1 files changed, 233 insertions, 0 deletions
diff --git a/spec/ruby/core/integer/right_shift_spec.rb b/spec/ruby/core/integer/right_shift_spec.rb
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+++ b/spec/ruby/core/integer/right_shift_spec.rb
@@ -0,0 +1,233 @@
+require_relative '../../spec_helper'
+
+describe "Integer#>> (with n >> m)" do
+  context "fixnum" do
+    it "returns n shifted right m bits when n > 0, m > 0" do
+      (2 >> 1).should == 1
+    end
+
+    it "returns n shifted right m bits when n < 0, m > 0" do
+      (-2 >> 1).should == -1
+      (-7 >> 1).should == -4
+      (-42 >> 2).should == -11
+    end
+
+    it "returns n shifted left m bits when n > 0, m < 0" do
+      (1 >> -1).should == 2
+    end
+
+    it "returns n shifted left m bits when n < 0, m < 0" do
+      (-1 >> -1).should == -2
+    end
+
+    it "returns 0 when n == 0" do
+      (0 >> 1).should == 0
+    end
+
+    it "returns n when n > 0, m == 0" do
+      (1 >> 0).should == 1
+    end
+
+    it "returns n when n < 0, m == 0" do
+      (-1 >> 0).should == -1
+    end
+
+    it "returns 0 when n > 0, m > 0 and n < 2**m" do
+      (3 >> 2).should == 0
+      (7 >> 3).should == 0
+      (127 >> 7).should == 0
+
+      # To make sure the exponent is not truncated
+      (7 >> 32).should == 0
+      (7 >> 64).should == 0
+    end
+
+    it "returns -1 when n < 0, m > 0 and n > -(2**m)" do
+      (-3 >> 2).should == -1
+      (-7 >> 3).should == -1
+      (-127 >> 7).should == -1
+
+      # To make sure the exponent is not truncated
+      (-7 >> 32).should == -1
+      (-7 >> 64).should == -1
+    end
+
+    it "returns a Bignum == fixnum_max * 2 when fixnum_max >> -1 and n > 0" do
+      result = fixnum_max >> -1
+      result.should be_an_instance_of(Integer)
+      result.should == fixnum_max * 2
+    end
+
+    it "returns a Bignum == fixnum_min * 2 when fixnum_min >> -1 and n < 0" do
+      result = fixnum_min >> -1
+      result.should be_an_instance_of(Integer)
+      result.should == fixnum_min * 2
+    end
+
+    it "calls #to_int to convert the argument to an Integer" do
+      obj = mock("2")
+      obj.should_receive(:to_int).and_return(2)
+      (8 >> obj).should == 2
+
+      obj = mock("to_int_bignum")
+      obj.should_receive(:to_int).and_return(bignum_value)
+      (8 >> obj).should == 0
+    end
+
+    it "raises a TypeError when #to_int does not return an Integer" do
+      obj = mock("a string")
+      obj.should_receive(:to_int).and_return("asdf")
+
+      -> { 3 >> obj }.should raise_error(TypeError)
+    end
+
+    it "raises a TypeError when passed nil" do
+      -> { 3 >> nil }.should raise_error(TypeError)
+    end
+
+    it "raises a TypeError when passed a String" do
+      -> { 3 >> "4" }.should raise_error(TypeError)
+    end
+  end
+
+  context "bignum" do
+    before :each do
+      @bignum = bignum_value * 8 # 2 ** 67
+    end
+
+    it "returns n shifted right m bits when n > 0, m > 0" do
+      (@bignum >> 1).should == 73786976294838206464
+    end
+
+    it "returns n shifted right m bits when n < 0, m > 0" do
+      (-@bignum >> 2).should == -36893488147419103232
+    end
+
+    it "respects twos complement signed shifting" do
+      # This explicit left hand value is important because it is the
+      # exact bit pattern that matters, so it's important it's right
+      # here to show the significance.
+      #
+
+      (-42949672980000000000000 >> 14).should == -2621440001220703125
+      (-42949672980000000000001 >> 14).should == -2621440001220703126
+      # Note the off by one -------------------- ^^^^^^^^^^^^^^^^^^^^
+      # This is because even though we discard the lowest bit, in twos
+      # complement it would influence the bits to the left of it.
