1 files changed, 83 insertions, 0 deletions
diff --git a/android/image.go b/android/image.go
new file mode 100644
index 000000000..5ec1b16f5
--- /dev/null
+++ b/android/image.go
@@ -0,0 +1,83 @@
+// Copyright 2019 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package android
+
+// ImageInterface is implemented by modules that need to be split by the ImageMutator.
+type ImageInterface interface {
+	// ImageMutatorBegin is called before any other method in the ImageInterface.
+	ImageMutatorBegin(ctx BaseModuleContext)
+
+	// CoreVariantNeeded should return true if the module needs a core variant (installed on the system image).
+	CoreVariantNeeded(ctx BaseModuleContext) bool
+
+	// RecoveryVariantNeeded should return true if the module needs a recovery variant (installed on the
+	// recovery partition).
+	RecoveryVariantNeeded(ctx BaseModuleContext) bool
+
+	// ExtraImageVariations should return a list of the additional variations needed for the module.  After the
+	// variants are created the SetImageVariation method will be called on each newly created variant with the
+	// its variation.
+	ExtraImageVariations(ctx BaseModuleContext) []string
+
+	// SetImageVariation will be passed a newly created recovery variant of the module.  ModuleBase implements
+	// SetImageVariation, most module types will not need to override it, and those that do must call the
+	// overridden method.  Implementors of SetImageVariation must be careful to modify the module argument
+	// and not the receiver.
+	SetImageVariation(ctx BaseModuleContext, variation string, module Module)
+}
+
+const (
+	// CoreVariation is the variant used for framework-private libraries, or
+	// SDK libraries. (which framework-private libraries can use), which
+	// will be installed to the system image.
+	CoreVariation string = "core"
+
+	// RecoveryVariation means a module to be installed to recovery image.
+	RecoveryVariation string = "recovery"
+)
+
+// ImageMutator creates variants for modules that implement the ImageInterface that
+// allow them to build differently for each partition (recovery, core, vendor, etc.).
+func ImageMutator(ctx BottomUpMutatorContext) {
+	if ctx.Os() != Android {
+		return
+	}
+
+	if m, ok := ctx.Module().(ImageInterface); ok {
+		m.ImageMutatorBegin(ctx)
+
+		var variations []string
+
+		if m.CoreVariantNeeded(ctx) {
+			variations = append(variations, CoreVariation)
+		}
+		if m.RecoveryVariantNeeded(ctx) {
+			variations = append(variations, RecoveryVariation)
+		}
+
+		extraVariations := m.ExtraImageVariations(ctx)
+		variations = append(variations, extraVariations...)
+
+		if len(variations) == 0 {
+			return
+		}
+
+		mod := ctx.CreateVariations(variations...)
+		for i, v := range variations {
+			mod[i].base().setImageVariation(v)
+			m.SetImageVariation(ctx, v, mod[i])
+		}
+	}
+}