Hardware: add helper to determine if an executable can be run

Library/Homebrew/hardware.rb

@@ -80,6 +80,18 @@ module Hardware
       def feature?(name)
         features.include?(name)
       end
+
+      def can_run?(arch)
+        if is_32_bit?
+          arch_32_bit == arch
+        elsif intel?
+          [:i386, :x86_64].include? arch
+        elsif ppc?
+          [:ppc, :ppc64].include? arch
+        else
+          false
+        end
+      end
     end
   end
 

Library/Homebrew/test/hardware_spec.rb

@@ -36,5 +36,52 @@ module Hardware
         ).to include(described_class.family)
       end
     end
+
+    describe "::can_run?" do
+      it "reports that Intel machines can run Intel executables" do
+        allow(Hardware::CPU).to receive(:type).and_return :intel
+        allow(Hardware::CPU).to receive(:bits).and_return 64
+        expect(Hardware::CPU.can_run?(:i386)).to be true
+        expect(Hardware::CPU.can_run?(:x86_64)).to be true
+      end
+
+      it "reports that PowerPC machines can run PowerPC executables" do
+        allow(Hardware::CPU).to receive(:type).and_return :ppc
+        allow(Hardware::CPU).to receive(:bits).and_return 64
+        expect(Hardware::CPU.can_run?(:ppc)).to be true
+        expect(Hardware::CPU.can_run?(:ppc64)).to be true
+      end
+
+      it "reports that 32-bit Intel machines can't run x86_64 executables" do
+        allow(Hardware::CPU).to receive(:type).and_return :intel
+        allow(Hardware::CPU).to receive(:bits).and_return 32
+        expect(Hardware::CPU.can_run?(:x86_64)).to be false
+      end
+
+      it "reports that 32-bit PowerPC machines can't run ppc64 executables" do
+        allow(Hardware::CPU).to receive(:type).and_return :ppc
+        allow(Hardware::CPU).to receive(:bits).and_return 32
+        expect(Hardware::CPU.can_run?(:ppc64)).to be false
+      end
+
+      it "identifies that Intel and PowerPC machines can't run each others' executables" do
+        allow(Hardware::CPU).to receive(:type).and_return :ppc
+        expect(Hardware::CPU.can_run?(:i386)).to be false
+        expect(Hardware::CPU.can_run?(:x86_64)).to be false
+
+        allow(Hardware::CPU).to receive(:type).and_return :intel
+        expect(Hardware::CPU.can_run?(:ppc)).to be false
+        expect(Hardware::CPU.can_run?(:ppc64)).to be false
+      end
+
+      it "returns false for unknown CPU types" do
+        allow(Hardware::CPU).to receive(:type).and_return :dunno
+        expect(Hardware::CPU.can_run?(:i386)).to be false
+      end
+
+      it "returns false for unknown arches" do
+        expect(Hardware::CPU.can_run?(:blah)).to be false
+      end
+    end
   end
 end