+
+      (-42949672980000000000000 >> 15).should == -1310720000610351563
+      (-42949672980000000000001 >> 15).should == -1310720000610351563
+
+      (-0xfffffffffffffffff >> 32).should == -68719476736
+    end
+
+    it "respects twos complement signed shifting for very large values" do
+      giant = 42949672980000000000000000000000000000000000000000000000000000000000000000000000000000000000
+      neg = -giant
+
+      (giant >> 84).should == 2220446050284288846538547929770901490087453566957265138626098632812
+      (neg >> 84).should == -2220446050284288846538547929770901490087453566957265138626098632813
+    end
+
+    it "returns n shifted left m bits when  n > 0, m < 0" do
+      (@bignum >> -2).should == 590295810358705651712
+    end
+
+    it "returns n shifted left m bits when  n < 0, m < 0" do
+      (-@bignum >> -3).should == -1180591620717411303424
+    end
+
+    it "returns n when n > 0, m == 0" do
+      (@bignum >> 0).should == @bignum
+    end
+
+    it "returns n when n < 0, m == 0" do
+      (-@bignum >> 0).should == -@bignum
+    end
+
+    it "returns 0 when m > 0 and m == p where 2**p > n >= 2**(p-1)" do
+      (@bignum >> 68).should == 0
+    end
+
+    it "returns a Fixnum == fixnum_max when (fixnum_max * 2) >> 1 and n > 0" do
+      result = (fixnum_max * 2) >> 1
+      result.should be_an_instance_of(Integer)
+      result.should == fixnum_max
+    end
+
+    it "returns a Fixnum == fixnum_min when (fixnum_min * 2) >> 1 and n < 0" do
+      result = (fixnum_min * 2) >> 1
+      result.should be_an_instance_of(Integer)
+      result.should == fixnum_min
+    end
+
+    it "calls #to_int to convert the argument to an Integer" do
+      obj = mock("2")
+      obj.should_receive(:to_int).and_return(2)
+
+      (@bignum >> obj).should == 36893488147419103232
+    end
+
+    it "raises a TypeError when #to_int does not return an Integer" do
+      obj = mock("a string")
+      obj.should_receive(:to_int).and_return("asdf")
+
+      -> { @bignum >> obj }.should raise_error(TypeError)
+    end
+
+    it "raises a TypeError when passed nil" do
+      -> { @bignum >> nil }.should raise_error(TypeError)
+    end
+
+    it "raises a TypeError when passed a String" do
+      -> { @bignum >> "4" }.should raise_error(TypeError)
+    end
+  end
+
+  context "when m is a bignum or larger than int" do
+    it "returns -1 when m > 0 and n < 0" do
+      (-1 >> bignum_value).should == -1
+      (-1 >> (2**40)).should == -1
+
+      (-bignum_value >> bignum_value).should == -1
+      (-bignum_value >> (2**40)).should == -1
+    end
+
+    it "returns 0 when m > 0 and n >= 0" do
+      (0 >> bignum_value).should == 0
+      (1 >> bignum_value).should == 0
+      (bignum_value >> bignum_value).should == 0
+
+      (0 >> (2**40)).should == 0
+      (1 >> (2**40)).should == 0
+      (bignum_value >> (2**40)).should == 0
+    end
+
+    it "returns 0 when m < 0 long and n == 0" do
+      (0 >> -(2**40)).should == 0
+    end
+
+    it "returns 0 when m < 0 bignum and n == 0" do
+      (0 >> -bignum_value).should == 0
+    end
+
+    it "raises RangeError when m < 0 and n != 0" do
+      # https://bugs.ruby-lang.org/issues/18518#note-9
+      limit = RUBY_ENGINE == 'ruby' ? 2**67 : 2**32
+
+      coerce_long = mock("long")
+      coerce_long.stub!(:to_int).and_return(-limit)
+      coerce_bignum = mock("bignum")
+      coerce_bignum.stub!(:to_int).and_return(-bignum_value)
+      exps = [-limit, coerce_long]
+      exps << -bignum_value << coerce_bignum if bignum_value >= limit
+
+      exps.each { |exp|
+        -> { (1 >> exp) }.should raise_error(RangeError, 'shift width too big')
+        -> { (-1 >> exp) }.should raise_error(RangeError, 'shift width too big')
+        -> { (bignum_value >> exp) }.should raise_error(RangeError, 'shift width too big')
+        -> { (-bignum_value >> exp) }.should raise_error(RangeError, 'shift width too big')
+      }
+    end
+  end
+end