diff --git a/binwriter.rb b/binwriter.rb
new file mode 100644
index 0000000..0288a69
--- /dev/null
+++ b/binwriter.rb
@@ -0,0 +1,123 @@
+16# 8 16 32 64
+# C S L Q - unsigned
+# c s l q - unsigned
+# < LE
+# > BE
+# A - binary string
+# z - null terminated
+# H - hex string
+
+
+class BinWriter
+  def initialize fn
+    @f = File.new fn, "wb"
+  end
+
+  def self.open fn, &block
+    f = BinWriter.new fn
+    block.call f
+    f.close
+  end
+
+  def seek pos
+    @f.seek pos
+  end
+
+  def tell
+    @f.tell
+  end
+
+  def write_str str
+    @f.write str
+  end
+
+  def write_str_varlen str
+    write_varlen_le str.size
+    @f.write str
+  end
+
+  def write_byte val
+    @f.write [val].pack("C")
+  end
+
+  def write_bool val
+    write_byte val ? 1 : 0
+  end
+
+  def write_u16_le val
+    @f.write [val].pack("S<")
+  end
+
+  def write_s16_le val
+    @f.write [val].pack("s<")
+  end
+
+  def write_u16_be val
+    @f.write [val].pack("S>")
+  end
+
+  def write_u32_le val
+    @f.write [val].pack("L<")
+  end
+
+  def write_s32_le val
+    @f.write [val].pack("l<")
+  end
+
+  def write_u32_be val
+    @f.write [val].pack("L>")
+  end
+
+  def write_f32_le val
+    @f.write [val].pack("e")
+  end
+
+  def write_u24_be val
+    write_byte val >> 16
+    write_u16_be val & 0xFFFF
+  end
+
+  def write_bin str
+    @f.write str
+  end
+
+  def write_varlen_be val
+    out = [val & 0x7F]
+    val = val >> 7
+    while val > 0
+        out << (val & 0x7f) + 0x80
+        val = val >> 7
+    end
+    out.reverse.each do |x|
+      write_byte x
+    end
+  end
+
+  def write_varlen_le val
+    out = [val & 0x7F]
+    val = val >> 7
+    while val > 0
+        out << (val & 0x7f)
+        val = val >> 7
+    end
+    out.each_with_index do |x, i|
+      write_byte(x + ((i == out.size - 1) ? 0 : 0x80))
+    end
+  end
+
+  def write_binswap str
+    togo = str.size
+    pos = 0
+    while togo > 0
+      r = @rom[pos..(pos+3)].unpack('L>')
+      d = r.pack('L<')
+      write_bin d
+      pos += 4
+      togo -= 4
+    end
+  end
+
+  def close
+    @f.close
+  end
+end