Merge pull request #52 from peelman/add-little-endian-float

Add extension method to support unpacking 32-bit Int using little-endian

lib/rmodbus/ext.rb

@@ -39,6 +39,12 @@ def to_32f
     self.each_slice(2).map { |(lsb, msb)| [msb, lsb].pack('n*').unpack('g')[0] }
   end
 
+  # Given an array of 16bit Fixnum, we turn it into 32bit Int in little-endian order, halving the size
+  def to_32f_le
+    raise "Array requires an even number of elements to pack to 32bits: was #{self.size}" unless self.size.even?
+    self.each_slice(2).map { |(lsb, msb)| [lsb, msb].pack('n*').unpack('g')[0] }
+  end
+
   # Given an array of 32bit Floats, we turn it into an array of 16bit Fixnums, doubling the size
   def from_32f
     self.pack('g*').unpack('n*').each_slice(2).map { |arr| arr.reverse }.flatten

spec/ext_spec.rb

@@ -24,10 +24,15 @@
     [20342, 17344, 20342, 17344].to_32i.size.should == 2
   end
 
-  it "should turn an array into 32b floats" do
+  it "should turn an array into 32b floats big endian" do
     [20342, 17344].to_32f[0].should be_within(0.1).of(384.620788574219)
     [20342, 17344, 20342, 17344].to_32f.size.should == 2
   end
+
+  it "should turn a an array into 32b floats (little endian)" do
+    [17344, 20342].to_32f_le[0].should be_within(0.1).of(384.620788574219)
+    [17344, 20342, 17344, 20342].to_32f_le.size.should == 2
+  end
 
   it "should turn an array from 32b ints into 16b ints, big endian" do
     [1136676726].from_32i.should == [20342, 17344]