android/prebuilt.go

// Copyright 2016 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

import (
	"fmt"

	"github.com/google/blueprint"
)

// This file implements common functionality for handling modules that may exist as prebuilts,
// source, or both.

type prebuiltDependencyTag struct {
	blueprint.BaseDependencyTag
}

var prebuiltDepTag prebuiltDependencyTag

type PrebuiltProperties struct {
	// When prefer is set to true the prebuilt will be used instead of any source module with
	// a matching name.
	Prefer bool `android:"arch_variant"`

	SourceExists bool `blueprint:"mutated"`
	UsePrebuilt  bool `blueprint:"mutated"`
}

type Prebuilt struct {
	properties PrebuiltProperties
	module     Module
	srcs       *[]string
}

func (p *Prebuilt) Name(name string) string {
	return "prebuilt_" + name
}

func (p *Prebuilt) SingleSourcePath(ctx ModuleContext) Path {
	if len(*p.srcs) == 0 {
		ctx.PropertyErrorf("srcs", "missing prebuilt source file")
		return nil
	}

	if len(*p.srcs) > 1 {
		ctx.PropertyErrorf("srcs", "multiple prebuilt source files")
		return nil
	}

	return PathForModuleSrc(ctx, (*p.srcs)[0])
}

func InitPrebuiltModule(module PrebuiltInterface, srcs *[]string) {
	p := module.Prebuilt()
	module.AddProperties(&p.properties)
	p.srcs = srcs
}

type PrebuiltInterface interface {
	Module
	Prebuilt() *Prebuilt
}

func RegisterPrebuiltsPreArchMutators(ctx RegisterMutatorsContext) {
	ctx.BottomUp("prebuilts", prebuiltMutator).Parallel()
}

func RegisterPrebuiltsPostDepsMutators(ctx RegisterMutatorsContext) {
	ctx.TopDown("prebuilt_select", PrebuiltSelectModuleMutator).Parallel()
	ctx.BottomUp("prebuilt_replace", PrebuiltReplaceMutator).Parallel()
}

// prebuiltMutator ensures that there is always a module with an undecorated name, and marks
// prebuilt modules that have both a prebuilt and a source module.
func prebuiltMutator(ctx BottomUpMutatorContext) {
	if m, ok := ctx.Module().(PrebuiltInterface); ok && m.Prebuilt() != nil {
		p := m.Prebuilt()
		name := m.base().BaseModuleName()
		if ctx.OtherModuleExists(name) {
			ctx.AddReverseDependency(ctx.Module(), prebuiltDepTag, name)
			p.properties.SourceExists = true
		} else {
			ctx.Rename(name)
		}
	}
}

// PrebuiltSelectModuleMutator marks prebuilts that are used, either overriding source modules or
// because the source module doesn't exist.  It also disables installing overridden source modules.
func PrebuiltSelectModuleMutator(ctx TopDownMutatorContext) {
	if m, ok := ctx.Module().(PrebuiltInterface); ok && m.Prebuilt() != nil {
		p := m.Prebuilt()
		if p.srcs == nil {
			panic(fmt.Errorf("prebuilt module did not have InitPrebuiltModule called on it"))
		}
		if !p.properties.SourceExists {
			p.properties.UsePrebuilt = p.usePrebuilt(ctx, nil)
		}
	} else if s, ok := ctx.Module().(Module); ok {
		ctx.VisitDirectDeps(func(m blueprint.Module) {
			if ctx.OtherModuleDependencyTag(m) == prebuiltDepTag {
				p := m.(PrebuiltInterface).Prebuilt()
				if p.usePrebuilt(ctx, s) {
					p.properties.UsePrebuilt = true
					s.SkipInstall()
				}
			}
		})
	}
}

// PrebuiltReplaceMutator replaces dependencies on the source module with dependencies on the
// prebuilt when both modules exist and the prebuilt should be used.  When the prebuilt should not
// be used, disable installing it.
func PrebuiltReplaceMutator(ctx BottomUpMutatorContext) {
	if m, ok := ctx.Module().(PrebuiltInterface); ok && m.Prebuilt() != nil {
		p := m.Prebuilt()
		name := m.base().BaseModuleName()
		if p.properties.UsePrebuilt {
			if p.properties.SourceExists {
				ctx.ReplaceDependencies(name)
			}
		} else {
			m.SkipInstall()
		}
	}
}

// usePrebuilt returns true if a prebuilt should be used instead of the source module.  The prebuilt
// will be used if it is marked "prefer" or if the source module is disabled.
func (p *Prebuilt) usePrebuilt(ctx TopDownMutatorContext, source Module) bool {
	if len(*p.srcs) == 0 {
		return false
	}

	// TODO: use p.Properties.Name and ctx.ModuleDir to override preference
	if p.properties.Prefer {
		return true
	}

	return source == nil || !source.Enabled()
}