Flatten cbor and bring back half

gems/aws-sdk-core/lib/aws-sdk-core/cbor.rb

@@ -1,6 +1,6 @@
 # frozen_string_literal: true
 
-require_relative 'cbor/engines/cbor_engine'
+require_relative 'cbor/cbor_engine'
 
 module Aws
   # @api private

gems/aws-sdk-core/lib/aws-sdk-core/cbor/engines/cbor_engine.rb → gems/aws-sdk-core/lib/aws-sdk-core/cbor/cbor_engine.rb

@@ -1,8 +1,8 @@
 # frozen_string_literal: true
 
-require_relative '../tagged'
-require_relative '../encoder'
-require_relative '../decoder'
+require_relative 'tagged'
+require_relative 'encoder'
+require_relative 'decoder'
 
 module Aws
   module Cbor

gems/aws-sdk-core/lib/aws-sdk-core/cbor/decoder.rb

@@ -203,25 +203,7 @@ def read_undefined
       # precision - 10 bits
       def read_half
         read_info
-        b16 = take(2).unpack1('n')
-        exp = b16 >> 10 & 0x1f
-        mant = b16 & 0x3ff
-        val =
-          case exp
-          when 0
-            Math.ldexp(mant, -24)
-          when 31
-            mant.zero? ? Float::INFINITY : Float::NAN
-          else
-            # exp bias is 15, but to use ldexp we divide by 1024 (2^10) to get
-            # exp-15-10
-            Math.ldexp(1024 + mant, exp - 25)
-          end
-        if b16[15] != 0
-          -val
-        else
-          val
-        end
+        Half.decode(take(2).unpack1('n'))
       end
 
       def read_float

gems/aws-sdk-core/lib/aws-sdk-core/cbor/half.rb

@@ -0,0 +1,34 @@
+# frozen_string_literal: true
+
+module Aws
+  module Cbor
+    # 16 bit IEEE 754 half-precision floats
+    # Support decoding only
+    # format:
+    # sign - 1 bit
+    # exponent - 5 bits
+    # precision - 10 bits
+    module Half
+      def self.decode(b16)
+        exp = b16 >> 10 & 0x1f
+        mant = b16 & 0x3ff
+        val =
+          case exp
+          when 0
+            Math.ldexp(mant, -24)
+          when 31
+            mant.zero? ? Float::INFINITY : Float::NAN
+          else
+            # exp bias is 15, but to use ldexp we divide by 1024 (2^10) to get
+            # exp-15-10
+            Math.ldexp(1024 + mant, exp - 25)
+          end
+        if b16[15] != 0
+          -val
+        else
+          val
+        end
+      end
+    end
+  end
+end

gems/aws-sdk-core/spec/aws/cbor/half_spec.rb

@@ -0,0 +1,23 @@
+# frozen_string_literal: true
+
+require_relative '../../spec_helper'
+
+module Aws
+  module Cbor
+    describe Half do
+
+      it 'correctly decodes half precision numbers' do
+        expect(Cbor::Half.decode(0)).to eq(0)
+        expect(Cbor::Half.decode(0x3c00)).to eq(1)
+        expect(Cbor::Half.decode(0x7bff)).to eq(65504)
+        expect(Cbor::Half.decode(0x3555)).to be_within(0.0001).of(0.3333)
+      end
+
+      it 'decodes inf and nan' do
+        expect(Cbor::Half.decode(0x7c00)).to eq(Float::INFINITY)
+        expect(Cbor::Half.decode(0xfc00)).to eq(-Float::INFINITY)
+        expect(Cbor::Half.decode(0x7c01).nan?).to be true
+      end
+    end
+  end
+end