Splits bits out from an input port

lib/rcircuit/splitter.rb

@@ -0,0 +1,36 @@
+## Outputs a specified subset of the bits from an input port
+class Splitter < Device
+  # @param port [Port] A the splitter input port
+  # @param bits [Integer,Array,Range] The bits from the input port that are output by the splitter
+  # @return [void]
+  def initialize(port, bits)
+    if bits.is_a?(Integer)
+      width = 1
+      @bitlist = [bits]
+    elsif bits.is_a?(Array) 
+      width = bits.size
+      @bitlist = bits.reverse #store in MSB order
+    elsif bits.is_a?(Range)
+      width = bits.size
+      @bitlist = bits.to_a.reverse #store in MSB order 
+    else
+      raise ArgumentError.new("bits argument must be of type Integer, Array , or Range")
+    end
+    @bits = bits
+    add_output("out", width)
+    port.add_callback { |val| on_change(val) }
+    on_change(port.val)
+  end
+
+  private
+  # Called when there is a change to inputs
+  def on_change(input_val)
+    outval = 0
+    @bitlist.each do |bit|
+      outval *= 2
+      outval += ((input_val >> bit) & 1)
+    end
+    out.setval(outval)
+  end
+  
+end

spec/splitter_spec.rb

@@ -0,0 +1,18 @@
+describe Splitter do
+  it "should extract bits from an input port" do
+    inp = Port.new(8)
+    splitter = Splitter.new(inp, [1,6])
+    inp.setval(0x03)
+    expect(splitter.out.val).to eq 1
+    inp.setval(0x18)
+    expect(splitter.out.val).to eq 0
+    inp.setval(0xC0)
+    expect(splitter.out.val).to eq 2
+    inp.setval(0xF3)
+    expect(splitter.out.val).to eq 3
+    #test port indexing
+    expect(inp[7].val).to eq 1 
+    expect(inp[4..7].val).to eq 15
+    expect(inp[2,3,4].val).to eq 4
+  end
+end