+  def serialize_eoo_element(buf)
+    buf.put(EOO)
+  end
+
+  def serialize_null_element(buf, key)
+    buf.put(NULL)
+    self.class.serialize_cstr(buf, key)
+  end
+
+  def serialize_dbref_element(buf, key, val)
+    oh = OrderedHash.new
+    oh['$ref'] = val.namespace
+    oh['$id'] = val.object_id
+    serialize_object_element(buf, key, oh, false)
+  end
+
+  def serialize_binary_element(buf, key, val)
+    buf.put(BINARY)
+    self.class.serialize_cstr(buf, key)
+
+    bytes = val.to_a
+    num_bytes = bytes.length
+    subtype = val.respond_to?(:subtype) ? val.subtype : Binary::SUBTYPE_BYTES
+    if subtype == Binary::SUBTYPE_BYTES
+      buf.put_int(num_bytes + 4)
+      buf.put(subtype)
+      buf.put_int(num_bytes)
+      buf.put_array(bytes)
+    else
+      buf.put_int(num_bytes)
+      buf.put(subtype)
+      buf.put_array(bytes)
+    end
+  end
+
+  def serialize_boolean_element(buf, key, val)
+    buf.put(BOOLEAN)
+    self.class.serialize_cstr(buf, key)
+    buf.put(val ? 1 : 0)
+  end
+
+  def serialize_date_element(buf, key, val)
+    buf.put(DATE)
+    self.class.serialize_cstr(buf, key)
+    millisecs = (val.to_f * 1000).to_i
+    buf.put_long(millisecs)
+  end
+
+  def serialize_number_element(buf, key, val, type)
+    if type == NUMBER
+      buf.put(type)
+      self.class.serialize_cstr(buf, key)
+      buf.put_double(val)
+    else
+      if val > 2**64 / 2 - 1 or val < -2**64 / 2
+        raise RangeError.new("MongoDB can only handle 8-byte ints")
+      end
+      if val > 2**32 / 2 - 1 or val < -2**32 / 2
+        buf.put(NUMBER_LONG)
+        self.class.serialize_cstr(buf, key)
+        buf.put_long(val)
+      else
+        buf.put(type)
+        self.class.serialize_cstr(buf, key)
+        buf.put_int(val)
+      end
+    end
+  end
+
+  def serialize_object_element(buf, key, val, check_keys, opcode=OBJECT)
+    buf.put(opcode)
+    self.class.serialize_cstr(buf, key)
+    buf.put_array(BSON.new.serialize(val, check_keys).to_a)
+  end
+
+  def serialize_array_element(buf, key, val, check_keys)
+    # Turn array into hash with integer indices as keys
+    h = OrderedHash.new
+    i = 0
+    val.each { |v| h[i] = v; i += 1 }
+    serialize_object_element(buf, key, h, check_keys, ARRAY)
+  end
+
+  def serialize_regex_element(buf, key, val)
+    buf.put(REGEX)
+    self.class.serialize_cstr(buf, key)
+
+    str = val.to_s.sub(/.*?:/, '')[0..-2] # Turn "(?xxx:yyy)" into "yyy"
+    self.class.serialize_cstr(buf, str)
+
+    options = val.options
+    options_str = ''
+    options_str << 'i' if ((options & Regexp::IGNORECASE) != 0)
+    options_str << 'm' if ((options & Regexp::MULTILINE) != 0)
+    options_str << 'x' if ((options & Regexp::EXTENDED) != 0)
+    options_str << val.extra_options_str if val.respond_to?(:extra_options_str)
+    # Must store option chars in alphabetical order
+    self.class.serialize_cstr(buf, options_str.split(//).sort.uniq.join)
+  end
+
+  def serialize_oid_element(buf, key, val)
+    buf.put(OID)
+    self.class.serialize_cstr(buf, key)
+
+    buf.put_array(val.to_a)
+  end
+
+  def serialize_string_element(buf, key, val, type)
+    buf.put(type)
+    self.class.serialize_cstr(buf, key)
+
+    # Make a hole for the length
+    len_pos = buf.position
+    buf.put_int(0)
+
+    # Save the string
+    start_pos = buf.position
+    self.class.serialize_cstr(buf, val)
+    end_pos = buf.position
+
+    # Put the string size in front
+    buf.put_int(end_pos - start_pos, len_pos)
+
+    # Go back to where we were
+    buf.position = end_pos
+  end
+
+  def serialize_code_w_scope(buf, key, val)
+    buf.put(CODE_W_SCOPE)
+    self.class.serialize_cstr(buf, key)
+
+    # Make a hole for the length
+    len_pos = buf.position
+    buf.put_int(0)
+
+    buf.put_int(val.length + 1)
+    self.class.serialize_cstr(buf, val)
+    buf.put_array(BSON.new.serialize(val.scope).to_a)
+
+    end_pos = buf.position
+    buf.put_int(end_pos - len_pos, len_pos)
+    buf.position = end_pos
+  end
+
+  def deserialize_cstr(buf)
+    chars = ""
+    while true
+      b = buf.get
+      break if b == 0
+      chars << b.chr
+    end
+    if RUBY_VERSION >= '1.9'
+      chars.force_encoding("utf-8") # Mongo stores UTF-8
+    end
+    chars
+  end
+
+  def bson_type(o)
+    case o
+    when nil
+      NULL
+    when Integer
+      NUMBER_INT
+    when Numeric
+      NUMBER
+    when ByteBuffer
+      BINARY
+    when Code
+      CODE_W_SCOPE
+    when String
+      STRING
+    when Array
+      ARRAY
+    when Regexp
+      REGEX
+    when ObjectID
+      OID
+    when DBRef
+      REF
+    when true, false
+      BOOLEAN
+    when Time
+      DATE
+    when Hash
+      OBJECT
+    when Symbol
+      SYMBOL
+    else
+      raise "Unknown type of object: #{o.class.name}"
+    end
+  end
+
+end