Add mapping binary search

lib/sprockets/source_map.rb

@@ -4,6 +4,8 @@
 module Sprockets
   class SourceMap
     class Offset
+      include Comparable
+
       def initialize(line, column)
         @line, @column = line, column
       end
@@ -17,7 +19,17 @@ def +(other)
         when Integer
           Offset.new(self.line + other, self.column)
         else
-          raise ArgumentError, "can't convert #{other} into Offset"
+          raise ArgumentError, "can't convert #{other} into #{self.class}"
+        end
+      end
+
+      def <=>(other)
+        case other
+        when Offset
+          diff = self.line - other.line
+          diff.zero? ? self.column - other.column : diff
+        else
+          raise ArgumentError, "can't convert #{other.class} into #{self.class}"
         end
       end
 
@@ -31,13 +43,26 @@ def inspect
     end
 
     class Mapping
+      include Comparable
+
       def initialize(source, generated, original, name = nil)
         @source, @generated, @original = source, generated, original
         @name = name
       end
 
       attr_reader :generated, :original, :source, :name
 
+      def <=>(other)
+        case other
+        when Mapping
+          self.generated <=> other.generated
+        when Offset
+          self.generated <=> other
+        else
+          raise ArgumentError, "can't convert #{other.class} into #{self.class}"
+        end
+      end
+
       def inspect
         "#<#{self.class} generated=#{generated}, original=#{original}, source=#{source}, name=#{name}>"
       end
@@ -73,6 +98,9 @@ def self.from_vlq(str, sources = [], names = [])
 
               source   = sources[source_id]
               original = Offset.new(original_line, original_column)
+            else
+              # TODO: Research this case
+              next
             end
 
             if segment[4]
@@ -141,6 +169,18 @@ def +(other)
         self.class.new(mappings)
       end
 
+      def bsearch(offset, low = 0, high = size - 1)
+        return self[low-1] if low > high
+        mid = (low + high) / 2
+        return self[mid] if self[mid] == offset
+        if self[mid] > offset
+          high = mid - 1
+        else
+          low = mid + 1
+        end
+        bsearch(offset, low, high)
+      end
+
       protected
         def build_vlq_string
           source_id        = 0

test/test_source_map.rb

@@ -116,8 +116,8 @@ class TestMappings < Test::Unit::TestCase
   def setup
     @mappings = Mappings.new([
       Mapping.new('a.js', Offset.new(0, 0), Offset.new(0, 0)),
-      Mapping.new('b.js', Offset.new(1, 0), Offset.new(0, 0)),
-      Mapping.new('c.js', Offset.new(2, 0), Offset.new(0, 0))
+      Mapping.new('b.js', Offset.new(1, 0), Offset.new(20, 0)),
+      Mapping.new('c.js', Offset.new(2, 0), Offset.new(30, 0))
     ])
   end
 
@@ -126,7 +126,7 @@ def test_line_count
   end
 
   def test_to_s
-    assert_equal "ACAA;ACAA;", @mappings.to_s
+    assert_equal "ACoBA;ACUA;", @mappings.to_s
   end
 
   def test_sources
@@ -147,6 +147,14 @@ def test_add
     assert_equal 2, mappings3[2].generated.line
     assert_equal 3, mappings3[3].generated.line
   end
+
+  def test_bsearch
+    assert_equal Offset.new(0, 0), @mappings.bsearch(Offset.new(0, 0)).original
+    assert_equal Offset.new(0, 0), @mappings.bsearch(Offset.new(0, 5)).original
+    assert_equal Offset.new(20, 0), @mappings.bsearch(Offset.new(1, 0)).original
+    assert_equal Offset.new(20, 0), @mappings.bsearch(Offset.new(1, 0)).original
+    assert_equal Offset.new(30, 0), @mappings.bsearch(Offset.new(2, 0)).original
+  end
 end
 
 class TestMapping < Test::Unit::TestCase
@@ -175,6 +183,34 @@ def test_name
     assert_equal 'hello', @mapping.name
   end
 
+  def test_compare
+    assert @mapping == @mapping
+    assert @mapping <= @mapping
+    assert @mapping >= @mapping
+
+    other = Mapping.new('script.js', Offset.new(2, 0), Offset.new(3, 0), 'goodbye')
+    assert @mapping < other
+    assert other > @mapping
+
+    other = Mapping.new('script.js', Offset.new(1, 9), Offset.new(3, 0), 'goodbye')
+    assert @mapping < other
+    assert other > @mapping
+  end
+
+  def test_compare_offset
+    other = Offset.new(1, 8)
+
+    assert @mapping == other
+    assert @mapping <= other
+    assert @mapping >= other
+
+    other = Offset.new(2, 0)
+    assert @mapping < other
+
+    other = Offset.new(1, 9)
+    assert @mapping < other
+  end
+
   def test_inspect
     assert_equal "#<Sprockets::SourceMap::Mapping generated=1:8, original=2:9, source=script.js, name=hello>", @mapping.inspect
   end
@@ -214,4 +250,12 @@ def test_add_line
     assert_equal 6, offset.line
     assert_equal 5, offset.column
   end
+
+  def test_compare
+    assert @offset < Offset.new(2, 0)
+    assert @offset < Offset.new(1, 6)
+    assert @offset > Offset.new(1, 4)
+    assert @offset >= Offset.new(1, 5)
+    assert @offset <= Offset.new(1, 5)
+  end
 end