ProtoParcelable.kt
/*
* Copyright (C) 2022 The Android Open Source Project
*
* 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 androidx.health.platform.client.impl.data
import android.annotation.SuppressLint
import android.os.Parcel
import android.os.Parcelable
import android.os.Parcelable.Creator
import android.os.SharedMemory
import androidx.annotation.RestrictTo
import androidx.health.platform.client.proto.MessageLite
/**
* Base class for parcelables backed by protos.
*
* Provided [proto] represents everything important to subclasses, they need not implement [equals]
* and [hashCode].
*/
@Suppress("ParcelCreator", "ParcelNotFinal")
@RestrictTo(RestrictTo.Scope.LIBRARY)
abstract class ProtoParcelable<T : MessageLite> : ProtoData<T>(), Parcelable {
/** Serialized representation of this object. */
private val bytes: ByteArray by lazy { proto.toByteArray() }
override fun describeContents(): Int {
return if (shouldStoreInPlace()) 0 else Parcelable.CONTENTS_FILE_DESCRIPTOR
}
/**
* Flattens the underlying proto into `dest`.
*
* @see Parcelable.writeToParcel
*/
override fun writeToParcel(dest: Parcel, flags: Int) {
if (shouldStoreInPlace()) {
dest.writeInt(STORE_IN_PLACE)
dest.writeByteArray(bytes)
} else {
dest.writeInt(STORE_SHARED_MEMORY)
@Suppress("NewApi") // API only ever used on SDK 27 and above.
SharedMemory27Impl.writeToParcelUsingSharedMemory("ProtoParcelable", bytes, dest, flags)
}
}
/** Returns whether the underlying proto should be stored as an in-place [ByteArray]. */
private fun shouldStoreInPlace(): Boolean {
return bytes.size <= MAX_IN_PLACE_SIZE
}
companion object {
/**
* Constructs and returns a [Creator] based on the provided [parser] accepting a [ByteArray]
* .
*/
internal inline fun <reified U : ProtoParcelable<*>> newCreator(
crossinline parser: (ByteArray) -> U
): Creator<U> {
return object : Creator<U> {
@SuppressLint("NewApi") // API only ever used on SDK 27 and above.
override fun createFromParcel(source: Parcel): U? {
when (val storage = source.readInt()) {
STORE_IN_PLACE -> {
val payload: ByteArray = source.createByteArray() ?: return null
return parser(payload)
}
STORE_SHARED_MEMORY -> {
return SharedMemory27Impl.parseParcelUsingSharedMemory(source) {
parser(it)
}
}
else -> throw IllegalArgumentException("Unknown storage: $storage")
}
}
override fun newArray(size: Int) = arrayOfNulls<U>(size)
}
}
}
}
/** Flag marking that a proto is stored as an in-place `byte[]` array. */
internal const val STORE_IN_PLACE = 0
/** Flag marking that a proto is stored in [SharedMemory]. */
internal const val STORE_SHARED_MEMORY = 1
/** Maximum size of a proto stored as an in-place `byte[]` array (16 KiB). */
private const val MAX_IN_PLACE_SIZE = 16 * 1024